draft-ietf-simple-message-sessions-19.txt   rfc4975.txt 
Network Working Group B. Campbell, Ed. Network Working Group B. Campbell, Ed.
Internet-Draft Estacado Systems Request for Comments: 4975 Estacado Systems
Intended status: Standards Track R. Mahy, Ed. Category: Standards Track R. Mahy, Ed.
Expires: August 27, 2007 Plantronics Plantronics
C. Jennings, Ed. C. Jennings, Ed.
Cisco Systems, Inc. Cisco Systems, Inc.
February 23, 2007 September 2007
The Message Session Relay Protocol
draft-ietf-simple-message-sessions-19
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This Internet-Draft will expire on August 27, 2007. The Message Session Relay Protocol (MSRP)
Copyright Notice Status of This Memo
Copyright (C) The IETF Trust (2007). This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
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and status of this protocol. Distribution of this memo is unlimited.
Abstract Abstract
This document describes the Message Session Relay Protocol, a This document describes the Message Session Relay Protocol, a
protocol for transmitting a series of related instant messages in the protocol for transmitting a series of related instant messages in the
context of a session. Message sessions are treated like any other context of a session. Message sessions are treated like any other
media stream when set up via a rendezvous or session creation media stream when set up via a rendezvous or session creation
protocol such as the Session Initiation Protocol. protocol such as the Session Initiation Protocol.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Conventions .....................................................5
3. Applicability of MSRP . . . . . . . . . . . . . . . . . . . . 5 3. Applicability of MSRP ...........................................5
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6 4. Protocol Overview ...............................................6
5. Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Key Concepts ....................................................9
5.1. MSRP Framing and Message Chunking . . . . . . . . . . . . 9 5.1. MSRP Framing and Message Chunking ..........................9
5.2. MSRP Addressing . . . . . . . . . . . . . . . . . . . . . 10 5.2. MSRP Addressing ...........................................10
5.3. MSRP Transaction and Report Model . . . . . . . . . . . . 11 5.3. MSRP Transaction and Report Model .........................11
5.4. MSRP Connection Model . . . . . . . . . . . . . . . . . . 12 5.4. MSRP Connection Model .....................................12
6. MSRP URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6. MSRP URIs ......................................................14
6.1. MSRP URI Comparison . . . . . . . . . . . . . . . . . . . 15 6.1. MSRP URI Comparison .......................................15
6.2. Resolving MSRP Host Device . . . . . . . . . . . . . . . 16 6.2. Resolving MSRP Host Device ................................16
7. Method-Specific Behavior . . . . . . . . . . . . . . . . . . . 17 7. Method-Specific Behavior .......................................17
7.1. Constructing Requests . . . . . . . . . . . . . . . . . . 17 7.1. Constructing Requests .....................................17
7.1.1. Sending SEND Requests . . . . . . . . . . . . . . . . 18 7.1.1. Sending SEND Requests ..............................18
7.1.2. Sending REPORT Requests . . . . . . . . . . . . . . . 21 7.1.2. Sending REPORT Requests ............................21
7.1.3. Generating Success Reports . . . . . . . . . . . . . . 22 7.1.3. Generating Success Reports .........................22
7.1.4. Generating Failure Reports . . . . . . . . . . . . . . 23 7.1.4. Generating Failure Reports .........................23
7.2. Constructing Responses . . . . . . . . . . . . . . . . . 24 7.2. Constructing Responses ....................................24
7.3. Receiving Requests . . . . . . . . . . . . . . . . . . . 25 7.3. Receiving Requests ........................................25
7.3.1. Receiving SEND Requests . . . . . . . . . . . . . . . 25 7.3.1. Receiving SEND Requests ............................25
7.3.2. Receiving REPORT Requests . . . . . . . . . . . . . . 26 7.3.2. Receiving REPORT Requests ..........................27
8. Using MSRP with SIP and SDP . . . . . . . . . . . . . . . . . 27 8. Using MSRP with SIP and SDP ....................................27
8.1. SDP Connection and Media Lines . . . . . . . . . . . . . 28 8.1. SDP Connection and Media-Lines ............................28
8.2. URI Negotiations . . . . . . . . . . . . . . . . . . . . 29 8.2. URI Negotiations ..........................................29
8.3. Path Attributes with Multiple URIs . . . . . . . . . . . 30 8.3. Path Attributes with Multiple URIs ........................30
8.4. Updated SDP Offers . . . . . . . . . . . . . . . . . . . 30 8.4. Updated SDP Offers ........................................31
8.5. Connection Negotiation . . . . . . . . . . . . . . . . . 31 8.5. Connection Negotiation ....................................31
8.6. Content Type Negotiation . . . . . . . . . . . . . . . . 31 8.6. Content Type Negotiation ..................................32
8.7. Example SDP Exchange . . . . . . . . . . . . . . . . . . 33 8.7. Example SDP Exchange ......................................34
8.8. MSRP User Experience with SIP . . . . . . . . . . . . . . 34 8.8. MSRP User Experience with SIP .............................35
8.9. SDP direction attribute and MSRP . . . . . . . . . . . . 35 8.9. SDP Direction Attribute and MSRP ..........................35
9. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 35 9. Formal Syntax ..................................................36
10. Response Code Descriptions . . . . . . . . . . . . . . . . . . 37 10. Response Code Descriptions ....................................38
10.1. 200 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.1. 200 ......................................................38
10.2. 400 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.2. 400 ......................................................38
10.3. 403 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.3. 403 ......................................................38
10.4. 408 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.4. 408 ......................................................39
10.5. 413 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.5. 413 ......................................................39
10.6. 415 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.6. 415 ......................................................39
10.7. 423 . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 10.7. 423 ......................................................39
10.8. 481 . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 10.8. 481 ......................................................39
10.9. 501 . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 10.9. 501 ......................................................39
10.10. 506 . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 10.10. 506 .....................................................40
11. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 11. Examples ......................................................40
11.1. Basic IM Session . . . . . . . . . . . . . . . . . . . . 39 11.1. Basic IM Session .........................................40
11.2. Message with XHTML Content . . . . . . . . . . . . . . . 42 11.2. Message with XHTML Content ...............................42
11.3. Chunked Message . . . . . . . . . . . . . . . . . . . . . 42 11.3. Chunked Message ..........................................43
11.4. Chunked Message with message/cpim payload . . . . . . . . 42 11.4. Chunked Message with Message/CPIM Payload ................43
11.5. System Message . . . . . . . . . . . . . . . . . . . . . 43 11.5. System Message ...........................................44
11.6. Positive Report . . . . . . . . . . . . . . . . . . . . . 44 11.6. Positive Report ..........................................44
11.7. Forked IM . . . . . . . . . . . . . . . . . . . . . . . . 44 11.7. Forked IM ................................................45
12. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 47 12. Extensibility .................................................48
13. CPIM Compatibility . . . . . . . . . . . . . . . . . . . . . . 47 13. CPIM Compatibility ............................................48
14. Security Considerations . . . . . . . . . . . . . . . . . . . 48 14. Security Considerations .......................................49
14.1. Secrecy of the MSRP URI . . . . . . . . . . . . . . . . . 49 14.1. Secrecy of the MSRP URI ..................................50
14.2. Transport Level Protection . . . . . . . . . . . . . . . 49 14.2. Transport Level Protection ...............................50
14.3. S/MIME . . . . . . . . . . . . . . . . . . . . . . . . . 50 14.3. S/MIME ...................................................51
14.4. Using TLS in Peer-to-Peer Mode . . . . . . . . . . . . . 51 14.4. Using TLS in Peer-to-Peer Mode ...........................52
14.5. Other Security Concerns . . . . . . . . . . . . . . . . . 52 14.5. Other Security Concerns ..................................53
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 54 15. IANA Considerations ...........................................55
15.1. MSRP Method Names . . . . . . . . . . . . . . . . . . . . 54 15.1. MSRP Method Names ........................................55
15.2. MSRP Header Fields . . . . . . . . . . . . . . . . . . . 54 15.2. MSRP Header Fields .......................................55
15.3. MSRP Status Codes . . . . . . . . . . . . . . . . . . . . 55 15.3. MSRP Status Codes ........................................56
15.4. MSRP Port . . . . . . . . . . . . . . . . . . . . . . . . 55 15.4. MSRP Port ................................................56
15.5. URI Schema . . . . . . . . . . . . . . . . . . . . . . . 55 15.5. URI Schema ...............................................56
15.5.1. MSRP Scheme . . . . . . . . . . . . . . . . . . . . . 55 15.5.1. MSRP Scheme .......................................56
15.5.2. MSRPS Scheme . . . . . . . . . . . . . . . . . . . . . 56 15.5.2. MSRPS Scheme ......................................57
15.6. SDP Transport Protocol . . . . . . . . . . . . . . . . . 56 15.6. SDP Transport Protocol ...................................57
15.7. SDP Attribute Names . . . . . . . . . . . . . . . . . . . 57 15.7. SDP Attribute Names ......................................58
15.7.1. Accept Types . . . . . . . . . . . . . . . . . . . . . 57 15.7.1. Accept Types ......................................58
15.7.2. Wrapped Types . . . . . . . . . . . . . . . . . . . . 57 15.7.2. Wrapped Types .....................................58
15.7.3. Max Size . . . . . . . . . . . . . . . . . . . . . . . 57 15.7.3. Max Size ..........................................58
15.7.4. Path . . . . . . . . . . . . . . . . . . . . . . . . . 57 15.7.4. Path ..............................................58
16. Contributors and Acknowledgments . . . . . . . . . . . . . . . 58 16. Contributors and Acknowledgments ..............................59
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 58 17. References ....................................................59
17.1. Normative References . . . . . . . . . . . . . . . . . . 58 17.1. Normative References .....................................59
17.2. Informational References . . . . . . . . . . . . . . . . 59 17.2. Informative References ...................................60
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 61
Intellectual Property and Copyright Statements . . . . . . . . . . 62
1. Introduction 1. Introduction
A series of related instant messages between two or more parties can A series of related instant messages between two or more parties can
be viewed as part of a "message session", that is, a conversational be viewed as part of a "message session", that is, a conversational
exchange of messages with a definite beginning and end. This is in exchange of messages with a definite beginning and end. This is in
contrast to individual messages each sent independently. Messaging contrast to individual messages each sent independently. Messaging
schemes that track only individual messages can be described as schemes that track only individual messages can be described as
"page-mode" messaging, whereas messaging that is part of a "session" "page-mode" messaging, whereas messaging that is part of a "session"
with a definite start and end is called "session-mode" messaging. with a definite start and end is called "session-mode" messaging.
Page-mode messaging is enabled in SIP via the SIP [4] MESSAGE method Page-mode messaging is enabled in SIP via the SIP [4] MESSAGE method
[22]. Session-mode messaging has a number of benefits over page-mode [22]. Session-mode messaging has a number of benefits over page-mode
messaging, however, such as explicit rendezvous, tighter integration messaging, however, such as explicit rendezvous, tighter integration
with other media-types, direct client-to-client operation, and with other media-types, direct client-to-client operation, and
brokered privacy and security. brokered privacy and security.
This document defines a session-oriented instant message transport This document defines a session-oriented instant message transport
protocol called the Message Session Relay Protocol (MSRP), whose protocol called the Message Session Relay Protocol (MSRP), whose
sessions can be negotiated with an offer or answer [3] using the sessions can be negotiated with an offer or answer [3] using the
Session Description Protocol(SDP [2]). The exchange is carried by Session Description Protocol (SDP) [2]. The exchange is carried by
some signaling protocol, such as the Session Initiation Protocol (SIP some signaling protocol, such as SIP [4]. This allows a
[4]). This allows a communication user agent to offer a messaging communication user agent to offer a messaging session as one of the
session as one of the possible media-types in a session. For possible media-types in a session. For instance, Alice may want to
instance, Alice may want to communicate with Bob. Alice doesn't know communicate with Bob. Alice doesn't know at the moment whether Bob
at the moment whether Bob has his phone or his IM client handy, but has his phone or his IM client handy, but she's willing to use
she's willing to use either. She sends an invitation to a session to either. She sends an invitation to a session to the address of
the address of record she has for Bob, sip:bob@example.com. Her record she has for Bob, sip:bob@example.com. Her invitation offers
invitation offers both voice and an IM session. The SIP services at both voice and an IM session. The SIP services at example.com
example.com forward the invitation to Bob at his currently registered forward the invitation to Bob at his currently registered clients.
clients. Bob accepts the invitation at his IM client and they begin Bob accepts the invitation at his IM client, and they begin a
a threaded chat conversation. threaded chat conversation.
When a user uses an IM URL, RFC 3861 [32] defines how DNS can be used When a user uses an Instant Messaging (IM) URL, RFC 3861 [32] defines
to map this to a particular protocol to establish the session such as how DNS can be used to map this to a particular protocol to establish
SIP. SIP can use an offer answer model to transport the MSRP URIs the session such as SIP. SIP can use an offer/answer model to
for the media in SDP. This document defines how the offer/answer transport the MSRP URIs for the media in SDP. This document defines
exchange works to establish MSRP connections and how messages are how the offer/answer exchange works to establish MSRP connections and
sent across the MSRP protocol, but it does not deal with the issues how messages are sent across the MSRP, but it does not deal with the
of mapping an IM URL to a session establishment protocol. issues of mapping an IM URL to a session establishment protocol.
This session model allows message sessions to be integrated into This session model allows message sessions to be integrated into
advanced communications applications with little to no additional advanced communications applications with little to no additional
protocol development. For example, during the above chat session, protocol development. For example, during the above chat session,
Bob decides Alice really needs to be talking to Carol. Bob can Bob decides Alice really needs to be talking to Carol. Bob can
transfer [21] Alice to Carol, introducing them into their own transfer [21] Alice to Carol, introducing them into their own
messaging session. Messaging sessions can then be easily integrated messaging session. Messaging sessions can then be easily integrated
into call-center and dispatch environments using third-party call into call-center and dispatch environments using third-party call
control [20] and conferencing [19] applications. control [20] and conferencing [19] applications.
skipping to change at page 5, line 17 skipping to change at page 5, line 17
[23] (referred to herein as "relays") are specified in a separate [23] (referred to herein as "relays") are specified in a separate
document. An endpoint that implements this specification, but not document. An endpoint that implements this specification, but not
the relay specification, will be unable to introduce relays into the the relay specification, will be unable to introduce relays into the
message path, but will still be able to interoperate with peers that message path, but will still be able to interoperate with peers that
do use relays. do use relays.
2. Conventions 2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [5]. document are to be interpreted as described in RFC 2119 [5].
This document consistently refers to a "message" as a complete unit This document consistently refers to a "message" as a complete unit
of MIME or text content. In some cases, a message is split and of MIME or text content. In some cases, a message is split and
delivered in more than one MSRP request. Each of these portions of delivered in more than one MSRP request. Each of these portions of
the complete message is called a "chunk". the complete message is called a "chunk".
3. Applicability of MSRP 3. Applicability of MSRP
MSRP is not designed for use as a standalone protocol. MSRP MUST be MSRP is not designed for use as a standalone protocol. MSRP MUST be
used only in the context of a rendezvous mechanism meeting the used only in the context of a rendezvous mechanism meeting the
following requirements: following requirements:
o The rendezvous mechanism MUST provide both MSRP URIs associated o The rendezvous mechanism MUST provide both MSRP URIs associated
with an MSRP session to each of the participating endpoints. The with an MSRP session to each of the participating endpoints. The
rendezvous mechanism MUST implement mechanisms to protect the rendezvous mechanism MUST implement mechanisms to protect the
confidentiality of these URIs - they MUST NOT be made available to confidentiality of these URIs -- they MUST NOT be made available
an untrusted third party or be easily discoverable. to an untrusted third party or be easily discoverable.
o The rendezvous mechanism MUST provide mechanisms for the o The rendezvous mechanism MUST provide mechanisms for the
negotiation of any supported MSRP extensions that are not negotiation of any supported MSRP extensions that are not
backwards compatible. backwards compatible.
o The rendezvous mechanism MUST be able to natively transport im: o The rendezvous mechanism MUST be able to natively transport im:
URIs or automatically translate im: URIs [27] into the addressing URIs or automatically translate im: URIs [27] into the addressing
identifiers of the rendezvous protocol. identifiers of the rendezvous protocol.
To use a rendezvous mechanism with MSRP, an RFC MUST be prepared To use a rendezvous mechanism with MSRP, an RFC MUST be prepared that
describing how it exchanges MSRP URIs and meets these requirements describes how it exchanges MSRP URIs and meets these requirements
listed here. This document provides such a description for the use listed here. This document provides such a description for the use
of MSRP in the context of SIP and SDP. of MSRP in the context of SIP and SDP.
SIP meets these requirements for a rendezvous mechanism. The MSRP SIP meets these requirements for a rendezvous mechanism. The MSRP
URIs are exchanged using SDP in an offer/answer exchange via SIP. URIs are exchanged using SDP in an offer/answer exchange via SIP.
The exchanged SDP can also be used to negotiate MSRP extensions. The exchanged SDP can also be used to negotiate MSRP extensions.
This SDP can be secured using any of the mechanisms available in SIP, This SDP can be secured using any of the mechanisms available in SIP,
including using the sips mechanism to ensure transport security including using the sips mechanism to ensure transport security
across intermediaries and S/MIME for end-to-end protection of the SDP across intermediaries and Secure/Multipurpose Internet Mail
body. SIP can carry arbitrary URIs (including im: URIs) in the Extensions (S/MIME) for end-to-end protection of the SDP body. SIP
Request-URI, and procedures are available to map i m: URIs to sip: or can carry arbitrary URIs (including im: URIs) in the Request-URI, and
sips: URIs. It is expected that initial deployments of MSRP will use procedures are available to map im: URIs to sip: or sips: URIs. It
SIP as its rendezvous mechanism. is expected that initial deployments of MSRP will use SIP as its
rendezvous mechanism.
4. Protocol Overview 4. Protocol Overview
MSRP is a text-based, connection-oriented protocol for exchanging MSRP is a text-based, connection-oriented protocol for exchanging
arbitrary (binary) MIME[8] content, especially instant messages. arbitrary (binary) MIME[8] content, especially instant messages.
This section is a non-normative overview of how MSRP works and how it This section is a non-normative overview of how MSRP works and how it
is used with SIP. is used with SIP.
MSRP sessions are typically arranged using SIP the same way a session MSRP sessions are typically arranged using SIP the same way a session
of audio or video media is set up. One SIP user agent (Alice) sends of audio or video media is set up. One SIP user agent (Alice) sends
the other (Bob) a SIP invitation containing an offered session- the other (Bob) a SIP invitation containing an offered session-
description which includes a session of MSRP. The receiving SIP user description that includes a session of MSRP. The receiving SIP user
agent can accept the invitation and include an answer session- agent can accept the invitation and include an answer session-
description which acknowledges the choice of media. Alice's session description that acknowledges the choice of media. Alice's session
description contains an MSRP URI that describes where she is willing description contains an MSRP URI that describes where she is willing
to receive MSRP requests from Bob, and vice-versa. (Note: Some lines to receive MSRP requests from Bob, and vice versa. (Note: Some lines
in the examples are removed for clarity and brevity.) in the examples are removed for clarity and brevity.)
Alice sends to Bob: Alice sends to Bob:
INVITE sip:bob@biloxi.example.com SIP/2.0 INVITE sip:bob@biloxi.example.com SIP/2.0
To: <sip:bob@biloxi.example.com> To: <sip:bob@biloxi.example.com>
From: <sip:alice@atlanta.example.com>;tag=786 From: <sip:alice@atlanta.example.com>;tag=786
Call-ID: 3413an89KU Call-ID: 3413an89KU
Content-Type: application/sdp Content-Type: application/sdp
c=IN IP4 atlanta.example.com c=IN IP4 atlanta.example.com
m=message 7654 TCP/MSRP * m=message 7654 TCP/MSRP *
skipping to change at page 8, line 18 skipping to change at page 8, line 18
Message-ID: 87652491 Message-ID: 87652491
Byte-Range: 1-25/25 Byte-Range: 1-25/25
Content-Type: text/plain Content-Type: text/plain
Hey Bob, are you there? Hey Bob, are you there?
-------a786hjs2$ -------a786hjs2$
MSRP a786hjs2 200 OK MSRP a786hjs2 200 OK
To-Path: msrp://atlanta.example.com:7654/jshA7weztas;tcp To-Path: msrp://atlanta.example.com:7654/jshA7weztas;tcp
From-Path: msrp://biloxi.example.com:12763/kjhd37s2s20w2a;tcp From-Path: msrp://biloxi.example.com:12763/kjhd37s2s20w2a;tcp
Byte-Range: 1-25/25
-------a786hjs2$ -------a786hjs2$
Figure 2: Example MSRP Exchange Figure 2: Example MSRP Exchange
Alice's request begins with the MSRP start line, which contains a Alice's request begins with the MSRP start line, which contains a
transaction identifier that is also used for request framing. Next transaction identifier that is also used for request framing. Next
she includes the path of URIs to the destination in the To-Path she includes the path of URIs to the destination in the To-Path
header field, and her own URI in the From-Path header field. In this header field, and her own URI in the From-Path header field. In this
typical case there is just one "hop", so there is only one URI in typical case, there is just one "hop", so there is only one URI in
each path header field. She also includes a message ID which she can each path header field. She also includes a message ID, which she
use to correlate status reports with the original message. Next she can use to correlate status reports with the original message. Next
puts the actual content. Finally she closes the request with an end- she puts the actual content. Finally, she closes the request with an
line of seven hyphens, the transaction identifier and a "$" to end-line of seven hyphens, the transaction identifier, and a "$" to
indicate this request contains the end of a complete message. indicate that this request contains the end of a complete message.
If Alice wants to deliver a very large message, she can split the If Alice wants to deliver a very large message, she can split the
message into chunks and deliver each chunk in a separate SEND message into chunks and deliver each chunk in a separate SEND
request. The message ID corresponds to the whole message, so the request. The message ID corresponds to the whole message, so the
receiver can also use it to reassemble the message and tell which receiver can also use it to reassemble the message and tell which
chunks belong with which message. Chunking is described in more chunks belong with which message. Chunking is described in more
detail in Section 5.1. The Byte-Range header field identifies the detail in Section 5.1. The Byte-Range header field identifies the
portion of the message carried in this chunk and the total size of portion of the message carried in this chunk and the total size of
the message. the message.
Alice can also specify what type of reporting she would like in Alice can also specify what type of reporting she would like in
response to her request. If Alice requests positive acknowledgments, response to her request. If Alice requests positive acknowledgments,
Bob sends a REPORT request to Alice confirming the delivery of her Bob sends a REPORT request to Alice confirming the delivery of her
complete message. This is especially useful if Alice sent a series complete message. This is especially useful if Alice sent a series
of SEND request containing chunks of a single message. More on of SEND requests containing chunks of a single message. More on
requesting types of reports and errors is described in Section 5.3. requesting types of reports and errors is described in Section 5.3.
Alice and Bob choose their MSRP URIs in such a way that is difficult Alice and Bob choose their MSRP URIs in such a way that it is
to guess the exact URI. Alice and Bob can reject requests to URIs difficult to guess the exact URI. Alice and Bob can reject requests
they are not expecting to service, and can correlate the specific URI to URIs they are not expecting to service and can correlate the
with the probable sender. Alice and Bob can also use TLS [1] to specific URI with the probable sender. Alice and Bob can also use
provide channel security over this hop. To receive MSRP requests TLS [1] to provide channel security over this hop. To receive MSRP
over a TLS protected connection, Alice or Bob could advertise URIs requests over a TLS protected connection, Alice or Bob could
with the "msrps" scheme instead of "msrp." advertise URIs with the "msrps" scheme instead of "msrp".
MSRP is designed with the expectation that MSRP can carry URIs for MSRP is designed with the expectation that MSRP can carry URIs for
nodes on the far side of relays. For this reason, a URI with the nodes on the far side of relays. For this reason, a URI with the
"msrps" scheme makes no assertion about the security properties of "msrps" scheme makes no assertion about the security properties of
other hops, just the next hop. The user agent knows the URI for each other hops, just the next hop. The user agent knows the URI for each
hop, so it can verify that each URI has the desired security hop, so it can verify that each URI has the desired security
properties. properties.
MSRP URIs are discussed in more detail in Section 6. MSRP URIs are discussed in more detail in Section 6.
An adjacent pair of busy MSRP nodes (for example two relays) can An adjacent pair of busy MSRP nodes (for example, two relays) can
easily have several sessions, and exchange traffic for several easily have several sessions, and exchange traffic for several
simultaneous users. The nodes can use existing connections to carry simultaneous users. The nodes can use existing connections to carry
new traffic with the same destination host, port, transport protocol, new traffic with the same destination host, port, transport protocol,
and scheme. MSRP nodes can keep track of how many sessions are using and scheme. MSRP nodes can keep track of how many sessions are using
a particular connection and close these connections when no sessions a particular connection and close these connections when no sessions
have used them for some period of time. Connection management is have used them for some period of time. Connection management is
discussed in more detail in Section 5.4. discussed in more detail in Section 5.4.
5. Key Concepts 5. Key Concepts
skipping to change at page 9, line 42 skipping to change at page 9, line 40
Messages sent using MSRP can be very large and can be delivered in Messages sent using MSRP can be very large and can be delivered in
several SEND requests, where each SEND request contains one chunk of several SEND requests, where each SEND request contains one chunk of
the overall message. Long chunks may be interrupted in mid- the overall message. Long chunks may be interrupted in mid-
transmission to ensure fairness across shared transport connections. transmission to ensure fairness across shared transport connections.
To support this, MSRP uses a boundary-based framing mechanism. The To support this, MSRP uses a boundary-based framing mechanism. The
start line of an MSRP request contains a unique identifier that is start line of an MSRP request contains a unique identifier that is
also used to indicate the end of the request. Included at the end of also used to indicate the end of the request. Included at the end of
the end-line, there is a flag that indicates whether this is the last the end-line, there is a flag that indicates whether this is the last
chunk of data for this message or whether the message will be chunk of data for this message or whether the message will be
continued in a subsequent chunk. There is also a Byte-Range header continued in a subsequent chunk. There is also a Byte-Range header
field in the request that indicates that the overall position of this field in the request that indicates the overall position of this
chunk inside the complete message. chunk inside the complete message.
For example, the following snippet of two SEND requests demonstrates For example, the following snippet of two SEND requests demonstrates
a message that contains the text "abcdEFGH" being sent as two chunks. a message that contains the text "abcdEFGH" being sent as two chunks.
MSRP dkei38sd SEND MSRP dkei38sd SEND
Message-ID: 4564dpWd Message-ID: 4564dpWd
Byte-Range: 1-*/8 Byte-Range: 1-*/8
Content-Type: text/plain Content-Type: text/plain
skipping to change at page 10, line 30 skipping to change at page 10, line 30
Figure 3: Breaking a Message into Chunks Figure 3: Breaking a Message into Chunks
This chunking mechanism allows a sender to interrupt a chunk part of This chunking mechanism allows a sender to interrupt a chunk part of
the way through sending it. The ability to interrupt messages allows the way through sending it. The ability to interrupt messages allows
multiple sessions to share a TCP connection, and for large messages multiple sessions to share a TCP connection, and for large messages
to be sent efficiently while not blocking other messages that share to be sent efficiently while not blocking other messages that share
the same connection, or even the same MSRP session. Any chunk that the same connection, or even the same MSRP session. Any chunk that
is larger than 2048 octets MUST be interruptible. While MSRP would is larger than 2048 octets MUST be interruptible. While MSRP would
be simpler to implement if each MSRP session used its own TCP be simpler to implement if each MSRP session used its own TCP
connection, there are compelling reasons to conserve connection. For connection, there are compelling reasons to conserve connections.
example, the TCP peer may be a relay device that connects to many For example, the TCP peer may be a relay device that connects to many
other peers. Such a device will scale better if each peer does not other peers. Such a device will scale better if each peer does not
create a large number of connections. (Note that in the above create a large number of connections. (Note that in the above
example, the initial chunk was interruptible for the sake of example, example, the initial chunk was interruptible for the sake of example,
even though its size is was well below the limit for which even though its size is well below the limit for which
interuptibility would be required.) interruptibility would be required.)
The chunking mechanism only applies to the SEND method, as it is the The chunking mechanism only applies to the SEND method, as it is the
only method used to transfer message content. only method used to transfer message content.
5.2. MSRP Addressing 5.2. MSRP Addressing
MSRP entities are addressed using URIs. The MSRP URI schemes are MSRP entities are addressed using URIs. The MSRP URI schemes are
defined in Section 6. The syntax of the To-Path and From-Path header defined in Section 6. The syntax of the To-Path and From-Path header
fields each allow for a list of URIs. This was done to allow the fields each allows for a list of URIs. This was done to allow the
protocol to work with relays, which are defined in a separate protocol to work with relays, which are defined in a separate
document, to provide a complete path to the end recipient. When two document, to provide a complete path to the end recipient. When two
MSRP nodes communicate directly they need only one URI in the To-Path MSRP nodes communicate directly, they need only one URI in the To-
list and one URI in the From-Path list. Path list and one URI in the From-Path list.
5.3. MSRP Transaction and Report Model 5.3. MSRP Transaction and Report Model
A sender sends MSRP requests to a receiver. The receiver MUST A sender sends MSRP requests to a receiver. The receiver MUST
quickly accept or reject the request. If the receiver initially quickly accept or reject the request. If the receiver initially
accepted the request, it still may then do things that take accepted the request, it still may then do things that take
significant time to succeed or fail. For example, if the receiver is significant time to succeed or fail. For example, if the receiver is
an MSRP to XMPP [30] gateway, it may forward the message over XMPP. an MSRP to Extensible Messaging and Presence Protocol (XMPP) [30]
The XMPP side may later indicate that the request did not work. At gateway, it may forward the message over XMPP. The XMPP side may
this point, the MSRP receiver may need to indicate that the request later indicate that the request did not work. At this point, the
did not succeed. There are two important concepts here: first, the MSRP receiver may need to indicate that the request did not succeed.
hop-by-hop delivery of the request may succeed or fail; second, the There are two important concepts here: first, the hop-by-hop delivery
end result of the request may be successfully processed or not. The of the request may succeed or fail; second, the end result of the
first type of status is referred to as "transaction status" and may request may or may not be successfully processed. The first type of
be returned in response to a request. The second type of status is status is referred to as "transaction status" and may be returned in
referred to as "delivery status" and may be returned in a REPORT response to a request. The second type of status is referred to as
transaction. "delivery status" and may be returned in a REPORT transaction.
The original sender of a request can indicate if they wish to receive The original sender of a request can indicate if they wish to receive
reports for requests that fail, and can independently indicate if reports for requests that fail, and can independently indicate if
they wish to receive reports for requests that succeed. A receiver they wish to receive reports for requests that succeed. A receiver
only sends a success REPORT if it knows that the request was only sends a success REPORT if it knows that the request was
successfully delivered, and the sender requested a success report. A successfully delivered, and the sender requested a success report. A
receiver only sends a failure REPORT if the request failed to be receiver only sends a failure REPORT if the request failed to be
delivered and the sender requested failure reports. delivered and the sender requested failure reports.
This document describes the behavior of MSRP endpoints. MSRP This document describes the behavior of MSRP endpoints. MSRP
relays will introduce additional conditions that indicate a relays will introduce additional conditions that indicate a
failure REPORT should be sent, such as the failure to receive a failure REPORT should be sent, such as the failure to receive a
positive response from the next hop. positive response from the next hop.
Two header fields control the sender's desire to receive reports. Two header fields control the sender's desire to receive reports.
The header field "Success-Report" can have a value of "yes" or "no" The Success-Report header field can have a value of "yes" or "no" and
and the "Failure-Report" header field can have a value of "yes", the Failure-Report header field can have a value of "yes", "no", or
"no", or "partial". "partial".
The combinations of reporting are needed to meet the various The combinations of reporting are needed to meet the various
scenarios of currently deployed IM systems. Success-Report might be scenarios of currently deployed IM systems. Success-Report might be
"no" in many public systems to reduce load but might be "yes" in "no" in many public systems to reduce load, but might be "yes" in
certain enterprise systems, such as systems used for securities certain enterprise systems, such as systems used for securities
trading. A Failure-Report value of "no" is useful for sending system trading. A Failure-Report value of "no" is useful for sending system
messages such as "the system is going down in 5 minutes" without messages such as "the system is going down in 5 minutes" without
causing a response explosion to the sender. A Failure-Report of causing a response explosion to the sender. A Failure-Report of
"yes" is used by many systems that wish to notify the user if the "yes" is used by many systems that wish to notify the user if the
message failed. A Failure-Report of "partial" is a way to report message failed. A Failure-Report of "partial" is a way to report
errors other than timeouts. The timeout error reporting requires the errors other than timeouts. Timeout error reporting requires the
sending hop to run a timer and the receiving hop to send an sending hop to run a timer and the receiving hop to send an
acknowledgment to stop the timer. Some systems don't want the acknowledgment to stop the timer. Some systems don't want the
overhead of doing this. "Partial" allows them to choose not to do overhead of doing this. "Partial" allows them to choose not to do
so, but still allows error responses to be sent in many cases. so, but still allows error responses to be sent in many cases.
The term "partial" denotes the fact that the hop-by-hop The term "partial" denotes that the hop-by-hop acknowledgment
acknowledgment mechanism that would be required if with a Failure- mechanism that would be required with a Failure-Report value of
Report value of "yes" is not invoked. Thus, each device uses only "yes" is not invoked. Thus, each device uses only "part" of the
"part" of the set of error detection tools available to them. set of error detection tools available to them. This allows a
This allows a compromise between no reporting of failures at all, compromise between no reporting of failures at all, and reporting
and reporting every possible failure. For example, with every possible failure. For example, with "partial", a sending
"partial", an sending device does not have to keep transaction device does not have to keep transaction state around waiting for
state around waiting for a positive acknowledgment. But it still a positive acknowledgment. But it still allows devices to report
allows devices to report other types of errors. The receiving other types of errors. The receiving device could still report a
device could still report a policy violation such as an policy violation such as an unacceptable content-type, or an ICMP
unacceptable content-type, or an ICMP error trying to connect to a error trying to connect to a downstream device.
downstream device.
5.4. MSRP Connection Model 5.4. MSRP Connection Model
When an MSRP endpoint wishes to send a request to a peer identified When an MSRP endpoint wishes to send a request to a peer identified
by an MSRP URI, it first needs a transport connection, with the by an MSRP URI, it first needs a transport connection, with the
appropriate security properties, to the host specified in the URI. appropriate security properties, to the host specified in the URI.
If the sender already has such a connection, that is, one associated If the sender already has such a connection, that is, one associated
with the same host, port, and URI scheme, then it SHOULD reuse that with the same host, port, and URI scheme, then it SHOULD reuse that
connection. connection.
When a new MSRP session is created, the initiating endpoint MUST act When a new MSRP session is created, the initiating endpoint MUST act
as the "active" endpoint, meaning that it is responsible for opening as the "active" endpoint, meaning that it is responsible for opening
the transport connection to the answerer, if a new connection is the transport connection to the answerer, if a new connection is
required. However, this requirement MAY be weakened if standardized required. However, this requirement MAY be weakened if standardized
mechanisms for negotiating the connection direction become available, mechanisms for negotiating the connection direction become available
and is implemented by both parties to the connection. and are implemented by both parties to the connection.
Likewise, the active endpoint MUST immediately issue a SEND request. Likewise, the active endpoint MUST immediately issue a SEND request.
This initial SEND request MAY have a body if the sender has content This initial SEND request MAY have a body if the sender has content
to send, or it MAY have no body at all. to send, or it MAY have no body at all.
The first SEND request serves to bind a connection to an MSRP The first SEND request serves to bind a connection to an MSRP
session from the perspective of the passive endpoint. If the session from the perspective of the passive endpoint. If the
connection is not authenticated with TLS, and the active endpoint connection is not authenticated with TLS, and the active endpoint
did not send an immediate request, the passive endpoint would have did not send an immediate request, the passive endpoint would have
no way to determine who had connected, and would not be able to no way to determine who had connected, and would not be able to
safely send any requests towards the active party until after the safely send any requests towards the active party until after the
active party sends its first request. active party sends its first request.
When an element needs to form a new connection, it looks at the URI When an element needs to form a new connection, it looks at the URI
to decide on the type of connection (TLS, TCP, etc.) then connects to to decide on the type of connection (TLS, TCP, etc.) then connects to
the host indicated by the URI, following the URI resolution rules in the host indicated by the URI, following the URI resolution rules in
Section 6.2. Connections using the "msrps" scheme MUST use TLS. The Section 6.2. Connections using the "msrps" scheme MUST use TLS. The
SubjectAltName in the received certificate MUST match the hostname SubjectAltName in the received certificate MUST match the hostname
part of the URI and the certificate MUST be valid according to RFC part of the URI and the certificate MUST be valid according to RFC
3280 [16], including having a date that is valid and being signed by 3280 [16], including having a date that is valid and being signed by
an acceptable certification authority. At this point the device that an acceptable certification authority. At this point, the device
initiated the connection can assume that this connection is with the that initiated the connection can assume that this connection is with
correct host. the correct host.
The rules on certificate name matching and CA signing MAY be relaxed The rules on certificate name matching and CA signing MAY be relaxed
when using TLS peer-to-peer. In this case, a mechanism to ensure when using TLS peer-to-peer. In this case, a mechanism to ensure
that the peer used a correct certificate MUST be used. See that the peer used a correct certificate MUST be used. See Section
Section 14.4 for details. 14.4 for details.
If the connection used mutual TLS authentication, and the TLS client If the connection used mutual TLS authentication, and the TLS client
presented a valid certificate, then the element accepting the presented a valid certificate, then the element accepting the
connection can verify the identity of the connecting device by connection can verify the identity of the connecting device by
comparing the hostname part of the target URI in the SDP provided by comparing the hostname part of the target URI in the SDP provided by
the peer device against the SubjectAltName in the client certificate. the peer device against the SubjectAltName in the client certificate.
When mutual TLS authentication is not used, the listening device MUST When mutual TLS authentication is not used, the listening device MUST
wait until it receives a request on the connection, at which time it wait until it receives a request on the connection, at which time it
infers the identity of the connecting device from the associated infers the identity of the connecting device from the associated
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it MUST NOT assume that the MSRP URIs in the SDP will be the same as it MUST NOT assume that the MSRP URIs in the SDP will be the same as
the old ones. the old ones.
A connection SHOULD NOT be closed while there are sessions associated A connection SHOULD NOT be closed while there are sessions associated
with it. with it.
6. MSRP URIs 6. MSRP URIs
URIs using the "msrp" and "msrps" schemes are used to identify a URIs using the "msrp" and "msrps" schemes are used to identify a
session of instant messages at a particular MSRP device, as well as session of instant messages at a particular MSRP device, as well as
to identify an MSRP Relay in general. This document describes the to identify an MSRP relay in general. This document describes the
former usage; The latter usage is described in the MSRP Relay former usage; the latter usage is described in the MSRP relay
specification [23]. MSRP URIs that identify sessions are ephemeral; specification [23]. MSRP URIs that identify sessions are ephemeral;
an MSRP device will use a different MSRP URI for each distinct an MSRP device will use a different MSRP URI for each distinct
session. An MSRP URI that identifies a session has no meaning session. An MSRP URI that identifies a session has no meaning
outside the scope of that session. outside the scope of that session.
An MSRP URI follows a subset of the URI syntax in Appendix A of An MSRP URI follows a subset of the URI syntax in Appendix A of RFC
RFC3986 [10], with a scheme of "msrp" or "msrps". The syntax is 3986 [10], with a scheme of "msrp" or "msrps". The syntax is
described in Section 9. described in Section 9.
MSRP URIs are primarily expected to be generated and exchanged MSRP URIs are primarily expected to be generated and exchanged
between systems, and are not intended for "human consumption". between systems, and are not intended for "human consumption".
Therefore, they are encoded entirely in US-ASCII. Therefore, they are encoded entirely in US-ASCII.
The constructions for "authority", "userinfo", and "unreserved" are The constructions for "authority", "userinfo", and "unreserved" are
detailed in RFC3986 [10]. URIs designating MSRP over TCP MUST detailed in RFC3986 [10]. URIs designating MSRP over TCP MUST
include the "tcp" transport parameter. include the "tcp" transport parameter.
skipping to change at page 15, line 13 skipping to change at page 15, line 17
bindings on other transports should define respective parameters bindings on other transports should define respective parameters
for those transports. for those transports.
The MSRP URI authority field identifies a participant in a particular The MSRP URI authority field identifies a participant in a particular
MSRP session. If the authority field contains a numeric IP address, MSRP session. If the authority field contains a numeric IP address,
it MUST also contain a port. The session-id part identifies a it MUST also contain a port. The session-id part identifies a
particular session of the participant. The absence of the session-id particular session of the participant. The absence of the session-id
part indicates a reference to an MSRP host device, but does not refer part indicates a reference to an MSRP host device, but does not refer
to a particular session at that device. A particular value of to a particular session at that device. A particular value of
session-id is only meaningful in the context of the associated session-id is only meaningful in the context of the associated
authority; thus the authority component can be thought of as a authority; thus, the authority component can be thought of as
identifying the "authority" governing a name space for the identifying the "authority" governing a namespace for the session-id.
session-id.
A scheme of "msrps" indicates that the underlying connection MUST be A scheme of "msrps" indicates that the underlying connection MUST be
protected with TLS. protected with TLS.
MSRP has an IANA-registered recommended port defined in Section 15.4. MSRP has an IANA-registered recommended port defined in Section 15.4.
This value is not a default, as the URI negotiation process described This value is not a default, as the URI negotiation process described
herein will always include explicit port numbers. However, the URIs herein will always include explicit port numbers. However, the URIs
SHOULD be configured so that the recommended port is used whenever SHOULD be configured so that the recommended port is used whenever
appropriate. This makes life easier for network administrators who appropriate. This makes life easier for network administrators who
need to manage firewall policy for MSRP. need to manage firewall policy for MSRP.
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msrp://host.example.com:8493/asfd34;tcp msrp://host.example.com:8493/asfd34;tcp
6.1. MSRP URI Comparison 6.1. MSRP URI Comparison
In the context of the MSRP protocol, MSRP URI comparisons MUST be In the context of the MSRP protocol, MSRP URI comparisons MUST be
performed according to the following rules: performed according to the following rules:
1. The scheme MUST match. Scheme comparison is case insensitive. 1. The scheme MUST match. Scheme comparison is case insensitive.
2. If the authority component contains an explicit IP address, 2. If the authority component contains an explicit IP address and/or
and/or port, these are compared for address and port equivalence. port, these are compared for address and port equivalence.
Percent-encoding normalization [10] applies; that is, any Percent-encoding normalization [10] applies; that is, if any
percent-encoded nonreserved characters exist in the authority percent-encoded nonreserved characters exist in the authority
component, they must be decoded prior to comparison. Userinfo component, they must be decoded prior to comparison. Userinfo
parts are not considered for URI comparison. Otherwise, the parts are not considered for URI comparison. Otherwise, the
authority component is compared as a case-insensitive character authority component is compared as a case-insensitive character
string. string.
3. If the port exists explicitly in either URI, then it MUST match 3. If the port exists explicitly in either URI, then it MUST match
exactly. A URI with an explicit port is never equivalent to exactly. A URI with an explicit port is never equivalent to
another with no port specified. another with no port specified.
4. The session-id part is compared as case sensitive. A URI without 4. The session-id part is compared as case sensitive. A URI without
a session-id part is never equivalent to one that includes one. a session-id part is never equivalent to one that includes one.
5. URIs with different "transport" parameters never match. Two URIs 5. URIs with different "transport" parameters never match. Two URIs
that are identical except for transport are not equivalent. The that are identical except for transport are not equivalent. The
transport parameter is case-insensitive. transport parameter is case insensitive.
Path normalization [10] is not relevant for MSRP URIs. Path normalization [10] is not relevant for MSRP URIs.
6.2. Resolving MSRP Host Device 6.2. Resolving MSRP Host Device
An MSRP host device is identified by the authority component of an An MSRP host device is identified by the authority component of an
MSRP URI. MSRP URI.
If the authority component contains a numeric IP address and port, If the authority component contains a numeric IP address and port,
they MUST be used as listed. they MUST be used as listed.
If the authority component contains a host name and a port, the If the authority component contains a host name and a port, the
connecting device MUST determine a host address by doing an A or AAAA connecting device MUST determine a host address by doing an A or AAAA
DNS query, and use the port as listed. DNS query and use the port as listed.
If a connection attempt fails, the device SHOULD attempt to connect If a connection attempt fails, the device SHOULD attempt to connect
to the addresses returned in any additional A or AAAA records, in the to the addresses returned in any additional A or AAAA records, in the
order the records were presented. order the records were presented.
This process assumes that the connection port is always known This process assumes that the connection port is always known
prior to resolution. This is always true for the MSRP URI uses prior to resolution. This is always true for the MSRP URI uses
described in this document, that is, URIs exchanged in the SDP described in this document, that is, URIs exchanged in the SDP
offer and answer. The introduction of relays creates situations offer and answer. The introduction of relays creates situations
where this is not the case. For example, the MSRP URI that a user where this is not the case. For example, when a user configures
enters into a client to configure it to use a relay may be her client to use a relay, it is desirable that the relay's MSRP
intended to be easily remembered and communicated by humans, and URI is easy to remember and communicate to humans. Often this
therefore is likely to omit the port. Therefore, the relay type of MSRP will omit the port number. Therefore, the relay
specification [23] describes additional steps to resolve the port specification [23] describes additional steps to resolve the port
number. number.
MSRP devices MAY use other methods for discovering other such MSRP devices MAY use other methods for discovering other such
devices, when appropriate. For example, MSRP endpoints may use other devices, when appropriate. For example, MSRP endpoints may use other
mechanisms to discover relays, which are beyond the scope of this mechanisms to discover relays, which are beyond the scope of this
document. document.
7. Method-Specific Behavior 7. Method-Specific Behavior
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Although this document does not discuss any particular usage of Although this document does not discuss any particular usage of
bodies in non-SEND requests, they may be useful in the future for bodies in non-SEND requests, they may be useful in the future for
carrying security or identity information, information about a carrying security or identity information, information about a
message in progress, etc. The 10K size limit was chosen to be message in progress, etc. The 10K size limit was chosen to be
large enough for most of such applications, but small enough to large enough for most of such applications, but small enough to
avoid the fairness issues caused by sending arbitrarily large avoid the fairness issues caused by sending arbitrarily large
content in non-interruptible method bodies. content in non-interruptible method bodies.
A request with no body MUST NOT include a Content-Type or any other A request with no body MUST NOT include a Content-Type or any other
MIME-specific header fields. A request without a body MUST contain a MIME-specific header fields. A request without a body MUST contain
end-line after the final header field. No extra CRLF will be present an end-line after the final header field. No extra CRLF will be
between the header section and the end-line. present between the header section and the end-line.
Requests with no bodies are useful when a client wishes to send Requests with no bodies are useful when a client wishes to send
"traffic", but does not wish to send content to be rendered to the "traffic", but does not wish to send content to be rendered to the
peer user. For example, the active endpoint sends a SEND request peer user. For example, the active endpoint sends a SEND request
immediately upon establishing a connection. If it has nothing to immediately upon establishing a connection. If it has nothing to
say at the moment, it can send a request with no body. Bodiless say at the moment, it can send a request with no body. Bodiless
requests may also be used in certain applications to keep NAT requests may also be used in certain applications to keep Network
bindings alive, etc. Address Translation (NAT) bindings alive, etc.
Bodiless requests are distinct from requests with empty bodies. A Bodiless requests are distinct from requests with empty bodies. A
request with an empty body will have a Content-Type header field request with an empty body will have a Content-Type header field
value, and will generally be rendered to the recipient according value and will generally be rendered to the recipient according to
to the rules for that type. the rules for that type.
The end-line that terminates the request MUST be composed of seven The end-line that terminates the request MUST be composed of seven
"-" (minus sign) characters, the transaction ID as used in the start "-" (minus sign) characters, the transaction ID as used in the start
line, and a flag character. If a body is present, the end-line MUST line, and a flag character. If a body is present, the end-line MUST
be preceded by a CRLF that is not part of the body. If the chunk be preceded by a CRLF that is not part of the body. If the chunk
represents the data that forms the end of the complete message, the represents the data that forms the end of the complete message, the
flag value MUST be a "$". If the sender is aborting an incomplete flag value MUST be a "$". If the sender is aborting an incomplete
message, and intends to send no further chunks in that message, it message, and intends to send no further chunks in that message, the
MUST be a "#". Otherwise it MUST be a "+". flag MUST be a "#". Otherwise, the flag MUST be a "+".
If the request contains a body, the sender MUST ensure that the end- If the request contains a body, the sender MUST ensure that the end-
line (seven hyphens, the transaction identifier, and a continuation line (seven hyphens, the transaction identifier, and a continuation
flag) is not present in the body. If the end-line is present in the flag) is not present in the body. If the end-line is present in the
body, the sender MUST choose a new transaction identifier that is not body, the sender MUST choose a new transaction identifier that is not
present in the body, and add a CRLF if needed, and the end-line, present in the body, and add a CRLF if needed, and the end-line,
including the "$", "#", or "+" character. including the "$", "#", or "+" character.
Some implementations may choose to scan for the closing sequence as Some implementations may choose to scan for the closing sequence as
they send the body, and if it is encountered, simply interrupt the they send the body, and if it is encountered, simply interrupt the
chunk at that point and start a new transaction with a different chunk at that point and start a new transaction with a different
transaction identifier to carry the rest of the body. Other transaction identifier to carry the rest of the body. Other
implementation may choose to scan the data an ensure that the body implementations may choose to scan the data and ensure that the body
does not contain the transaction identifier before they start sending does not contain the transaction identifier before they start sending
the transaction. the transaction.
Once a request is ready for delivery, the sender follows the Once a request is ready for delivery, the sender follows the
connection management (Section 5.4) rules to forward the request over connection management (Section 5.4) rules to forward the request over
an existing open connection or create a new connection. an existing open connection or create a new connection.
7.1.1. Sending SEND Requests 7.1.1. Sending SEND Requests
When an endpoint has a message to deliver, it first generates a new When an endpoint has a message to deliver, it first generates a new
skipping to change at page 19, line 10 skipping to change at page 19, line 10
term "Message" in this context refers to a unit of content that term "Message" in this context refers to a unit of content that
the sender wishes to convey to the recipient. While such a the sender wishes to convey to the recipient. While such a
message may be broken into chunks, the Message-ID refers to the message may be broken into chunks, the Message-ID refers to the
entire message, not a chunk of the message. entire message, not a chunk of the message.
The uniqueness of the message identifier is ensured by the host The uniqueness of the message identifier is ensured by the host
that generates it. This message identifier is intended to be that generates it. This message identifier is intended to be
machine readable and not necessarily meaningful to humans. A machine readable and not necessarily meaningful to humans. A
message identifier pertains to exactly one version of a particular message identifier pertains to exactly one version of a particular
message; subsequent revisions to the message each receive new message; subsequent revisions to the message each receive new
message identifiers. message identifiers. Endpoints can ensure sufficient uniqueness
Endpoints can ensure sufficient uniqueness in any number of ways, in any number of ways, the selection of which is an implementation
the selection of which is an implementation choice. For example, choice. For example, an endpoint could concatenate an instance
an endpoint could concatenate an instance identifier such as a MAC identifier such as a MAC address, its idea of the number of
address, its idea of the number of seconds since the epoque, a seconds since the epoch, a process ID, and a monotonically
process ID, and a monotonically increasing 16 bit integer, all increasing 16-bit integer, all base-64 encoded. Alternately, an
base-64 encoded. Alternately, an endpoint without an on-board endpoint without an on-board clock could simply use a 64-bit
clock could simply use a 64-bit random number. random number.
Each chunk of a message MUST contain a Message-ID header field Each chunk of a message MUST contain a Message-ID header field
containing the Message-ID. If the sender wishes non-default status containing the Message-ID. If the sender wishes non-default status
reporting, it MUST insert a Failure-Report and/or Success-Report reporting, it MUST insert a Failure-Report and/or Success-Report
header field with an appropriate value. All chunks of the same header field with an appropriate value. All chunks of the same
message MUST use the same Failure-Report and Success-Report values in message MUST use the same Failure-Report and Success-Report values in
their SEND requests. their SEND requests.
If success reports are requested, i.e. the value of the Success- If success reports are requested, i.e., the value of the Success-
Report header field is "yes", the sending device MAY wish to run a Report header field is "yes", the sending device MAY wish to run a
timer of some value that makes sense for its application and take timer of some value that makes sense for its application and take
action if a success report is not received in this time. There is no action if a success report is not received in this time. There is no
universal value for this timer. For many IM applications, it may be universal value for this timer. For many IM applications, it may be
2 minutes while for some trading systems it may be under a second. 2 minutes while for some trading systems it may be under a second.
Regardless of whether such a timer is used, if the success report has Regardless of whether such a timer is used, if the success report has
not been received by the time the session is ended, the device SHOULD not been received by the time the session is ended, the device SHOULD
inform the user. inform the user.
If the value of "Failure-Report" is set to "yes", then the sender of If the value of "Failure-Report" is set to "yes", then the sender of
the request runs a timer. If a 200 response to the transaction is the request runs a timer. If a 200 response to the transaction is
not received within 30 seconds from the time the last byte of the not received within 30 seconds from the time the last byte of the
transaction is sent, or submitted to the operating system for transaction is sent, or submitted to the operating system for
sending, the element MUST inform the user that the request probably sending, the element MUST inform the user that the request probably
failed. If the value is set to "partial", then the element sending failed. If the value is set to "partial", then the element sending
the transaction does not have to run a timer, but MUST inform the the transaction does not have to run a timer, but MUST inform the
user if it receives a non-recoverable error response to the user if it receives a non-recoverable error response to the
transaction. transaction. Regardless of the Failure-Report value, there is no
requirement to wait for a response prior to sending the next request.
The treatment of timers for success reports and failure reports is The treatment of timers for success reports and failure reports is
intentionally inconsistent. An explicit timeout value makes sense intentionally inconsistent. An explicit timeout value makes sense
for failure reports since such reports will usually refer to a for failure reports since such reports will usually refer to a
message "chunk" which is acknowledged on a hop-by-hop basis. This message "chunk" that is acknowledged on a hop-by-hop basis. This
is not the case for success reports, which are end-to-end and may is not the case for success reports, which are end-to-end and may
refer to the entire message content, which can be arbitrarily refer to the entire message content, which can be arbitrarily
large. large.
If no Success-Report header field is present in a SEND request, it If no Success-Report header field is present in a SEND request, it
MUST be treated the same as a Success-Report header field with value MUST be treated the same as a Success-Report header field with a
of "no". If no Failure-Report header field is present, it MUST be value of "no". If no Failure-Report header field is present, it MUST
treated the same as a Failure-Report header field with value of be treated the same as a Failure-Report header field with a value of
"yes". If an MSRP endpoint receives a REPORT for a Message-ID it "yes". If an MSRP endpoint receives a REPORT for a Message-ID it
does not recognize, it SHOULD silently ignore the REPORT. does not recognize, it SHOULD silently ignore the REPORT.
The Byte-Range header field value contains a starting value (range- The Byte-Range header field value contains a starting value (range-
start) followed by a "-", an ending value (range-end) followed by a start) followed by a "-", an ending value (range-end) followed by a
"/", and finally the total length. The first octet in the message "/", and finally the total length. The first octet in the message
has a position of one, rather than a zero. has a position of one, rather than a zero.
The first chunk of the message SHOULD, and all subsequent chunks MUST The first chunk of the message SHOULD, and all subsequent chunks
include a Byte-Range header field. The range-start field MUST MUST, include a Byte-Range header field. The range-start field MUST
indicate the position of the first byte in the body in the overall indicate the position of the first byte in the body in the overall
message (for the first chunk this field will have a value of one). message (for the first chunk this field will have a value of one).
The range-end field SHOULD indicate the position of the last byte in The range-end field SHOULD indicate the position of the last byte in
the body, if known. It MUST take the value of "*" if the position is the body, if known. It MUST take the value of "*" if the position is
unknown, or if the request needs to be interruptible. The total unknown, or if the request needs to be interruptible. The total
field SHOULD contain the total size of the message, if known. The field SHOULD contain the total size of the message, if known. The
total field MAY contain a "*" if the total size of the message is not total field MAY contain a "*" if the total size of the message is not
known in advance. The sender MUST send all chunks in Byte-Range known in advance. The sender MUST send all chunks in Byte-Range
order. (However, the receiver cannot assume that the requests will order. (However, the receiver cannot assume that the requests will
be delivered in order, as intervening relays may have changed the be delivered in order, as intervening relays may have changed the
order.) order.)
There are some circumstances where an endpoint may choose to send an There are some circumstances where an endpoint may choose to send an
empty SEND request. For the sake of consistency, a Byte-Range header empty SEND request. For the sake of consistency, a Byte-Range header
field referring to nonexistent or zero-length content MUST still have field referring to nonexistent or zero-length content MUST still have
a range-start value of 1. For example, "1-0/0" a range-start value of 1. For example, "1-0/0".
To ensure fairness over a connection, senders MUST NOT send chunks To ensure fairness over a connection, senders MUST NOT send chunks
with a body larger than 2048 octets unless they are prepared to with a body larger than 2048 octets unless they are prepared to
interrupt them (meaning that any chunk with a body of greater than interrupt them (meaning that any chunk with a body of greater than
2048 octets will have a "*" character in the range-end field). A 2048 octets will have a "*" character in the range-end field). A
sender can use one of the following two strategies to satisfy this sender can use one of the following two strategies to satisfy this
requirement. The sender is STRONGLY RECOMMENDED to send messages requirement. The sender is STRONGLY RECOMMENDED to send messages
larger than 2048 octets using as few chunks as possible, interrupting larger than 2048 octets using as few chunks as possible, interrupting
chunks (at least 2048 octets long) only when other traffic is waiting chunks (at least 2048 octets long) only when other traffic is waiting
to use the same connection. Alternatively, the sender MAY simply to use the same connection. Alternatively, the sender MAY simply
send chunks in 2048 octet increments until the final chunk. Note send chunks in 2048-octet increments until the final chunk. Note
that the former strategy results in markedly more efficient use of that the former strategy results in markedly more efficient use of
the connection. All MSRP nodes MUST be able to receive chunks of any the connection. All MSRP nodes MUST be able to receive chunks of any
size from zero octets to the maximum number of octets they can size from zero octets to the maximum number of octets they can
receive for a complete message. Senders SHOULD NOT break messages receive for a complete message. Senders SHOULD NOT break messages
into chunks smaller than 2048 octets, except for the final chunk of a into chunks smaller than 2048 octets, except for the final chunk of a
complete message. complete message.
A SEND request is interrupted while a body is in the process of being A SEND request is interrupted while a body is in the process of being
written to the connection by simply noting how much of the message written to the connection by simply noting how much of the message
has already been written to the connection, then writing out the end- has already been written to the connection, then writing out the end-
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REPORT requests will normally not include a body, as the REPORT REPORT requests will normally not include a body, as the REPORT
request header fields can carry sufficient information in most cases. request header fields can carry sufficient information in most cases.
However, REPORT requests MAY include a body containing additional However, REPORT requests MAY include a body containing additional
information about the status of the associated SEND request. Such a information about the status of the associated SEND request. Such a
body is informational only, and the sender of the REPORT request body is informational only, and the sender of the REPORT request
SHOULD NOT assume that the recipient pays any attention to the body. SHOULD NOT assume that the recipient pays any attention to the body.
REPORT requests are not interruptible. REPORT requests are not interruptible.
Success-Report and Failure-Report header fields MUST NOT be present Success-Report and Failure-Report header fields MUST NOT be present
in REPORT requests. MSRP nodes MUST NOT send REPORT requests in in REPORT requests. MSRP nodes MUST NOT send REPORT requests in
response to REPORT requests. MSRP Nodes MUST NOT send MSRP responses response to REPORT requests. MSRP nodes MUST NOT send MSRP responses
to REPORT requests. to REPORT requests.
Endpoints SHOULD NOT send REPORT requests if they have reason to Endpoints SHOULD NOT send REPORT requests if they have reason to
believe the request will not be delivered. For example, they SHOULD believe the request will not be delivered. For example, they SHOULD
NOT send a REPORT request for a session that is no longer valid. NOT send a REPORT request for a session that is no longer valid.
7.1.3. Generating Success Reports 7.1.3. Generating Success Reports
When an endpoint receives a message in one or more chunks that When an endpoint receives a message in one or more chunks that
contain a Success-Reports value of "yes", it MUST send a success contain a Success-Report value of "yes", it MUST send a success
report or reports covering all bytes that are received successfully. report or reports covering all bytes that are received successfully.
The success reports are sent in the form of REPORT requests, The success reports are sent in the form of REPORT requests,
following the normal procedures (Section 7.1), with a few additional following the normal procedures (Section 7.1), with a few additional
requirements. requirements.
The receiver MAY wait until it receives the last chunk of a message, The receiver MAY wait until it receives the last chunk of a message,
and send a success report that covers the complete message. and send a success report that covers the complete message.
Alternately, it MAY generate incremental success REPORTs as the Alternately, it MAY generate incremental success REPORTs as the
chunks are received. These can be sent periodically and cover all chunks are received. These can be sent periodically and cover all
the bytes that have been received so far, or they can be sent after a the bytes that have been received so far, or they can be sent after a
chunk arrives and cover just the part from that chunk. chunk arrives and cover just the part from that chunk.
It is helpful to think of a success REPORT as reporting on a It is helpful to think of a success REPORT as reporting on a
particular range of bytes, rather than on a particular chunk sent particular range of bytes, rather than on a particular chunk sent
by a client. The sending client cannot depend on the Byte-Range by a client. The sending client cannot depend on the Byte-Range
header field in a given success report matching that of a header field in a given success report matching that of a
particular SEND request. For example, an intervening MSRP relay particular SEND request. For example, an intervening MSRP relay
may break chunks into smaller chunks, or aggregate multiple chunks may break chunks into smaller chunks, or aggregate multiple chunks
into larger ones. into larger ones. A side effect of this is, even if no relay is
A side effect of this is, even if no relay is used, the receiving used, the receiving client may report on byte ranges that do not
client may report on byte ranges that do not exactly match those exactly match those in the original chunks sent by the sender. It
in the original chunks sent by the sender. It can wait until all can wait until all bytes in a message are received and report on
bytes in a message are received and report on the whole, it can the whole, it can report as it receives each chunk, or it can
report as it receives each chunk, or it can report on any other report on any other received range. Reporting on ranges smaller
received range. than the entire message contents allows certain improved user
Reporting on ranges smaller than the entire message contents experiences for the sender. For example, a sending client could
allows certain improved user experiences for the sender. For display incremental status information showing which ranges of
example, a sending client could display incremental status bytes have been acknowledged by the receiver. However, the choice
information showing which ranges of bytes have been acknowledged on whether to report incrementally is entirely up to the receiving
by the receiver. client. There is no mechanism for the sender to assert its desire
However, the choice on whether to report incrementally is entirely to receive incremental reports or not. Since the presence of a
up to the receiving client. There is no mechanism for the sender relay can cause the receiver to see a very different chunk
to assert its desire to receive incremental reports or not. Since allocation than the sender, such a mechanism would be of
the presence of a relay can cause the receiver to see a very questionable value.
different chunk allocation than the sender, such a mechanism would
be of questionable value.
When generating a REPORT request, the endpoint inserts a To-Path When generating a REPORT request, the endpoint inserts a To-Path
header field containing the From-Path value from the original header field containing the From-Path value from the original
request, and a From-Path header field containing the URI identifying request, and a From-Path header field containing the URI identifying
itself in the session. The endpoint then inserts a Status header itself in the session. The endpoint then inserts a Status header
field with a namespace of "000", a status-code of "200" and an field with a namespace of "000", a status-code of "200", and an
implementation-defined comment phrase. It also inserts a Message-ID implementation-defined comment phrase. It also inserts a Message-ID
header field containing the value from the original request. header field containing the value from the original request.
The namespace field denotes the context of the status-code field. The namespace field denotes the context of the status-code field.
The namespace value of "000" means the status-code should be The namespace value of "000" means the status-code should be
interpreted in the same way as the matching MSRP transaction interpreted in the same way as the matching MSRP transaction
response code. If a future specification uses the status-code response code. If a future specification uses the status-code
field for some other purpose, it MUST define a new namespace field field for some other purpose, it MUST define a new namespace field
value. value.
The endpoint MUST NOT send a success report for a SEND request that The endpoint MUST NOT send a success report for a SEND request that
either contained no Success-Report header field, or contained such a either contained no Success-Report header field or contained such a
field with a value of "no". That is, if no Success-Report header field with a value of "no". That is, if no Success-Report header
field is present, it is treated identically to one with a value of field is present, it is treated identically to one with a value of
"no." "no".
7.1.4. Generating Failure Reports 7.1.4. Generating Failure Reports
If an MSRP endpoint receives a SEND request that it cannot process If an MSRP endpoint receives a SEND request that it cannot process
for some reason, and the Failure-Report header field either was not for some reason, and the Failure-Report header field either was not
present in the original request, or had a value of "yes", it SHOULD present in the original request or had a value of "yes", it SHOULD
simply include the appropriate error code in the transaction simply include the appropriate error code in the transaction
response. However, there may be situations where the error cannot be response. However, there may be situations where the error cannot be
determined quickly, such as when the endpoint is a gateway that waits determined quickly, such as when the endpoint is a gateway that waits
for a downstream network to indicate an error. In this situation, it for a downstream network to indicate an error. In this situation, it
MAY send a 200 OK response to the request, and then send a failure MAY send a 200 OK response to the request, and then send a failure
REPORT request when the error is detected. REPORT request when the error is detected.
If the endpoint receives a SEND request with a Failure-Report header If the endpoint receives a SEND request with a Failure-Report header
field value of "no", then it MUST NOT send a failure REPORT request, field value of "no", then it MUST NOT send a failure REPORT request,
and MUST NOT send a transaction response. If the value is "partial", and MUST NOT send a transaction response. If the value is "partial",
it MUST NOT send a 200 transaction response to the request, but it MUST NOT send a 200 transaction response to the request, but
SHOULD send an appropriate non-200 class response if a failure SHOULD send an appropriate non-200 class response if a failure
occurs. occurs.
As stated above, if no Failure-Report header field is present, it As stated above, if no Failure-Report header field is present, it
MUST be treated the same as a Failure-Report header field with value MUST be treated the same as a Failure-Report header field with a
of "yes". value of "yes".
Construction of failure REPORT requests is identical to that for Construction of failure REPORT requests is identical to that for
success REPORT requests, except the Status header field code and success REPORT requests, except the Status header field code field
reason fields MUST contain appropriate error codes. Any error MUST contain the appropriate error code. Any error response code
response code defined in this specification MAY also be used in defined in this specification MAY also be used in failure reports.
failure reports.
If a failure REPORT request is sent in response to a SEND request If a failure REPORT request is sent in response to a SEND request
that contained a chunk, it MUST include a Byte-Range header field that contained a chunk, it MUST include a Byte-Range header field
indicating the actual range being reported on. It can take the indicating the actual range being reported on. It can take the
range-start and total values from the original SEND request, but MUST range-start and total values from the original SEND request, but MUST
calculate the range-end field from the actual body data. calculate the range-end field from the actual body data.
This section only describes failure report generation behavior for This section only describes failure report generation behavior for
MSRP endpoints. Relay behavior is beyond the scope of this MSRP endpoints. Relay behavior is beyond the scope of this
document, and will be considered in a separate document [23]. We document, and will be considered in a separate document [23]. We
expect failure reports to be more commonly generated by relays expect failure reports to be more commonly generated by relays
than by endpoints. than by endpoints.
7.2. Constructing Responses 7.2. Constructing Responses
If an MSRP endpoint receives a request that either contains a If an MSRP endpoint receives a request that either contains a
Failure-Report header field value of "yes", or does not contain a Failure-Report header field value of "yes" or does not contain a
Failure-Report header field at all, it MUST immediately generate a Failure-Report header field at all, it MUST immediately generate a
response. Likewise, if an MSRP endpoint receives a request that response. Likewise, if an MSRP endpoint receives a request that
contains a Failure-Report header field value of "partial", and the contains a Failure-Report header field value of "partial", and the
receiver is unable to process the request, it SHOULD immediately receiver is unable to process the request, it SHOULD immediately
generate a response. generate a response.
To construct the response, the endpoint first creates the response To construct the response, the endpoint first creates the response
start-line, inserting appropriate response code and reason fields. start line, inserting the appropriate response code and optionally a
The transaction identifier in the response start line MUST match the comment. The transaction identifier in the response start line MUST
transaction identifier from the original request. match the transaction identifier from the original request.
The endpoint then inserts an appropriate To-Path header field. If The endpoint then inserts an appropriate To-Path header field. If
the request triggering the response was a SEND request, the To-Path the request triggering the response was a SEND request, the To-Path
header field is formed by copying the last (right-most) URI in the header field is formed by copying the first (leftmost) URI in the
From-Path header field of the request. (Responses to SEND requests From-Path header field of the request. (Responses to SEND requests
are returned only to the previous hop.) For responses to all other are returned only to the previous hop.) For responses to all other
request methods, the To-Path header field contains the full path back request methods, the To-Path header field contains the full path back
to the original sender. This full path is generated by taking the to the original sender. This full path is generated by copying the
list of URIs from the From-Path of the original request, reversing list of URIs from the From-Path of the original request into the To-
the list, and writing the reversed list into the To-Path of the Path of the response. (Legal REPORT requests do not request
response. (Legal REPORT requests do not request responses, so this responses, so this specification doesn't exercise the behavior
specification doesn't exercise the behavior described above, however described above; however, we expect that extensions for gateways and
we expect that extensions for gateways and relays will need such relays will need such behavior.)
behavior.)
Finally, the endpoint inserts a From-Path header field containing the Finally, the endpoint inserts a From-Path header field containing the
URI that identifies it in the context of the session, followed by the URI that identifies it in the context of the session, followed by the
end-line after the last header field. The response MUST be end-line after the last header field. Since a response is never
transmitted back on the same connection on which the original request chunked, the continuation flag in the end-line will always contain a
arrived. dollar sign ("$"). The response MUST be transmitted back on the same
connection on which the original request arrived.
7.3. Receiving Requests 7.3. Receiving Requests
The receiving endpoint MUST first check the URI in the To-Path to The receiving endpoint MUST first check the URI in the To-Path to
make sure the request belongs to an existing session. When the make sure the request belongs to an existing session. When the
request is received, the To-Path will have exactly one URI, which request is received, the To-Path will have exactly one URI, which
MUST map to an existing session that is associated with the MUST map to an existing session that is associated with the
connection on which the request arrived. If this is not true, then connection on which the request arrived. If this is not true, then
the receiver MUST generate a 481 error and ignore the request. Note the receiver MUST generate a 481 error and ignore the request. Note
that if the Failure-Report header field had a value of "no", then no that if the Failure-Report header field had a value of "no", then no
error report would be sent. error report would be sent.
Further request processing by the receiver is method specific. Further request processing by the receiver is method specific.
7.3.1. Receiving SEND Requests 7.3.1. Receiving SEND Requests
When the receiving endpoint receives a SEND request, it first When the receiving endpoint receives a SEND request, it first
determines if it contains a complete message, or a chunk from a determines if it contains a complete message or a chunk from a larger
larger message. If the request contains no Byte-Range header field, message. If the request contains no Byte-Range header field, or
or contains one with a range-start value of "1", and the closing line contains one with a range-start value of "1", and the closing line
continuation flag has a value of "$", then the request contained the continuation flag has a value of "$", then the request contained the
entire message. Otherwise, the receiver looks at the Message-ID entire message. Otherwise, the receiver looks at the Message-ID
value to associate chunks together into the original message. It value to associate chunks together into the original message. The
forms a virtual buffer to receive the message, keeping track of which receiver forms a virtual buffer to receive the message, keeping track
bytes have been received and which are missing. The receiver takes of which bytes have been received and which are missing. The
the data from the request and places it in the appropriate place in receiver takes the data from the request and places it in the
the buffer. The receiver SHOULD determine the actual length of each appropriate place in the buffer. The receiver SHOULD determine the
chunk by inspecting the payload itself; it is possible the body is actual length of each chunk by inspecting the payload itself; it is
shorter than the range-end field indicates. This can occur if the possible the body is shorter than the range-end field indicates.
sender interrupted a SEND request unexpectedly. It is worth noting This can occur if the sender interrupted a SEND request unexpectedly.
that the chunk that has a termination character of "$" defines the It is worth noting that the chunk that has a termination character of
total length of the message. "$" defines the total length of the message.
It is technically illegal for the sender to prematurely interrupt It is technically illegal for the sender to prematurely interrupt
a request that had anything other than "*" in the last-byte a request that had anything other than "*" in the last-byte
position of the Byte-Range header field. But having the receiver position of the Byte-Range header field. But having the receiver
calculate a chunk length based on actual content adds resilience calculate a chunk length based on actual content adds resilience
in the face of sender errors. Since this should never happen with in the face of sender errors. Since this should never happen with
compliant senders, this only has a SHOULD strength. compliant senders, this only has a "SHOULD" strength.
Receivers MUST not assume that the chunks will be delivered in order Receivers MUST not assume that the chunks will be delivered in order
or that they will receive all the chunks with "+" flags before they or that they will receive all the chunks with "+" flags before they
receive the chunk with the "$" flag. In certain cases of connection receive the chunk with the "$" flag. In certain cases of connection
failure, it is possible for information to be duplicated. If chunk failure, it is possible for information to be duplicated. If chunk
data is received that overlaps already received data for the same data is received that overlaps already received data for the same
message, the last chunk received SHOULD take precedence (even though message, the last chunk received SHOULD take precedence (even though
this may not have been the last chunk transmitted). For example, if this may not have been the last chunk transmitted). For example, if
bytes 1 to 100 were received and a chunk arrives that contains bytes bytes 1 to 100 were received and a chunk arrives that contains bytes
50 to 150, this second chunk will overwrite bytes 50 to 100 of the 50 to 150, this second chunk will overwrite bytes 50 to 100 of the
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the receiver MUST generate a response with a status code of 415. All the receiver MUST generate a response with a status code of 415. All
MSRP endpoints MUST be able to receive the multipart/mixed [15] and MSRP endpoints MUST be able to receive the multipart/mixed [15] and
multipart/alternative [15] media-types. multipart/alternative [15] media-types.
If the Success-Report header field was set to "yes", the receiver If the Success-Report header field was set to "yes", the receiver
must construct and send one or more success reports, as described in must construct and send one or more success reports, as described in
Section 7.1.3. Section 7.1.3.
7.3.2. Receiving REPORT Requests 7.3.2. Receiving REPORT Requests
When an endpoint receives a REPORT request, it correlates it to the When an endpoint receives a REPORT request, it correlates the report
original SEND request using the Message-ID and the Byte-Range, if to the original SEND request using the Message-ID and the Byte-Range,
present. If it requested success reports, then it SHOULD keep enough if present. If it requested success reports, then it SHOULD keep
state about each outstanding sent message so that it can correlate enough state about each outstanding sent message so that it can
REPORT requests to the original messages. correlate REPORT requests to the original messages.
An endpoint that receives a REPORT request containing a Status header An endpoint that receives a REPORT request containing a Status header
field with a namespace field of "000" MUST interpret the report in field with a namespace field of "000" MUST interpret the report in
exactly the same way it would interpret an MSRP transaction response exactly the same way it would interpret an MSRP transaction response
with a response code matching the status-code field. with a response code matching the status-code field.
It is possible to receive a failure report or a failure transaction It is possible to receive a failure report or a failure transaction
response for a chunk that is currently being delivered. In this response for a chunk that is currently being delivered. In this
case, the entire message corresponding to that chunk SHOULD be case, the entire message corresponding to that chunk SHOULD be
aborted, by including the "#" character in the continuation field of aborted, by including the "#" character in the continuation field of
the end-line. the end-line.
It is possible that an endpoint will receive a REPORT request on a It is possible that an endpoint will receive a REPORT request on a
session that is no longer valid. The endpoint's behavior if this session that is no longer valid. The endpoint's behavior if this
happens is a matter of local policy. The endpoint is not required to happens is a matter of local policy. The endpoint is not required to
take any steps to facilitate such late delivery, i.e. it is not take any steps to facilitate such late delivery; i.e., it is not
expected to keep a connection active in case late REPORTs might expected to keep a connection active in case late REPORTs might
arrive. arrive.
When an endpoint that sent a SEND request receives a failure REPORT When an endpoint that sent a SEND request receives a failure REPORT
indicating that a particular byte range was not received, it MUST indicating that a particular byte range was not received, it MUST
treat the session as failed. If it wishes to recover, it MUST first treat the session as failed. If it wishes to recover, it MUST first
re-negotiate the URIs at the signaling level then resend that range re-negotiate the URIs at the signaling level then resend that range
of bytes of the message on the resulting new session. of bytes of the message on the resulting new session.
MSRP nodes MUST NOT send MSRP REPORT requests in response to other MSRP nodes MUST NOT send MSRP REPORT requests in response to other
skipping to change at page 27, line 45 skipping to change at page 28, line 4
Description Protocol (SDP) [2] via the SIP offer/answer mechanism Description Protocol (SDP) [2] via the SIP offer/answer mechanism
[3]. [3].
This document defines a handful of new SDP parameters to set up MSRP This document defines a handful of new SDP parameters to set up MSRP
sessions. These are detailed below and in the IANA Considerations sessions. These are detailed below and in the IANA Considerations
section. section.
An MSRP media-line (that is, a media-line proposing MSRP) in the An MSRP media-line (that is, a media-line proposing MSRP) in the
session description is accompanied by a mandatory "path" attribute. session description is accompanied by a mandatory "path" attribute.
This attribute contains a space-separated list of URIs to be visited This attribute contains a space-separated list of URIs to be visited
to contact the user agent advertising this session-description. If to contact the user agent advertising this session description. If
more than one URI is present, the leftmost URI is the first URI to be more than one URI is present, the leftmost URI is the first URI to be
visited to reach the target resource. (The path list can contain visited to reach the target resource. (The path list can contain
multiple URIs to allow for the deployment of gateways or relays in multiple URIs to allow for the deployment of gateways or relays in
the future.) MSRP implementations that can accept incoming the future.) MSRP implementations that can accept incoming
connections without the need for relays will typically only provide a connections without the need for relays will typically only provide a
single URI here. single URI here.
An MSRP media line is also accompanied by an "accept-types" An MSRP media line is also accompanied by an "accept-types"
attribute, and optionally an "accept-wrapped-types" attribute. These attribute, and optionally an "accept-wrapped-types" attribute. These
attributes are used to specify the media-types that are acceptable to attributes are used to specify the media-types that are acceptable to
the endpoint. the endpoint.
8.1. SDP Connection and Media Lines 8.1. SDP Connection and Media-Lines
An SDP connection-line takes the following format: An SDP connection-line takes the following format:
c=<network type> <address type> <connection address> c=<network type> <address type> <connection address>
Figure 4: Standard SDP Connection Line Figure 4: Standard SDP Connection Line
The network type and address type fields are used as normal for SDP. The network type and address type fields are used as normal for SDP.
The connection address field MUST be set to the IP address or fully The connection address field MUST be set to the IP address or fully
qualified domain name from the MSRP URI identifying the endpoint in qualified domain name from the MSRP URI identifying the endpoint in
its path attribute. its path attribute.
The general format of an SDP media-line is: The general format of an SDP media-line is:
m=<media> <port> <protocol> <format list> m=<media> <port> <protocol> <format list>
Figure 5: Standard SDP Medial Line Figure 5: Standard SDP Media Line
An offered or accepted media-line for MSRP over TCP MUST include a An offered or accepted media-line for MSRP over TCP MUST include a
protocol field value of "TCP/MSRP", or "TCP/TLS/MSRP" for TLS. The protocol field value of "TCP/MSRP", or "TCP/TLS/MSRP" for TLS. The
media field value MUST be "message". The format list field MUST be media field value MUST be "message". The format list field MUST be
set to "*". set to "*".
The port field value MUST match the port value used in the endpoint's The port field value MUST match the port value used in the endpoint's
MSRP URI in the path attribute, except that, as described in [3], a MSRP URI in the path attribute, except that, as described in [3], a
user agent that wishes to accept an offer, but not a specific media- user agent that wishes to accept an offer, but not a specific media-
line, MUST set the port number of that media-line to zero (0) in the line, MUST set the port number of that media-line to zero (0) in the
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where MSRP-URI is an "msrp" or "msrps" URI as defined in Section 6. where MSRP-URI is an "msrp" or "msrps" URI as defined in Section 6.
MSRP URIs included in an SDP offer or answer MUST include explicit MSRP URIs included in an SDP offer or answer MUST include explicit
port numbers. port numbers.
An MSRP device uses the URI to determine a host address, port, An MSRP device uses the URI to determine a host address, port,
transport, and protection level when connecting, and to identify the transport, and protection level when connecting, and to identify the
target when sending requests and responses. target when sending requests and responses.
The offerer and answerer each selects a URI to represent itself and The offerer and answerer each selects a URI to represent itself and
sends it to the peer device in the SDP document. Each device stores sends that URI to its peer in the SDP document. Each peer stores the
the path value received from the peer and uses that value as the path value received from the other peer and uses that value as the
target for requests inside the resulting session. If the path target for requests inside the resulting session. If the path
attribute received from the peer contains more than one URI, then the attribute received from the peer contains more than one URI, then the
target URI is the rightmost, while the leftmost entry represents the target URI is the rightmost, while the leftmost entry represents the
adjacent hop. If only one entry is present, then it is both the peer adjacent hop. If only one entry is present, then it is both the peer
and adjacent hop URI. The target path is the entire path attribute and adjacent hop URI. The target path is the entire path attribute
value received from the peer. value received from the peer.
The following example shows an SDP offer with a session URI of The following example shows an SDP offer with a session URI of
"msrp://alice.example.com:7394/2s93i9ek2a;tcp" "msrp://alice.example.com:7394/2s93i9ek2a;tcp"
v=0 v=0
o=alice 2890844526 2890844527 IN IP4 alice.example.com o=alice 2890844526 2890844527 IN IP4 alice.example.com
s= - s= -
c=IN IP4 alice.example.com c=IN IP4 alice.example.com
t=0 0 t=0 0
m=message 7394 TCP/MSRP * m=message 7394 TCP/MSRP *
a=accept-types:text/plain a=accept-types:text/plain
a=path:msrp://alice.example.com:7394/2s93i9ek2a;tcp a=path:msrp://alice.example.com:7394/2s93i9ek2a;tcp
Figure 7: Example SDP with Path Attribute Figure 7: Example SDP with Path Attribute
skipping to change at page 30, line 14 skipping to change at page 30, line 27
endpoint wishes to receive requests associated with the session. It endpoint wishes to receive requests associated with the session. It
MUST be assigned for this particular session, and MUST NOT duplicate MUST be assigned for this particular session, and MUST NOT duplicate
any URI in use for any other session in which the endpoint is any URI in use for any other session in which the endpoint is
currently participating. It SHOULD be hard to guess, and protected currently participating. It SHOULD be hard to guess, and protected
from eavesdroppers. This is discussed in more detail in Section 14. from eavesdroppers. This is discussed in more detail in Section 14.
8.3. Path Attributes with Multiple URIs 8.3. Path Attributes with Multiple URIs
As mentioned previously, this document describes MSRP for peer-to- As mentioned previously, this document describes MSRP for peer-to-
peer scenarios, that is, when no relays are used. The use of relays peer scenarios, that is, when no relays are used. The use of relays
are described in a separate document [23]. In order to allow an MSRP is described in a separate document [23]. In order to allow an MSRP
device that only implements the core specification to interoperate device that only implements the core specification to interoperate
with devices that use relays, this document must include a few with devices that use relays, this document must include a few
assumptions about how relays work. assumptions about how relays work.
An endpoint that uses one or more relays will indicate that by An endpoint that uses one or more relays will indicate that by
putting a URI for each device in the relay chain into the SDP path putting a URI for each device in the relay chain into the SDP path
attribute. The final entry will point to the endpoint itself. The attribute. The final entry will point to the endpoint itself. The
other entries will indicate each proposed relay, in order. The first other entries will indicate each proposed relay, in order. The first
entry will point to the first relay in the chain from the perspective entry will point to the first relay in the chain from the perspective
of the peer; that is, the relay to which the peer device, or a relay of the peer, that is, the relay to which the peer device, or a relay
operating on its behalf, should connect. operating on its behalf, should connect.
Endpoints that do not wish to insert a relay, including those that do Endpoints that do not wish to insert a relay, including those that do
not support relays at all, will put exactly one URI into the path not support relays at all, will put exactly one URI into the path
attribute. This URI represents both the endpoint for the session, attribute. This URI represents both the endpoint for the session and
and the connection point. the connection point.
Even though endpoints that implement only this specification will Even though endpoints that implement only this specification will
never introduce a relay, they need to be able to interoperate with never introduce a relay, they need to be able to interoperate with
other endpoints that do use relays. Therefore, they MUST be prepared other endpoints that do use relays. Therefore, they MUST be prepared
to receive more than one URI in the SDP path attribute. When an to receive more than one URI in the SDP path attribute. When an
endpoint receives more than one URI in a path attribute, only the endpoint receives more than one URI in a path attribute, only the
first entry is relevant for purposes of resolving the address and first entry is relevant for purposes of resolving the address and
port, and establishing the network connection, as it describes the port, and establishing the network connection, as it describes the
first adjacent hop. first adjacent hop.
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Either peer may initiate an updated exchange at any time. The Either peer may initiate an updated exchange at any time. The
endpoint that sends the new offer assumes the role of offerer for all endpoint that sends the new offer assumes the role of offerer for all
purposes. The answerer MUST respond with a path attribute that purposes. The answerer MUST respond with a path attribute that
represents a valid path to itself at the time of the updated represents a valid path to itself at the time of the updated
exchange. This new path may be the same as its previous path, but exchange. This new path may be the same as its previous path, but
may be different. The new offerer MUST NOT assume that the peer will may be different. The new offerer MUST NOT assume that the peer will
answer with the same path it used previously. answer with the same path it used previously.
If either party wishes to send an SDP document that changes nothing If either party wishes to send an SDP document that changes nothing
at all, then it MUST have the same o-line as in the previous at all, then it MUST use the same o-line as in the previous exchange.
exchange.
8.5. Connection Negotiation 8.5. Connection Negotiation
Previous versions of this document included a mechanism to negotiate Previous versions of this document included a mechanism to negotiate
the direction for any required TCP connection. The mechanism was the direction for any required TCP connection. The mechanism was
loosely based on the COMEDIA [26] work being done in the MMUSIC loosely based on the Connection-Oriented Media (COMEDIA) [26] work
working group. The primary motivation was to allow MSRP sessions to done by the MMUSIC working group. The primary motivation was to
succeed in situations where the offerer could not accept connections allow MSRP sessions to succeed in situations where the offerer could
but the answerer could. For example, the offerer might be behind a not accept connections but the answerer could. For example, the
NAT, while the answerer might have a globally routable address. offerer might be behind a NAT, while the answerer might have a
globally routable address.
The SIMPLE working group chose to remove that mechanism from MSRP, as The SIMPLE working group chose to remove that mechanism from MSRP, as
it added a great deal of complexity to connection management. it added a great deal of complexity to connection management.
Instead, MSRP now specifies a default connection direction. The Instead, MSRP now specifies a default connection direction. The
party that sent the original offer is responsible for connecting to party that sent the original offer is responsible for connecting to
its peer. its peer.
8.6. Content Type Negotiation 8.6. Content Type Negotiation
An SDP media-line proposing MSRP MUST be accompanied by an accept- An SDP media-line proposing MSRP MUST be accompanied by an accept-
skipping to change at page 32, line 11 skipping to change at page 32, line 27
explicit entries SHOULD be considered preferred over any non-listed explicit entries SHOULD be considered preferred over any non-listed
types. This feature is needed as, otherwise, the list of formats for types. This feature is needed as, otherwise, the list of formats for
rich IM devices may be prohibitively large. rich IM devices may be prohibitively large.
This specification requires the support of certain data formats. This specification requires the support of certain data formats.
Mandatory formats MUST be signaled like any other, either explicitly Mandatory formats MUST be signaled like any other, either explicitly
or by the use of a "*". or by the use of a "*".
The accept-types attribute may include container types, that is, MIME The accept-types attribute may include container types, that is, MIME
formats that contain other types internally. If compound types are formats that contain other types internally. If compound types are
used, the types listed in the accept-types attribute may be used both used, the types listed in the accept-types attribute may be used as
as the root payload, or may be wrapped in a listed container type. the root payload or may be wrapped in a listed container type. Any
Any container types MUST also be listed in the accept-types container types MUST also be listed in the accept-types attribute.
attribute.
Occasionally an endpoint will need to specify a MIME media-type that Occasionally, an endpoint will need to specify a MIME media-type that
can only be used if wrapped inside a listed container type. can only be used if wrapped inside a listed container type.
Endpoints MAY specify media-types that are only allowed when wrapped Endpoints MAY specify media-types that are only allowed when wrapped
inside compound types using the "accept-wrapped-types" attribute in inside compound types using the "accept-wrapped-types" attribute in
an SDP a-line. an SDP a-line.
The semantics for accept-wrapped-types are identical to those of the The semantics for accept-wrapped-types are identical to those of the
accept-types attribute, with the exception that the specified types accept-types attribute, with the exception that the specified types
may only be used when wrapped inside container types listed in may only be used when wrapped inside container types listed in the
accept-types attribute. Only types listed in the accept-types accept-types attribute. Only types listed in the accept-types
attribute may be used as the "root" type for the entire body. Since attribute may be used as the "root" type for the entire body. Since
any type listed in accept-types may be used both as a root body, and any type listed in accept-types may be both used as a root body and
wrapped in other bodies, format entries from accept-types SHOULD NOT wrapped in other bodies, format entries from accept-types SHOULD NOT
be repeated in this attribute. be repeated in this attribute.
This approach does not allow for specifying distinct lists of This approach does not allow for specifying distinct lists of
acceptable wrapped types for different types of containers. If an acceptable wrapped types for different types of containers. If an
endpoint understands a media-type in the context of one wrapper, it endpoint understands a media-type in the context of one wrapper, it
is assumed to understand it in the context of any other acceptable is assumed to understand it in the context of any other acceptable
wrappers, subject to any constraints defined by the wrapper types wrappers, subject to any constraints defined by the wrapper types
themselves. themselves.
The approach of specifying types that are only allowed inside of The approach of specifying types that are only allowed inside of
containers separately from the primary payload types allows an containers separately from the primary payload types allows an
endpoint to force the use of certain wrappers. For example, a endpoint to force the use of certain wrappers. For example, a
CPIM [12] gateway device may require all messages to be wrapped Common Presence and Instant Messaging (CPIM) [12] gateway device
inside message/cpim bodies, but may allow several content types may require all messages to be wrapped inside message/cpim bodies,
inside the wrapper. If the gateway were to specify the wrapped but may allow several content types inside the wrapper. If the
types in the accept-types attribute, its peer might attempt to use gateway were to specify the wrapped types in the accept-types
those types without the wrapper. attribute, its peer might attempt to use those types without the
wrapper.
If the recipient of an offer does not understand any of the payload If the recipient of an offer does not understand any of the payload
types indicated in the offered SDP, it SHOULD indicate that using the types indicated in the offered SDP, it SHOULD indicate that using the
appropriate mechanism of the rendezvous protocol. For example, in appropriate mechanism of the rendezvous protocol. For example, in
SIP, it SHOULD return a SIP 488 response. SIP, it SHOULD return a SIP 488 response.
An endpoint MAY indicate the maximum size message they wish to An MSRP endpoint MUST NOT send content of a type not signaled by the
peer in either an accept-types or an accept-wrapped-types attribute.
Furthermore, it MUST NOT send a top-level (i.e., not wrapped) MIME
document of a type not signaled in the accept-types attribute. In
either case, the signaling could be explicit, or implicit through the
use of the "*" character.
An endpoint MAY indicate the maximum size message it wishes to
receive using the max-size a-line attribute. Max-size refers to the receive using the max-size a-line attribute. Max-size refers to the
complete message in octets, not the size of any one chunk. Senders complete message in octets, not the size of any one chunk. Senders
SHOULD NOT exceed the max-size limit for any message sent in the SHOULD NOT exceed the max-size limit for any message sent in the
resulting session. However, the receiver should consider max-size resulting session. However, the receiver should consider max-size
value as a hint. value as a hint.
Media format entries may include parameters. The interpretation of Media format entries may include parameters. The interpretation of
such parameters varies between media-types. For the purposes of such parameters varies between media-types. For the purposes of
media-type negotiation, a format-entry with one or more parameters is media-type negotiation, a format-entry with one or more parameters is
assumed to match the same format-entry with no parameters. assumed to match the same format-entry with no parameters.
The formal syntax for these attributes are as follows: The formal syntax for these attributes is as follows:
accept-types = accept-types-label ":" format-list accept-types = accept-types-label ":" format-list
accept-types-label = "accept-types" accept-types-label = "accept-types"
accept-wrapped-types = wrapped-types-label ":" format-list accept-wrapped-types = wrapped-types-label ":" format-list
wrapped-types-label = "accept-wrapped-types" wrapped-types-label = "accept-wrapped-types"
format-list = format-entry *( SP format-entry) format-list = format-entry *( SP format-entry)
format-entry = ( ( (type "/" subtype) format-entry = ( ( (type "/" subtype)
/ (type "/" "*") ) / (type "/" "*") )
*( ";" type-param ) ) *( ";" type-param ) )
/ ("*") / ("*")
type = token type = token
subtype = token subtype = token
type-param = parm-attribute "=" parm-value type-param = parm-attribute "=" parm-value
attribute = token parm-attribute = token
value = token / quoted-string parm-value = token / quoted-string
max-size = max-size-label ":" max-size-value max-size = max-size-label ":" max-size-value
max-size-label = "max-size" max-size-label = "max-size"
max-size-value = 1*(DIGIT) ;max size in octets max-size-value = 1*(DIGIT) ;max size in octets
Figure 8: Attribute Syntax Figure 8: Attribute Syntax
8.7. Example SDP Exchange 8.7. Example SDP Exchange
Endpoint A wishes to invite Endpoint B to an MSRP session. A offers Endpoint A wishes to invite Endpoint B to an MSRP session. A offers
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v=0 v=0
o=userb 2890844530 2890844532 IN IP4 bob.example.com o=userb 2890844530 2890844532 IN IP4 bob.example.com
s= - s= -
c=IN IP4 bob.example.com c=IN IP4 bob.example.com
t=0 0 t=0 0
m=message 8493 TCP/MSRP * m=message 8493 TCP/MSRP *
a=accept-types:message/cpim text/plain a=accept-types:message/cpim text/plain
a=path:msrp://bob.example.com:8493/si438dsaodes;tcp a=path:msrp://bob.example.com:8493/si438dsaodes;tcp
Figure 10: SDP From Endpoint B Figure 10: SDP from Endpoint B
8.8. MSRP User Experience with SIP 8.8. MSRP User Experience with SIP
In typical SIP applications, when an endpoint receives an INVITE In typical SIP applications, when an endpoint receives an INVITE
request, it alerts the user, and waits for user input before request, it alerts the user, and waits for user input before
responding. This is analogous to the typical telephone user responding. This is analogous to the typical telephone user
experience, where the callee "answers" the call. experience, where the callee "answers" the call.
In contrast, the typical user experience for instant messaging In contrast, the typical user experience for instant messaging
applications is that the initial received message is immediately applications is that the initial received message is immediately
displayed to the user, without waiting for the user to "join" the displayed to the user, without waiting for the user to "join" the
conversation. Therefore, the principle of least surprise would conversation. Therefore, the principle of least surprise would
suggest that MSRP endpoints using SIP signaling SHOULD allow a mode suggest that MSRP endpoints using SIP signaling SHOULD allow a mode
where the endpoint quietly accepts the session, and begins displaying where the endpoint quietly accepts the session and begins displaying
messages. messages.
This guideline may not make sense for all situations, such as for This guideline may not make sense for all situations, such as for
mixed media applications, where both MSRP and audio sessions are mixed-media applications, where both MSRP and audio sessions are
offered in the same INVITE. In general, good application design offered in the same INVITE. In general, good application design
should take precedence. should take precedence.
SIP INVITE requests may be forked by a SIP proxy, resulting in more SIP INVITE requests may be forked by a SIP proxy, resulting in more
than one endpoint receiving the same INVITE. SIP early media [29] than one endpoint receiving the same INVITE. SIP early media [29]
techniques can be used to establish a preliminary session with each techniques can be used to establish a preliminary session with each
endpoint so the initial message(s) are displayed on each endpoint, endpoint so the initial message(s) are displayed on each endpoint,
and canceling the INVITE transaction for any endpoints that do not and canceling the INVITE transaction for any endpoints that do not
send MSRP traffic after some period of time, so that they cease send MSRP traffic after some period of time, so that they cease
receiving MSRP traffic from the inviter. receiving MSRP traffic from the inviter.
8.9. SDP direction attribute and MSRP 8.9. SDP Direction Attribute and MSRP
SDP defines a number of attributes that modify the direction of media SDP defines a number of attributes that modify the direction of media
flows. These are the "sendonly", "recvonly", "inactive", and flows. These are the "sendonly", "recvonly", "inactive", and
"sendrecv" attributes. "sendrecv" attributes.
If a "sendonly" or "recvonly" attribute modifies an MSRP media If a "sendonly" or "recvonly" attribute modifies an MSRP media
description line, the attribute indicates the direction of MSRP SEND description line, the attribute indicates the direction of MSRP SEND
requests that contain regular message payloads. Unless otherwise requests that contain regular message payloads. Unless otherwise
specified, these attributes do not affect the direction of other specified, these attributes do not affect the direction of other
types of requests, such as REPORT. SEND requests that contain some types of requests, such as REPORT. SEND requests that contain some
kind of control or reporting protocol rather than regular message kind of control or reporting protocol rather than regular message
payload (e.g., IMDN reports) should be generated according to the payload (e.g., Instant Message Delivery Notification (IMDN) reports)
protocol rules as if no direction attribute were present. should be generated according to the protocol rules as if no
direction attribute were present.
9. Formal Syntax 9. Formal Syntax
MSRP is a text protocol that uses the UTF-8 [14] transformation MSRP is a text protocol that uses the UTF-8 [14] transformation
format. format.
The following syntax specification uses the augmented Backus-Naur The following syntax specification uses the augmented Backus-Naur
Form (BNF) as described in RFC 4234 [6]. Form (BNF) as described in RFC 4234 [6].
msrp-req-or-resp = msrp-request / msrp-response msrp-req-or-resp = msrp-request / msrp-response
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other-method = 1*UPALPHA other-method = 1*UPALPHA
status-code = 3DIGIT ; any code defined in this document status-code = 3DIGIT ; any code defined in this document
; or an extension document ; or an extension document
MSRP-URI = msrp-scheme "://" authority MSRP-URI = msrp-scheme "://" authority
["/" session-id] ";" transport *( ";" URI-parameter) ["/" session-id] ";" transport *( ";" URI-parameter)
; authority as defined in RFC3986 ; authority as defined in RFC3986
msrp-scheme = "msrp" / "msrps" msrp-scheme = "msrp" / "msrps"
session-id = 1*( unreserved / "+" / "=" / ) session-id = 1*( unreserved / "+" / "=" / "/" )
; unreserved as defined in RFC3986 ; unreserved as defined in RFC3986
transport = "tcp" / 1*ALPHANUM transport = "tcp" / 1*ALPHANUM
URI-parameter = token ["=" token] URI-parameter = token ["=" token]
headers = To-Path CRLF From-Path CRLF 1*( header CRLF ) headers = To-Path CRLF From-Path CRLF 1*( header CRLF )
header = Message-ID header = Message-ID
/ Success-Report / Success-Report
/ Failure-Report / Failure-Report
/ Byte-Range / Byte-Range
/ Status / Status
/ ext-header / ext-header
To-Path = "To-Path:" SP MSRP-URI *( SP MSRP-URI ) To-Path = "To-Path:" SP MSRP-URI *( SP MSRP-URI )
From-Path = "From-Path:" SP MSRP-URI *( SP MSRP-URI ) From-Path = "From-Path:" SP MSRP-URI *( SP MSRP-URI )
Message-ID = "Message-ID:" SP ident Message-ID = "Message-ID:" SP ident
skipping to change at page 36, line 31 skipping to change at page 37, line 21
To-Path = "To-Path:" SP MSRP-URI *( SP MSRP-URI ) To-Path = "To-Path:" SP MSRP-URI *( SP MSRP-URI )
From-Path = "From-Path:" SP MSRP-URI *( SP MSRP-URI ) From-Path = "From-Path:" SP MSRP-URI *( SP MSRP-URI )
Message-ID = "Message-ID:" SP ident Message-ID = "Message-ID:" SP ident
Success-Report = "Success-Report:" SP ("yes" / "no" ) Success-Report = "Success-Report:" SP ("yes" / "no" )
Failure-Report = "Failure-Report:" SP ("yes" / "no" / "partial" ) Failure-Report = "Failure-Report:" SP ("yes" / "no" / "partial" )
Byte-Range = "Byte-Range:" SP range-start "-" range-end "/" total Byte-Range = "Byte-Range:" SP range-start "-" range-end "/" total
range-start = 1*DIGIT range-start = 1*DIGIT
range-end = 1*DIGIT / "*" range-end = 1*DIGIT / "*"
total = 1*DIGIT / "*" total = 1*DIGIT / "*"
Status = "Status:" SP namespace SP status-code [SP text-reason] Status = "Status:" SP namespace SP status-code [SP comment]
namespace = 3(DIGIT); "000" for all codes defined in this document. namespace = 3(DIGIT); "000" for all codes defined in this document.
text-reason = utf8text
ident = ALPHANUM 3*31ident-char ident = ALPHANUM 3*31ident-char
ident-char = ALPHANUM / "." / "-" / "+" / "%" / "=" ident-char = ALPHANUM / "." / "-" / "+" / "%" / "="
content-stuff = *(Other-Mime-header CRLF) content-stuff = *(Other-Mime-header CRLF)
Content-Type 2CRLF data CRLF Content-Type 2CRLF data CRLF
Content-Type = "Content-Type:" SP media-type Content-Type = "Content-Type:" SP media-type
media-type = type "/" subtype *( ";" gen-param ) media-type = type "/" subtype *( ";" gen-param )
type = token type = token
skipping to change at page 37, line 13 skipping to change at page 38, line 4
/ %x30-39 / %x41-5A / %x5E-7E) / %x30-39 / %x41-5A / %x5E-7E)
; token is compared case-insensitive ; token is compared case-insensitive
quoted-string = DQUOTE *(qdtext / qd-esc) DQUOTE quoted-string = DQUOTE *(qdtext / qd-esc) DQUOTE
qdtext = SP / HTAB / %x21 / %x23-5B / %x5D-7E qdtext = SP / HTAB / %x21 / %x23-5B / %x5D-7E
/ UTF8-NONASCII / UTF8-NONASCII
qd-esc = (BACKSLASH BACKSLASH) / (BACKSLASH DQUOTE) qd-esc = (BACKSLASH BACKSLASH) / (BACKSLASH DQUOTE)
BACKSLASH = "\" BACKSLASH = "\"
UPALPHA = %x41-5A UPALPHA = %x41-5A
ALPHANUM = ALPHA / DIGIT ALPHANUM = ALPHA / DIGIT
Other-Mime-header = (Content-ID Other-Mime-header = (Content-ID
/ Content-Description / Content-Description
/ Content-Disposition / Content-Disposition
/ mime-extension-field); / mime-extension-field)
; Content-ID, and Content-Description are defined in RFC2045. ; Content-ID, and Content-Description are defined in RFC2045.
; Content-Disposition is defined in RFC2183 ; Content-Disposition is defined in RFC2183
; MIME-extension-field indicates additional MIME extension ; MIME-extension-field indicates additional MIME extension
; header fields as described in RFC2045 ; header fields as described in RFC2045
data = *OCTET data = *OCTET
end-line = "-------" transact-id continuation-flag CRLF end-line = "-------" transact-id continuation-flag CRLF
continuation-flag = "+" / "$" / "#" continuation-flag = "+" / "$" / "#"
skipping to change at page 38, line 11 skipping to change at page 38, line 45
This section summarizes the semantics of various response codes that This section summarizes the semantics of various response codes that
may be used in MSRP transaction responses. These codes may also be may be used in MSRP transaction responses. These codes may also be
used in the Status header field in REPORT requests. used in the Status header field in REPORT requests.
10.1. 200 10.1. 200
The 200 response code indicates a successful transaction. The 200 response code indicates a successful transaction.
10.2. 400 10.2. 400
A 400 response indicates a request was unintelligible. The sender A 400 response indicates that a request was unintelligible. The
may retry the request after correcting the error. sender may retry the request after correcting the error.
10.3. 403 10.3. 403
A 403 response indicates the attempted action is not allowed. The A 403 response indicates that the attempted action is not allowed.
sender should not try the request again. The sender should not try the request again.
10.4. 408 10.4. 408
A 408 response indicates that a downstream transaction did not A 408 response indicates that a downstream transaction did not
complete in the alloted time. It is never sent by any elements complete in the allotted time. It is never sent by any elements
described in this specification. However, 408 is used in the MSRP described in this specification. However, 408 is used in the MSRP
Relay extension; therefore MSRP endpoints may receive it. An relay extension; therefore, MSRP endpoints may receive it. An
endpoint MUST treat a 408 response in the same manner as it would endpoint MUST treat a 408 response in the same manner as it would
treat a local timeout. treat a local timeout.
10.5. 413 10.5. 413
A 413 response indicates that the receiver wishes the sender to stop A 413 response indicates that the receiver wishes the sender to stop
sending the particular message. Typically, a 413 is sent in response sending the particular message. Typically, a 413 is sent in response
to a chunk of an undesired message. to a chunk of an undesired message.
If a message sender receives a 413 in a response, or in a REPORT If a message sender receives a 413 in a response, or in a REPORT
request, it MUST NOT send any further chunks in the message, that is, request, it MUST NOT send any further chunks in the message, that is,
any further chunks with the same Message-ID value. If the sender any further chunks with the same Message-ID value. If the sender
receives the 413 while in the process of sending a chunk, and the receives the 413 while in the process of sending a chunk, and the
chunk is interruptible, the sender MUST interrupt it. chunk is interruptible, the sender MUST interrupt it.
10.6. 415 10.6. 415
A 415 response indicates the SEND request contained a media type that A 415 response indicates that the SEND request contained a media type
is not understood by the receiver. The sender should not send any that is not understood by the receiver. The sender should not send
further messages with the same content-type for the duration of the any further messages with the same content-type for the duration of
session. the session.
10.7. 423 10.7. 423
A 423 response indicates that one of the requested parameters is out A 423 response indicates that one of the requested parameters is out
of bounds. It is used by the relay extensions to this document. of bounds. It is used by the relay extensions to this document.
10.8. 481 10.8. 481
A 481 response indicates that the indicated session does not exist. A 481 response indicates that the indicated session does not exist.
The sender should terminate the session. The sender should terminate the session.
10.9. 501 10.9. 501
A 501 response indicates that the recipient does not understand the A 501 response indicates that the recipient does not understand the
request method. request method.
The 501 response code exists to allow some degree of method The 501 response code exists to allow some degree of method
extensibility. It is not intended as a license to ignore methods extensibility. It is not intended as a license to ignore methods
defined in this document; rather it is a mechanism to report lack defined in this document; rather, it is a mechanism to report lack
of support of extension methods. of support of extension methods.
10.10. 506 10.10. 506
A 506 response indicates that a request arrived on a session which is A 506 response indicates that a request arrived on a session that is
already bound to another network connection. The sender should cease already bound to another network connection. The sender should cease
sending messages for that session on this connection. sending messages for that session on this connection.
11. Examples 11. Examples
11.1. Basic IM Session 11.1. Basic IM Session
This section shows an example flow for the most common scenario. The This section shows an example flow for the most common scenario. The
example assumes SIP is used to transport the SDP exchange. Details example assumes SIP is used to transport the SDP exchange. Details
of the SIP messages and SIP proxy infrastructure are omitted for the of the SIP messages and SIP proxy infrastructure are omitted for the
skipping to change at page 42, line 39 skipping to change at page 43, line 25
</body> </body>
</html> </html>
-------dsdfoe38sd$ -------dsdfoe38sd$
Figure 13: Example Message with XHTML Figure 13: Example Message with XHTML
11.3. Chunked Message 11.3. Chunked Message
For an example of a chunked message, see the example in Section 5.1. For an example of a chunked message, see the example in Section 5.1.
11.4. Chunked Message with message/cpim payload 11.4. Chunked Message with Message/CPIM Payload
This example shows a chunked message containing a CPIM message that This example shows a chunked message containing a CPIM message that
wraps a text/plain payload. It is worth noting that MSRP considers wraps a text/plain payload. It is worth noting that MSRP considers
the complete CPIM message before chunking the message, thus, the CPIM the complete CPIM message before chunking the message; thus, the CPIM
headers are included in only the first chunk. The MSRP Content-Type headers are included in only the first chunk. The MSRP Content-Type
and Byte-Range headers, present in both chunks, refer to the whole and Byte-Range headers, present in both chunks, refer to the whole
CPIM message. CPIM message.
MSRP d93kswow SEND MSRP d93kswow SEND
To-Path: msrp://bobpc.example.com:8888/9di4eae923wzd;tcp To-Path: msrp://bobpc.example.com:8888/9di4eae923wzd;tcp
From-Path: msrp://alicepc.example.com:7654/iau39soe2843z;tcp From-Path: msrp://alicepc.example.com:7654/iau39soe2843z;tcp
Message-ID: 12339sdqwer Message-ID: 12339sdqwer
Byte-Range: 1-137/148 Byte-Range: 1-137/148
Content-Type: message/cpim Content-Type: message/cpim
skipping to change at page 44, line 50 skipping to change at page 45, line 36
Traditional IM systems generally do a poor job of handling multiple Traditional IM systems generally do a poor job of handling multiple
simultaneous IM clients online for the same person. While some do a simultaneous IM clients online for the same person. While some do a
better job than many existing systems, handling of multiple clients better job than many existing systems, handling of multiple clients
is fairly crude. This becomes a much more significant issue when is fairly crude. This becomes a much more significant issue when
always-on mobile devices are available, but it is desirable to use always-on mobile devices are available, but it is desirable to use
them only if another IM client is not available. them only if another IM client is not available.
Using SIP makes rendezvous decisions explicit, deterministic, and Using SIP makes rendezvous decisions explicit, deterministic, and
very flexible. In contrast, "page-mode" IM systems use implicit very flexible. In contrast, "page-mode" IM systems use implicit
implementation-specific decisions which IM clients cannot influence. implementation-specific decisions that IM clients cannot influence.
With SIP session-mode messaging, rendezvous decisions can be under With SIP session-mode messaging, rendezvous decisions can be under
control of the client in a predictable, interoperable way for any control of the client in a predictable, interoperable way for any
host that implements callee capabilities [31]. As a result, host that implements callee capabilities [31]. As a result,
rendezvous policy is managed consistently for each address of record. rendezvous policy is managed consistently for each address of record.
The following example shows Juliet with several IM clients where she The following example shows Juliet with several IM clients where she
can be reached. Each of these has a unique SIP Contact and MSRP can be reached. Each of these has a unique SIP contact and MSRP
session. The example takes advantage of SIP's capability to "fork" session. The example takes advantage of SIP's capability to "fork"
an invitation to several Contacts in parallel, in sequence, or in an invitation to several contacts in parallel, in sequence, or in
combination. Juliet has registered from her chamber, the balcony, combination. Juliet has registered from her chamber, the balcony,
her PDA, and as a last resort, you can leave a message with her her PDA, and as a last resort, you can leave a message with her
Nurse. Juliet's contacts are listed below. The q-values express nurse. Juliet's contacts are listed below. The q-values express
relative preference (q=1.0 is the highest preference). relative preference (q=1.0 is the highest preference).
When Romeo opens his IM program, he selects Juliet and types the When Romeo opens his IM program, he selects Juliet and types the
message "art thou hither?" (instead of "you there?"). His client message "art thou hither?" (instead of "you there?"). His client
sends a SIP invitation to sip:juliet@thecapulets.example.com. The sends a SIP invitation to sip:juliet@thecapulets.example.com. The
proxy there tries first the balcony and the chamber simultaneously. proxy there tries first the balcony and the chamber simultaneously.
A client is running on each of those systems, both of which set up A client is running on each of those systems, both of which set up
early sessions of MSRP with Romeo's client. The client automatically early sessions of MSRP with Romeo's client. The client automatically
sends the message over MSRP to the two MSRP URIs involved. After a sends the message over MSRP to the two MSRP URIs involved. After a
delay of a several seconds with no reply or activity from Juliet, the delay of a several seconds with no reply or activity from Juliet, the
proxy cancels the invitation at her first two contacts, and forwards proxy cancels the invitation at her first two contacts, and forwards
the invitation on to Juliet's PDA. Since her father is talking to the invitation on to Juliet's PDA. Since her father is talking to
her about her wedding, she selects "Do Not Disturb" on her PDA, which her about her wedding, she selects "Do Not Disturb" on her PDA, which
sends a "Busy Here" response. The proxy then tries the Nurse, who sends a "Busy Here" response. The proxy then tries the nurse, who
answers and tells Romeo what is going on. answers and tells Romeo what is going on.
Romeo Juliet's Juliet/ Juliet/ Juliet/ Nurse Romeo Juliet's Juliet/ Juliet/ Juliet/ Nurse
Proxy balcony chamber PDA Proxy balcony chamber PDA
| | | | | | | | | | | |
|--INVITE--->| | | | | |--INVITE--->| | | | |
| |--INVITE--->| | | | | |--INVITE--->| | | |
| |<----180----| | | | | |<----180----| | | |
|<----180----| | | | | |<----180----| | | | |
|---PRACK---------------->| | | | |---PRACK---------------->| | | |
|<----200-----------------| | | | |<----200-----------------| | | |
|<===Early MSRP Session==>| art thou hither? | | |<===Early MSRP Session==>| art thou hither? | |
| | | | | | | | | | | |
| |--INVITE---------------->| | | | |--INVITE---------------->| | |
skipping to change at page 47, line 4 skipping to change at page 47, line 51
| |<---200 OK---------------------------------------| | |<---200 OK---------------------------------------|
|<--200 OK---| | | | | |<--200 OK---| | | | |
|---ACK------------------------------------------------------->| |---ACK------------------------------------------------------->|
|<================MSRP Session================================>| |<================MSRP Session================================>|
| | | | | | | | | | | |
| Hi Romeo, Juliet is | | Hi Romeo, Juliet is |
| with her father now | | with her father now |
| can I take a message?| | can I take a message?|
| | | |
| Tell her to go to confession tomorrow.... | | Tell her to go to confession tomorrow.... |
Figure 18: Forking Example Figure 18: Forking Example
12. Extensibility 12. Extensibility
MSRP was designed to be only minimally extensible. New MSRP Methods, MSRP was designed to be only minimally extensible. New MSRP methods,
header fields, and status codes can be defined in standards track header fields, and status codes can be defined in standards-track
RFCs. MSRP does not contain a version number or any negotiation RFCs. MSRP does not contain a version number or any negotiation
mechanism to require or discover new features. If an extension is mechanism to require or discover new features. If an extension is
specified in the future that requires negotiation, the specification specified in the future that requires negotiation, the specification
will need to describe how the extension is to be negotiated in the will need to describe how the extension is to be negotiated in the
encapsulating signaling protocol. If a non-interoperable update or encapsulating signaling protocol. If a non-interoperable update or
extension occurs in the future, it will be treated as a new protocol, extension occurs in the future, it will be treated as a new protocol,
and MUST describe how its use will be signaled. and MUST describe how its use will be signaled.
In order to allow extension header fields without breaking In order to allow extension header fields without breaking
interoperability, if an MSRP device receives a request or response interoperability, if an MSRP device receives a request or response
skipping to change at page 47, line 32 skipping to change at page 48, line 31
field was not present. If an MSRP device receives a request with an field was not present. If an MSRP device receives a request with an
unknown method, it MUST return a 501 response. unknown method, it MUST return a 501 response.
MSRP was designed to use lists of URIs instead of a single URI in the MSRP was designed to use lists of URIs instead of a single URI in the
To-Path and From-Path header fields in anticipation of relay or To-Path and From-Path header fields in anticipation of relay or
gateway functionality being added. In addition, "msrp" and "msrps" gateway functionality being added. In addition, "msrp" and "msrps"
URIs can contain parameters that are extensible. URIs can contain parameters that are extensible.
13. CPIM Compatibility 13. CPIM Compatibility
MSRP sessions may go to a gateway to other CPIM [27] compatible MSRP sessions may go to a gateway to other Common Profile for Instant
protocols. If this occurs, the gateway MUST maintain session state, Messaging (CPIM) [27] compatible protocols. If this occurs, the
and MUST translate between the MSRP session semantics and CPIM gateway MUST maintain session state, and MUST translate between the
semantics, which do not include a concept of sessions. Furthermore, MSRP session semantics and CPIM semantics, which do not include a
when one endpoint of the session is a CPIM gateway, instant messages concept of sessions. Furthermore, when one endpoint of the session
SHOULD be wrapped in "message/cpim" [12] bodies. Such a gateway MUST is a CPIM gateway, instant messages SHOULD be wrapped in
include "message/cpim" as the first entry in its SDP accept-types "message/cpim" [12] bodies. Such a gateway MUST include
attribute. MSRP endpoints sending instant messages to a peer that "message/cpim" as the first entry in its SDP accept-types attribute.
has included "message/cpim" as the first entry in the accept-types MSRP endpoints sending instant messages to a peer that has included
attribute SHOULD encapsulate all instant message bodies in "message/ "message/cpim" as the first entry in the accept-types attribute
cpim" wrappers. All MSRP endpoints MUST support the message/cpim SHOULD encapsulate all instant message bodies in "message/ cpim"
type, and SHOULD support the S/MIME[7] features of that format. wrappers. All MSRP endpoints MUST support the message/cpim type, and
SHOULD support the S/MIME[7] features of that format.
If a message is to be wrapped in a message/cpim envelope, the If a message is to be wrapped in a message/cpim envelope, the
wrapping MUST be done prior to breaking the message into chunks, if wrapping MUST be done prior to breaking the message into chunks, if
needed. needed.
All MSRP endpoints MUST recognize the From, To, DateTime, and Require All MSRP endpoints MUST recognize the From, To, DateTime, and Require
header fields as defined in RFC3862. Such applications SHOULD header fields as defined in RFC3862. Such applications SHOULD
recognize the CC header field, and MAY recognize the Subject header recognize the CC header field, and MAY recognize the Subject header
field. Any MSRP application that recognizes any message/cpim header field. Any MSRP application that recognizes any message/cpim header
field MUST understand the NS (name space) header field. field MUST understand the NS (name space) header field.
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Extension header fields MAY occur more than once, depending on the Extension header fields MAY occur more than once, depending on the
definition of such header fields. definition of such header fields.
Using message/cpim envelopes is also useful if an MSRP device Using message/cpim envelopes is also useful if an MSRP device
wishes to send a message on behalf of some other identity. The wishes to send a message on behalf of some other identity. The
device may add a message/cpim envelope with the appropriate From device may add a message/cpim envelope with the appropriate From
header field value. header field value.
14. Security Considerations 14. Security Considerations
Instant Messaging systems are used to exchange a variety of sensitive Instant messaging systems are used to exchange a variety of sensitive
information ranging from personal conversations, to corporate information ranging from personal conversations, to corporate
confidential information, to account numbers and other financial confidential information, to account numbers and other financial
trading information. IM is used by individuals, corporations, and trading information. IM is used by individuals, corporations, and
governments for communicating important information. IM systems need governments for communicating important information. IM systems need
to provide the properties of integrity and confidentiality for the to provide the properties of integrity and confidentiality for the
exchanged information, the knowledge that you are communicating with exchanged information, and the knowledge that you are communicating
the correct party, and allow the possibility of anonymous with the correct party, and they need to allow the possibility of
communication. MSRP pushes many of the hard problems to SIP when SIP anonymous communication. MSRP pushes many of the hard problems to
sets up the session, but some of the problems remain. Spam and DoS SIP when SIP sets up the session, but some of the problems remain.
attacks are also very relevant to IM systems. Spam and Denial of Service (DoS) attacks are also very relevant to IM
systems.
MSRP needs to provide confidentiality and integrity for the messages MSRP needs to provide confidentiality and integrity for the messages
it transfers. It also needs to provide assurances that the connected it transfers. It also needs to provide assurances that the connected
host is the host that it meant to connect to and that the connection host is the host that it meant to connect to and that the connection
has not been hijacked. has not been hijacked.
14.1. Secrecy of the MSRP URI 14.1. Secrecy of the MSRP URI
When an endpoint sends an MSRP URI to its peer in a rendez-vous When an endpoint sends an MSRP URI to its peer in a rendezvous
protocol, that URI is effectively a secret shared between the peers. protocol, that URI is effectively a secret shared between the peers.
If an attacker learns or guesses the URI prior to the completion of If an attacker learns or guesses the URI prior to the completion of
session setup, it may be able to impersonate one of the peers. session setup, it may be able to impersonate one of the peers.
Assuming the URI exchange in the rendez-vous protocol is sufficiently Assuming the URI exchange in the rendezvous protocol is sufficiently
protected, it is critical that the URI remain difficult to "guess" protected, it is critical that the URI remain difficult to "guess"
via brute force methods. Most components of the URI, such as the via brute force methods. Most components of the URI, such as the
scheme and the authority components, are common knowledge. The scheme and the authority components, are common knowledge. The
secrecy is entirely provided by the session-id component. secrecy is entirely provided by the session-id component.
Therefore, when an MSRP device generates an MSRP URI to be used in Therefore, when an MSRP device generates an MSRP URI to be used in
the initiation of an MSRP session, the session-id component MUST the initiation of an MSRP session, the session-id component MUST
contain at least 80 bits of randomness. contain at least 80 bits of randomness.
14.2. Transport Level Protection 14.2. Transport Level Protection
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using a rendezvous protocol. Although MSRP requires the use of a using a rendezvous protocol. Although MSRP requires the use of a
rendezvous protocol with the ability to protect this exchange, there rendezvous protocol with the ability to protect this exchange, there
is no guarantee that the protection will be used all the time. If is no guarantee that the protection will be used all the time. If
such protection is not used, anyone can see this secret. Host A then such protection is not used, anyone can see this secret. Host A then
connects to the provided host name and passes the secret in the clear connects to the provided host name and passes the secret in the clear
across the connection to B. Host A assumes that it is talking to B across the connection to B. Host A assumes that it is talking to B
based on where it sent the SYN packet and then delivers the secret in based on where it sent the SYN packet and then delivers the secret in
plain text across the connections. Host B assumes it is talking to A plain text across the connections. Host B assumes it is talking to A
because the host on the other end of the connection delivered the because the host on the other end of the connection delivered the
secret. An attacker that could ACK the SYN packet could insert secret. An attacker that could ACK the SYN packet could insert
itself as a man in the middle in the connection. itself as a man-in-the-middle in the connection.
When using TLS connections, the security is significantly improved. When using TLS connections, the security is significantly improved.
We assume that the host accepting the connection has a certificate We assume that the host accepting the connection has a certificate
from a well-known certification authority. Furthermore, we assume from a well-known certification authority. Furthermore, we assume
that the signaling to set up the session is protected by the that the signaling to set up the session is protected by the
rendezvous protocol. In this case, when host A contacts host B, the rendezvous protocol. In this case, when host A contacts host B, the
secret is passed through a confidential channel to A. A connects with secret is passed through a confidential channel to A. A connects
TLS to B. B presents a valid certificate, so A knows it really is with TLS to B. B presents a valid certificate, so A knows it really
connected to B. A then delivers the secret provided by B, so that B is connected to B. A then delivers the secret provided by B, so that
can verify it is connected to A. In this case, a rogue SIP Proxy can B can verify it is connected to A. In this case, a rogue SIP Proxy
see the secret in the SIP signaling traffic and could potentially can see the secret in the SIP signaling traffic and could potentially
insert itself as a man-in-the-middle. insert itself as a man-in-the-middle.
Realistically, using TLS with certificates from well known Realistically, using TLS with certificates from well-known
certification authorities is difficult for peer-to-peer connections, certification authorities is difficult for peer-to-peer connections,
as the types of hosts that end clients use for sending instant as the types of hosts that end clients use for sending instant
messages are unlikely to have long-term stable IP addresses or DNS messages are unlikely to have long-term stable IP addresses or DNS
names that certificates can bind to. In addition, the cost of server names that the certificates can bind to. In addition, the cost of
certificates from well-known certification authorities is currently server certificates from well-known certification authorities is
expensive enough to discourage their use for each client. Using TLS currently expensive enough to discourage their use for each client.
in a peer-to-peer mode without well known certificate is discussed in Using TLS in a peer-to-peer mode without well-known certificates is
Section 14.4. discussed in Section 14.4.
TLS becomes much more practical when some form of relay is TLS becomes much more practical when some form of relay is
introduced. Clients can then form TLS connections to relays, which introduced. Clients can then form TLS connections to relays, which
are much more likely to have TLS certificates. While this are much more likely to have TLS certificates. While this
specification does not address such relays, they are described by a specification does not address such relays, they are described by a
companion document [23]. That document makes extensive use of TLS to companion document [23]. That document makes extensive use of TLS to
protect traffic between clients and relays, and between one relay and protect traffic between clients and relays, and between one relay and
another. another.
TLS is used to authenticate devices and to provide integrity and TLS is used to authenticate devices and to provide integrity and
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The only strong security for non-TLS connections is achieved using The only strong security for non-TLS connections is achieved using
S/MIME. S/MIME.
Since MSRP carries arbitrary MIME content, it can trivially carry Since MSRP carries arbitrary MIME content, it can trivially carry
S/MIME protected messages as well. All MSRP implementations MUST S/MIME protected messages as well. All MSRP implementations MUST
support the multipart/signed media-type even if they do not support support the multipart/signed media-type even if they do not support
S/MIME. Since SIP can carry a session key, S/MIME messages in the S/MIME. Since SIP can carry a session key, S/MIME messages in the
context of a session could also be protected using a key-wrapped context of a session could also be protected using a key-wrapped
shared secret [28] provided in the session setup. MSRP can carry shared secret [28] provided in the session setup. MSRP can carry
unencoded binary payloads. Therefore MIME bodies MUST be transferred unencoded binary payloads. Therefore, MIME bodies MUST be
with a transfer encoding of binary. If a message is both signed and transferred with a transfer encoding of binary. If a message is both
encrypted, it SHOULD be signed first, then encrypted. If S/MIME is signed and encrypted, it SHOULD be signed first, then encrypted. If
supported, SHA-1, SHA-256, RSA, and AES-128 MUST be supported. For S/MIME is supported, SHA-1, SHA-256, RSA, and AES-128 MUST be
RSA, implementations MUST support key sizes of at least 1024 bits and supported. For RSA, implementations MUST support key sizes of at
SHOULD support key sizes of 2048 bits or more. least 1024 bits and SHOULD support key sizes of 2048 bits or more.
This does not actually require the endpoint to have certificates from This does not actually require the endpoint to have certificates from
a well-known certification authority. When MSRP is used with SIP, a well-known certification authority. When MSRP is used with SIP,
the Identity [17] and Certificates [25] mechanisms provide S/MIME the Identity [17] and Certificates [25] mechanisms provide S/MIME-
based delivery of a secret between A and B. No SIP intermediary based delivery of a secret between A and B. No SIP intermediary
except the explicitly trusted authentication service (one per user) except the explicitly trusted authentication service (one per user)
can see the secret. The S/MIME encryption of the SDP can also be can see the secret. The S/MIME encryption of the SDP can also be
used by SIP to exchange keying material that can be used in MSRP. used by SIP to exchange keying material that can be used in MSRP.
The MSRP session can then use S/MIME with this keying material to The MSRP session can then use S/MIME with this keying material to
sign and encrypt messages sent over MSRP. The connection can still sign and encrypt messages sent over MSRP. The connection can still
be hijacked since the secret is sent in clear text to the other end be hijacked since the secret is sent in clear text to the other end
of the TCP connection, but the consequences are mitigated if all the of the TCP connection, but the consequences are mitigated if all the
MSRP content is signed and encrypted with S/MIME. Although out of MSRP content is signed and encrypted with S/MIME. Although out of
scope for this document, the SIP negotiation of MSRP session can scope for this document, the SIP negotiation of an MSRP session can
negotiate symmetric keying material to be used with S/MIME for negotiate symmetric keying material to be used with S/MIME for
integrity and privacy. integrity and privacy.
14.4. Using TLS in Peer-to-Peer Mode 14.4. Using TLS in Peer-to-Peer Mode
TLS can be used with a self-signed certificate as long as there is a TLS can be used with a self-signed certificate as long as there is a
mechanism for both sides to ascertain that the other side used the mechanism for both sides to ascertain that the other side used the
correct certificate. When used with SDP and SIP, the correct correct certificate. When used with SDP and SIP, the correct
certificate can be verified by passing a fingerprint of the certificate can be verified by passing a fingerprint of the
certificate in the SDP and ensuring that the SDP has suitable certificate in the SDP and ensuring that the SDP has suitable
integrity protection. When SIP is used to transport the SDP, the integrity protection. When SIP is used to transport the SDP, the
integrity can be provided by the SIP Identity mechanism[17]. The integrity can be provided by the SIP Identity mechanism[17]. The
rest of this section describes the details of this approach. rest of this section describes the details of this approach.
If self-signed certificates are used, the content of the If self-signed certificates are used, the content of the
subjectAltName attribute inside the certificate MAY use the uniform subjectAltName attribute inside the certificate MAY use the URI of
resource identifier (URI) of the user. In SIP, this URI of the user the user. In SIP, this URI of the user is the User's Address of
is the User's Address of Record (AOR). This is useful for debugging Record (AOR). This is useful for debugging purposes only and is not
purposes only and is not required to bind the certificate to one of required to bind the certificate to one of the communication
the communication endpoints. Unlike normal TLS operations in this endpoints. Unlike normal TLS operations in this protocol, when doing
protocol, when doing peer-to-peer TLS, the subjectAltName is not an peer-to-peer TLS, the subjectAltName is not an important component of
important component of the certificate verification. If the endpoint the certificate verification. If the endpoint is also able to make
is also able to make anonymous sessions, a distinct, unique anonymous sessions, a distinct, unique certificate MUST be used for
certificate MUST be used for this purpose. For a client that works this purpose. For a client that works with multiple users, each user
with multiple users, each user SHOULD have its own certificate. SHOULD have its own certificate. Because the generation of
Because the generation of public/private key pairs is relatively public/private key pairs is relatively expensive, endpoints are not
expensive, endpoints are not required to generate certificates for required to generate certificates for each session.
each session.
A certificate fingerprint is the output of a one-way hash function A certificate fingerprint is the output of a one-way hash function
computed over the distinguished encoding rules (DER) form of the computed over the Distinguished Encoding Rules (DER) form of the
certificate. The endpoint MUST use the certificate fingerprint certificate. The endpoint MUST use the certificate fingerprint
attribute as specified in [18] and MUST include this in the SDP. The attribute as specified in [18] and MUST include this in the SDP. The
certificate presented during the TLS handshake needs to match the certificate presented during the TLS handshake needs to match the
fingerprint exchanged via the SDP and if the fingerprint does not fingerprint exchanged via the SDP, and if the fingerprint does not
match the hashed certificate then the endpoint MUST tear down the match the hashed certificate then the endpoint MUST tear down the
media session immediately. media session immediately.
When using SIP, the integrity of the fingerprint can be ensured When using SIP, the integrity of the fingerprint can be ensured
through the SIP Identity mechanism [17]. When a client wishes to use through the SIP Identity mechanism [17]. When a client wishes to use
SIP to set up a secure MSRP session with another endpoint it sends an SIP to set up a secure MSRP session with another endpoint, it sends
SDP offer in a SIP message to the other endpoint. This offer an SDP offer in a SIP message to the other endpoint. This offer
includes, as part of the SDP payload, the fingerprint of the includes, as part of the SDP payload, the fingerprint of the
certificate that the endpoint wants to use. The SIP message certificate that the endpoint wants to use. The SIP message
containing the offer is sent to the offerer's SIP proxy which will containing the offer is sent to the offerer's SIP proxy, which will
add an Identity header according to the procedures outlined in [17]. add an Identity header according to the procedures outlined in [17].
When the far endpoint receives the SIP message it can verify the When the far endpoint receives the SIP message, it can verify the
identity of the sender using the Identity header. Since the Identity identity of the sender using the Identity header. Since the Identity
header is a digital signature across several SIP headers, in addition header is a digital signature across several SIP headers, in addition
to the body or bodies of the SIP message, the receiver can also be to the body or bodies of the SIP message, the receiver can also be
certain that the message has not been tampered with after the digital certain that the message has not been tampered with after the digital
signature was added to the SIP message. signature was added to the SIP message.
An example of SDP with a fingerprint attribute is shown in the An example of SDP with a fingerprint attribute is shown in the
following figure. Note the fingerprint is shown spread over two following figure. Note the fingerprint is shown spread over two
lines due to formatting consideration but should all be on one line. lines due to formatting consideration but should all be on one line.
skipping to change at page 54, line 25 skipping to change at page 55, line 28
15. IANA Considerations 15. IANA Considerations
This specification instructs IANA to create a new registry for MSRP This specification instructs IANA to create a new registry for MSRP
parameters. The MSRP Parameter registry is a container for sub- parameters. The MSRP Parameter registry is a container for sub-
registries. This section further introduces sub-registries for MSRP registries. This section further introduces sub-registries for MSRP
method names, status codes, and header field names. method names, status codes, and header field names.
Additionally, Section 15.4 through Section 15.7 register new Additionally, Section 15.4 through Section 15.7 register new
parameters in existing IANA registries. parameters in existing IANA registries.
[NOTE TO IANA/RFC Editor: Please replace all occurrences of RFCXXXX
in this section with the actual number assigned to this document.]
15.1. MSRP Method Names 15.1. MSRP Method Names
This specification establishes the Method sub-registry under MSRP This specification establishes the Methods sub-registry under MSRP
Parameters and initiates its population as follows. New parameters Parameters and initiates its population as follows. New parameters
in this sub-registry must be published in an RFC (either as an IETF in this sub-registry must be published in an RFC (either as an IETF
submission or RFC Editor submission). submission or RFC Editor submission).
SEND - [RFCXXXX] SEND - [RFC4975]
REPORT - [RFCXXXX] REPORT - [RFC4975]
The following information MUST be provided in an RFC publication in The following information MUST be provided in an RFC publication in
order to register a new MSRP Method: order to register a new MSRP method:
o The method name. o The method name.
o The RFC number in which the method is registered. o The RFC number in which the method is registered.
15.2. MSRP Header Fields 15.2. MSRP Header Fields
This specification establishes the header field-Field sub-registry This specification establishes the header field-Field sub-registry
under MSRP Parameters. New parameters in this sub-registry must be under MSRP Parameters. New parameters in this sub-registry must be
published in an RFC (either as an IETF submission or RFC Editor published in an RFC (either as an IETF submission or RFC Editor
submission). Its initial population is defined as follows: submission). Its initial population is defined as follows:
To-Path - [RFCXXXX] To-Path - [RFC4975]
From-Path - [RFCXXXX] From-Path - [RFC4975]
Message-ID - [RFCXXXX] Message-ID - [RFC4975]
Success-Report - [RFCXXXX] Success-Report - [RFC4975]
Failure-Report - [RFCXXXX] Failure-Report - [RFC4975]
Byte-Range - [RFCXXXX] Byte-Range - [RFC4975]
Status - [RFCXXXX] Status - [RFC4975]
The following information MUST be provided in an RFC publication in The following information MUST be provided in an RFC publication in
order to register a new MSRP header field: order to register a new MSRP header field:
o The header field name. o The header field name.
o The RFC number in which the method is registered. o The RFC number in which the method is registered.
15.3. MSRP Status Codes 15.3. MSRP Status Codes
This specification establishes the Status-Code sub-registry under This specification establishes the Status-Code sub-registry under
skipping to change at page 55, line 37 skipping to change at page 56, line 37
Code [RFC Number] Code [RFC Number]
The following information MUST be provided in an RFC publication in The following information MUST be provided in an RFC publication in
order to register a new MSRP status code: order to register a new MSRP status code:
o The status code number. o The status code number.
o The RFC number in which the method is registered. o The RFC number in which the method is registered.
15.4. MSRP Port 15.4. MSRP Port
MSRP uses TCP port XYZ, from the "registered" port range. Usage of MSRP uses TCP port 2855, from the "registered" port range. Usage of
this value is described in Section 6. this value is described in Section 6.
[NOTE TO IANA/RFC Editor: Please replace XYZ in this section with the
assigned port number.]
15.5. URI Schema 15.5. URI Schema
This document requests permanent registration the URI schemes of This document requests permanent registration the URI schemes of
"msrp" and "msrps". "msrp" and "msrps".
15.5.1. MSRP Scheme 15.5.1. MSRP Scheme
URI Scheme Name "msrp"
URI Scheme Syntax See the ABNF construction for "MSRP-URI" in URI Scheme Name: "msrp"
Section 9 of RFCXXXX. URI Scheme Syntax: See the ABNF construction for "MSRP-URI" in
URI Scheme Semantics See Section 6 of RFCXXXX. Section 9 of RFC 4975.
Encoding Considerations See Section 6 of RFCXXXX. URI Scheme Semantics: See Section 6 of RFC 4975.
Applications/Protocols that use this URI Scheme The Message Session Encoding Considerations: See Section 6 of RFC 4975.
Applications/Protocols that use this URI Scheme: The Message Session
Relay Protocol (MSRP). Relay Protocol (MSRP).
Interoperability Considerations MSRP URIs are expected to be used Interoperability Considerations: MSRP URIs are expected to be used
only by implemetations of MSRP. No additional interoperability only by implementations of MSRP. No additional interoperability
issues are expected. issues are expected.
Security Considerations See Section 14.1 of RFCXXXX for specific Security Considerations: See Section 14.1 of RFC 4975 for specific
security considerations for MSRP URIs, and Section 14 of RFCXXXX security considerations for MSRP URIs, and Section 14 of RFC 4975
for security considerations for MSRP in general. for security considerations for MSRP in general.
Contact Ben Campbell (ben@estacado.net). Contact: Ben Campbell (ben@estacado.net).
Author/Change Controller This is a permanent registration request. Author/Change Controller: This is a permanent registration request.
Change control does not apply. Change control does not apply.
15.5.2. MSRPS Scheme 15.5.2. MSRPS Scheme
URI Scheme Name "msrps" URI Scheme Name: "msrps"
URI Scheme Syntax See the ABNF construction for "MSRP-URI" in URI Scheme Syntax: See the ABNF construction for "MSRP-URI" in
Section 9 of RFCXXXX. Section 9 of RFC 4975.
URI Scheme Semantics See Section 6 of RFCXXXX. URI Scheme Semantics: See Section 6 of RFC 4975.
Encoding Considerations See Section 6 of RFCXXXX. Encoding Considerations: See Section 6 of RFC 4975.
Applications/Protocols that use this URI Scheme The Message Session Applications/Protocols that use this URI Scheme: The Message Session
Relay Protocol (MSRP). Relay Protocol (MSRP).
Interoperability Considerations MSRP URIs are expected to be used Interoperability Considerations: MSRP URIs are expected to be used
only by implementations of MSRP. No additional interoperability only by implementations of MSRP. No additional interoperability
issues are expected. issues are expected.
Security Considerations See Section 14.1 of RFCXXXX for specific Security Considerations: See Section 14.1 of RFC 4975 for specific
security considerations for MSRP URIs, and Section 14 of RFCXXXX security considerations for MSRP URIs, and Section 14 of RFC 4975
for security considerations for MSRP in general. for security considerations for MSRP in general.
Contact Ben Campbell (ben@estacado.net). Contact: Ben Campbell (ben@estacado.net).
Author/Change Controller This is a permanent registration request. Author/Change Controller: This is a permanent registration request.
Change control does not apply. Change control does not apply.
15.6. SDP Transport Protocol 15.6. SDP Transport Protocol
MSRP defines the a new SDP protocol field values "TCP/MSRP" and "TCP/ MSRP defines the new SDP protocol field values "TCP/MSRP" and "TCP/
TLS/MSRP", which should be registered in the sdp-parameters registry TLS/MSRP", which should be registered in the sdp-parameters registry
under "proto". This first value indicates the MSRP protocol when TCP under "proto". This first value indicates the MSRP protocol when TCP
is used as an underlying transport. The second indicates that TLS is is used as an underlying transport. The second indicates that TLS
used. over TCP is used.
Specifications defining new protocol values must define the rules for Specifications defining new protocol values must define the rules for
the associated media format namespace. The "TCP/MSRP" and "TCP/TLS/ the associated media format namespace. The "TCP/MSRP" and "TCP/TLS/
MSRP" protocol values allow only one value in the format field (fmt), MSRP" protocol values allow only one value in the format field (fmt),
which is a single occurrence of "*". Actual format determination is which is a single occurrence of "*". Actual format determination is
made using the "accept-types" and "accept-wrapped-types" attributes. made using the "accept-types" and "accept-wrapped-types" attributes.
15.7. SDP Attribute Names 15.7. SDP Attribute Names
This document registers the following SDP attribute parameter names This document registers the following SDP attribute parameter names
in the sdp-parameters registry. These names are to be used in the in the sdp-parameters registry. These names are to be used in the
SDP att-name field. SDP att-name field.
15.7.1. Accept Types 15.7.1. Accept Types
Contact Information: Ben Campbell (ben@estacado.net) Contact Information: Ben Campbell (ben@estacado.net)
Attribute-name: accept-types Attribute-name: accept-types
Long-form Attribute Name: Acceptable Media Types Long-form Attribute Name: Acceptable media types
Type: Media level Type: Media level
Subject to Charset Attribute: No Subject to Charset Attribute: No
Purpose and Appropriate Values: The "accept-types" attribute Purpose and Appropriate Values: The "accept-types" attribute
contains a list of media-types that the endpoint is willing to contains a list of media types that the endpoint is willing to
receive. It may contain zero or more registered media-types, or receive. It may contain zero or more registered media-types, or
"*" in a space delimited string. "*" in a space-delimited string.
15.7.2. Wrapped Types 15.7.2. Wrapped Types
Contact Information: Ben Campbell (ben@estacado.net) Contact Information: Ben Campbell (ben@estacado.net)
Attribute-name: accept-wrapped-types Attribute-name: accept-wrapped-types
Long-form Attribute Name: Acceptable media-types Inside Wrappers Long-form Attribute Name: Acceptable media types Inside Wrappers
Type: Media level Type: Media level
Subject to Charset Attribute: No Subject to Charset Attribute: No
Purpose and Appropriate Values: The "accept-wrapped-types" attribute Purpose and Appropriate Values: The "accept-wrapped-types" attribute
contains a list of media types that the endpoint is willing to contains a list of media types that the endpoint is willing to
receive in an MSRP message with multipart content, but may not be receive in an MSRP message with multipart content, but may not be
used as the outermost type of the message. It may contain zero or used as the outermost type of the message. It may contain zero or
more registered media-types, or "*" in a space delimited string. more registered media-types, or "*" in a space-delimited string.
15.7.3. Max Size 15.7.3. Max Size
Contact Information: Ben Campbell (ben@estacado.net) Contact Information: Ben Campbell (ben@estacado.net)
Attribute-name: max-size Attribute-name: max-size
Long-form Attribute Name: Maximum message size. Long-form Attribute Name: Maximum message size
Type: Media level Type: Media level
Subject to Charset Attribute: No Subject to Charset Attribute: No
Purpose and Appropriate Values: The "max-size" attribute indicates Purpose and Appropriate Values: The "max-size" attribute indicates
the largest message an endpoint wishes to accept. It may take any the largest message an endpoint wishes to accept. It may take any
numeric value, specified in octets. whole numeric value, specified in octets.
15.7.4. Path 15.7.4. Path
Contact Information: Ben Campbell (ben@estacado.net) Contact Information: Ben Campbell (ben@estacado.net)
Attribute-name: path Attribute-name: path
Long-form Attribute Name: MSRP URI Path Long-form Attribute Name: MSRP URI Path
Type: Media level Type: Media level
Subject to Charset Attribute: No Subject to Charset Attribute: No
Purpose and Appropriate Values: The "path" attribute indicates a Purpose and Appropriate Values: The "path" attribute indicates a
series of MSRP devices that must be visited by messages sent in series of MSRP devices that must be visited by messages sent in
the session, including the final endpoint. The attribute contains the session, including the final endpoint. The attribute contains
one or more MSRP URIs, delimited by the space character. one or more MSRP URIs, delimited by the space character.
skipping to change at page 58, line 30 skipping to change at page 59, line 26
The following people contributed substantial discussion and feedback The following people contributed substantial discussion and feedback
to this ongoing effort: Eric Burger, Allison Mankin, Jon Peterson, to this ongoing effort: Eric Burger, Allison Mankin, Jon Peterson,
Brian Rosen, Dean Willis, Aki Niemi, Hisham Khartabil, Pekka Pessi, Brian Rosen, Dean Willis, Aki Niemi, Hisham Khartabil, Pekka Pessi,
Miguel Garcia, Peter Ridler, Sam Hartman, and Jean Mahoney. Miguel Garcia, Peter Ridler, Sam Hartman, and Jean Mahoney.
17. References 17. References
17.1. Normative References 17.1. Normative References
[1] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", [1] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
RFC 2246, January 1999. Protocol Version 1.1", RFC 4346, April 2006.
[2] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [2] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[3] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [3] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002. Session Description Protocol (SDP)", RFC 3264, June 2002.
[4] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., [4] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002. Session Initiation Protocol", RFC 3261, June 2002.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[6] Crocker, D. and P. Overell, "Augmented BNF for Syntax [6] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005. Specifications: ABNF", RFC 4234, October 2005.
[7] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions [7] Ramsdell, B., "Secure/Multipurpose Internet Mail Extensions
(S/MIME) Version 3.1 Message Specification", RFC 3851, (S/MIME) Version 3.1 Message Specification", RFC 3851, July
July 2004. 2004.
[8] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [8] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies", Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996. RFC 2045, November 1996.
[9] Troost, R., Dorner, S., and K. Moore, "Communicating [9] Troost, R., Dorner, S., and K. Moore, "Communicating
Presentation Information in Internet Messages: The Content- Presentation Information in Internet Messages: The Content-
Disposition header field", RFC 2183, August 1997. Disposition Header Field", RFC 2183, August 1997.
[10] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [10] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 3986, Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
January 2005. January 2005.
[11] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and [11] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and
T. Wright, "Transport Layer Security (TLS) Extensions", T. Wright, "Transport Layer Security (TLS) Extensions", RFC
RFC 3546, June 2003. 4366, April 2006.
[12] Klyne, G. and D. Atkins, "Common Presence and Instant Messaging [12] Klyne, G. and D. Atkins, "Common Presence and Instant Messaging
(CPIM): Message Format", RFC 3862, August 2004. (CPIM): Message Format", RFC 3862, August 2004.
[13] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for [13] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for
Transport Layer Security (TLS)", RFC 3268, June 2002. Transport Layer Security (TLS)", RFC 3268, June 2002.
[14] Yergeau, F., "UTF-8, a transformation format of ISO 10646", [14] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
RFC 3629, November 2003. 63, RFC 3629, November 2003.
[15] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [15] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, Extensions (MIME) Part Two: Media Types", RFC 2046, November
November 1996. 1996.
[16] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509 [16] Housley, R., Polk, W., Ford, W., and D. Solo, "Internet X.509
Public Key Infrastructure: Certificate and Certificate Public Key Infrastructure Certificate and Certificate
Revocation List (CRL) Profile", RFC 3280, April 2002. Revocation List (CRL) Profile", RFC 3280, April 2002.
[17] Peterson, J. and C. Jennings, "Enhancements for Authenticated [17] Peterson, J. and C. Jennings, "Enhancements for Authenticated
Identity Management in the Session Initiation Protocol (SIP)", Identity Management in the Session Initiation Protocol (SIP)",
RFC 4474, August 2006. RFC 4474, August 2006.
[18] Lennox, J., "Connection-Oriented Media Transport over the [18] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006. Description Protocol (SDP)", RFC 4572, July 2006.
17.2. Informational References 17.2. Informative References
[19] Johnston, A. and O. Levin, "Session Initiation Protocol Call [19] Johnston, A. and O. Levin, "Session Initiation Protocol (SIP)
Control - Conferencing for User Agents", RFC 4579, August 2006. Call Control - Conferencing for User Agents", BCP 119, RFC
4579, August 2006.
[20] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo, [20] Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo,
"Best Current Practices for Third Party Call Control in the "Best Current Practices for Third Party Call Control (3pcc) in
Session Initiation Protocol", RFC 3725, April 2004. the Session Initiation Protocol (SIP)", BCP 85, RFC 3725, April
2004.
[21] Sparks, R., Johnston, A., and D. Petrie, "Session Initiation [21] Sparks, R., Johnston, A., and D. Petrie, "Session Initiation
Protocol Call Control - Transfer", Protocol Call Control - Transfer", Work in Progress, October
draft-ietf-sipping-cc-transfer-07 (work in progress), 2006.
October 2006.
[22] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and [22] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., and
D. Gurle, "Session Initiation Protocol (SIP) Extension for D. Gurle, "Session Initiation Protocol (SIP) Extension for
Instant Messaging", RFC 3428, December 2002. Instant Messaging", RFC 3428, December 2002.
[23] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions for [23] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions for the
Message Sessions Relay Protocol (MSRP)", Message Session Relay Protocol (MSRP)", RFC 4976, September
draft-ietf-simple-msrp-relays-10 (work in progress), 2007.
December 2006.
[24] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE [24] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE
Method", RFC 3311, October 2002. Method", RFC 3311, October 2002.
[25] Jennings, C., Peterson, J., and J. Fischl, "Certificate [25] Jennings, C., Peterson, J., and J. Fischl, "Certificate
Management Service for SIP", draft-ietf-sip-certs-02 (work in Management Service for SIP", Work in Progress, July 2007.
progress), October 2006.
[26] Yon, D. and G. Camarillo, "Connection-Oriented Media Transport [26] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the
in SDP", RFC 4145, September 2005. Session Description Protocol (SDP)", RFC 4145, September 2005.
[27] Peterson, J., "A Common Profile for Instant Messaging (CPIM)", [27] Peterson, J., "Common Profile for Instant Messaging (CPIM)",
RFC 3860, August 2004. RFC 3860, August 2004.
[28] Housley, R., "Triple-DES and RC2 Key Wrapping", RFC 3217, [28] Housley, R., "Triple-DES and RC2 Key Wrapping", RFC 3217,
December 2001. December 2001.
[29] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing Tone [29] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing Tone
Generation in the Session Initiation Protocol (SIP)", RFC 3960, Generation in the Session Initiation Protocol (SIP)", RFC 3960,
December 2004. December 2004.
[30] Saint-Andre, P., "Extensible Messaging and Presence Protocol [30] Saint-Andre, P., "Extensible Messaging and Presence Protocol
(XMPP): Instant Messaging and Presence", RFC 3921, (XMPP): Instant Messaging and Presence", RFC 3921, October
October 2004. 2004.
[31] Rosenberg, J., "Indicating User Agent Capabilities in the [31] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating
Session Initiation Protocol (SIP)", RFC 3840, August 2004. User Agent Capabilities in the Session Initiation Protocol
(SIP)", RFC 3840, August 2004.
[32] Peterson, J., "Address Resolution for Instant Messaging and [32] Peterson, J., "Address Resolution for Instant Messaging and
Presence", RFC 3861, August 2004. Presence", RFC 3861, August 2004.
Authors' Addresses Authors' Addresses
Ben Campbell (editor) Ben Campbell (editor)
Estacado Systems Estacado Systems
17210 Campbell Road 17210 Campbell Road
Suite 250 Suite 250
Dallas, TX 75252 Dallas, TX 75252
USA USA
Email: ben@estacado.net EMail: ben@estacado.net
Rohan Mahy (editor) Rohan Mahy (editor)
Plantronics Plantronics
345 Encincal Street 345 Encincal Street
Santa Cruz, CA Santa Cruz, CA 95060
USA USA
Email: rohan@ekabal.com EMail: rohan@ekabal.com
Cullen Jennings (editor) Cullen Jennings (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
170 West Tasman Dr. 170 West Tasman Dr.
MS: SJC-21/2 MS: SJC-21/2
San Jose, CA 95134 San Jose, CA 95134
USA USA
Phone: +1 408 421-9990 Phone: +1 408 421-9990
Email: fluffy@cisco.com EMail: fluffy@cisco.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
skipping to change at page 62, line 44 skipping to change at line 2802
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
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ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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