draft-ietf-simple-message-sessions-08.txt   draft-ietf-simple-message-sessions-09.txt 
SIMPLE WG B. Campbell, Ed. SIMPLE WG B. Campbell, Ed.
Internet-Draft Estacado Systems Internet-Draft Estacado Systems
Expires: February 23, 2005 R. Mahy, Ed. Expires: April 24, 2005 R. Mahy, Ed.
Airespace
C. Jennings, Ed. C. Jennings, Ed.
Cisco Systems, Inc. Cisco Systems, Inc.
August 25, 2004 October 24, 2004
The Message Session Relay Protocol The Message Session Relay Protocol
draft-ietf-simple-message-sessions-08.txt draft-ietf-simple-message-sessions-09.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with which he or she become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
skipping to change at page 1, line 38 skipping to change at page 1, line 39
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 23, 2005. This Internet-Draft will expire on April 24, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). Copyright (C) The Internet Society (2004).
Abstract Abstract
This document describes the Message Session Relay Protocol (MSRP), a This document describes the Message Session Relay Protocol (MSRP), 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 setup via a rendezvous or session setup protocol media stream when setup via a rendezvous or session setup protocol
such as the Session Initiation Protocol (SIP). such as the Session Initiation Protocol (SIP).
Table of Contents Table of Contents
1. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction and Background . . . . . . . . . . . . . . . . 4 2. Introduction and Background . . . . . . . . . . . . . . . . 4
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 5 3. Applicability of MSRP . . . . . . . . . . . . . . . . . . . 5
4. Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 5
4.1 MSRP Framing and Message Chunking . . . . . . . . . . . . 8 5. Key Concepts . . . . . . . . . . . . . . . . . . . . . . . . 8
4.2 MSRP Addressing . . . . . . . . . . . . . . . . . . . . . 9 5.1 MSRP Framing and Message Chunking . . . . . . . . . . . . 8
4.3 MSRP Transaction and Report Model . . . . . . . . . . . . 9 5.2 MSRP Addressing . . . . . . . . . . . . . . . . . . . . . 9
4.4 MSRP Connection Model . . . . . . . . . . . . . . . . . . 10 5.3 MSRP Transaction and Report Model . . . . . . . . . . . . 9
5. MSRP URLs . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.4 MSRP Connection Model . . . . . . . . . . . . . . . . . . 10
5.1 MSRP URL Comparison . . . . . . . . . . . . . . . . . . . 13 6. MSRP URLs . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2 Resolving MSRP Host Device . . . . . . . . . . . . . . . . 14 6.1 MSRP URL Comparison . . . . . . . . . . . . . . . . . . . 13
6. Method-Specific Behavior . . . . . . . . . . . . . . . . . . 14 6.2 Resolving MSRP Host Device . . . . . . . . . . . . . . . . 14
6.1 Constructing Requests . . . . . . . . . . . . . . . . . . 14 7. Method-Specific Behavior . . . . . . . . . . . . . . . . . . 14
6.1.1 Delivering SEND requests . . . . . . . . . . . . . . . 15 7.1 Constructing Requests . . . . . . . . . . . . . . . . . . 14
6.1.2 Sending REPORT requests . . . . . . . . . . . . . . . 18 7.1.1 Delivering SEND requests . . . . . . . . . . . . . . . 15
6.1.3 Failure REPORT Generation . . . . . . . . . . . . . . 18 7.1.2 Sending REPORT requests . . . . . . . . . . . . . . . 17
6.2 Constructing Responses . . . . . . . . . . . . . . . . . . 19 7.1.3 Failure REPORT Generation . . . . . . . . . . . . . . 18
6.3 Receiving Requests . . . . . . . . . . . . . . . . . . . . 20 7.2 Constructing Responses . . . . . . . . . . . . . . . . . . 19
6.3.1 Receiving SEND requests . . . . . . . . . . . . . . . 20 7.3 Receiving Requests . . . . . . . . . . . . . . . . . . . . 20
6.3.2 Receiving REPORT requests . . . . . . . . . . . . . . 21 7.3.1 Receiving SEND requests . . . . . . . . . . . . . . . 20
7. Using MSRP with SIP . . . . . . . . . . . . . . . . . . . . 22 7.3.2 Receiving REPORT requests . . . . . . . . . . . . . . 22
7.1 SDP Offer-Answer Exchanges for MSRP Sessions . . . . . . . 22 8. Using MSRP with SIP . . . . . . . . . . . . . . . . . . . . 22
7.1.1 URL Negotiations . . . . . . . . . . . . . . . . . . . 24 8.1 SDP Offer-Answer Exchanges for MSRP Sessions . . . . . . . 22
7.1.2 Path Attributes with Multiple URLs . . . . . . . . . . 25 8.1.1 URL Negotiations . . . . . . . . . . . . . . . . . . . 25
7.1.3 Updated SDP Offers . . . . . . . . . . . . . . . . . . 26 8.1.2 Path Attributes with Multiple URLs . . . . . . . . . . 26
7.1.4 Example SDP Exchange . . . . . . . . . . . . . . . . . 26 8.1.3 Updated SDP Offers . . . . . . . . . . . . . . . . . . 27
7.1.5 Connection Negotiation . . . . . . . . . . . . . . . . 27 8.1.4 Example SDP Exchange . . . . . . . . . . . . . . . . . 27
7.2 MSRP User Experience with SIP . . . . . . . . . . . . . . 27 8.1.5 Connection Negotiation . . . . . . . . . . . . . . . . 28
8. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 28 8.2 MSRP User Experience with SIP . . . . . . . . . . . . . . 28
9. Response Code Descriptions . . . . . . . . . . . . . . . . . 30 9. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . 28
9.1 200 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 10. Response Code Descriptions . . . . . . . . . . . . . . . . . 31
9.2 400 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 10.1 200 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.3 403 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 10.2 400 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.4 415 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 10.3 403 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.5 426 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10.4 415 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.6 481 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10.5 426 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
9.7 506 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10.6 481 . . . . . . . . . . . . . . . . . . . . . . . . . . 31
10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 31 10.7 501 . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.1 Basic IM session . . . . . . . . . . . . . . . . . . . . 31 10.8 506 . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.2 Chunked Message . . . . . . . . . . . . . . . . . . . . 33 11. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 32
10.3 System Message . . . . . . . . . . . . . . . . . . . . . 33 11.1 Basic IM session . . . . . . . . . . . . . . . . . . . . 32
10.4 Positive Report . . . . . . . . . . . . . . . . . . . . 34 11.2 Message with XHTML Content . . . . . . . . . . . . . . . 34
10.5 Forked IM . . . . . . . . . . . . . . . . . . . . . . . 34 11.3 Chunked Message . . . . . . . . . . . . . . . . . . . . 35
11. Extensibility . . . . . . . . . . . . . . . . . . . . . . . 37 11.4 System Message . . . . . . . . . . . . . . . . . . . . . 35
12. CPIM compatibility . . . . . . . . . . . . . . . . . . . . . 37 11.5 Positive Report . . . . . . . . . . . . . . . . . . . . 36
13. Security Considerations . . . . . . . . . . . . . . . . . . 38 11.6 Forked IM . . . . . . . . . . . . . . . . . . . . . . . 36
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . 40 12. Extensibility . . . . . . . . . . . . . . . . . . . . . . . 39
14.1 MSRP Port . . . . . . . . . . . . . . . . . . . . . . . 40 13. CPIM compatibility . . . . . . . . . . . . . . . . . . . . . 39
14.2 MSRP URL Schemes . . . . . . . . . . . . . . . . . . . . 40 14. Security Considerations . . . . . . . . . . . . . . . . . . 40
14.3 SDP Parameters . . . . . . . . . . . . . . . . . . . . . 40 15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 44
14.3.1 Accept Types . . . . . . . . . . . . . . . . . . . . 40 15.1 MSRP Port . . . . . . . . . . . . . . . . . . . . . . . 44
14.3.2 Wrapped Types . . . . . . . . . . . . . . . . . . . 40 15.2 MSRP URL Schemes . . . . . . . . . . . . . . . . . . . . 44
14.3.3 Max Size . . . . . . . . . . . . . . . . . . . . . . 41 15.3 SDP Parameters . . . . . . . . . . . . . . . . . . . . . 44
14.3.4 Path . . . . . . . . . . . . . . . . . . . . . . . . 41 15.3.1 Accept Types . . . . . . . . . . . . . . . . . . . . 44
15. Change History . . . . . . . . . . . . . . . . . . . . . . . 41 15.3.2 Wrapped Types . . . . . . . . . . . . . . . . . . . 44
15.1 draft-ietf-simple-message-sessions-08 . . . . . . . . . 41 15.3.3 Max Size . . . . . . . . . . . . . . . . . . . . . . 44
15.2 draft-ietf-simple-message-sessions-07 . . . . . . . . . 41 15.3.4 Path . . . . . . . . . . . . . . . . . . . . . . . . 45
15.3 draft-ietf-simple-message-sessions-06 . . . . . . . . . 42 16. Change History . . . . . . . . . . . . . . . . . . . . . . . 45
15.4 draft-ietf-simple-message-sessions-05 . . . . . . . . . 42 16.1 draft-ietf-simple-message-sessions-09 . . . . . . . . . 45
15.5 draft-ietf-simple-message-sessions-04 . . . . . . . . . 43 16.2 draft-ietf-simple-message-sessions-08 . . . . . . . . . 45
15.6 draft-ietf-simple-message-sessions-03 . . . . . . . . . 43 16.3 draft-ietf-simple-message-sessions-07 . . . . . . . . . 46
15.7 draft-ietf-simple-message-sessions-02 . . . . . . . . . 43 16.4 draft-ietf-simple-message-sessions-06 . . . . . . . . . 46
15.8 draft-ietf-simple-message-sessions-01 . . . . . . . . . 44 16.5 draft-ietf-simple-message-sessions-05 . . . . . . . . . 47
15.9 draft-ietf-simple-message-sessions-00 . . . . . . . . . 44 16.6 draft-ietf-simple-message-sessions-04 . . . . . . . . . 47
15.10 draft-campbell-simple-im-sessions-01 . . . . . . . . . . 45 16.7 draft-ietf-simple-message-sessions-03 . . . . . . . . . 47
16. Contributors and Acknowledgments . . . . . . . . . . . . . . 45 16.8 draft-ietf-simple-message-sessions-02 . . . . . . . . . 48
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 45 16.9 draft-ietf-simple-message-sessions-01 . . . . . . . . . 48
17.1 Normative References . . . . . . . . . . . . . . . . . . . 45 16.10 draft-ietf-simple-message-sessions-00 . . . . . . . . . 49
17.2 Informational References . . . . . . . . . . . . . . . . . 46 16.11 draft-campbell-simple-im-sessions-01 . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 48 17. Contributors and Acknowledgments . . . . . . . . . . . . . . 49
Intellectual Property and Copyright Statements . . . . . . . 49 18. References . . . . . . . . . . . . . . . . . . . . . . . . . 50
18.1 Normative References . . . . . . . . . . . . . . . . . . . 50
18.2 Informational References . . . . . . . . . . . . . . . . . 51
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 52
Intellectual Property and Copyright Statements . . . . . . . 53
1. Conventions 1. 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".
2. Introduction and Background 2. Introduction and Background
A series of related textual 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 session with a definite start and end. This be viewed as part of a "message session", that is, an conversational
is in contrast to individual messages each sent completely exchange of messages with a definite beginning and end. This is in
independently. The SIMPLE Working Group describes messaging schemes contrast to individual messages each sent completely independently.
that only track individual messages as "page-mode" messages, whereas The SIMPLE Working Group describes messaging schemes that only track
messaging that is part of a "session" with a definite start and end individual messages as "page-mode" messages, whereas messaging that
is called session-mode messaging. is part of a "session" with a definite start and end is called
session-mode messaging.
Page-mode messaging is enabled in SIMPLE via the SIP [4]MESSAGE Page-mode messaging is enabled in SIMPLE via the SIP [4]MESSAGE
method [19]. Session-mode messaging has a number of benefits [20] method [18]. Session-mode messaging has a number of benefits [19]
over page-mode messaging however, such as explicit rendezvous, over page-mode messaging however, such as explicit rendezvous,
tighter integration with other media types, direct client-to-client tighter integration with other media types, direct client-to-client
operation, and brokered privacy and security. operation, and 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 included in an offer or answer [3] using the Session sessions can be included in an offer or answer [3] using the Session
Description Protocol(SDP [2]). The exchange is carried by some Description Protocol(SDP [2]). The exchange is carried by some
signaling protocol, such as SIP [4]. This allows a communication signaling protocol, such as the Session Initiation Protocol (SIP
user agent to offer a messaging session as one of the possible media [4]). This allows a communication user agent to offer a messaging
types in a session. For instance, Alice may want to communicate with session as one of the possible media types in a session. For
Bob. Alice doesn't know at the moment whether Bob has his phone or instance, Alice may want to communicate with Bob. Alice doesn't know
his IM client handy, but she's willing to use either. She sends an at the moment whether Bob has his phone or his IM client handy, but
invitation to a session to the address of record she has for Bob, she's willing to use either. She sends an invitation to a session to
sip:bob@example.com. Her invitation offers both voice and an IM the address of record she has for Bob, sip:bob@example.com. Her
session. The SIP services at example.com forward the invitation to invitation offers both voice and an IM session. The SIP services at
Bob at his currently registered clients. Bob accepts the invitation example.com forward the invitation to Bob at his currently registered
at his IM client and they begin a threaded chat conversation. clients. Bob accepts the invitation at his IM client and they begin
a threaded chat conversation.
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 [18] Alice to Carol, introducing them into their own transfer [17] 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 utilizing third-party call into call-center and dispatch environments utilizing third-party call
control [17] and conferencing [16] applications. control [16] and conferencing [15] applications.
3. Protocol Overview 3. Applicability of MSRP
MSRP is not designed for use as a standalone protocol. MSRP MUST
only be used in the context of a rendezvous mechanism meeting the
following requirements:
The rendezvous mechanism MUST provide both MSRP URLs associated
with an MSRP session to each of the participating endpoints. The
rendezvous mechanism MUST implement mechanisms to provide these
URLs securely - they MUST NOT be made available to an untrusted
third party or be easily discoverable.
The rendezvous mechanism MUST provide mechanisms for the
negotiation of any supported MSRP extensions that are not
backwards compatible.
The rendezvous mechanism MUST be able to natively transport im:
URIs or automatically translate im: URIs [24] into the addressing
identifiers of the rendezvous protocol.
To use a rendezvous mechanism with MSRP, an RFC must be prepared
describing how it exchanges MSRP URIs and meets these requirements
listed here. This document provides such a description for the use
of MSRP in the context of SIP and SDP.
SIP meets these requirements for a rendezvous mechanism. The MSRP
URLs are exchanged using SDP in an offer/answer exchange via SIP.
The exchanged SDP can also be used to negotiate MSRP extensions.
This SDP can be secured using any of the mechanisms available in SIP,
including using the sips mechanism to ensure transport security
across intermediaries and S/MIME for end-to-end protection of the SDP
entity. SIP can carry arbitrary URIs (including im: URIs) in the
Request-URI, and procedures are available to map im: URIs to sip: or
sips: URIs. It is expected that initial deployments of MSRP will use
SIP as its rendezvous mechanism.
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 content, especially instant messages. This arbitrary (binary) MIME content, especially instant messages. This
section is a non-normative overview of how MSRP works and how it is section is a non-normative overview of how MSRP works and how it is
used with SIP. 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 setup. One SIP user agent (Alice) sends of audio or video media is setup. One SIP user agent (Alice) sends
the other (Bob) a SIP invitation containing an offer the other (Bob) a SIP invitation containing an offer
session-description which includes a session of MSRP. The receiving session-description which includes a session of MSRP. The receiving
skipping to change at page 7, line 37 skipping to change at page 7, line 40
Next she puts the actual content. Finally she closes the request Next she puts the actual content. Finally she closes the request
with an end line: seven hyphens, the transaction identifier / with an end line: seven hyphens, the transaction identifier /
boundary marker and a "$" to indicate this request contains the end boundary marker and a "$" to indicate this request contains the end
of a complete message. 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 4.1. detail in Section 5.1.
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 response to her request. If Alice requests positive acknowledgments,
acknowledgements, Bob sends a REPORT request to Alice confirming the Bob sends a REPORT request to Alice confirming the delivery of her
delivery of her complete message. This is especially useful if Alice complete message. This is especially useful if Alice sent a series
sent a series of SEND request containing chunks of a single message. of SEND request containing chunks of a single message. More on
More on requesting types of reports and errors is described in requesting types of reports and errors is described in Section 5.3.
Section 4.3.
Alice and Bob generally choose their MSRP URLs in such a way that is Alice and Bob generally choose their MSRP URLs in such a way that is
difficult to guess the exact URL. Alice and Bob can reject requests difficult to guess the exact URL. Alice and Bob can reject requests
to URLs they are not expecting to service, and can correlate the to URLs they are not expecting to service, and can correlate the
specific URL with the probable sender. Alice and Bob can also use specific URL with the probable sender. Alice and Bob can also use
TLS [1] to provide channel security over this hop. To receive MSRP TLS [1] to provide channel security over this hop. To receive MSRP
requests over a TLS protected connection, Alice or Bob could requests over a TLS protected connection, Alice or Bob could
advertise URLs with the "msrps" scheme instead of "msrp." advertise URLs with the "msrps" scheme instead of "msrp."
This document specifies MSRP behavior only peer-to-peer session, that This document specifies MSRP behavior only peer-to-peer sessions,
is, for a single hop. But is designed with the expectation that MSRP that is, sessions crossing only a single hop. However, work to
can carry URLs for nodes on the far side of gateways or relays. For specify behavior for MSRP relay devices [20] (referred to herein as
this reason, a URL with the "msrps" scheme makes no assertion about "relays") is occuring as a separate effort. MSRP is designed with
the security properties of other hops, just the next hop. the expectation that MSRP can carry URLs for nodes on the far side of
such relays. For this reason, a URL with the "msrps" scheme makes no
assertion about the security properties of other hops, just the next
hop. The user agent knows the URL for each hop, so it can verify
that each URL has the desired security properties.
MSRP URLs are discussed in more detail in Section 5. MSRP URLs are discussed in more detail in Section 6.
An adjacent pair of busy MSRP nodes (for example two gateways) 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 4.4. discussed in more detail in Section 5.4.
4. Key Concepts 5. Key Concepts
4.1 MSRP Framing and Message Chunking 5.1 MSRP Framing and Message Chunking
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. To support this, MSRP uses a boundary based the overall message. Long chunks may be interruped to ensure
framing mechanism. The header of an MSRP request contains a unique fairness across shared transport connections. To support this, MSRP
boundary string that is used to indicate the end of the request. uses a boundary based framing mechanism. The start line of an MSRP
Following the boundary string at the end of the body data, there is a request contains a unique boundary string that is used to indicate
flag that indicates whether this is the last chunk of data for this the end of the request. Following the boundary string at the end of
message or whether the message will be continued in a subsequent the body data, there is a flag that indicates whether this is the
chunk. There is also a Byte-Range header in the request that last chunk of data for this message or whether the message will be
indicates the overall position of this chunk inside the complete continued in a subsequent chunk. There is also a Byte-Range header
message. in the request that indicates the overall position of this 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: 456 Message-ID: 456
Byte-Range: 1-4/8 Byte-Range: 1-4/8
Content-Type: text/plain Content-Type: text/plain
abcd abcd
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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. the same connection.
The ability to interrupt messages is needed so that TCP connections The ability to interrupt messages is needed so that TCP connections
can be shared. Connection sharing is necessary for "fair" allocation can be shared. Connection sharing is necessary for "fair" allocation
of bandwidth in congestion situations and for allowing MSRP network of bandwidth in congestion situations and for allowing MSRP network
elements that have a very large number of concurrent connections to elements that have a very large number of concurrent connections to
different users. different users.
4.2 MSRP Addressing 5.2 MSRP Addressing
MSRP entities are addressed using URLs. The MSRP URL schemes are MSRP entities are addressed using URLs. The MSRP URL schemes are
defined in Section 5. The syntax of the To-Path and From-Path defined in Section 6. The syntax of the To-Path and From-Path
headers allow for a list of URLs. This was done to allow the headers each allow for a list of URLs. This was done to allow the
protocol to work with gateways or relays defined in the future, to protocol to work with gateways or relays defined in the future, to
provide a complete path to the end recipient. When two MSRP nodes provide a complete path to the end recipient. When two MSRP nodes
communicate directly they need only one URL in the To-Path list and communicate directly they need only one URL in the To-Path list and
one URL in the From-Path list. one URL in the From-Path list.
4.3 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 [29] gateway, it may forward the message over XMPP. an MSRP to XMPP [28] gateway, it may forward the message over XMPP.
The XMPP side may later indicate that the request did not work. At The XMPP side may later indicate that the request did not work. At
this point, the MSRP receiver may need to indicate that the request this point, the MSRP receiver may need to indicate that the request
did not succeed. There are two important concepts here: first, the did not succeed. There are two important concepts here: first, the
hop by hop delivery of the request may succeed or fail; second, the hop by hop delivery of the request may succeed or fail; second, the
end result of the request may be successfully processed or not. The end result of the request may be successfully processed or not. The
first type of status is referred to as "transaction status" and may first type of status is referred to as "transaction status" and may
be returned in response to a request. The second type of status is be returned in response to a request. The second type of status is
referred to as "request status" and may be returned in a REPORT referred to as "request status" and may be returned in a REPORT
transaction. transaction.
skipping to change at page 10, line 41 skipping to change at page 10, line 41
"no" in many public systems to reduce load but is used in some "no" in many public systems to reduce load but is used in some
current enterprise systems, such as systems used for securities current enterprise systems, such as systems used for securities
trading. A Report-Failure value of "no" is useful for sending system trading. A Report-Failure 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 Report-Failure of causing a response explosion to the sender. A Report-Failure 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 but some other systems choose to use a value of message failed but some other systems choose to use a value of
"partial" to reduce the load on the servers caused by 200 OK "partial" to reduce the load on the servers caused by 200 OK
responses, but still allow error responses to be sent in many cases. responses, but still allow error responses to be sent in many cases.
4.4 MSRP Connection Model 5.4 MSRP Connection Model
When MSRP wishes to send a request to a peer identified by an MSRP When MSRP wishes to send a request to a peer identified by an MSRP
URL, it first needs a connection, with the appropriate security URL, it first needs a transport connection, with the appropriate
properties, to the host specified in the URL. If the sender already security properties, to the host specified in the URL. If the sender
has such a connection, that is, one associated with the same host, already has such a connection, that is, one associated with the same
port, and URL scheme, then it SHOULD reuse that connection. host, port, and URL scheme, then it SHOULD reuse that connection.
When a new MSRP session is created, the convention is that the When a new MSRP session is created, the element that sent the SDP
element that sent the SDP offer MUST immediately issue a SEND request offer MUST immediately issue a SEND request to the answerer. This
to the answerer. This request MAY have a empty body, or MAY carry request MAY have a empty body, or MAY carry content.
content.
When a new connection needs to be formed, the element looks at the Likewise, the offerer MUST open the transport connection to the
URL to decide on the type of connection (TLS, TCP, etc.) then answerer, if a new connection is required. However, this requirement
connects to the host indicated by the URL, following the URL may be weakened if standardized mechanisms for negotiating the
resolution rules in Section 5.2. For connections using the msrps: connection direction become available, and is implemented by both
scheme, the SubjectAltName in the received certificate MUST match the parties to the connection.
hostname part of the URL and the certificate MUST be valid, including
having a date that is valid and being signed by an acceptable When an element needs to form a new connection, it looks at the URL
certificate authority. At this point the device that initiated the to decide on the type of connection (TLS, TCP, etc.) then connects to
connection can assume that this connection is with the correct host. the host indicated by the URL, following the URL resolution rules in
Section 6.2. Connections using the msrps: scheme MUST use TLS. The
SubjectAltName in the received certificate MUST match the hostname
part of the URL and the certificate MUST be valid, including having a
date that is valid and being signed by an acceptable certificate
authority. At this point the device that initiated the connection
can assume that this connection is with the correct host.
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 know the identity of the connecting host. When mutual connection can immediately know the identity of the connecting host.
TLS authentication is not used, the listening device MUST wait until When mutual TLS authentication is not used, the listening device MUST
it receives a request on the connection to determine the identity of wait until it receives a request on the connection, at which it
the connecting device. infers the identity of the connecting device from the associated SDP.
When the first request arrives, its To-Path header field should When the first request arrives, its To-Path header field should
contain a URL that the listening element handed out in the SDP for a contain a URL that the listening element handed out in the SDP for a
session. The element that accepted the connection looks up the URL session. The element that accepted the connection looks up the URL
in the received request, and determines which session it matches. If in the received request, and determines which session it matches. If
a match exists, the node MUST assume that the host that formed the a match exists, the node MUST assume that the host that formed the
connection is the host that this URL was given to. If no match connection is the host that this URL was given to. If no match
exists, the node MUST reject the request with a 481 response. The exists, the node MUST reject the request with a 481 response. The
node MUST also check to make sure the session is not already in use node MUST also check to make sure the session is not already in use
on another connection. If so, it MUST reject the request with a 506 on another connection. If so, it MUST reject the request with a 506
response. response.
If it were legal to have multiple connections associated with the If it were legal to have multiple connections associated with the
same session, a security problem would exist. If the initial SEND same session, a security problem would exist. If the initial SEND
request is not protected, an eavesdropper might learn the URL, and request is not protected, an eavesdropper might learn the URL, and
use it to insert messages into the session via a different use it to insert messages into the session via a different
connection. connection.
If a connection fails for any reason, then an MSRP endpoint MUST If a connection fails for any reason, then an MSRP endpoint MUST
consider failed any sessions associated with the connection as well. consider any sessions associated with the connection as also having
When an endpoint notices such a failure, it MAY attempt to re-create failed. When an endpoint notices such a failure, it MAY attempt to
any such sessions. If it chooses to do so, it MUST use new SDP re-create any such sessions. If it chooses to do so, it MUST use new
exchange. If a replacement session is successfully created, SDP exchange, for example, in a SIP re-invite or update [11]. If a
endpoints MAY attempt to resend any content for which delivery on the replacement session is successfully created, endpoints MAY attempt to
original session could not be confirmed. If it does this, the resend any content for which delivery on the original session could
Message-ID values for the resent messages MUST match those used in not be confirmed. If it does this, the Message-ID values for the
the initial attempts. If the receiving endpoint receives more than resent messages MUST match those used in the initial attempts. If
one message with the same Message-ID. It SHOULD assume that the the receiving endpoint receives more than one message with the same
messages are duplicates. It MAY take any action based on that Message-ID. It SHOULD assume that the messages are duplicates. It
knowledge, but SHOULD NOT present the duplicate messages to the user MAY take any action based on that knowledge, but SHOULD NOT present
without warning of the duplicates. the duplicate messages to the user without warning of the
duplication.
In this situation, the endpoint MUST choose Message-ID values so that In this situation, the endpoint MUST choose Message-ID values so that
they are unique in the context of both the original session and the they are unique in the context of both the original session and the
replacement session. replacement session.
When endpoints create a new session in this fashion, the chunks for a When endpoints create a new session in this fashion, the chunks for a
given logical message MAY be split across the sessions. However, given logical message MAY be split across the sessions. However,
endpoints SHOULD NOT split chunks between sessions under normal endpoints SHOULD NOT split chunks between sessions under non-failure
circumstances. circumstances.
If a connection fails, the sender SHOULD attempt to re-setup the URL If an endpoint attempts to re-create a failed session in this manner,
path using a new offer, for example, in a SIP re-invite or update it MUST NOT assume that the MSRP URLs in the SDP will be the same as
[12]. It MUST not assume that the new URLs in the SDP will be the the old ones.
same as the old ones. A connection SHOULD not be closed while there
are sessions that are using this connection.
5. MSRP URLs A connection SHOULD not be closed while there are sessions associated
with it.
An MSRP URL follows a subset of the URL syntax in Appendix A of 6. MSRP URLs
RFC2396 [10], with a scheme of "msrp" or "msrps":
MSRP_urls = msrp-scheme "://" [userinfo "@"] hostport ["/" URLs using the MSRP and MSRPS schema are used to identify a session
resource] ";" transport of instant messages at a particular MSRP device. MSRP URLs are
msrp-scheme = "msrp" / "msrps" ephemeral; an MSRP device may use a different MSRP URL in a different
resource = 1*unreserved session. An MSRP URL generally has no meaning outside of the
transport = "tcp" / ALPHANUM associated session.
The constructions for "userinfo", "hostport", and "unreserved" are An MSRP URL follows a subset of the URL syntax in Appendix A of
detailed in RFC2396 [10]. URLs designating MSRP over TCP MUST RFC2396bis [9], with a scheme of "msrp" or "msrps". The syntax is
include the "tcp" parameter. If some other transport is used, the described in Section 9.
"tcp" parameter MUST NOT be present.
The constructions for "userinfo", and "unreserved" are detailed in
RFC2396bis [9]. In order to allow IPV6 addressing, the construction
for hostport is that used for SIP in RFC3261. URLs designating MSRP
over TCP MUST include the "tcp" transport parameter.
Since this document only specifies MSRP over TCP, all MSRP URLs Since this document only specifies MSRP over TCP, all MSRP URLs
herein use the "tcp" parameter. Documents that provide bindings herein use the "tcp" transport parameter. Documents that provide
on other transports should define respective parameters for those bindings on other transports should define respective parameters
transports. for those transports.
An MSRP URL hostport field identifies a participant in an MSRP An MSRP URL hostport field identifies a participant in a particular
session. If the hostport contains a numeric IP address, it MUST also MSRP session. If the hostport contains a numeric IP address, it MUST
contain a port. The resource part identifies a particular session also contain a port. The session-id part identifies a particular
the participant. The absence of the resource part indicates a session the participant. The absence of the session-id part
reference to an MSRP host device, but does not specifically refer to indicates a reference to an MSRP host device, but does not
a particular session resource. specifically refer to a particular session.
A scheme of "msrps" indicates the underlying connection MUST be A scheme of "msrps" indicates the underlying connection MUST be
protected with TLS. protected with TLS.
MSRP has an IANA registered recommended port defined in Section 14.1. MSRP has an IANA registered recommended port defined in Section 15.1.
This value is not a default, as the URL negotiation process described This value is not a default, as the URL negotiation process described
herein will always include explicit port numbers. However, the URLs herein will always include explicit port numbers. However, the URLs
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.
The server part will typically not contain a userinfo component, but The server part will typically not contain a userinfo component, but
MAY do so to indicate a user account for which the session is valid. MAY do so to indicate a user account for which the session is valid.
Note that this is not the same thing as identifying the session Note that this is not the same thing as identifying the session
itself. If a userinfo component exists, it MUST be constructed only itself. If a userinfo component exists, it MUST be constructed only
from "unreserved" characters, to avoid a need for escape processing. from "unreserved" characters, to avoid a need for escape processing.
Escaping MUST NOT be used in an MSRP URL. Furthermore, a userinfo Escaping MUST NOT be used in an MSRP URL. Furthermore, a userinfo
part MUST NOT contain password information. part MUST NOT contain password information.
The limitation of userinfo to unreserved characters is an
additional restriction to the userinfo definition in RFC2396bis.
That version allows reserved characters. The additional
restriction is to avoid the need for escaping.
The following is an example of a typical MSRP URL: The following is an example of a typical MSRP URL:
msrp://host.example.com:8493/asfd34;tcp msrp://host.example.com:8493/asfd34;tcp
5.1 MSRP URL Comparison 6.1 MSRP URL Comparison
MSRP URL comparisons MUST be performed according to the following MSRP URL comparisons MUST be performed according to the following
rules: rules:
1. The scheme must match exactly. 1. The scheme must match exactly.
2. If the hostpart contains an eplicit IP address, and/or port, 2. If the hostpart contains an explicit IP address, and/or port,
these are compared numerically. Otherwise, hostpart is compared these are compared for address and port equivalency. Otherwise,
as a case insensitive character string. hostpart is compared as a case insensitive character string.
3. If the port exists explicitly in either URL, then it must match 3. If the port exists explicitly in either URL, then it must match
exactly. An URL with an explicit port is never equivalent to exactly. An URL with and explicit port is never equivalent to
another with no port specified. another with no port specified.
4. The resource part is compared as case sensitive. A URL without a 4. The session-id part is compared as case sensitive. A URL without
resource part is never equivalent to one that includes a resource a session-id part is never equivalent to one that includes one.
part.
5. URLs with different "transport" parameters never match. Two URLs 5. URLs with different "transport" parameters never match. Two URLs
that are identical except for transport are not equivalent. that are identical except for transport are not equivalent.
6. Userinfo parts are not considered for URL comparison. 6. Userinfo parts are not considered for URL comparison.
Path normalization is not relevant for MSRP URLs. Escape Path normalization is not relevant for MSRP URLs. Escape
normalization is not required, since the relevant parts are limited normalization is not required, since the relevant parts are limited
to unreserved characters. to unreserved characters.
5.2 Resolving MSRP Host Device 6.2 Resolving MSRP Host Device
An MSRP host device is identified by the server part of an MSRP URL. An MSRP host device is identified by the server part of an MSRP URL.
If the server part contains a numeric IP address and port, they MUST If the server part contains a numeric IP address and port, they MUST
be used as listed. be used as listed.
If the server part contains a host name and a port, the connecting If the server part contains a host name and a port, the connecting
device MUST determine a host address by doing an A or AAAA DNS query, device MUST determine a host address by doing an A or AAAA DNS query,
and use the port as listed. 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 URL uses prior to resolution. This is always true for the MSRP URL uses
described in this document, that is, URLs always created and described in this document, that is, URLs exchanged in the SDP
consumed by automata, rather than by humans. The introduction of offer and answer. The introduction of relays may create
relays may create situations where this is not the case. For situations where this is not the case. For example, the MSRP URL
example, the MSRP URL that a user enters into a client to that a user enters into a client to configure it to use a relay
configure it to use a relay may be intended to be easily may be intended to be easily remembered and communicated by
remembered and communicated by humans, and therefore is likely to humans, and therefore is likely to omit the port. Therefore, the
omit the port. Therefore, the relay specification [21] may relay specification [20] may describe additional steps to resolve
describe additional steps to resolve the port number. the port 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.
6. Method-Specific Behavior 7. Method-Specific Behavior
6.1 Constructing Requests 7.1 Constructing Requests
To form a new request, the sender creates a unique transaction To form a new request, the sender creates a unique transaction
identifier and uses this and the method name to create an MSRP identifier and uses this and the method name to create an MSRP
request start line. Next, the sender places the target path in a request start line. Next, the sender places the target path in a
To-Path header, and the sender's URL in a From-Path header. If To-Path header, and the sender's URL in a From-Path header. If
multiple URLs are present in the To-Path, the leftmost is the first multiple URLs are present in the To-Path, the leftmost is the first
URL visited; the rightmost URL is the last URL visited. The URL visited; the rightmost URL is the last URL visited. The
processing then becomes method specific. Additional method-specific processing then becomes method specific. Additional method-specific
headers are added as described in the following sections. headers are added as described in the following sections.
After any method-specific headers are added, processing continues to After any method-specific headers are added, processing continues to
handle a body, if present. A body in a Non-SEND request MUST NOT be handle a body, if present. A body in a Non-SEND request MUST NOT be
longer than 2048 octets. If the request has a body, it must contain longer than 2048 octets. If the request has a body, it must contain
a Content-Type header field. It may contain other MIME specific a Content-Type header field. It may contain other MIME specific
headers. The Content-Type header MUST be the last header line. The headers. The Content-Type header MUST be the last header line. The
body MUST be separated from the headers with an extra CRLF. body MUST be separated from the headers with an extra CRLF.
The boundary marker that terminates the body MUST be preceded by a The boundary marker that terminates the body MUST be preceded by a
CRLF that is not part of the body and then seven "-" (minus sign) CRLF that is not part of the body and then seven "-" (minus sign)
characters. After the boundary marker, there MUST be a flag characters. After the boundary marker, there MUST be a flag
character that is a "$" (for the last chunk of the complete character. If the chunk represents the data that forms the end of
message), "#" (for the last chunk of an aborted message), or "+" (for the complete message, the flag value MUST be a "$". If sender is
chunks other than the last). If the chunk represents the data that abandoning an incomplete message, and intends to send no further
forms the end of the complete message, the flag value MUST be a "$". chunks in that message, it MUST be a "#". Otherwise it MUST be a
If sender is abandoning an incomplete message, and intends to send no "+".
further chunks in that message, it MUST be a "#". Otherwise it MUST
be a "+".
If the request contains a body, the sender MUST check the body to If the request contains a body, the sender MUST ensure that the
insure that the closing sequence (a CRLF, seven hyphens, and the closing sequence (a CRLF, seven hyphens, and the transaction
transaction identifier) is not present in the body. If the closing identifier) is not present in the body. If the closing sequence is
sequence is present in the body, the sender MUST choose a new present in the body, the sender MUST choose a new transaction
transaction identifier that is not present in the body, and add the identifier that is not present in the body, and add the closing
closing sequence, including the "$", "#", or "+" character, and a sequence, including the "$", "#", or "+" character, and a final CRLF.
final CRLF.
Finally, requests which have no body MUST NOT contain a Content-Type Finally, requests which have no body MUST NOT contain a Content-Type
header or any other MIME specific header. Bodiless requests MUST header or any other MIME specific header. Bodiless requests MUST
contain a closing sequence after the final header. contain a closing sequence after the final header.
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 4.4) 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.
6.1.1 Delivering SEND requests 7.1.1 Delivering 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
unique Message-ID. This ID MUST be unique within the scope of the unique Message-ID. This ID MUST be unique within the scope of the
session. If the message is larger than 2048 octets in length, it session. If necessary, it breaks the message into chunks. It then
either generates an interruptible chunk (which is RECOMMENDED), or it generates a SEND request for each chunk, following the procedures for
MAY break the complete message into chunks of 2048 octets. It then constructing requests (Section 7.1).
generates a SEND request for each chunk, following the procedures
for constructing requests (Section 6.1).
Each chunk MUST contain a Message-ID header field containing the Each chunk MUST contain a Message-ID header field containing the
Message-ID. If the sender wishes non-default status reporting, it Message-ID. If the sender wishes non-default status reporting, it
MUST insert a Report-Failure and/or Report-Success header field with MUST insert a Report-Failure and/or Report-Success header field with
an appropriate value. All chunks of the same message MUST use the an appropriate value. All chunks of the same message MUST use the
same Report-Failure and Report-Success values in their SEND requests. same Report-Failure and Report-Success values in their SEND requests.
If success reports are requested, i.e. the value of the If success reports are requested, i.e. the value of the
Report-Success header is "yes", the sending device MAY wish to run a Report-Success header 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
skipping to change at page 16, line 48 skipping to change at page 16, line 51
by a one, rather than a zero. by a 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 MUST
include a Byte-Range header field. The range-start field 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 (that is, a value of one). The range-end field SHOULD message (that is, a value of one). The range-end field SHOULD
indicate the position of the last byte in the body, if known. It indicate the position of the last byte in the body, if known. It
MUST take the value of "*" if the position is unknown, or if the MUST take the value of "*" if the position is unknown, or if the
request needs to be interruptible. The total field SHOULD contain request needs to be interruptible. The total field SHOULD contain
the total size of the message, if known. The total field MAY contain the total size of the message, if known. The total field MAY contain
a "*" if the total size of the message is not known in advance. All a "*" if the total size of the message is not known in advance. The
chunks other than the last MUST include a "+" character in the sender MUST send all chunks in Byte-Range order. (However, the
continuation field of the closing line. The final chunk MUST use a receiver cannot assume the requests will be delivered in order, as
"$" character if it completes the message, or a "#" if the sender is intervening relays may have changed the order.)
aborting the message. The sender MUST send all chunks in Byte-Range
order. (However, the receiver cannot assume the requests will be
delivered in order, as an intervening relay may have changed the
order.)
To insure fairness over a connection, senders MUST NOT send chunks To insure 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. A sender can use one of the following two strategies interrupt them (meaning that any chunk with a body of greater than
to satisfy this requirement. The sender is STRONGLY RECOMMENDED to 2048 octets will have a "*" character in the range-end field). A
send messages larger than 2048 octets using as few chunks as sender can use one of the following two strategies to satisfy this
possible, interrupting chunks (at least 2048 octets long) when other requirement. The sender is STRONGLY RECOMMENDED to send messages
traffic is waiting to use the same connection. Alternatively, the larger than 2048 octets using as few chunks as possible, interrupting
sender MAY simply send chunks in 2048 octet increments until the chunks (at least 2048 octets long) when other traffic is waiting to
final chunk. Note that the former strategy results in markedly more use the same connection. Alternatively, the sender MAY simply send
efficient use of the connection. All MSRP nodes MUST be able to chunks in 2048 octet increments until the final chunk. Note that the
receive chunks of any size from 0 octets to the maximum number of former strategy results in markedly more efficient use of the
octets they can receive for a complete message. Senders SHOULD NOT connection. All MSRP nodes MUST be able to receive chunks of any
break messages into chunks smaller than 2048 octets, except for the size from 0 octets to the maximum number of octets they can receive
final chunk of a complete message. for a complete message. Senders SHOULD NOT break messages into
chunks smaller than 2048 octets, except for the final chunk of a
A SEND request is interruptible if it either has no Byte-Range header complete message.
field, or has such a field with a "*" in the last-byte sub-field.
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 has already been written to the connection, then writing out the
boundary string to end the chunk. It can then be resumed in a boundary string to end the chunk. It can then be resumed in a
another chunk with the same Message-ID and a Byte-Range header range another chunk with the same Message-ID and a Byte-Range header range
start field containing the position of the first byte after the start field containing the position of the first byte after the
interruption occurred. interruption occurred.
SEND requests larger than 2k MUST be interrupted to send pending SEND requests larger than 2k MUST be interrupted to send pending
response or REPORT requests. If multiple SEND requests from response or REPORT requests. If multiple SEND requests from
different sessions are concurrently being sent over the same different sessions are concurrently being sent over the same
connection, the device SHOULD implement some scheme to alternate connection, the device SHOULD implement some scheme to alternate
between them such that each concurrent request gets a chance to send between them such that each concurrent request gets a chance to send
some fair portion of data at regular intervals suitable to the some fair portion of data at regular intervals suitable to the
application. application.
The sender MUST NOT assume that a message is received by the peer The sender MUST NOT assume that a message is received by the peer
with the same chunk allocation it was sent with. An intervening with the same chunk allocation with which it was sent. An
relay could possibly break SEND requests into smaller chunks, or intervening relay could possibly break SEND requests into smaller
aggregate multiple chunks into larger ones. chunks, or aggregate multiple chunks into larger ones.
The default disposition of body is "render". If the sender wants The default disposition of body is "render". If the sender wants
different disposition, it MAY insert a Content-Disposition header. different disposition, it MAY insert a Content-Disposition header.
Since MSRP is a binary protocol, transfer encoding MUST be "binary". Since MSRP is a binary protocol, transfer encoding MUST be "binary".
6.1.2 Sending REPORT requests 7.1.2 Sending REPORT requests
REPORT requests are similar to SEND requests, except that report REPORT requests are similar to SEND requests, except that report
requests MUST NOT include Report-Success or Report-Failure header requests MUST NOT include Report-Success or Report-Failure header
fields, and MUST contain a Status header field. REPORT requests MUST fields, and MUST contain a Status header field. REPORT requests MUST
contain the Message-ID header from the original SEND request. contain the Message-ID header from the original SEND request.
If an MSRP element receives a REPORT for a Message-ID it does not If an MSRP element receives a REPORT for a Message-ID it does not
recognize, it SHOULD silently ignore the REPORT. recognize, it SHOULD silently ignore the REPORT.
An MSRP endpoint MUST be able to generate success REPORT requests. An MSRP endpoint MUST be able to generate success REPORT requests.
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 assocated 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.
Since REPORT requests are not interruptible, the size of such a body Since REPORT requests are not interruptible, the size of such a body
MUST NOT exceed 2 kilobytes. MUST NOT exceed 2048 octets.
An endpoint MUST send a success report if it successfully receives a An endpoint MUST send a success report if it successfully receives a
SEND request which contained a Report-Success value of "yes" and SEND request which contained a Report-Success value of "yes" and
either contains a complete message, or contains the last chunk needed either contains a complete message, or contains the last chunk needed
to complete the message. This request is sent following the normal to complete the message. This request is sent following the normal
procedures (Section 6.1), with a few additional requirements. procedures (Section 7.1), with a few additional requirements.
The endpoint inserts a To-Path header field containing the From-Path The endpoint inserts a To-Path header field containing the From-Path
value from the original request, and a From-Path header containing value from the original request, and a From-Path header containing
the URL identifying itself in the session. The endpoint then inserts the URL identifying itself in the session. The endpoint then inserts
a Status header field with a namespace of "000", a short-status of a Status header field with a namespace of "000", a short-status of
"200" and a relevant Reason phrase, and a Message-ID header field "200" and a relevant Reason phrase, and a Message-ID header field
containing the value from the original request. containing the value from the original request.
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 Report-Success header field, or contained such a either contained no Report-Success header field, or contained such a
field with a value of "no". That is, if no Report-Success header field with a value of "no". That is, if no Report-Success 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."
6.1.3 Failure REPORT Generation 7.1.3 Failure REPORT Generation
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 Report-Failure header either was not present for some reason, and the Report-Failure header either was not present
in the original request, or had a value of "yes", it SHOULD simply in the original request, or had a value of "yes", it SHOULD simply
include the appopriate error code in the transaction respons. include the appropriate error code in the transaction response.
However, there may be situations where the error cannot be determined However, there may be situations where the error cannot be determined
quickly, such as when the endpoint is a gateway that must wait for a quickly, such as when the endpoint is a gateway that must wait for a
downstream network to indicate an error. In this situation, it MAY downstream network to indicate an error. In this situation, it MAY
send a 200 OK response to the request, and then send a failure REPORT send a 200 OK response to the request, and then send a failure REPORT
request when the error is detected. request when the error is detected.
If the endpoint receives a SEND request with a Report-Failure header If the endpoint receives a SEND request with a Report-Failure 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 SHOULD NOT send an MSRP response. If the value is "partial", it and MUST NOT send a transaction response. If the value is "partial",
SHOULD NOT send a 200 response to the request, but SHOULD send a it MUST NOT send a transaction response to the request, but SHOULD
non-200 class response if appropriate. send an appropriate non-200 class responsea failure occurs.
As stated above, if no Report-Failure header is present, it MUST be As stated above, if no Report-Failure header is present, it MUST be
treated the same as a Report-Failure header with value of "yes". treated the same as a Report-Failure header with value of "yes".
Construction of failure REPORT requests is identical to that for Construction of failure REPORT requests is identical to that for
success reports, except the Status header code and reason fields MUST success reports, except the Status header code and reason fields MUST
contain appropriate error codes. Any error response code defined in contain appropriate error codes. Any error response code defined in
this specification MAY also be used in failure reports. this specification MAY also be used in failure reports.
If a failure report is sent in response to a SEND request that If a failure report is sent in response to a SEND request that
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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 on a session that is no longer valid. NOT send a REPORT request on a session that is no longer valid.
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. We document, and will be considered in a separate document. 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.
6.2 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
Report-Failure header value of "yes", or does not contain a Report-Failure header value of "yes", or does not contain a
Report-Failure header field at all, it MUST immediately generate a Report-Failure 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 Report-Failure header value of "partial", and the receiver contains a Report-Failure header value of "partial", and the receiver
is unable to process the request, it SHOULD immediately generate a is unable to process the request, it SHOULD immediately generate a
response. 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 appropriate response code and reason fields.
The transaction identifier in the response start line MUST match the The transaction identifier in the response start line MUST match the
transaction identifier from the original request. 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 last (right-most) URI in the
From-Path header field of the request. (Unlike other methods, From-Path header field of the request. (Responses to SEND requests
responses to SEND requests are returned only to the previous hop.) are returned only to the previous hop.) For responses to all other
For responses to all other requests, the To-Path header field request methods, the To-Path header field contains the full path back
contains the full path back to the original sender. This full path to the original sender. This full path is generated by taking the
is generated by taking the list of URLs from the From-Path of the list of URLs from the From-Path of the original request, reversing
original request, reversing the list, and writing the reversed list the list, and writing the reversed list into the To-Path of the
into the To-Path of the response. (Legal REPORT requests do not response. (Legal REPORT requests do not request responses, so this
request responses, so this specification doesn't exercise the specification doesn't exercise the behavior described above, however
behavior described above, however we expect that extensions for we expect that extensions for gateways and relays will need such
gateways and 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
URL that identifies it in the context of the session, followed by the URL that identifies it in the context of the session, followed by the
closing sequence after the last header field. The response MUST be closing sequence after the last header field. The response MUST be
transmitted back on the same connection on which the original request transmitted back on the same connection on which the original request
arrived. arrived.
6.3 Receiving Requests 7.3 Receiving Requests
The receiving endpoint must first check the URL in the To-Path to The receiving endpoint must first check the URL 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 URL, which request is received, the To-Path will have exactly one URL, 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, and connection on which the request arrived. If this is not true, and
the request contained a Report-Failure header value of "no", then the the request contained a Report-Failure header value of "no" or
receiver SHOULD quietly ignore the request. If the Report-Failure "partial", then the receiver SHOULD quietly ignore the request. If
header is not present, or had any other value, then the receiver MUST the Report-Failure header is not present, or had a value of "yes",
return a 481 response. then the receiver MUST return a 481 response.
Further request processing by the receiver is method specific. Further request processing by the receiver is method specific.
6.3.1 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 message. If the request contains no Byte-Range header, or larger message. If the request contains no Byte-Range header, 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. It
forms a virtual buffer to receive the message, keeping track of which forms a virtual buffer to receive the message, keeping track of which
bytes have been received and which are missing. The receiver takes bytes have been received and which are missing. The receiver takes
the data from the request and places it in the appropriate place in the data from the request and places it in the appropriate place in
the buffer. The receiver MUST determine the actual length of each the buffer. The receiver SHOULD determine the actual length of each
chunk by inspecting the payload itself; it is possible the body is chunk by inspecting the payload itself; it is possible the body is
shorter than the range-end field indicates. This can occur if the shorter than the range-end field indicates. This can occur if the
sender interrupted a SEND request unexpectedly. It is worth nothing sender interrupted a SEND request unexpectedly. It is worth nothing
that the chunk that has a termination character of "$" defines the that the chunk that has a termination character of "$" defines the
total length of the message. total length of the message.
It is technically illegal for the sender to prematurely interrupt
a request that had anything other "*" in the last-byte position.
But having the receiver calculate a chunk length based on actual
content adds resilience in the face of sender erros. errors.
Since this should never happen with compliant senders, this only
has a SHOULD strength.
Receivers MUST not assume the chunks will be delivered in order or Receivers MUST not assume the chunks will be delivered in order or
that they will receive all the chunks with "+" flags before they 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 chunks failure, it is possible for information to be duplicated. If chunks
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 takes precedence (even though this message, the last chunk received takes precedence (even though this
may not have been the last chunk transmitted). For example, if bytes may not have been the last chunk transmitted). For example, if bytes
1 to 100 was received and a chunk arrives that contains bytes 50 to 1 to 100 was received and a chunk arrives that contains bytes 50 to
150, this second chunk will overwrite bytes 50 to 100 of the data 150, this second chunk will overwrite bytes 50 to 100 of the data
that had already been received. Although other schemes work, this is that had already been received. Although other schemes work, this is
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copy could be done. This approach results in a system that is as copy could be done. This approach results in a system that is as
fast as framing based on specifying the body length in the headers of fast as framing based on specifying the body length in the headers of
the request, but also allows for the interruption of messages. the request, but also allows for the interruption of messages.
What is done with the body is outside the scope of MSRP and largely What is done with the body is outside the scope of MSRP and largely
determined by the MIME Content-Type and Content-Disposition. The determined by the MIME Content-Type and Content-Disposition. The
body MAY be rendered after the whole message is received or partially body MAY be rendered after the whole message is received or partially
rendered as it is being received. rendered as it is being received.
If the SEND request contained a Content-Type header field indicating If the SEND request contained a Content-Type header field indicating
an unsupported MIME type, the receiver SHOULD send a 415 response, if an unsupported MIME type, the receiver SHOULD send a 415 response or
allowed by the Report-Failure header field. All MSRP endpoints MUST failure report, as appropriate for the Report-Failure header field
be able to receive the multipart/mixed and multipart/alternative MIME value. All MSRP endpoints MUST be able to receive the
types. multipart/mixed and multipart/alternative MIME types.
6.3.2 Receiving REPORT requests If the Report-Success header was set to "yes", then when a complete
message has been received, the receiver MUST send a sucess REPORT
with a byte range covering the whole message. If the Report-Success
header is not set to "no", then the receiver MAY generate incremental
success REPORTs as the chunks are recieved. These can be sent
periodically and cover all 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.
When an endpoint receives a REPORT request, it may correlate it to 7.3.2 Receiving REPORT requests
the original SEND request using the Message-ID and the Byte-Range, if
When an endpoint receives a REPORT request, it correlates it to the
original SEND request using the Message-ID and the Byte-Range, if
present. If it requested success reports, then it SHOULD keep enough present. If it requested success reports, then it SHOULD keep enough
state about each outstanding sent message so that it can correlate state about each outstanding sent message so that it can correlate
REPORT requests to the original messages. 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
with a namespace field of "000", it SHOULD interpret the report in with a namespace field of "000", it SHOULD 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 short-code field. with a response code matching the short-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 case response for a chunk that is currently being delivered. In this case
the entire message corresponding to that chunk should be aborted. the entire message corresponding to that chunk should be aborted, by
including the "#" character in the continuation field of the closing.
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.
MSRP Modes MUST NOT send MSRP responses to REPORT requests. When a device that sent a SEND request receives a failure REPORT
indicating that a particular byte range was not received,it MUST
treat the session as failed. If it wishes to recover, it MUST first
re-negotiate the URLs at the signaling level then resend that range
of bytes of the message on the resulting new session.
7. Using MSRP with SIP MSRP Modes MUST NOT send a MSRP REPORT in responses to REPORT
requests.
7.1 SDP Offer-Answer Exchanges for MSRP Sessions 8. Using MSRP with SIP
8.1 SDP Offer-Answer Exchanges for MSRP Sessions
MSRP sessions will typically be initiated using the Session MSRP sessions will typically be initiated using the Session
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 setup MSRP This document defines a handful of new SDP parameters to setup MSRP
sessions. These are detailed below and in the IANA Considerations sessions. These are detailed below and in the IANA Considerations
section. section.
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>
An offered or accepted MSRP media-line MUST have the following value An offered or accepted MSRP media-line MUST have the following value
exactly, with the exception that the port field MAY be set to zero. exactly, with the exception that the port field MAY be set to any
(According to [3], a user agent that wishes to accept an offer, but value. (The port value will be ignored, unless it is zero.
According to [3], a user agent that wishes to accept an offer, but
not a specific media-line MUST set the port number of that media-line not a specific media-line MUST set the port number of that media-line
to zero (0).) to zero (0) in the response.)
m=message 9 msrp * m=message 9 msrp *
While MSRP could theoretically carry any media type, "message" is While MSRP could theoretically carry any media type, "message" is
appropriate. For MSRP, the port number is always ignored--the appropriate. For MSRP, the port number is always ignored--the
actual port number is provided in an MSRP URL. Instead a dummy actual port number is provided in an MSRP URL. Instead a dummy
value is used, which is always ignored if non-zero. The protocol value is used, which is not meaningful if non-zero. The protocol
is always "msrp", and the value of the format list is always a is always "msrp", and the value of the format list is always a
single asterisk character ("*"). single asterisk character ("*").
An MSRP media-line is always accompanied by a mandatory "path" An MSRP media-line is always accompanied by a mandatory "path"
attribute. This attribute contains a space separated list of URLs attribute. This attribute contains a space separated list of URLs
that must be visited to contact the user agent advertising this that must be visited to contact the user agent advertising this
session-description. If more than one URL is present, the leftmost session-description. If more than one URL is present, the leftmost
URL is the first URL that must be visited to reach the target URL is the first URL that must be visited to reach the target
resource. (The path list can contain multiple URLs to allow for the resource. (The path list can contain multiple URLs to allow for the
deployment of gateways or relays in the future.) MSRP deployment of gateways or relays in the future.) MSRP
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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 MIME type in the context of one wrapper, it is endpoint understands a MIME type in the context of one wrapper, it is
assumed to understand it in the context of any other acceptable 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 [13] gateway device may require all messages to be wrapped CPIM [12] gateway device may require all messages to be wrapped
inside message/cpim bodies, but may allow several content types inside message/cpim bodies, but may allow several content types
inside the wrapper. If the gateway were to specify the wrapped inside the wrapper. If the gateway were to specify the wrapped
types in the accept-types attribute, its peer might attempt to use types in the accept-types attribute, its peer might attempt to use
those types without the wrapper. those types without the wrapper.
An endpoint MAY indicate the maximim size message they wish to If the recipient of an offer does not understand any of the
receive using the max-size a-line attribute Max-size refers to the payload types indicated in the offered SDP, it SHOULD indicate
complete message, not the size of any one chunk. Senders SHOULD that using the appropriate mechanism of the rendezvous protocol.
NOT exceed the max-size limit for any message sent in the For example, in SIP, it SHOULD return a SIP 488 response.
resulting session. However, the receiver should consider max-size An endpoint MAY indicate the maximum size message they wish to
value as a hint. 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 SHOULD NOT exceed the max-size limit for any message sent
in the resulting session. However, the receiver should consider
max-size value as a hint.
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) / (type "/" "*") / ("*") format-entry = (type "/" subtype) / (type "/" "*") / ("*")
type = token type = token
subtype = token subtype = token
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-value = 1*(DIGIT) ;max size in octets
7.1.1 URL Negotiations Note: RFC2327 does not allow the hyphen in att-field, which is
defined as alphanumeric. However, this is expected to be allowed
in an update to that specification, which should be available
shortly.
8.1.1 URL Negotiations
Each endpoint in an MSRP session is identified by a URL. These URLs Each endpoint in an MSRP session is identified by a URL. These URLs
are negotiated in the SDP exchange. Each SDP offer or answer MUST are negotiated in the SDP exchange. Each SDP offer or answer MUST
contain one or more MSRP URL in a path attribute. This attribute has contain one or more MSRP URL in a path attribute. This attribute has
the following syntax: the following syntax:
"a=path:" MSRP_URL *(SP MSRP_URL) "a=path:" MSRP_URL *(SP MSRP_URL)
where MSRP_URL is an msrp: or msrps: URL as defined in Section 5. where MSRP_URL is an msrp: or msrps: URL as defined in Section 6.
MSRP URLs included in an SDP offer or answer MUST include explicit MSRP URLs included in an SDP offer or answer MUST include explicit
port numbers. port numbers.
An MSRP device uses the URL to determine a host address, port, An MSRP device uses the URL 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 URL to represent itself, and The offerer and answerer each selects a URL to represent itself, and
send it to the peer device in the SDP document. Each device stores send it to the peer device in the SDP document. Each device stores
the path value received from the peer, and uses that value as the the path value received from the peer, and uses that value as the
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m=message 9 msrp * m=message 9 msrp *
a=accept-types:text/plain a=accept-types:text/plain
a=path:msrp://a.example.com:7394/2s93i;tcp a=path:msrp://a.example.com:7394/2s93i;tcp
The rightmost URI in the path attribute MUST identify the endpoint The rightmost URI in the path attribute MUST identify the endpoint
that generated the SDP document, or some other location where that that generated the SDP document, or some other location where that
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 13. from eavesdroppers. This is discussed in more detail in Section 14.
7.1.2 Path Attributes with Multiple URLs 8.1.2 Path Attributes with Multiple URLs
As mentioned previously, this document describes MSRP for As mentioned previously, this document describes MSRP for
peer-to-peer scenarios, that is, when no relays are used. However, peer-to-peer scenarios, that is, when no relays are used. However,
we expect a separate document to describe the use of relays. In we expect a separate document to describe the use of relays. In
order to allow an MSRP device that only implements the core order to allow an MSRP device that only implements the core
specification to interoperate with devices that use relays, this specification to interoperate with devices that use relays, this
document must include a few assumptions about how relays work. document must include a few 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 URL for each device in the relay chain into the SDP path putting a URL for each device in the relay chain into the SDP path
attribute. The final entry would point to the endpoint itself. The attribute. The final entry would point to the endpoint itself. The
other entries would indicate each proposed relay, in order. The other entries would indicate each proposed relay, in order. The
first entry would point to the first relay in the chain; that is, the first entry would point to the first relay in the chain from the
relay to which the peer device, or a relay operation on its behalf, perspective of the peer; that is, the relay to which the peer device,
should connect. or a relay 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 URL into the path not support relays at all, will put exactly one URL into the path
attribute. This URL represents both the endpoint for the session, attribute. This URL represents both the endpoint for the session,
and the connection point. and the connection point.
While endpoints that implement only this specification will never Even though endpoints that implement only this specification will
introduce a relay, they will 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 URL in the SDP path attribute. When an to receive more than one URL in the SDP path attribute. When an
endpoint receives more than one URL in a path header, only the first endpoint receives more than one URL in a path header, only the first
entry is relevant for purposes of resolving the address and port, and entry is relevant for purposes of resolving the address and port, and
establishing the network connection, as it describes the first establishing the network connection, as it describes the first
adjacent hop. adjacent hop.
If an endpoint puts more than one URL in a path attribute, the final If an endpoint puts more than one URL in a path attribute, the final
URL in the path (the peer URL) attribute MUST exhibit the uniqueness URL in the path (the peer URL) attribute MUST exhibit the uniqueness
properties described above. Uniqueness requirements for other properties described above. Uniqueness requirements for other
entries in the attribute are out of scope for this document. entries in the attribute are out of scope for this document.
7.1.3 Updated SDP Offers 8.1.3 Updated SDP Offers
MSRP endpoints may sometimes need to send additional SDP exchanges MSRP endpoints may sometimes need to send additional SDP exchanges
for an existing session. They may need to send periodic exchanges for an existing session. They may need to send periodic exchanges
with no change to refresh state in the network, for example, SIP with no change to refresh state in the network, for example, SIP
Session Timers. They may need to change some other stream in a Session Timers. They may need to change some other stream in a
session without affecting the MSRP stream, or they may need to change session without affecting the MSRP stream, or they may need to change
an MSRP stream without affecting some other stream. an MSRP stream without affecting some other stream.
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 have the same o-line as in the previous
exchange. exchange.
7.1.4 Example SDP Exchange 8.1.4 Example SDP Exchange
Endpoint A wishes to invite Endpoint B to a MSRP session. A offers Endpoint A wishes to invite Endpoint B to a MSRP session. A offers
the following session description: the following session description:
v=0 v=0
o=usera 2890844526 2890844527 IN IP4 alice.example.com o=usera 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 9 msrp * m=message 9 msrp *
skipping to change at page 27, line 25 skipping to change at page 28, line 6
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 9 msrp * m=message 9 msrp *
a=accept-types:message/cpim text/plain a=accept-types:message/cpim text/plain
a=path:msrp://bob.example.com:8493/si438ds;tcp a=path:msrp://bob.example.com:8493/si438ds;tcp
7.1.5 Connection Negotiation 8.1.5 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 [24] work being done in the MMUSIC loosely based on the COMEDIA [23] work being done in the MMUSIC
working group. The primary motivation was to allow MSRP sessions to working group. The primary motivation was to allow MSRP sessions to
succeed in situations where the offerer could not accept connections succeed in situations where the offerer could not accept connections
but the answerer could. For example, the offerer might be behind a but the answerer could. For example, the offerer might be behind a
NAT, while the answerer might have a globally routable address. 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. Instead, MSRP now specifies a default connection direction.
7.2 MSRP User Experience with SIP 8.2 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.
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 [28] than one endpoint receiving the same INVITE. SIP early media [27]
techniques can be used to establish a preliminary session with each techniques can be used to establish a preliminary session with each
endpoint, and canceling the INVITE transaction for any endpoints that endpoint, and canceling the INVITE transaction for any endpoints that
do not send MSRP traffic after some period of time. do not send MSRP traffic after some period of time.
8. Formal Syntax 9. Formal Syntax
MSRP is a text protocol that uses the UTF-8 [15] 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-2234 [6]. Form (BNF) as described in RFC-2234 [6].
msrp-req-or-resp = msrp-request / msrp-response msrp-req-or-resp = msrp-request / msrp-response
msrp-request = req-start headers [content-stuff] end-line msrp-request = req-start headers [content-stuff] end-line
msrp-response = resp-start headers end-line msrp-response = resp-start headers end-line
req-start = pMSRP SP transact-id SP method CRLF req-start = pMSRP SP transact-id SP method CRLF
resp-start = pMSRP SP transact-id SP status-code [SP phrase] CRLF resp-start = pMSRP SP transact-id SP status-code [SP phrase] CRLF
phrase = utf8text phrase = utf8text
pMSRP = %x4D.53.52.50 ; MSRP in caps pMSRP = %x4D.53.52.50 ; MSRP in caps
transact-id = ident transact-id = ident
method = mSEND / mREPORT / other-method method = mSEND / mREPORT / other-method
mSEND = %53.45.4e.44 ; SEND in caps mSEND = %x53.45.4e.44 ; SEND in caps
mREPORT = %52.45.50.4f.52.54; REPORT in caps mREPORT = %x52.45.50.4f.52.54; REPORT in caps
other-method = 1*UPALPHA other-method = 1*UPALPHA
status-code = 3DIGIT status-code = 3DIGIT ; any code defined in this document
; or an extension document
headers = 1*( header CRLF ) MSRP_url = msrp-scheme "://" [userinfo "@"] hostport
["/" session-id] ";" transport
; userinfo as defined in RFC2396, except
; limited to unreserved.
; hostport as defined in RFC3261
; [Todo: update with RFC number for 2396bis]
header = ( To-Path msrp-scheme = "msrp" / "msrps"
/ From-Path session-id = 1*unreserved ; unreserved as defined in RFC2396
/ Message-ID transport = "tcp" / ALPHANUM
headers = To-Path CRLF From-Path CRLF 1*( header CRLF )
header = Message-ID
/ Report-Success / Report-Success
/ Report-Failure / Report-Failure
/ Byte-Range / Byte-Range
/ Status / Status
/ ext-header ) / ext-header
To-Path = "To-Path:" SP URL *( SP URL ) To-Path = "To-Path:" SP MSRP-url *( SP URL )
From-Path = "From-Path:" SP URL *( SP URL ) From-Path = "From-Path:" SP MSRP-url *( SP URL )
Message-ID = "Message-ID:" SP ident Message-ID = "Message-ID:" SP ident
Report-Success = "Report-Success:" SP ("yes" / "no" ) Report-Success = "Report-Success:" SP ("yes" / "no" )
Report-Failure = "Report-Failure:" SP ("yes" / "no" / "partial" ) Report-Failure = "Report-Failure:" 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 / "*"
dUmMy= "Status:" SP namespace SP short-status [SP text-reason] Status = "Status:" SP namespace SP status-code [SP text-reason]
namespace = "000"
text-reason = *(VCHAR / WSP) ; All visible charcters / SP / HTAB
; (defined in RFC2234 CORE)
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
subtype = token subtype = token
gen-param = pname [ "=" pval ] gen-param = pname [ "=" pval ]
pname = token pname = token
pval = token / quoted-string pval = token / quoted-string
token = 1*(%x21 / %xx23-27 / %x2A-2B / %x2D-2E token = 1*(%x21 / %x23-27 / %x2A-2B / %x2D-2E
/ %x30-39 / %x41-5A / %x5E-7E) / %x30-39 / %x41-5A / %x5E-7E)
quoted-string = DQUOTE *(qdtext / qd-esc) DQUOTE quoted-string = DQUOTE *(qdtext / qd-esc) DQUOTE
qdtext = SP / HT / %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 = "\"
DQUOTE = %x22
CRLF = %x0D.0A
HT = %x09
SP = %x20
UPALPHA = %x41-5A UPALPHA = %x41-5A
LOWALPHA = %x61-7A ALPHANUM = ALPHA / DIGIT
DIGIT = %x30-39
ALPHANUM = LOWALPHA / UPALPHA / 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
; headers as described in RFC2045 ; headers as described in RFC2045
data = *OCTET data = *OCTET
end-line = "-------" transact-id continuation-flag CRLF end-line = "-------" transact-id continuation-flag CRLF
continuation-flag = "+" / "$" / "#" continuation-flag = "+" / "$" / "#"
ext-header = hname ":" SP hval CRLF ext-header = hname ":" SP hval CRLF
hname = alpha *token hname = ALPHA *token
hval = utf8text hval = utf8text
utf8text = *(HT / %x20-7E / UTF8-NONASCII) utf8text = *(HTAB / %x20-7E / UTF8-NONASCII)
UTF8-NONASCII = %xC0-DF 1UTF8-CONT UTF8-NONASCII = %xC0-DF 1UTF8-CONT
/ %xE0-EF 2UTF8-CONT / %xE0-EF 2UTF8-CONT
/ %xF0-F7 3UTF8-CONT / %xF0-F7 3UTF8-CONT
/ %xF8-Fb 4UTF8-CONT / %xF8-Fb 4UTF8-CONT
/ %xFC-FD 5UTF8-CONT / %xFC-FD 5UTF8-CONT
UTF8-CONT = %x80-BF UTF8-CONT = %x80-BF
9. Response Code Descriptions 10. Response Code Descriptions
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 in REPORT requests. used in the Status header in REPORT requests.
9.1 200 10.1 200
The 200 response code indicates a successful transaction. The 200 response code indicates a successful transaction.
9.2 400 10.2 400
A 400 response indicates a request was unintelligible. A 400 response indicates a request was unintelligible.
9.3 403 10.3 403
The action is not allowed The action is not allowed
9.4 415 10.4 415
A 415 response indicates the SEND request contained a MIME A 415 response indicates the SEND request contained a MIME
content-type that is not understood by the receiver. content-type that is not understood by the receiver.
9.5 426 10.5 426
A 426 response indicates that the request is only allowed over TLS A 426 response indicates that the request is only allowed over TLS
protected connections. protected connections.
9.6 481 10.6 481
A 481 response indicates that no session exists for the connection. A 481 response indicates that the indicated session does not exist.
9.7 506 10.7 501
A 501 response indicates that the recipient does not understand the
request method.
The 501 response code exists to allow some degree of method
extensibility. It is not intended as a license to ignore methods
defined in this document; rather it is a mechanism to report lack
of support of extension methods.
10.8 506
A 506 response indicates that a request arrived on a session which is A 506 response indicates that a request arrived on a session which is
already bound to another network connection. already bound to another network connection.
10. Examples 11. Examples
10.1 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
sake of brevity. In the example, assume the offerer is sake of brevity. In the example, assume the offerer is
sip:alice@example.com and the answerer is sip:bob@example.com. sip:alice@example.com and the answerer is sip:bob@example.com.
Alice Bob Alice Bob
| | | |
| | | |
skipping to change at page 33, line 28 skipping to change at page 34, line 28
-------dkei38sd$ -------dkei38sd$
8. Alice->Bob (SIP): BYE 8. Alice->Bob (SIP): BYE
Alice invalidates local session state. Alice invalidates local session state.
9. Bob invalidates local state for the session. 9. Bob invalidates local state for the session.
Bob->Alice (SIP): 200 OK Bob->Alice (SIP): 200 OK
10.2 Chunked Message 11.2 Message with XHTML Content
For an example of a chunked message, see the example in Section 4.1. MSRP dsdfoe38sd SEND
To-Path:msrp://alice.atlanta.com:7777/iau39;tcp
From-Path:msrp://bob.atlanta.com:8888/9di4ea;tcp
Message-ID: 456
Content-Type:application/xhtml+xml
10.3 System Message <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"_http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd_">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>FY2005 Results</title>
</head>
<body>
<p>See the results at<a
href="http://example.org/">example.org</a>.</p>
</body>
</html>
-------dsdfoe38sd$
11.3 Chunked Message
For an example of a chunked message, see the example in Section 5.1.
11.4 System Message
Sysadmin->Alice (MSRP): Sysadmin->Alice (MSRP):
MSRP d93kswow SEND MSRP d93kswow SEND
To-Path:msrp://alicepc.example.com:8888/9di4ea;tcp To-Path:msrp://alicepc.example.com:8888/9di4ea;tcp
From-Path:msrp://example.com:7777/iau39;tcp From-Path:msrp://example.com:7777/iau39;tcp
Message-ID: 12339sdqwer Message-ID: 12339sdqwer
Report-Failure: no Report-Failure: no
Report-Success: no Report-Success: no
Content-Type:text/plain Content-Type:text/plain
This conference will end in 5 minutes This conference will end in 5 minutes
-------d93kswow$ -------d93kswow$
10.4 Positive Report 11.5 Positive Report
Alice->Bob (MSRP): Alice->Bob (MSRP):
MSRP d93kswow SEND MSRP d93kswow SEND
To-Path:msrp://bob.example.com:8888/9di4ea;tcp To-Path:msrp://bob.example.com:8888/9di4ea;tcp
From-Path:msrp://alicepc.example.com:7777/iau39;tcp From-Path:msrp://alicepc.example.com:7777/iau39;tcp
Message-ID: 12339sdqwer Message-ID: 12339sdqwer
Report-Success: yes Report-Success: yes
Content-Type:text/html Content-Type:text/html
skipping to change at page 34, line 39 skipping to change at page 36, line 39
Bob->Alice (MSRP): Bob->Alice (MSRP):
MSRP dkei38sd REPORT MSRP dkei38sd REPORT
To-Path:msrp://alicepc.example.com:7777/iau39;tcp To-Path:msrp://alicepc.example.com:7777/iau39;tcp
From-Path:msrp://bob.example.com:8888/9di4ea;tcp From-Path:msrp://bob.example.com:8888/9di4ea;tcp
Message-ID: 12339sdqwer Message-ID: 12339sdqwer
Status: 000 200 OK Status: 000 200 OK
-------dkei38sd$ -------dkei38sd$
10.5 Forked IM 11.6 Forked IM
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 when it is desirable to always-on mobile devices are available, but when it is desirable to
use them only if another IM client is not available. use 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; instead "pager-mode" IM systems use implicit very flexible; instead "pager-mode" IM systems use implicit
implementation-specific decisions which IM clients cannot influence. implementation-specific decisions which 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 [30]. As a result, host that implements callee capabilities [29]. 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).
The example uses REGISTER to learn of Juliet's registered
contacts. This does not constitute an endorsement of that
approach; it is used here to avoid cluttering the example with too
many SIP details. A more realistic application would be the use a
SIP proxy or redirect server for this purpose.
We query for a list of Juliet's contacts by sending a REGISTER: We query for a list of Juliet's contacts by sending a REGISTER:
REGISTER sip:thecapulets.example.com SIP/2.0 REGISTER sip:thecapulets.example.com SIP/2.0
To: Juliet <sip:juliet@thecapulets.example.com> To: Juliet <sip:juliet@thecapulets.example.com>
From: Juliet <sip:juliet@thecapulets.example.com>;tag=12345 From: Juliet <sip:juliet@thecapulets.example.com>;tag=12345
Call-ID: 09887877 Call-ID: 09887877
CSeq: 772 REGISTER CSeq: 772 REGISTER
The Response contains her Contacts: The Response contains her Contacts:
skipping to change at page 37, line 10 skipping to change at page 39, line 16
|<--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 tommorrow.... | | Tell her to go to confession tommorrow.... |
11. 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,
Headers, and status codes can be defined in standards track RFCs. Headers, and status codes can be defined in standards track RFCs.
There is no registry of headers, methods, or status codes, since the There is no registry of headers, methods, or status codes, since the
number of new elements and total extensions is expected to be very number of new elements and total extensions is expected to be very
small. MSRP does not contain a version number or any negotiation small. MSRP does not contain a version number or any negotiation
mechanism to require or discover new features. If a mechanism to require or discover new features. If a
non-interoperable update or extension occurs in the future, it will non-interoperable update or extension occurs in the future, it will
be treated as a new protocol, and must describe how its use will be be treated as a new protocol, and must describe how its use will be
signaled. signaled.
In order to allow extension header fields without breaking In order to allow extension header fields without breaking
interoperablility, if an MSRP device receives a request or response interoperability, if an MSRP device receives a request or response
containing a header field that it does not understand, it MUST ignore containing a header field that it does not understand, it MUST ignore
the header field and process the request or response as if the header the header field and process the request or response as if the header
field was not present. field was not present. If an MSRP device receives a request with an
unknown method, it MUST return a 501 response.
MSRP was designed to use lists of URLs instead of a single URL in the MSRP was designed to use lists of URLs instead of a single URL in the
To-Path and From-Path headers in anticipation of relay or gateway To-Path and From-Path headers in anticipation of relay or gateway
functionality being added. In addition, msrp: and msrps: URLs can functionality being added. In addition, msrp: and msrps: URLs can
contain parameters which are extensible. contain parameters which are extensible.
12. CPIM compatibility 13. CPIM compatibility
MSRP sessions may be gatewayed to other CPIM [25]compatible MSRP sessions may go to a gateway to other CPIM [24] compatible
protocols. If this occurs, the gateway MUST maintain session state, protocols. If this occurs, the gateway MUST maintain session state,
and MUST translate between the MSRP session semantics and CPIM and MUST translate between the MSRP session semantics and CPIM
semantics that do not include a concept of sessions. Furthermore, semantics that do not include a concept of sessions. Furthermore,
when one endpoint of the session is a CPIM gateway, instant messages when one endpoint of the session is a CPIM gateway, instant messages
SHOULD be wrapped in "message/cpim" [7] bodies. Such a gateway MUST SHOULD be wrapped in "message/cpim" [12] bodies. Such a gateway MUST
include "message/cpim" as the first entry in its SDP accept-types include "message/cpim" as the first entry in its SDP accept-types
attribute. MSRP endpoints sending instant messages to a peer that attribute. MSRP endpoints sending instant messages to a peer that
has included 'message/cpim" as the first entry in the accept-types has included 'message/cpim" as the first entry in the accept-types
attribute SHOULD encapsulate all instant message bodies in "message/ attribute SHOULD encapsulate all instant message bodies in
cpim" wrappers. All MSRP endpoints MUST support the message/cpim "message/cpim" wrappers. All MSRP endpoints MUST support the
type, and SHOULD support the S/MIME features of that format. message/cpim type, and SHOULD support the S/MIME 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 chuncks, if wrapping MUST be done prior to breaking the message into chunks, if
needed. needed.
13. Security Considerations All MSRP endpoints MUST recognize the From, To, DateTime, and Require
headers as defined in RFC3862. Such applications SHOULD recognize
the CC header, and MAY recognize the Subject header. Any MSRP
application that recognizes any message/cpim header MUST understand
the NS (name space) header.
All message/cpim body parts send by an MSRP endpoint MUST include the
From and To headers. If the message/cpim body part is protected
using S/MIME, then it MUST also include the DateTime header.
The NS, To, and CC headers may occur multiple times. Other headers
defined in RFC3862 MUST NOT occur more than once in a given
message/cpim body part in an MSRP message. The Require header MAY
include multiple values. The NS header MAY occur zero or more times,
depending on how many name spaces are being referenced.
Extension headers MAY occur more than once, depending on the
definition of such headers.
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. Like many governments for communicating important information. Like many
communications systems, the properties of Integrity and communications systems, the properties of Integrity and
Confidentiality of the exchanged information, along with the Confidentiality of the exchanged information, along with the
possibility of Anonymous communications, and knowing you are possibility of Anonymous communications, and knowing you are
communicating with the correct other party are required. MSRP pushes communicating with the correct other party are required. MSRP pushes
skipping to change at page 38, line 28 skipping to change at page 41, line 7
some of the problems remain. Spam and DoS attacks are also very some of the problems remain. Spam and DoS attacks are also very
relevant to IM systems. 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 the connected host it transfers. It also needs to provide assurances the connected host
is the host that it meant to connect to and that the connection has is the host that it meant to connect to and that the connection has
not been hijacked. not been hijacked.
When using only TCP connections, MSRP security is fairly weak. If When using only TCP connections, MSRP security is fairly weak. If
host A is contacting B, B passes its hostname and a secret to A using host A is contacting B, B passes its hostname and a secret to A using
SIP. If the SIP offer or answer is not TLS or S/MIME [27] protected, SIP. If the SIP offer or answer is not TLS or S/MIME [26] protected,
anyone can see this secret. A then connects to the provided host anyone can see this secret. A then connects to the provided host
name and passes the secret in the clear across the connection to B. name and passes the secret in the clear across the connection to B.
A assumes that it is talking to B based on where it sent the SYN A assumes that it is talking to B based on where it sent the SYN
packet and then delivers the secret in plain text across the packet and then delivers the secret in plain text across the
connections. B assumes it is talking to A because the host on the connections. B assumes it is talking to A because the host on the
other end of the connection delivered the secret. An attacker that other end of the connection delivered the secret. An attacker that
could ACK the SYN packet could insert itself as a man in the middle could ACK the SYN packet could insert itself as a man in the middle
in the connection. in the connection.
When using TLS connections, the security is significantly improved. When using TLS connections, the security is significantly improved.
skipping to change at page 39, line 10 skipping to change at page 41, line 37
insert itself as a man-in-the-middle. insert itself as a man-in-the-middle.
Realistically, using TLS is only feasible when connecting to gateways Realistically, using TLS is only feasible when connecting to gateways
or relays , as the types of hosts that end clients use for sending or relays , as the types of hosts that end clients use for sending
instant messages are unlikely to have a long term stable IP address instant messages are unlikely to have a long term stable IP address
or a stable DNS name that a certificate can bind to. In addition, or a stable DNS name that a certificate can bind to. In addition,
the cost of server certificates from well known certificate the cost of server certificates from well known certificate
authorities is currently too high for the vast majority of end users authorities is currently too high for the vast majority of end users
to even consider getting one for each client. to even consider getting one for each client.
The only real security for connections without relays is achieved The only strong security for connections without relays is achieved
using S/MIME. This does not require the actual endpoint to have using S/MIME. This does not require the actual endpoint to have
certificates from a well known certificate authority. The Identity certificates from a well known certificate authority. The Identity
[22] and Certificates [23] mechanism with SIP provides S/MIME based [21] and Certificates [22] mechanism with SIP provides S/MIME based
delivery of a secret between A and B. No SIP intermediary except the delivery of a secret between A and B. No SIP intermediary except the
explicitly trusted authentication service (one per user) can see the explicitly trusted authentication service (one per user) can see the
secret. The S/MIME encryption of the SDP can also be used by SIP to secret. The S/MIME encryption of the SDP can also be used by SIP to
exchange keying material that can be used in MRSP. The MSRP session exchange keying material that can be used in MRSP. The MSRP session
can then use S/MIME with this keying material to encrypt and sign can then use S/MIME with this keying material to encrypt and sign
messages sent over MSRP. The connection can still be hijacked since messages sent over MSRP. The connection can still be hijacked since
the secret is sent in clear text to the other end of the TCP the secret is sent in clear text to the other end of the TCP
connection, but this risk is mitigated if all the MSRP content is connection, but this risk is mitigated if all the MSRP content is
encrypted and signed with S/MIME. encrypted and signed with S/MIME. It is out of scope for this
document but thre is nothing stopping the SIP negoatiation of MSRP
session from negoatating symetric keying material that is used with
S/MIME for intgrity and privacy. Using TLS with a DH profile is also
possible.
MSRP can not be used as an amplifier for DoS attacks, but it can be MSRP can not be used as an amplifier for DoS attacks, but it can be
used to form a distributed attack to consume TCP connection resource used to form a distributed attack to consume TCP connection resource
on servers. The attacker, Eve, sends an SIP INVITE with no offer to on servers. The attacker, Eve, sends an SIP INVITE with no offer to
Alice. Alice returns a 200 with an offer and Eve returns an answer Alice. Alice returns a 200 with an offer and Eve returns an answer
with the SDP that indicates that her MSRP address is the address of with the SDP that indicates that her MSRP address is the address of
Tom. Since Alice sent the offer, Alice will initiate a connection to Tom. Since Alice sent the offer, Alice will initiate a connection to
Tom using up resources on Tom's server. Given the huge number of IM Tom using up resources on Tom's server. Given the huge number of IM
clients, and the relatively few TCP connections that most servers clients, and the relatively few TCP connections that most servers
support, this is a fairly straightforward attack. support, this is a fairly straightforward attack.
SIP is attempting to address issues in dealing with spam. The spam SIP is attempting to address issues in dealing with spam. The spam
issue is probably best dealt with at the SIP level when an MSRP issue is probably best dealt with at the SIP level when an MSRP
session is initiated and not at the MSRP level. session is initiated and not at the MSRP level.
TLS is used to authenticate devices and to provide integrity and TLS is used to authenticate devices and to provide integrity and
confidentiality for the headers being transported. MSRP elements confidentiality for the headers being transported. MSRP elements
MUST implement TLS and MUST also implement the TLS MUST implement TLS and MUST also implement the TLS
ClientExtendedHello extended hello information for server name ClientExtendedHello extended hello information for server name
indication as described in [11]. A TLS cipher-suite of indication as described in [10]. A TLS cipher-suite of
TLS_RSA_WITH_AES_128_CBC_SHA [14] MUST be supported (other TLS_RSA_WITH_AES_128_CBC_SHA [13] MUST be supported (other
cipher-suites MAY also be supported). cipher-suites MAY also be supported).
Since MSRP carries arbitrary MIME content, it can trivially carry S/ Since MSRP carries arbitrary MIME content, it can trivially carry
MIME protected messages as well. All MSRP implementations MUST S/MIME protected messages as well. All MSRP implementations MUST
support the multipart/signed MIME type even if they do not support S/ support the multipart/signed MIME type even if they do not support
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 [26] provided in the session setup. shared secret [25] provided in the session setup. MSRP is a binary
protocol and MIME bodies MUST be transfered with a transfer encoding
of binary. If a message is both signed and encrypted, it SHOULD be
signed first, then encrypted. If S/MIME is supported, SHA-1, RSA,
and AES-128 MUST be supported.
If a sender chooses to employ S/MIME to protect a message, all S/MIME If a sender chooses to employ S/MIME to protect a message, all S/MIME
operations MUST occur prior to breaking the message into chunks, if operations MUST occur prior to breaking the message into chunks, if
needed. needed.
14. IANA Considerations The signaling will have set up the session to or from some specific
URLs that will often have "im:" or "sip:" URI schemes. When the
signaling has been set up to a specific end users, and S/MIME is
implemented, then the client needs to verify that the name in the
SubjectAltName of the certificate contains an entry that matches the
URI that was used for the other end in the signaling. There are some
cases, such as IM conferencing, where the S/MIME certificate name and
the signaled identity will not match. In these cases the client
should ensure that the user is informed that the message came from
the user identified in the certificate and does not assume that the
message came from the party they signaled.
14.1 MSRP Port In some cases, a sending device may need to attribute a message to
some other identity, and may use different identities for different
messages in the same session. For example, a conference server may
send messages on behalf of multiple users on the same session.
Rather than add additional headers to MSRP for this purpose, MSRP
relies on the message/cpim format for this purpose. The sender may
envelope such a message in a message/cpim body, and place the actual
sender identity in the From field. The trustworthiness of such an
attribution is affected by the security properties of the session in
the same way that the trustworthiness of the identity of the actual
peer is affected, with the additional issue of determining whether
the recipient trusts the sender to assert the identity.
This approach can result in nesting of message/cpim envelopes. For
example, a message originates from a CPIM gateway, and is then
forwarded by a conference server onto a new session. Both the
gateway and the conference server introduce envelopes. In this case,
the recipient client SHOULD indicate the chain of identity assertions
to the user, rather than allow the user to assume that either the
gateway or the conference server originated the message.
It is possible that a recipient might receive messages that are
attributed to the same sender via different MSRP sessions. For
example, Alice might be in a conversation with Bob via an MSRP
session over a TLS protected channel. Alice might then receive a
different message from Bob over a different session, perhaps with a
conference server that asserts Bob's identity in a message/cpim
envelope signed by the server.
MSRP does not in any way prohibit multiple simultaneous sessions
between the same pair of identities. Nor does it prohibit an
endpoint sending a message on behalf of another identity, such as may
be the case for a conference server. The recipient's endpoint should
determine its level of trust of the authenticity of the sender
independently for each session. The fact that an endpoint trusts the
authenticity of the sender on any given session should not affect the
level of trust it assigns for apparently the same sender on a
different session.
When MSRP clients from or acquire a certificate, they SHOULD ensure
that the subjectAltName has a GeneralName entry of type
uniformResourceIdentifier for each URI corresponding to this client
and should always include an "im:" URI as well as a "sip:" URI. It
is fine if the certificate contains other URIs such as an "xmpp:"
URI.
15. IANA Considerations
15.1 MSRP Port
MSRP uses TCP port XYX, to be determined by IANA after this document MSRP uses TCP port XYX, to be determined by IANA after this document
is approved for publication. Usage of this value is described in is approved for publication. Usage of this value is described in
Section 5 Section 6
14.2 MSRP URL Schemes 15.2 MSRP URL Schemes
This document defines the URL schemes of "msrp" and "msrps". This document defines the URL schemes of "msrp" and "msrps".
Syntax See Section 5. Syntax See Section 6.
Character Encoding See Section 5. Character Encoding See Section 6.
Intended Usage See Section 5. Intended Usage See Section 6.
Protocols The Message Session Relay Protocol (MSRP). Protocols The Message Session Relay Protocol (MSRP).
Security Considerations See Section 13. Security Considerations See Section 14.
Relevant Publications RFCXXXX Relevant Publications RFCXXXX
[Note to RFC Editor: Please replace RFCXXXX in the above [Note to RFC Editor: Please replace RFCXXXX in the above
paragraph with the actual number assigned to this document. paragraph with the actual number assigned to this document.
14.3 SDP Parameters 15.3 SDP Parameters
This document registers the following SDP parameters in the This document registers the following SDP parameters in the
sdp-parameters registry: sdp-parameters registry:
14.3.1 Accept Types 15.3.1 Accept Types
Attribute-name: accept-types Attribute-name: accept-types
Long-form Attribute Name Acceptable MIME Types Long-form Attribute Name Acceptable MIME Types
Type: Media level Type: Media level
Subject to Charset Attribute No Subject to Charset Attribute No
Purpose and Appropriate Values See Section 7.1. Purpose and Appropriate Values See Section 8.1.
14.3.2 Wrapped Types 15.3.2 Wrapped Types
Attribute-name: accept-wrapped-types Attribute-name: accept-wrapped-types
Long-form Attribute Name Acceptable MIME Types Inside Wrappers Long-form Attribute Name Acceptable MIME Types Inside Wrappers
Type: Media level Type: Media level
Subject to Charset Attribute No Subject to Charset Attribute No
Purpose and Appropriate Values See Section 7.1. Purpose and Appropriate Values See Section 8.1.
14.3.3 Max Size 15.3.3 Max Size
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 See Section 7.1. Purpose and Appropriate Values See Section 8.1.
14.3.4 Path 15.3.4 Path
Attribute-name: path Attribute-name: path
Long-form Attribute Name MSRP URL Path Long-form Attribute Name MSRP URL Path
Type: Media level Type: Media level
Subject to Charset Attribute No Subject to Charset Attribute No
Purpose and Appropriate Values See Section 7.1.1. Purpose and Appropriate Values See Section 8.1.1.
15. Change History 16. Change History
15.1 draft-ietf-simple-message-sessions-08 16.1 draft-ietf-simple-message-sessions-09
Removed DSN section. Removed statements that an error report o Updated retransmission when receiving a failure report.
o Added applicability statement.
o Added CPIM application considerations.
o Added language to security considerations about receiving messages
from the same sender over different sessions.
o Added 501 response code.
o Various scrubbing of the ABNF
o Change resource construction name to session-id in MSRP syntax.
o Added language to define the purpose of msrp URLs.
o Change RFC2396 reference to 2396bis
o Clarify that max-size is in octets.
o Clarify that userinfo is restricted to unreserved characters,
which is an additional restriction over the RFC2396 version.
o Consolidated the ABNF for the MSRP URL into the formal syntax
section.
o Clarified that if an MSRP endpoint receives and SDP offer and does
not understand any of the media types, it SHOULD return a SIP 488
response, or whatever is appropriate for the rendezvous protocol.
o Added more text around using message/cpim for identity
attribution.
16.2 draft-ietf-simple-message-sessions-08
o Removed DSN section. Removed statements that an error report
SHOULD contain a body. REPORT requests may now contain SHOULD contain a body. REPORT requests may now contain
informational bodies no larger than 2K, but the recipient is free informational bodies no larger than 2K, but the recipient is free
to ignore them. to ignore them.
Added the "#" value for the continuation-flag to indicate the last o Added the "#" value for the continuation-flag to indicate the last
chunk of an abandoned message. chunk of an abandoned message.
Added direction that s/mime and cpim envelops must be applied o Added direction that s/mime and cpim envelops must be applied
before chunking. before chunking.
Added direction to set the last-byte field in byte-range to "*" if
o Added direction to set the last-byte field in byte-range to "*" if
there is any chance of interrupting a SEND request. there is any chance of interrupting a SEND request.
Changed max-size to refer to entire message, instead of a o Changed to refer to entire message, instead of a particular MIME
particular MIME content-type content-type
Added requirent for the use of UTF-8, and reference to RFC3629 o Added requirent for the use of UTF-8, and reference to RFC3629
Added requrement to ignore unknown headers. o Added requrement to ignore unknown headers.
Several ABNF fixes o Several ABNF fixes
Removed redundant material between normative sections. o Removed redundant material between normative sections.
Numerous editorial fixes. o Numerous editorial fixes.
15.2 draft-ietf-simple-message-sessions-07 16.3 draft-ietf-simple-message-sessions-07
Significant re-write to attempt to improve readability. o Significant re-write to attempt to improve readability.
Added maximum size parameter in accept-types o Added maximum size parameter in accept-types
Changed the Boundary field to be part of the start-line rather o Changed the Boundary field to be part of the start-line rather
than a header field. than a header field.
Removed the TR-IDheader, and changed request-response matching to o Removed the TR-IDheader, and changed request-response matching to
be based on the Boundary field value. Responses still contain the be based on the Boundary field value. Responses still contain the
TR-ID header, which must match the Boundary from the request. TR-ID header, which must match the Boundary from the request.
o Removed transport selection from URL scheme and added the "tcp"
Removed transport selection from URL scheme and added the "tcp"
parameter. parameter.
Added description of the "simple" mode with no transaction o Added description of the "simple" mode with no transaction
responses, and made mode selection dependent on the reporting responses, and made mode selection dependent on the reporting
level requested for a give message. level requested for a give message.
Changed the DSN section to reflect separate request of success and o Changed the DSN section to reflect separate request of success and
failure reports. Enhanced REPORT method to be useful even without failure reports. Enhanced REPORT method to be useful even without
a payload. a payload.
removed SRV usage for URL resolution. This is only used for relay o removed SRV usage for URL resolution. This is only used for relay
discovery, and therefore should be moved to the relay draft. discovery, and therefore should be moved to the relay draft.
Added discussion about late REPORT handling. Asserted that REPORT o Added discussion about late REPORT handling. Asserted that REPORT
requests are always sent in simple mode. requests are always sent in simple mode.
Removed the dependency on multipart/byteranges for fragmentation. o Removed the dependency on multipart/byteranges for fragmentation.
Incorporated the Byte-Range header into the base MSRP header set. Incorporated the Byte-Range header into the base MSRP header set.
Removed the VISIT method. Change to use SEND to serve the purpose o Removed the VISIT method. Change to use SEND to serve the purpose
formerly reserved to VISIT. formerly reserved to VISIT.
15.3 draft-ietf-simple-message-sessions-06 16.4 draft-ietf-simple-message-sessions-06
Changed To and From header names to To-Path and From-Path. Added o Changed To and From header names to To-Path and From-Path. Added
more clarification to path handling, and commentary on how it more clarification to path handling, and commentary on how it
enables relay usage. enables relay usage.
Changed mechanism for signaling transport and TLS protection into o Changed mechanism for signaling transport and TLS protection into
the MSRP URL, rather than the SDP M-Line. the MSRP URL, rather than the SDP M-Line.
Removed length field from start line and added Boundary header o Removed length field from start line and added Boundary header
field and Closing field. field and Closing field.
Added recommendation to fragment any content over 2k. o Added recommendation to fragment any content over 2k.
Added Rohan's proposal to make offerer connect to answerer. (With o Added Rohan's proposal to make offerer connect to answerer. (With
open issue for more discussion.) open issue for more discussion.)
Changed To-Path and From-Path usage in responses to indicate the o Changed To-Path and From-Path usage in responses to indicate the
destination and source of the response, rather than merely copy destination and source of the response, rather than merely copy
from the associated request. from the associated request.
Updated DSN section. Added text on field usage. o Updated DSN section. Added text on field usage.
Fixed change TR-ID header from version 05 were erroneously o Fixed change TR-ID header from version 05 were erroneously
attributed to 04. attributed to 04.
15.4 draft-ietf-simple-message-sessions-05 16.5 draft-ietf-simple-message-sessions-05
Changed the use of session URLs. Instead of a single session URL, o Changed the use of session URLs. Instead of a single session URL,
each endpoint is identified by a distinct URL. MSRP requests will each endpoint is identified by a distinct URL. MSRP requests will
put the destination URL in a To header, and the sender URL in a put the destination URL in a To header, and the sender URL in a
From header. From header.
Changed the SDP exchange of MSRP URLs to handle the URL for each o Changed the SDP exchange of MSRP URLs to handle the URL for each
endpoint. Further, changed the SDP attribute to support a list of endpoint. Further, changed the SDP attribute to support a list of
URLs in each direction. This may be used with relays to exchange URLs in each direction. This may be used with relays to exchange
paths, rather than single URLs. MSRP endpoints must be able to paths, rather than single URLs. MSRP endpoints must be able to
intelligently process such a list if received. This document does intelligently process such a list if received. This document does
not, however, describe how to generate such a list. not, however, describe how to generate such a list.
o Added section for Delivery Status Notification handling, and added
Added section for Delivery Status Notification handling, and added
associated entries into the syntax definition. associated entries into the syntax definition.
Added content fragmentation section. o Added content fragmentation section.
Removed recommendation to start separate session for large o Removed recommendation to start separate session for large
transfers. transfers.
Corrected some mistakes in the syntax definitions. o Corrected some mistakes in the syntax definitions.
Added Chris Boulton as a co-author for his contribution of the DSN o Added Chris Boulton as a co-author for his contribution of the DSN
text. text.
15.5 draft-ietf-simple-message-sessions-04 16.6 draft-ietf-simple-message-sessions-04
Removed the direction attribute. Rather than using a comedia o Removed the direction attribute. Rather than using a comedia
styled direction negotiation, we just state that the answerer styled direction negotiation, we just state that the answerer
opens any needed connection. opens any needed connection.
15.6 draft-ietf-simple-message-sessions-03 16.7 draft-ietf-simple-message-sessions-03
Removed all specification of relays, and all features specific to o Removed all specification of relays, and all features specific to
the use of relays. The working group has chosen to move relay the use of relays. The working group has chosen to move relay
work into a separate effort, in order to advance the base work into a separate effort, in order to advance the base
specification. (The MSRP acronym is unchanged for the sake of specification. (The MSRP acronym is unchanged for the sake of
convenience.) This included removal of the BIND method, all convenience.) This included removal of the BIND method, all
response codes specific to BIND, Digest Authentication, and the response codes specific to BIND, Digest Authentication, and the
inactivity timeout. inactivity timeout.
Removed text indicating that an endpoint could retry failed o Removed text indicating that an endpoint could retry failed
requests on the same connection. Rather, the endpoint should requests on the same connection. Rather, the endpoint should
consider the connection dead, and either signal a reconnection or consider the connection dead, and either signal a reconnection or
end the session. end the session.
Added text describing subsequent SDP exchanges. Added mandatory
o Added text describing subsequent SDP exchanges. Added mandatory
"count" parameter to the direction attribute to allow explicit "count" parameter to the direction attribute to allow explicit
signaling of the need to reconnect. signaling of the need to reconnect.
Added text to describe the use of send and receive only indicators o Added text to describe the use of send and receive only indicators
in SDP for one-way transfer of large content. in SDP for one-way transfer of large content.
Added text requiring unique port field values if multiple M-line's o Added text requiring unique port field values if multiple M-line's
exist. exist.
Corrected a number of editorial mistakes. o Corrected a number of editorial mistakes.
15.7 draft-ietf-simple-message-sessions-02 16.8 draft-ietf-simple-message-sessions-02
Moved all content type negotiation from the "m"-line format list o Moved all content type negotiation from the "m"-line format list
into "a"-line attributes. Added the accept-types attribute. This into "a"-line attributes. Added the accept-types attribute. This
is due to the fact that the sdp format-list syntax is not is due to the fact that the sdp format-list syntax is not
conducive to encoding MIME content types values. conducive to encoding MIME content types values.
Added "other-method" construction to the message syntax to allow o Added "other-method" construction to the message syntax to allow
for extensible methods. for extensible methods.
Consolidated all syntax definitions into the same section. o Consolidated all syntax definitions into the same section.
Cleaned up ABNF for digest challenge and response syntax. Cleaned up ABNF for digest challenge and response syntax.
o Changed the session inactivity timeout to 12 minutes.
o Required support for the SHA1 algorithm.
o Required support for the message/cpim format.
o Fixed lots of editorial issues.
o Documented a number of open issues from recent list discussions.
Changed the session inactivity timeout to 12 minutes. 16.9 draft-ietf-simple-message-sessions-01
Required support for the SHA1 algorithm.
Required support for the message/cpim format.
Fixed lots of editorial issues.
Documented a number of open issues from recent list discussions.
15.8 draft-ietf-simple-message-sessions-01
Abstract rewritten. o Abstract rewritten.
Added architectural considerations section. o Added architectural considerations section.
The m-line format list now only describes the root body part for a o The m-line format list now only describes the root body part for a
request. Contained body part types may be described in the request. Contained body part types may be described in the
"accept-wrapped-types" a-line attribute. "accept-wrapped-types" a-line attribute.
Added a standard dummy value for the m-line port field. Clarified o Added a standard dummy value for the m-line port field. Clarified
that a zero in this field has normal SDP meaning. that a zero in this field has normal SDP meaning.
Clarified that an endpoint is globally configured as to whether or o Clarified that an endpoint is globally configured as to whether or
not to use a relay. There is no relay discovery mechanism not to use a relay. There is no relay discovery mechanism
intrinsic to MSRP. intrinsic to MSRP.
Changed digest algorithm to SHA1. Added TR-ID and S-URI to the o Changed digest algorithm to SHA1. Added TR-ID and S-URI to the
hash for digest authentication. hash for digest authentication.
CMS usage replaced with S/MIME. o CMS usage replaced with S/MIME.
TLS and msrps: usage clarified. o TLS and msrps: usage clarified.
Session state timeout is now based on SEND activity, rather than o Session state timeout is now based on SEND activity, rather than
BIND and VISIT refreshes. BIND and VISIT refreshes.
Default port added. o Default port added.
Added sequence diagrams to the example message flows. o Added sequence diagrams to the example message flows.
Added discussion of self-signed certificates in the security o Added discussion of self-signed certificates in the security
considerations section. considerations section.
15.9 draft-ietf-simple-message-sessions-00 16.10 draft-ietf-simple-message-sessions-00
Name changed to reflect status as a work group item. o Name changed to reflect status as a work group item.
This version no longer supports the use of multiple sessions o This version no longer supports the use of multiple sessions
across a single TCP session. This has several related changes: across a single TCP session. This has several related changes:
There is now a single session URI, rather than a separate one for There is now a single session URI, rather than a separate one for
each endpoint. The session URI is not required to be in requests each endpoint. The session URI is not required to be in requests
other than BIND and VISIT, as the session can be determined based other than BIND and VISIT, as the session can be determined based
on the connection on which it arrives. on the connection on which it arrives.
BIND and VISIT now create soft state, eliminating the need for the o BIND and VISIT now create soft state, eliminating the need for the
RELEASE and LEAVE methods. RELEASE and LEAVE methods.
The MSRP URL format was changed to better reflect generic URL o The MSRP URL format was changed to better reflect generic URL
standards. URL comparison and resolution rules were added. SRV standards. URL comparison and resolution rules were added. SRV
usage added. usage added.
Determination of host and visitor roles now uses a direction o Determination of host and visitor roles now uses a direction
attribute much like the one used in COMEDIA. attribute much like the one used in COMEDIA.
Format list negotiation expanded to allow a "prefer these formats o Format list negotiation expanded to allow a "prefer these formats
but try anything" semantic but try anything" semantic
Clarified handling of direction notification failures. o Clarified handling of direction notification failures.
Clarified signaling associated with session failure due to dropped o Clarified signaling associated with session failure due to dropped
connections. connections.
Clarified security related motivations for MSRP. o Clarified security related motivations for MSRP.
Removed MIKEY dependency for session key exchange. Simple usage o Removed MIKEY dependency for session key exchange. Simple usage
of k-lines in SDP, where the SDP exchange is protected end-to-end of k-lines in SDP, where the SDP exchange is protected end-to-end
seems sufficient. seems sufficient.
15.10 draft-campbell-simple-im-sessions-01 16.11 draft-campbell-simple-im-sessions-01
Version 01 is a significant re-write. References to COMEDIA were Version 01 is a significant re-write. References to COMEDIA were
removed, as it was determined that COMEDIA would not allow removed, as it was determined that COMEDIA would not allow
connections to be used bidirectional in the presence of NATs. connections to be used bidirectional in the presence of NATs.
Significantly more discussion of a concrete mechanism has been added Significantly more discussion of a concrete mechanism has been added
to make up for no longer using COMEDIA. Additionally, this draft and to make up for no longer using COMEDIA. Additionally, this draft and
draft-campbell-cpimmsg-sessions (which would have also changed draft-campbell-cpimmsg-sessions (which would have also changed
drastically) have now been combined into this single draft. drastically) have now been combined into this single draft.
16. Contributors and Acknowledgments 17. Contributors and Acknowledgments
In addition to the editors, The following people contributed In addition to the editors, The following people contributed
extensive work to this document: Chris Boulton, Paul Kyzivat, Orit extensive work to this document: Chris Boulton, Paul Kyzivat, Orit
Levin, Adam Roach, Jonathan Rosenberg, and Robert Sparks. Levin, Adam Roach, Jonathan Rosenberg, and Robert Sparks.
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,
and Orit Levin. Miguel Garcia, Peter Ridler, and Sam Hartman.
17. References 18. References
17.1 Normative References 18.1 Normative References
[1] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC [1] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
2246, January 1999. 2246, January 1999.
[2] Handley, M. and V. Jacobson, "SDP: Session Description [2] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998. Protocol", RFC 2327, April 1998.
[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 2234, November 1997. Specifications: ABNF", RFC 2234, November 1997.
[7] Atkins, D. and G. Klyne, "Common Presence and Instant Messaging [7] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Message Format", draft-ietf-impp-cpim-msgfmt-08 (work in
progress), January 2003.
[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 [8] Troost, R., Dorner, S. and K. Moore, "Communicating
Presentation Information in Internet Messages: The Presentation Information in Internet Messages: The
Content-Disposition Header Field", RFC 2183, August 1997. Content-Disposition Header Field", RFC 2183, August 1997.
[10] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform [9] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396, August Resource Identifiers (URI): Generic Syntax",
1998. draft-fielding-uri-rfc2396bis-07 (work in progress), September
2004.
[11] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J. and [10] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J. and
T. Wright, "Transport Layer Security (TLS) Extensions", RFC T. Wright, "Transport Layer Security (TLS) Extensions", RFC
3546, June 2003. 3546, June 2003.
[12] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE [11] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE
Method", RFC 3311, October 2002. Method", RFC 3311, October 2002.
[13] Atkins, D. and G. Klyne, "Common Presence and Instant [12] Klyne, G. and D. Atkins, "Common Presence and Instant Messaging
Messaging: Message Format", draft-ietf-impp-cpim-msgfmt-08 (CPIM): Message Format", RFC 3862, August 2004.
(work in progress), January 2003.
[14] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for [13] Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for
Transport Layer Secur ity (TLS)", RFC 3268, June 2002. Transport Layer Secur ity (TLS)", RFC 3268, June 2002.
[15] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC [14] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC
3269, November 2003. 3269, November 2003.
17.2 Informational References 18.2 Informational References
[16] Johnston, A. and O. Levin, "Session Initiation Protocol Call [15] Johnston, A. and O. Levin, "Session Initiation Protocol Call
Control - Conferencing for User Agents", Control - Conferencing for User Agents",
draft-ietf-sipping-cc-conferencing-03 (work in progress), draft-ietf-sipping-cc-conferencing-05 (work in progress),
February 2004. October 2004.
[17] Rosenberg, J., Peterson, J., Schulzrinne, H. and G. Camarillo, [16] 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 in the
Session Initiation Protocol", draft-ietf-sipping-3pcc-06 (work Session Initiation Protocol", rfc 3725, April 2004.
in progress), January 2004.
[18] Sparks, R. and A. Johnston, "Session Initiation Protocol Call [17] Sparks, R. and A. Johnston, "Session Initiation Protocol Call
Control - Transfer", draft-ietf-sipping-cc-transfer-02 (work in Control - Transfer", draft-ietf-sipping-cc-transfer-03 (work in
progress), February 2004. progress), October 2004.
[19] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C. and [18] 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.
[20] Mahy, R., "Benefits and Motivation for Session Mode Instant [19] Mahy, R., "Benefits and Motivation for Session Mode Instant
Messaging", draft-mahy-simple-why-session-mode-00 (work in Messaging", draft-mahy-simple-why-session-mode-01 (work in
progress), February 2004. progress), February 2004.
[21] Mahy, R. and C. Jennings, "Relays for the Message Session Relay [20] Jennings, C. and R. Mahy, "Relay Extensions for Message
Protocol (MSRP)", draft-ietf-simple-msrp-relays-01.txt (work in Sessions Relay Protocol (MSRP)",
progress), July 2004. draft-ietf-simple-msrp-relays-02 (work in progress), October
2004.
[22] Peterson, J. and C. Jennings, "Enhancements for Authenticated [21] Peterson, J. and C. Jennings, "Enhancements for Authenticated
Identity Management in the Session Initiation Protocol (SIP)", Identity Management in the Session Initiation Protocol (SIP)",
draft-ietf-sip-identity-02 (work in progress), May 2004. draft-ietf-sip-identity-03 (work in progress), September 2004.
[23] Jennings, C. and J. Peterson, "Certificate Management Service [22] Jennings, C. and J. Peterson, "Certificate Management Service
for SIP", draft-jennings-sipping-certs-03 (work in progress), for SIP", draft-ietf-sipping-certs-00 (work in progress),
May 2004. October 2004.
[24] Yon, D., "Connection-Oriented Media Transport in SDP", [23] Yon, D., "Connection-Oriented Media Transport in SDP",
draft-ietf-mmusic-sdp-comedia-05 (work in progress), March draft-ietf-mmusic-sdp-comedia-09 (work in progress), September
2003. 2004.
[25] Peterson, J., "A Common Profile for Instant Messaging (CPIM)", [24] Peterson, J., "A Common Profile for Instant Messaging (CPIM)",
draft-ietf-impp-im-04 (work in progress), August 2003. rfc 3860, August 2004.
[26] Housley, R., "Triple-DES and RC2 Key Wrapping", RFC 3217, [25] Housley, R., "Triple-DES and RC2 Key Wrapping", RFC 3217,
December 2001. December 2001.
[27] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC [26] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC
2633, June 1999. 2633, June 1999.
[28] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing Tone [27] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing Tone
Generation in the Session Initiation Protocol (SIP)", Generation in the Session Initiation Protocol (SIP)",
draft-ietf-sipping-early-media-02 (work in progress), June draft-ietf-sipping-early-media-02 (work in progress), June
2004. 2004.
[29] Saint-Andre, P., "Extensible Messaging and Presence Protocol [28] Saint-Andre, P., "Extensible Messaging and Presence Protocol
(XMPP): Instant Messaging and Presence", draft-ietf-xmpp-im-22 (XMPP): Instant Messaging and Presence", rfc 3921, October
(work in progress), April 2004. 2004.
[30] Rosenberg, J., "Indicating User Agent Capabilities in the [29] Rosenberg, J., "Indicating User Agent Capabilities in the
Session Initiation Protocol (SIP)", Session Initiation Protocol (SIP)", rfc 3840, August 2004.
draft-ietf-sip-callee-caps-03 (work in progress), January 2004.
Authors' Addresses Authors' Addresses
Ben Campbell (editor) Ben Campbell (editor)
Estacado Systems Estacado Systems
EMail: ben@nostrum.com EMail: ben@estacado.net
Rohan Mahy (editor) Rohan Mahy (editor)
Cisco Systems, Inc. Airespace
5617 Scotts Valley Drive, Suite 200 110 Nortech Parkway
Scotts Valley, CA 95066 San Jose, CA 95134
USA USA
EMail: rohan@cisco.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
EMail: fluffy@cisco.com EMail: fluffy@cisco.com
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
 End of changes. 

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