draft-ietf-dtn-tcpclv4-08.txt   draft-ietf-dtn-tcpclv4-09.txt 
Delay Tolerant Networking B. Sipos Delay Tolerant Networking B. Sipos
Internet-Draft RKF Engineering Internet-Draft RKF Engineering
Obsoletes: 7242 (if approved) M. Demmer Obsoletes: 7242 (if approved) M. Demmer
Intended status: Standards Track UC Berkeley Intended status: Standards Track UC Berkeley
Expires: November 21, 2018 J. Ott Expires: December 26, 2018 J. Ott
Aalto University Aalto University
S. Perreault S. Perreault
May 20, 2018 June 24, 2018
Delay-Tolerant Networking TCP Convergence Layer Protocol Version 4 Delay-Tolerant Networking TCP Convergence Layer Protocol Version 4
draft-ietf-dtn-tcpclv4-08 draft-ietf-dtn-tcpclv4-09
Abstract Abstract
This document describes a revised protocol for the TCP-based This document describes a revised protocol for the TCP-based
convergence layer (TCPCL) for Delay-Tolerant Networking (DTN). The convergence layer (TCPCL) for Delay-Tolerant Networking (DTN). The
protocol revision is based on implementation issues in the original protocol revision is based on implementation issues in the original
TCPCL Version 3 and updates to the Bundle Protocol contents, TCPCL Version 3 of [RFC7242] and updates to the Bundle Protocol
encodings, and convergence layer requirements in Bundle Protocol contents, encodings, and convergence layer requirements in Bundle
Version 7. Specifically, the TCPCLv4 uses CBOR-encoded BPv7 bundles Protocol Version 7. Specifically, the TCPCLv4 uses CBOR-encoded BPv7
as its service data unit being transported and provides a reliable bundles as its service data unit being transported and provides a
transport of such bundles. Several new IANA registries are defined reliable transport of such bundles. Several new IANA registries are
for TCPCLv4 which define some behaviors inherited from TCPCLv3 but defined for TCPCLv4 which define some behaviors inherited from
with updated encodings and/or semantics. TCPCLv3 but with updated encodings and/or semantics.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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."
This Internet-Draft will expire on November 21, 2018. This Internet-Draft will expire on December 26, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 21 skipping to change at page 2, line 21
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Convergence Layer Services . . . . . . . . . . . . . . . 4 1.1. Convergence Layer Services . . . . . . . . . . . . . . . 4
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6
2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 6 2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 6
3. General Protocol Description . . . . . . . . . . . . . . . . 8 3. General Protocol Description . . . . . . . . . . . . . . . . 9
3.1. TCPCL Session Overview . . . . . . . . . . . . . . . . . 8 3.1. TCPCL Session Overview . . . . . . . . . . . . . . . . . 9
3.2. Transfer Segmentation Policies . . . . . . . . . . . . . 10 3.2. TCPCL States and Transitions . . . . . . . . . . . . . . 11
3.3. Example Message Exchange . . . . . . . . . . . . . . . . 11 3.3. Transfer Segmentation Policies . . . . . . . . . . . . . 16
4. Session Establishment . . . . . . . . . . . . . . . . . . . . 13 3.4. Example Message Exchange . . . . . . . . . . . . . . . . 17
4.1. TCP Connection . . . . . . . . . . . . . . . . . . . . . 13 4. Session Establishment . . . . . . . . . . . . . . . . . . . . 19
4.2. Contact Header . . . . . . . . . . . . . . . . . . . . . 13 4.1. TCP Connection . . . . . . . . . . . . . . . . . . . . . 19
4.3. Contact Validation and Negotiation . . . . . . . . . . . 14 4.2. Contact Header . . . . . . . . . . . . . . . . . . . . . 19
4.4. Session Security . . . . . . . . . . . . . . . . . . . . 15 4.3. Contact Validation and Negotiation . . . . . . . . . . . 20
4.4.1. TLS Handshake Result . . . . . . . . . . . . . . . . 16 4.4. Session Security . . . . . . . . . . . . . . . . . . . . 21
4.4.2. Example TLS Initiation . . . . . . . . . . . . . . . 16 4.4.1. TLS Handshake Result . . . . . . . . . . . . . . . . 22
4.5. Message Type Codes . . . . . . . . . . . . . . . . . . . 17 4.4.2. Example TLS Initiation . . . . . . . . . . . . . . . 22
4.6. Session Initialization Message (SESS_INIT) . . . . . . . 18 4.5. Message Type Codes . . . . . . . . . . . . . . . . . . . 23
4.6.1. Session Extension Items . . . . . . . . . . . . . . . 20 4.6. Session Initialization Message (SESS_INIT) . . . . . . . 24
4.7. Session Parameter Negotiation . . . . . . . . . . . . . . 21 4.6.1. Session Extension Items . . . . . . . . . . . . . . . 26
5. Established Session Operation . . . . . . . . . . . . . . . . 22 4.7. Session Parameter Negotiation . . . . . . . . . . . . . . 27
5.1. Upkeep and Status Messages . . . . . . . . . . . . . . . 22 5. Established Session Operation . . . . . . . . . . . . . . . . 28
5.1.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 22 5.1. Upkeep and Status Messages . . . . . . . . . . . . . . . 28
5.1.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 23 5.1.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 28
5.2. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 24 5.1.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 29
5.2.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 24 5.2. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 30
5.2.2. Transfer Initialization (XFER_INIT) . . . . . . . . . 25 5.2.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 30
5.2.3. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 28 5.2.2. Transfer Initialization (XFER_INIT) . . . . . . . . . 31
5.2.4. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 29 5.2.3. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 34
5.2.5. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 30 5.2.4. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 35
6. Session Termination . . . . . . . . . . . . . . . . . . . . . 32 5.2.5. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 36
6.1. Session Termination Message (SESS_TERM) . . . . . . . . . 32 6. Session Termination . . . . . . . . . . . . . . . . . . . . . 38
6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 35 6.1. Session Termination Message (SESS_TERM) . . . . . . . . . 38
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 35 6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 40
8. Security Considerations . . . . . . . . . . . . . . . . . . . 35 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 41
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 8. Security Considerations . . . . . . . . . . . . . . . . . . . 41
9.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 37 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 43
9.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 37 9.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 43
9.3. Session Extension Types . . . . . . . . . . . . . . . . . 38 9.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 43
9.4. Transfer Extension Types . . . . . . . . . . . . . . . . 38 9.3. Session Extension Types . . . . . . . . . . . . . . . . . 44
9.5. Message Types . . . . . . . . . . . . . . . . . . . . . . 39 9.4. Transfer Extension Types . . . . . . . . . . . . . . . . 44
9.6. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 40 9.5. Message Types . . . . . . . . . . . . . . . . . . . . . . 45
9.7. SESS_TERM Reason Codes . . . . . . . . . . . . . . . . . 41 9.6. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 46
9.8. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 42 9.7. SESS_TERM Reason Codes . . . . . . . . . . . . . . . . . 47
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42 9.8. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 48
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48
11.1. Normative References . . . . . . . . . . . . . . . . . . 42 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 48
11.2. Informative References . . . . . . . . . . . . . . . . . 43 11.1. Normative References . . . . . . . . . . . . . . . . . . 48
Appendix A. Significant changes from RFC7242 . . . . . . . . . . 44 11.2. Informative References . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45 Appendix A. Significant changes from RFC7242 . . . . . . . . . . 50
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
1. Introduction 1. Introduction
This document describes the TCP-based convergence-layer protocol for This document describes the TCP-based convergence-layer protocol for
Delay-Tolerant Networking. Delay-Tolerant Networking is an end-to- Delay-Tolerant Networking. Delay-Tolerant Networking is an end-to-
end architecture providing communications in and/or through highly end architecture providing communications in and/or through highly
stressed environments, including those with intermittent stressed environments, including those with intermittent
connectivity, long and/or variable delays, and high bit error rates. connectivity, long and/or variable delays, and high bit error rates.
More detailed descriptions of the rationale and capabilities of these More detailed descriptions of the rationale and capabilities of these
networks can be found in "Delay-Tolerant Network Architecture" networks can be found in "Delay-Tolerant Network Architecture"
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are defined elsewhere in [RFC5050] and [I-D.ietf-dtn-bpbis]. This are defined elsewhere in [RFC5050] and [I-D.ietf-dtn-bpbis]. This
includes the concept of bundle fragmentation or bundle includes the concept of bundle fragmentation or bundle
encapsulation. The TCPCL transfers bundles as opaque data blocks. encapsulation. The TCPCL transfers bundles as opaque data blocks.
o Mechanisms for locating or identifying other bundle entities o Mechanisms for locating or identifying other bundle entities
within an internet. within an internet.
1.1. Convergence Layer Services 1.1. Convergence Layer Services
This version of the TCPCL provides the following services to support This version of the TCPCL provides the following services to support
the overlaying Bundle Protocol agent: the overlaying Bundle Protocol agent. In all cases, this is not an
API defintion but a logical description of how the CL may interact
with the BP agent. Each of these interactions may be associated with
any number of additional metadata items as necessary to support the
operation of the CL or BP agent.
Attempt Session The TCPCL allows a BP agent to pre-emptively attempt Attempt Session The TCPCL allows a BP agent to pre-emptively attempt
to establish a TCPCL session with a peer entity. Each session to establish a TCPCL session with a peer entity. Each session
attempt can send a different set of contact header parameters as attempt can send a different set of session negotiation parameters
directed by the BP agent. as directed by the BP agent.
Shutdown Session The TCPCL allows a BP agent to pre-emptively Terminate Session The TCPCL allows a BP agent to pre-emptively
shutdown an established TCPCL session with a peer entity. The terminate an established TCPCL session with a peer entity. The
shutdown request is on a per-session basis. terminate request is on a per-session basis.
Session is Started The TCPCL supports indication when a new TCP Session State Changed The TCPCL supports indication when the session
connection has been started (as either client or server) before state changes. The top-level session states indicated are:
the TCPCL handshake has begun.
Session is Established The TCPCL supports indication when a new Contact Negotating: A TCP connection has been made (as either
session has been fully established and is ready for its first active or passive entity) and contact negotiation has begun.
transfer.
Session is Shutdown The TCPCL supports indication when an Session Negotiating: Contact negotation has been completed
established session has been ended by normal exchange of SESS_TERM (including possible TLS use) and session negotiation has begun.
messages with all transfers completed.
Session is Failed The TCPCL supports indication when a session Established: The session has been fully established and is ready
fails, either during contact negotiation, TLS negotiation, or for its first transfer.
after establishement for any reason other than normal shutdown.
Closing: The entity received a SESS_TERM message and is in the
closing state.
Terminated: The session has finished normal termination
sequencing..
Failed: The session ended without normal termination sequencing.
Session Idle Changed The TCPCL supports indication when the live/
idle sub-state changes. This occurs only when the top-level
session state is Established. Because TCPCL transmits serially
over a TCP connection, it suffers from "head of queue blocking"
this indication provides information about when a session is
available for immediate transfer start.
Begin Transmission The principal purpose of the TCPCL is to allow a Begin Transmission The principal purpose of the TCPCL is to allow a
BP agent to transmit bundle data over an established TCPCL BP agent to transmit bundle data over an established TCPCL
session. Transmission request is on a per-session basis, the CL session. Transmission request is on a per-session basis, the CL
does not necessarily perform any per-session or inter-session does not necessarily perform any per-session or inter-session
queueing. Any queueing of transmissions is the obligation of the queueing. Any queueing of transmissions is the obligation of the
BP agent. BP agent.
Transmission Availability Because TCPCL transmits serially over a
TCP connection, it suffers from "head of queue blocking" and
supports indication of when an established session is live-but-
idle (i.e. available for immediate transfer start) or live-and-
not-idle.
Transmission Success The TCPCL supports positive indication when a Transmission Success The TCPCL supports positive indication when a
bundle has been fully transferred to a peer entity. bundle has been fully transferred to a peer entity.
Transmission Intermediate Progress The TCPCL supports positive Transmission Intermediate Progress The TCPCL supports positive
indication of intermediate progress of transferr to a peer entity. indication of intermediate progress of transferr to a peer entity.
This intermediate progress is at the granularity of each This intermediate progress is at the granularity of each
transferred segment. transferred segment.
Transmission Failure The TCPCL supports positive indication of Transmission Failure The TCPCL supports positive indication of
certain reasons for bundle transmission failure, notably when the certain reasons for bundle transmission failure, notably when the
peer entity rejects the bundle or when a TCPCL session ends before peer entity rejects the bundle or when a TCPCL session ends before
transferr success. The TCPCL itself does not have a notion of transferr success. The TCPCL itself does not have a notion of
transfer timeout. transfer timeout.
Reception Initialized The TCPCL supports indication to the reciver
just before any transmssion data is sent. This corresponds to
reception of the XFER_INIT message.
Interrupt Reception The TCPCL allows a BP agent to interrupt an Interrupt Reception The TCPCL allows a BP agent to interrupt an
individual transfer before it has fully completed (successfully or individual transfer before it has fully completed (successfully or
not). not). Interruption can occur any time after the reception is
initialized.
Reception Success The TCPCL supports positive indication when a Reception Success The TCPCL supports positive indication when a
bundle has been fully transferred from a peer entity. bundle has been fully transferred from a peer entity.
Reception Intermediate Progress The TCPCL supports positive Reception Intermediate Progress The TCPCL supports positive
indication of intermediate progress of transfer from the peer indication of intermediate progress of transfer from the peer
entity. This intermediate progress is at the granularity of each entity. This intermediate progress is at the granularity of each
transferred segment. Intermediate reception indication allows a transferred segment. Intermediate reception indication allows a
BP agent the chance to inspect bundle header contents before the BP agent the chance to inspect bundle header contents before the
entire bundle is available, and thus supports the "Reception entire bundle is available, and thus supports the "Reception
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transmitter of information to another entity in the network. transmitter of information to another entity in the network.
A TCPCL Entity MAY support zero or more passive listening A TCPCL Entity MAY support zero or more passive listening
elements that listen for connection requests from other TCPCL elements that listen for connection requests from other TCPCL
Entities operating on other entitys in the network. Entities operating on other entitys in the network.
A TCPCL Entity MAY passivley initiate any number of TCPCL A TCPCL Entity MAY passivley initiate any number of TCPCL
Sessions from requests received by its passive listening Sessions from requests received by its passive listening
element(s) if the entity uses such elements. element(s) if the entity uses such elements.
For most TCPCL behavior within a session, the two entities are These relationships are illustrated in Figure 2. For most TCPCL
symmetric and there is no protocol distinction between them. Some behavior within a session, the two entities are symmetric and
specific behavior, particularly during session establishment, there is no protocol distinction between them. Some specific
distinguishes between the active entity and the passive entity. behavior, particularly during session establishment, distinguishes
For the remainder of this document, the term "entity" without the between the active entity and the passive entity. For the
prefix "TCPCL" refers to a TCPCL entity. remainder of this document, the term "entity" without the prefix
"TCPCL" refers to a TCPCL entity.
TCP Connection: The term Connection in this specification TCP Connection: The term Connection in this specification
exclusively refers to a TCP connection and any and all behaviors, exclusively refers to a TCP connection and any and all behaviors,
sessions, and other states association with that TCP connection. sessions, and other states association with that TCP connection.
TCPCL Session: A TCPCL session (as opposed to a TCP connection) is a TCPCL Session: A TCPCL session (as opposed to a TCP connection) is a
TCPCL communication relationship between two TCPCL entities. TCPCL communication relationship between two TCPCL entities.
Within a single TCPCL session there are two possible transfer Within a single TCPCL session there are two possible transfer
streams; one in each direction, with one stream from each entity streams; one in each direction, with one stream from each entity
being the outbound stream and the other being the inbound stream. being the outbound stream and the other being the inbound stream.
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Idle Session: A TCPCL session is idle while the only messages being Idle Session: A TCPCL session is idle while the only messages being
transmitted or received are KEEPALIVE messages. transmitted or received are KEEPALIVE messages.
Live Session: A TCPCL session is live while any messages are being Live Session: A TCPCL session is live while any messages are being
transmitted or received. transmitted or received.
Reason Codes: The TCPCL uses numeric codes to encode specific Reason Codes: The TCPCL uses numeric codes to encode specific
reasons for individual failure/error message types. reasons for individual failure/error message types.
The relationship between connections, sessions, and streams is shown The relationship between connections, sessions, and streams is shown
in Figure 2. in Figure 3.
+--------------------------------------------+
| TCPCL Entity |
| | +----------------+
| +--------------------------------+ | | |-+
| | Actively Inititated Session #1 +------------->| Other | |
| +--------------------------------+ | | TCPCL Entity's | |
| ... | | Passive | |
| +--------------------------------+ | | Listener | |
| | Actively Inititated Session #n +------------->| | |
| +--------------------------------+ | +----------------+ |
| | +-----------------+
| +---------------------------+ |
| +---| +---------------------------+ | +----------------+
| | | | Optional Passive | | | |-+
| | +-| Listener(s) +<-------------+ | |
| | +---------------------------+ | | | |
| | | | Other | |
| | +---------------------------------+ | | TCPCL Entity's | |
| +--->| Passively Inititated Session #1 +-------->| Active | |
| | +---------------------------------+ | | Initiator(s) | |
| | | | | |
| | +---------------------------------+ | | | |
| +--->| Passively Inititated Session #n +-------->| | |
| +---------------------------------+ | +----------------+ |
| | +-----------------+
+--------------------------------------------+
Figure 2: The relationships between TCPCL entities
+----------------------------+ +--------------------------+ +----------------------------+ +--------------------------+
| TCPCL Session | | TCPCL "Other" Session | | TCPCL Session | | TCPCL "Other" Session |
| | | | | | | |
| +-----------------------+ | | +---------------------+ | | +-----------------------+ | | +---------------------+ |
| | TCP Connection | | | | TCP Connection | | | | TCP Connection | | | | TCP Connection | |
| | | | | | | | | | | | | | | |
| | +-------------------+ | | | | +-----------------+ | | | | +-------------------+ | | | | +-----------------+ | |
| | | Optional Inbound | | | | | | Peer Outbound | | | | | | Optional Inbound | | | | | | Peer Outbound | | |
| | | Transfer Stream |<-[Seg]--[Seg]--[Seg]-| | Transfer Stream | | | | | | Transfer Stream |<-[Seg]--[Seg]--[Seg]-| | Transfer Stream | | |
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| | | | | | | | | | | | | | | |
| | +-------------------+ | | | | +-----------------+ | | | | +-------------------+ | | | | +-----------------+ | |
| | | Optional Outbound | | | | | | Peer Inbound | | | | | | Optional Outbound | | | | | | Peer Inbound | | |
| | | Transfer Stream |------[Seg]---[Seg]---->| Transfer Stream | | | | | | Transfer Stream |------[Seg]---[Seg]---->| Transfer Stream | | |
| | | ----- | | | | | | ----- | | | | | | ----- | | | | | | ----- | | |
| | | SENDER | | | | | | RECEIVER | | | | | | SENDER | | | | | | RECEIVER | | |
| | +-------------------+ | | | | +-----------------+ | | | | +-------------------+ | | | | +-----------------+ | |
| +-----------------------+ | | +---------------------+ | | +-----------------------+ | | +---------------------+ |
+----------------------------+ +--------------------------+ +----------------------------+ +--------------------------+
Figure 2: The relationship within a TCPCL Session of its two streams Figure 3: The relationship within a TCPCL Session of its two streams
3. General Protocol Description 3. General Protocol Description
The service of this protocol is the transmission of DTN bundles via The service of this protocol is the transmission of DTN bundles via
the Transmission Control Protocol (TCP). This document specifies the the Transmission Control Protocol (TCP). This document specifies the
encapsulation of bundles, procedures for TCP setup and teardown, and encapsulation of bundles, procedures for TCP setup and teardown, and
a set of messages and node requirements. The general operation of a set of messages and node requirements. The general operation of
the protocol is as follows. the protocol is as follows.
3.1. TCPCL Session Overview 3.1. TCPCL Session Overview
First, one node establishes a TCPCL session to the other by First, one node establishes a TCPCL session to the other by
initiating a TCP connection in accordance with [RFC0793]. After initiating a TCP connection in accordance with [RFC0793]. After
setup of the TCP connection is complete, an initial contact header is setup of the TCP connection is complete, an initial contact header is
exchanged in both directions to set parameters of the TCPCL session exchanged in both directions to establish a shared TCPCL version and
and exchange a singleton endpoint identifier for each node (not the possibly initiate TLS security. Once contact negotiation is
singleton Endpoint Identifier (EID) of any application running on the complete, TCPCL messaging is available and the session negotiation is
node) to denote the bundle-layer identity of each DTN node. This is used to set parameters of the TCPCL session. One of these parameters
used to assist in routing and forwarding messages (e.g. to prevent is a singleton endpoint identifier for each node (not the singleton
loops). Endpoint Identifier (EID) of any application running on the node) to
denote the bundle-layer identity of each DTN node. This is used to
assist in routing and forwarding messages (e.g. to prevent loops).
Once negotiated, the parameters of a TCPCL session cannot change and
if there is a desire by either peer to transfer data under different
parameters then a new session must be established. This makes CL
logic simpler but relies on the assumption that establishing a TCP
connection is lightweight enough that TCP connection overhead is
negligable compared to TCPCL data sizes.
Once the TCPCL session is established and configured in this way, Once the TCPCL session is established and configured in this way,
bundles can be transferred in either direction. Each transfer is bundles can be transferred in either direction. Each transfer is
performed by an initialization (XFER_INIT) message followed by one or performed by an initialization (XFER_INIT) message followed by one or
more logical segments of data within an XFER_SEGMENT message. more logical segments of data within an XFER_SEGMENT message.
Multiple bundles can be transmitted consecutively on a single TCPCL Multiple bundles can be transmitted consecutively on a single TCPCL
connection. Segments from different bundles are never interleaved. connection. Segments from different bundles are never interleaved.
Bundle interleaving can be accomplished by fragmentation at the BP Bundle interleaving can be accomplished by fragmentation at the BP
layer or by establishing multiple TCPCL sessions between the same layer or by establishing multiple TCPCL sessions between the same
peers. peers.
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information during otherwise message-less time intervals. information during otherwise message-less time intervals.
A SESS_TERM message is used to start the closing of a TCPCL session A SESS_TERM message is used to start the closing of a TCPCL session
(see Section 6.1). During shutdown sequencing, in-progress transfers (see Section 6.1). During shutdown sequencing, in-progress transfers
can be completed but no new transfers can be initiated. A SESS_TERM can be completed but no new transfers can be initiated. A SESS_TERM
message can also be used to refuse a session setup by a peer (see message can also be used to refuse a session setup by a peer (see
Section 4.3). It is an implementation matter to determine whether or Section 4.3). It is an implementation matter to determine whether or
not to close a TCPCL session while there are no transfers queued or not to close a TCPCL session while there are no transfers queued or
in-progress. in-progress.
TCPCL is a symmetric protocol between the peers of a session. Both Once a session is established established, TCPCL is a symmetric
sides can start sending data segments in a session, and one side's protocol between the peers. Both sides can start sending data
bundle transfer does not have to complete before the other side can segments in a session, and one side's bundle transfer does not have
start sending data segments on its own. Hence, the protocol allows to complete before the other side can start sending data segments on
for a bi-directional mode of communication. Note that in the case of its own. Hence, the protocol allows for a bi-directional mode of
concurrent bidirectional transmission, acknowledgment segments MAY be communication. Note that in the case of concurrent bidirectional
interleaved with data segments. transmission, acknowledgment segments MAY be interleaved with data
segments.
3.2. Transfer Segmentation Policies 3.2. TCPCL States and Transitions
The states of a nominal TCPCL session (i.e. without session failures)
are indicated in Figure 4.
+-------+
| START |
+-------+
|
TCP Establishment
|
V
+-----------+ +---------------------+
| TCP |----------->| Contact / Session |
| Connected | | Negotiation |
+-----------+ +---------------------+
|
+-----Session Parameters-----+
| Negotiated
V
+-------------+ +-------------+
| Established |----New Transfer---->| Established |
| Session | | Session |
| Idle |<---Transfers Done---| Live |
+-------------+ +-------------+
| |
+------------------------------------+
|
SESS_TERM Exchange
|
V
+-------------+
| Established | +-------------+
| Session |----Transfers------>| TCP |
| Ending | Done | Terminating |
+-------------+ +-------------+
|
+------------Close Message------------+
|
V
+-------+
| END |
+-------+
Figure 4: Top-level states of a TCPCL session
Notes on Established Session states:
Session "Live" means transmitting or reeiving over a transfer
stream.
Session "Idle" means no transmission/reception over a transfer
stream.
Session "Closing" means no new transfers will be allowed.
The contact negotiation sequencing is performed either as the active
or passive peer, and is illustrated in Figure 5 and Figure 6
respectively which both share the data validation and analyze final
states of Figure 7.
+-------+
| START |-----TCP-----+
+-------+ Connecting |
V
+-----------+ +---------+
| Connected |--OK-->| Send CH |--OK-->[PCH]
+-----------+ +---------+
| |
Error Error
| |
V |
[TCPTERM]<-------------+
Figure 5: Contact Initiation as Active peer
+-------+
| START |-----TCP----->[PCH]
+-------+ Connected
Figure 6: Contact Initiation as Passive peer
+-------->[TCPTERM]<----------+
| |
Timeout Error
or Error |
| |
+-------+ +---------+ Contact +----------+
| START |---->| Waiting |---- Header --->| Validate |
+-------+ +---------+ Received +----------+
|
+---------------------------+
|
V
+---------+
+--Error--| Analyze |---No TLS---->[SI]
| | | ^
| +---------+ |
| | |
V TLS |
[TCPTERM] Negotiated |
^ | |
| V |
| +-----------+ |
| | Establish |---Success---+
+--Error--| TLS |
+-----------+
Figure 7: Processing of Contact Header (PCH)
The session negotiation sequencing is performed either as the active
or passive peer, and is illustrated in Figure 8 and Figure 9
respectively which both share the data validation and analyze final
states of Figure 10.
+-------+ TCPCL
| START |--Messaging--+
+-------+ Available |
V
+----------------+
| Send SESS_INIT |--OK-->[PSI]
+----------------+
|
Error
|
V
[SESSTERM]
Figure 8: Session Initiation as Active peer
+-------+ TCPCL
| START |---Messaging-->[PSI]
+-------+ Available
Figure 9: Session Initiation as Passive peer
+------->[SESSTERM]<--------+
| |
Timeout Error
or Error |
| |
+-------+ +---------+ +----------+
| START |---->| Waiting |---SESS_INIT--->| Validate |
+-------+ +---------+ Received +----------+
|
+---------------------------+
|
V
+---------+ +--------------+
+--Error--| Analyze |---->| Established |
| | | | Session Idle |
| +---------+ +--------------+
V
[SESSTERM]
Figure 10: Processing of Session Initiation (PSI)
Transfers can occur after a session is established and it's not in
the ending state. Each transfer occurs within a single logical
transfer stream between a sender and a receiver, as illustrated in
Figure 11 and Figure 12 respectively.
+--Send XFER_DATA--+
+--------+ | |
| Stream | +-------------+ |
| Idle |---Send XFER_INIT-->| In Progress |<---------+
+--------+ +-------------+
|
+------All segments sent-------+
|
V
+---------+ +--------+
| Waiting |---- Receive Final---->| Stream |
| for Ack | Ack | IDLE |
+---------+ +--------+
Figure 11: Transfer sender states
Notes on transfer sending:
Pipelining of transfers can occur when the sending entity begins a
new transfer while in the "Waiting for Ack" state.
+-Receive XFER_DATA-+
+--------+ | Send Ack |
| Stream | +-------------+ |
| IDLE |--Receive XFER_INIT-->| In Progress |<----------+
+--------+ +-------------+
|
+---------Sent Final Ack---------+
|
V
+--------+
| Stream |
| IDLE |
+--------+
Figure 12: Transfer receiver states
3.3. Transfer Segmentation Policies
Each TCPCL session allows a negotiated transfer segmentation polcy to Each TCPCL session allows a negotiated transfer segmentation polcy to
be applied in each transfer direction. A receiving node can set the be applied in each transfer direction. A receiving node can set the
Segment MRU in its contact header to determine the largest acceptable Segment MRU in its contact header to determine the largest acceptable
segment size, and a transmitting node can segment a transfer into any segment size, and a transmitting node can segment a transfer into any
sizes smaller than the receiver's Segment MRU. It is a network sizes smaller than the receiver's Segment MRU. It is a network
administration matter to determine an appropriate segmentation policy administration matter to determine an appropriate segmentation policy
for entities operating TCPCL, but guidance given here can be used to for entities operating TCPCL, but guidance given here can be used to
steer policy toward performance goals. steer policy toward performance goals. It is also advised to
consider the Segment MRU in relation to chunking/packetization
performed by TLS, TCP, and any intermediate network-layer nodes.
Minimum Overhead For a simple network expected to exchange Minimum Overhead For a simple network expected to exchange
relatively small bundles, the Segment MRU can be set to be relatively small bundles, the Segment MRU can be set to be
identical to the Transfer MRU which indicates that all transfers identical to the Transfer MRU which indicates that all transfers
can be sent with a single data segment (i.e. no actual can be sent with a single data segment (i.e. no actual
segmentation). If the network is closed and all transmitters are segmentation). If the network is closed and all transmitters are
known to follow a single-segment transfer policy, then receivers known to follow a single-segment transfer policy, then receivers
can avoid the necessity of segment reassembly. Because this CL can avoid the necessity of segment reassembly. Because this CL
operates over a TCP stream, which suffers from a form of head-of- operates over a TCP stream, which suffers from a form of head-of-
queue blocking between messages, while one node is transmitting a queue blocking between messages, while one node is transmitting a
skipping to change at page 11, line 5 skipping to change at page 17, line 24
MRU. In a situation where network "goodput" is dynamic, the MRU. In a situation where network "goodput" is dynamic, the
transfer segmentation size can also be dynamic in order to control transfer segmentation size can also be dynamic in order to control
message transmission duration. message transmission duration.
Many other policies can be established in a TCPCL network between Many other policies can be established in a TCPCL network between
these two extremes. Different policies can be applied to each these two extremes. Different policies can be applied to each
direction to/from any particular node. Additionally, future header direction to/from any particular node. Additionally, future header
and transfer extension types can apply further nuance to transfer and transfer extension types can apply further nuance to transfer
policies and policy negotiation. policies and policy negotiation.
3.3. Example Message Exchange 3.4. Example Message Exchange
The following figure depicts the protocol exchange for a simple The following figure depicts the protocol exchange for a simple
session, showing the session establishment and the transmission of a session, showing the session establishment and the transmission of a
single bundle split into three data segments (of lengths "L1", "L2", single bundle split into three data segments (of lengths "L1", "L2",
and "L3") from Entity A to Entity B. and "L3") from Entity A to Entity B.
Note that the sending node MAY transmit multiple XFER_SEGMENT Note that the sending node MAY transmit multiple XFER_SEGMENT
messages without necessarily waiting for the corresponding XFER_ACK messages without necessarily waiting for the corresponding XFER_ACK
responses. This enables pipelining of messages on a channel. responses. This enables pipelining of messages on a transfer stream.
Although this example only demonstrates a single bundle transmission, Although this example only demonstrates a single bundle transmission,
it is also possible to pipeline multiple XFER_SEGMENT messages for it is also possible to pipeline multiple XFER_SEGMENT messages for
different bundles without necessarily waiting for XFER_ACK messages different bundles without necessarily waiting for XFER_ACK messages
to be returned for each one. However, interleaving data segments to be returned for each one. However, interleaving data segments
from different bundles is not allowed. from different bundles is not allowed.
No errors or rejections are shown in this example. No errors or rejections are shown in this example.
Entity A Entity B Entity A Entity B
======== ======== ======== ========
skipping to change at page 12, line 51 skipping to change at page 18, line 51
<- | XFER_ACK (end) | <- | XFER_ACK (end) |
| Transfer ID [I1] | | Transfer ID [I1] |
| Length [L1+L2+L3] | | Length [L1+L2+L3] |
+-------------------------+ +-------------------------+
+-------------------------+ +-------------------------+
| SESS_TERM | -> +-------------------------+ | SESS_TERM | -> +-------------------------+
+-------------------------+ <- | SESS_TERM | +-------------------------+ <- | SESS_TERM |
+-------------------------+ +-------------------------+
Figure 3: An example of the flow of protocol messages on a single TCP Figure 13: An example of the flow of protocol messages on a single
Session between two entities TCP Session between two entities
4. Session Establishment 4. Session Establishment
For bundle transmissions to occur using the TCPCL, a TCPCL session For bundle transmissions to occur using the TCPCL, a TCPCL session
MUST first be established between communicating entities. It is up MUST first be established between communicating entities. It is up
to the implementation to decide how and when session setup is to the implementation to decide how and when session setup is
triggered. For example, some sessions MAY be opened proactively and triggered. For example, some sessions MAY be opened proactively and
maintained for as long as is possible given the network conditions, maintained for as long as is possible given the network conditions,
while other sessions MAY be opened only when there is a bundle that while other sessions MAY be opened only when there is a bundle that
is queued for transmission and the routing algorithm selects a is queued for transmission and the routing algorithm selects a
skipping to change at page 14, line 15 skipping to change at page 20, line 15
The format for the Contact Header is as follows: The format for the Contact Header is as follows:
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| magic='dtn!' | | magic='dtn!' |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Version | Flags | | Version | Flags |
+---------------+---------------+ +---------------+---------------+
Figure 4: Contact Header Format Figure 14: Contact Header Format
See Section 4.3 for details on the use of each of these contact See Section 4.3 for details on the use of each of these contact
header fields. The fields of the contact header are: header fields. The fields of the contact header are:
magic: A four-octet field that always contains the octet sequence magic: A four-octet field that always contains the octet sequence
0x64 0x74 0x6e 0x21, i.e., the text string "dtn!" in US-ASCII (and 0x64 0x74 0x6e 0x21, i.e., the text string "dtn!" in US-ASCII (and
UTF-8). UTF-8).
Version: A one-octet field value containing the value 4 (current Version: A one-octet field value containing the value 4 (current
version of the protocol). version of the protocol).
skipping to change at page 15, line 31 skipping to change at page 21, line 31
operation to conform to the older version of the protocol. The operation to conform to the older version of the protocol. The
decision of version fall-back is an implementation matter. decision of version fall-back is an implementation matter.
4.4. Session Security 4.4. Session Security
This version of the TCPCL supports establishing a Transport Layer This version of the TCPCL supports establishing a Transport Layer
Security (TLS) session within an existing TCP connection. When TLS Security (TLS) session within an existing TCP connection. When TLS
is used within the TCPCL it affects the entire session. Once is used within the TCPCL it affects the entire session. Once
established, there is no mechanism available to downgrade a TCPCL established, there is no mechanism available to downgrade a TCPCL
session to non-TLS operation. If this is desired, the entire TCPCL session to non-TLS operation. If this is desired, the entire TCPCL
session MUST be shutdown and a new non-TLS-negotiated session session MUST be terminated and a new non-TLS-negotiated session
established. established.
The use of TLS is negotated using the Contact Header as described in The use of TLS is negotated using the Contact Header as described in
Section 4.3. After negotiating an Enable TLS parameter of true, and Section 4.3. After negotiating an Enable TLS parameter of true, and
before any other TCPCL messages are sent within the session, the before any other TCPCL messages are sent within the session, the
session entities SHALL begin a TLS handshake in accordance with session entities SHALL begin a TLS handshake in accordance with
[RFC5246]. The parameters within each TLS negotiation are [RFC5246]. The parameters within each TLS negotiation are
implementation dependent but any TCPCL node SHOULD follow all implementation dependent but any TCPCL node SHOULD follow all
recommended best practices of [RFC7525]. By convention, this recommended best practices of [RFC7525]. By convention, this
protocol uses the node which initiated the underlying TCP connection protocol uses the node which initiated the underlying TCP connection
as the "client" role of the TLS handshake request. as the "client" role of the TLS handshake request.
The TLS handshake, if it occurs, is considered to be part of the The TLS handshake, if it occurs, is considered to be part of the
contact negotiation before the TCPCL session itself is established. contact negotiation before the TCPCL session itself is established.
Specifics about sensitive data exposure are discussed in Section 8. Specifics about sensitive data exposure are discussed in Section 8.
4.4.1. TLS Handshake Result 4.4.1. TLS Handshake Result
If a TLS handshake cannot negotiate a TLS session, both entities of If a TLS handshake cannot negotiate a TLS session, both entities of
the TCPCL session SHALL start a TCPCL shutdown with reason "TLS the TCPCL session SHALL terminate the TCP connection. At this point
Failure". the TCPCL session has not yet been established so there is no TCPCL
session to terminate. This also avoids any potential security issues
assoicated with further TCP communication with an untrusted peer.
After a TLS session is successfully established, both TCPCL entities After a TLS session is successfully established, the active peer
SHALL re-exchange TCPCL Contact Header messages. Any information SHALL send a SESS_INIT message to begin session negotiation. This
cached from the prior Contact Header exchange SHALL be discarded. session negotation and all subsequent messaging are secured.
This re-exchange avoids a "man-in-the-middle" attack in identical
fashion to [RFC2595]. Each re-exchange header CAN_TLS flag SHALL be
identical to the original header CAN_TLS flag from the same node.
The CAN_TLS logic (TLS negotiation) SHALL NOT apply during header re-
exchange. This reinforces the fact that there is no TLS downgrade
mechanism.
4.4.2. Example TLS Initiation 4.4.2. Example TLS Initiation
A summary of a typical CAN_TLS usage is shown in the sequence in A summary of a typical CAN_TLS usage is shown in the sequence in
Figure 5 below. Figure 15 below.
Entity A Entity B Entity A Entity B
======== ======== ======== ========
+-------------------------+ +-------------------------+
| Open TCP Connnection | -> | Open TCP Connnection | ->
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
<- | Accept Connection | <- | Accept Connection |
+-------------------------+ +-------------------------+
+-------------------------+
| Contact Header | ->
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
| Contact Header | -> <- | Contact Header | <- | Contact Header |
+-------------------------+ +-------------------------+ +-------------------------+
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
| TLS Negotiation | -> <- | TLS Negotiation | | TLS Negotiation | -> <- | TLS Negotiation |
| (as client) | | (as server) | | (as client) | | (as server) |
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
... secured TCPCL messaging, starting with SESS_INIT ... ... secured TCPCL messaging, starting with SESS_INIT ...
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
| SESS_TERM | -> <- | SESS_TERM | | SESS_TERM | -> <- | SESS_TERM |
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
Figure 5: A simple visual example of TCPCL TLS Establishment between Figure 15: A simple visual example of TCPCL TLS Establishment between
two entities two entities
4.5. Message Type Codes 4.5. Message Type Codes
After the initial exchange of a contact header, all messages After the initial exchange of a contact header, all messages
transmitted over the session are identified by a one-octet header transmitted over the session are identified by a one-octet header
with the following structure: with the following structure:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------+ +---------------+
| Message Type | | Message Type |
+---------------+ +---------------+
Figure 6: Format of the Message Header Figure 16: Format of the Message Header
The message header fields are as follows: The message header fields are as follows:
Message Type: Indicates the type of the message as per Table 2 Message Type: Indicates the type of the message as per Table 2
below. Encoded values are listed in Section 9.5. below. Encoded values are listed in Section 9.5.
+--------------+----------------------------------------------------+ +--------------+----------------------------------------------------+
| Type | Description | | Type | Description |
+--------------+----------------------------------------------------+ +--------------+----------------------------------------------------+
| SESS_INIT | Contains the session parameter inputs from one of | | SESS_INIT | Contains the session parameter inputs from one of |
skipping to change at page 18, line 44 skipping to change at page 24, line 44
Table 2: TCPCL Message Types Table 2: TCPCL Message Types
4.6. Session Initialization Message (SESS_INIT) 4.6. Session Initialization Message (SESS_INIT)
Before a session is established and ready to transfer bundles, the Before a session is established and ready to transfer bundles, the
session parameters are negotiated between the connected entities. session parameters are negotiated between the connected entities.
The SESS_INIT message is used to convey the per-entity parameters The SESS_INIT message is used to convey the per-entity parameters
which are used together to negotiate the per-session parameters. which are used together to negotiate the per-session parameters.
The format of a SESS_INIT message is as follows in Figure 7. The format of a SESS_INIT message is as follows in Figure 17.
+-------------------------------+ +-------------------------------+
| Message Header | | Message Header |
+-------------------------------+ +-------------------------------+
| Keepalive Interval (U16) | | Keepalive Interval (U16) |
+-------------------------------+ +-------------------------------+
| Segment MRU (U64) | | Segment MRU (U64) |
+-------------------------------+ +-------------------------------+
| Transfer MRU (U64) | | Transfer MRU (U64) |
+-------------------------------+ +-------------------------------+
| EID Length (U16) | | EID Length (U16) |
+-------------------------------+ +-------------------------------+
| EID Data (variable) | | EID Data (variable) |
+-------------------------------+ +-------------------------------+
| Session Extension Length (U64)| | Session Extension Length (U64)|
+-------------------------------+ +-------------------------------+
| Session Extension Items (var.)| | Session Extension Items (var.)|
+-------------------------------+ +-------------------------------+
Figure 7: SESS_INIT Format Figure 17: SESS_INIT Format
A 16-bit unsigned integer indicating the interval, in seconds, A 16-bit unsigned integer indicating the interval, in seconds,
between any subsequent messages being transmitted by the peer. between any subsequent messages being transmitted by the peer.
The peer receiving this contact header uses this interval to The peer receiving this contact header uses this interval to
determine how long to wait after any last-message transmission and determine how long to wait after any last-message transmission and
a necessary subsequent KEEPALIVE message transmission. a necessary subsequent KEEPALIVE message transmission.
A 64-bit unsigned integer indicating the largest allowable single- A 64-bit unsigned integer indicating the largest allowable single-
segment data payload size to be received in this session. Any segment data payload size to be received in this session. Any
XFER_SEGMENT sent to this peer SHALL have a data payload no longer XFER_SEGMENT sent to this peer SHALL have a data payload no longer
skipping to change at page 20, line 21 skipping to change at page 26, line 21
Session Extension Item list. The encoding of each Session Session Extension Item list. The encoding of each Session
Extension Item is within a consistent data container as described Extension Item is within a consistent data container as described
in Section 4.6.1. The full set of Session Extension Items apply in Section 4.6.1. The full set of Session Extension Items apply
for the duration of the TCPCL session to follow. The order and for the duration of the TCPCL session to follow. The order and
mulitplicity of these Session Extension Items MAY be significant, mulitplicity of these Session Extension Items MAY be significant,
as defined in the associated type specification(s). as defined in the associated type specification(s).
4.6.1. Session Extension Items 4.6.1. Session Extension Items
Each of the Session Extension Items SHALL be encoded in an identical Each of the Session Extension Items SHALL be encoded in an identical
Type-Length-Value (TLV) container form as indicated in Figure 8. The Type-Length-Value (TLV) container form as indicated in Figure 18.
fields of the Session Extension Item are: The fields of the Session Extension Item are:
Flags: A one-octet field containing generic bit flags about the Flags: A one-octet field containing generic bit flags about the
Item, which are listed in Table 3. If a TCPCL entity receives a Item, which are listed in Table 3. If a TCPCL entity receives a
Session Extension Item with an unknown Item Type and the CRITICAL Session Extension Item with an unknown Item Type and the CRITICAL
flag set, the entity SHALL close the TCPCL session with SESS_TERM flag set, the entity SHALL close the TCPCL session with SESS_TERM
reason code of "Contact Failure". If the CRITICAL flag is not reason code of "Contact Failure". If the CRITICAL flag is not
set, an entity SHALL skip over and ignore any item with an unknown set, an entity SHALL skip over and ignore any item with an unknown
Item Type. Item Type.
Item Type: A 16-bit unsigned integer field containing the type of Item Type: A 16-bit unsigned integer field containing the type of
skipping to change at page 21, line 15 skipping to change at page 27, line 15
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Item Flags | Item Type | Item Length...| | Item Flags | Item Type | Item Length...|
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| length contd. | Item Value... | | length contd. | Item Value... |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| value contd. | | value contd. |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
Figure 8: Session Extension Item Format Figure 18: Session Extension Item Format
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| Name | Code | Description | | Name | Code | Description |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| CRITICAL | 0x01 | If bit is set, indicates that the receiving | | CRITICAL | 0x01 | If bit is set, indicates that the receiving |
| | | peer must handle the extension item. | | | | peer must handle the extension item. |
| | | | | | | |
| Reserved | others | | Reserved | others |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
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each transmitted segment is an implementation matter. each transmitted segment is an implementation matter.
Session Keepalive: Negotiation of the Session Keepalive parameter is Session Keepalive: Negotiation of the Session Keepalive parameter is
performed by taking the minimum of this two contact headers' performed by taking the minimum of this two contact headers'
Keepalive Interval. The Session Keepalive interval is a parameter Keepalive Interval. The Session Keepalive interval is a parameter
for the behavior described in Section 5.1.1. for the behavior described in Section 5.1.1.
Enable TLS: Negotiation of the Enable TLS parameter is performed by Enable TLS: Negotiation of the Enable TLS parameter is performed by
taking the logical AND of the two contact headers' CAN_TLS flags. taking the logical AND of the two contact headers' CAN_TLS flags.
A local security policy is then applied to determine of the A local security policy is then applied to determine of the
negotated value of Enable TLS is acceptable. If not, the node negotated value of Enable TLS is acceptable. It can be a
SHALL shutdown the session with a reason code of "Contact reasonable security policy to both require or disallow the use of
Failure". Note that this contact failure is different than a "TLS TLS depending upon the desired network flows. If the Enable TLS
Failure" after an agreed-upon and acceptable Enable TLS state. If state is unacceptable, the node SHALL terminate the session with a
the negotiated Enable TLS value is true and acceptable then TLS reason code of "Contact Failure". Note that this contact failure
negotiation feature (described in Section 4.4) begins immediately is different than a failure of TLS handshake after an agreed-upon
following the contact header exchange. and acceptable Enable TLS state. If the negotiated Enable TLS
value is true and acceptable then TLS negotiation feature
(described in Section 4.4) begins immediately following the
contact header exchange.
Once this process of parameter negotiation is completed (which Once this process of parameter negotiation is completed (which
includes a possible completed TLS handshake of the connection to use includes a possible completed TLS handshake of the connection to use
TLS), this protocol defines no additional mechanism to change the TLS), this protocol defines no additional mechanism to change the
parameters of an established session; to effect such a change, the parameters of an established session; to effect such a change, the
TCPCL session MUST be terminated and a new session established. TCPCL session MUST be terminated and a new session established.
5. Established Session Operation 5. Established Session Operation
This section describes the protocol operation for the duration of an This section describes the protocol operation for the duration of an
skipping to change at page 23, line 25 skipping to change at page 29, line 27
5.1.2. Message Rejection (MSG_REJECT) 5.1.2. Message Rejection (MSG_REJECT)
If a TCPCL node receives a message which is unknown to it (possibly If a TCPCL node receives a message which is unknown to it (possibly
due to an unhandled protocol mismatch) or is inappropriate for the due to an unhandled protocol mismatch) or is inappropriate for the
current session state (e.g. a KEEPALIVE message received after current session state (e.g. a KEEPALIVE message received after
contact header negotiation has disabled that feature), there is a contact header negotiation has disabled that feature), there is a
protocol-level message to signal this condition in the form of a protocol-level message to signal this condition in the form of a
MSG_REJECT reply. MSG_REJECT reply.
The format of a MSG_REJECT message is as follows in Figure 9. The format of a MSG_REJECT message is as follows in Figure 19.
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Reason Code (U8) | | Reason Code (U8) |
+-----------------------------+ +-----------------------------+
| Rejected Message Header | | Rejected Message Header |
+-----------------------------+ +-----------------------------+
Figure 9: Format of MSG_REJECT Messages Figure 19: Format of MSG_REJECT Messages
The fields of the MSG_REJECT message are: The fields of the MSG_REJECT message are:
Reason Code: A one-octet refusal reason code interpreted according Reason Code: A one-octet refusal reason code interpreted according
to the descriptions in Table 4. to the descriptions in Table 4.
Rejected Message Header: The Rejected Message Header is a copy of Rejected Message Header: The Rejected Message Header is a copy of
the Message Header to which the MSG_REJECT message is sent as a the Message Header to which the MSG_REJECT message is sent as a
response. response.
skipping to change at page 25, line 39 skipping to change at page 31, line 39
prepare storage on the receiving node for the upcoming bundle data. prepare storage on the receiving node for the upcoming bundle data.
See Section 5.2.5 for details on when refusal based on XFER_INIT See Section 5.2.5 for details on when refusal based on XFER_INIT
content is acceptable. content is acceptable.
The Total Bundle Length field within a XFER_INIT message SHALL be The Total Bundle Length field within a XFER_INIT message SHALL be
treated as authoritative by the receiver. If, for whatever reason, treated as authoritative by the receiver. If, for whatever reason,
the actual total length of bundle data received differs from the the actual total length of bundle data received differs from the
value indicated by the XFER_INIT message, the receiver SHOULD treat value indicated by the XFER_INIT message, the receiver SHOULD treat
the transmitted data as invalid. the transmitted data as invalid.
The format of the XFER_INIT message is as follows in Figure 10. The format of the XFER_INIT message is as follows in Figure 20.
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
| Total Bundle Length (U64) | | Total Bundle Length (U64) |
+-----------------------------+ +-----------------------------+
| Transfer Extension | | Transfer Extension |
| Length (U64) | | Length (U64) |
+-----------------------------+ +-----------------------------+
| Transfer Extension Items... | | Transfer Extension Items... |
+-----------------------------+ +-----------------------------+
Figure 10: Format of XFER_INIT Messages Figure 20: Format of XFER_INIT Messages
The fields of the XFER_INIT message are: The fields of the XFER_INIT message are:
Transfer ID: A 64-bit unsigned integer identifying the transfer Transfer ID: A 64-bit unsigned integer identifying the transfer
about to begin. about to begin.
Total Bundle Length: A 64-bit unsigned integer indicating the size Total Bundle Length: A 64-bit unsigned integer indicating the size
of the data-to-be-transferred. of the data-to-be-transferred.
Transfer Extension Length and Transfer Extension Items: Together Transfer Extension Length and Transfer Extension Items: Together
skipping to change at page 26, line 48 skipping to change at page 32, line 48
An XFER_INIT message SHALL be sent as the first message in a transfer An XFER_INIT message SHALL be sent as the first message in a transfer
sequence, before transmission of any XFER_SEGMENT messages for the sequence, before transmission of any XFER_SEGMENT messages for the
same Transfer ID. XFER_INIT messages MUST NOT be sent unless the same Transfer ID. XFER_INIT messages MUST NOT be sent unless the
next XFER_SEGMENT message has the 'START' bit set to "1" (i.e., just next XFER_SEGMENT message has the 'START' bit set to "1" (i.e., just
before the start of a new transfer). before the start of a new transfer).
5.2.2.1. Transfer Extension Items 5.2.2.1. Transfer Extension Items
Each of the Transfer Extension Items SHALL be encoded in an identical Each of the Transfer Extension Items SHALL be encoded in an identical
Type-Length-Value (TLV) container form as indicated in Figure 11. Type-Length-Value (TLV) container form as indicated in Figure 21.
The fields of the Transfer Extension Item are: The fields of the Transfer Extension Item are:
Flags: A one-octet field containing generic bit flags about the Flags: A one-octet field containing generic bit flags about the
Item, which are listed in Table 5. If a TCPCL node receives a Item, which are listed in Table 5. If a TCPCL node receives a
Transfer Extension Item with an unknown Item Type and the CRITICAL Transfer Extension Item with an unknown Item Type and the CRITICAL
flag set, the node SHALL close the TCPCL session with SESS_TERM flag set, the node SHALL refuse the transfer with an XFER_REFUSE
reason code of "Contact Failure". If the CRITICAL flag is not reason code of "Extension Failure". If the CRITICAL flag is not
set, an entity SHALL skip over and ignore any item with an unknown set, an entity SHALL skip over and ignore any item with an unknown
Item Type. Item Type.
Item Type: A 16-bit unsigned integer field containing the type of Item Type: A 16-bit unsigned integer field containing the type of
the extension item. This specification does not define any the extension item. This specification does not define any
extension types directly, but does allocate an IANA registry for extension types directly, but does allocate an IANA registry for
such codes (see Section 9.4). such codes (see Section 9.4).
Item Length: A 32-bit unsigned integer field containing the number Item Length: A 32-bit unsigned integer field containing the number
of Item Value octets to follow. of Item Value octets to follow.
skipping to change at page 27, line 35 skipping to change at page 33, line 35
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Item Flags | Item Type | Item Length...| | Item Flags | Item Type | Item Length...|
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| length contd. | Item Value... | | length contd. | Item Value... |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| value contd. | | value contd. |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
Figure 11: Transfer Extension Item Format Figure 21: Transfer Extension Item Format
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| Name | Code | Description | | Name | Code | Description |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| CRITICAL | 0x01 | If bit is set, indicates that the receiving | | CRITICAL | 0x01 | If bit is set, indicates that the receiving |
| | | peer must handle the extension item. | | | | peer must handle the extension item. |
| | | | | | | |
| Reserved | others | | Reserved | others |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
Table 5: Transfer Extension Item Flags Table 5: Transfer Extension Item Flags
5.2.3. Data Transmission (XFER_SEGMENT) 5.2.3. Data Transmission (XFER_SEGMENT)
Each bundle is transmitted in one or more data segments. The format Each bundle is transmitted in one or more data segments. The format
of a XFER_SEGMENT message follows in Figure 12. of a XFER_SEGMENT message follows in Figure 22.
+------------------------------+ +------------------------------+
| Message Header | | Message Header |
+------------------------------+ +------------------------------+
| Message Flags (U8) | | Message Flags (U8) |
+------------------------------+ +------------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+------------------------------+ +------------------------------+
| Data length (U64) | | Data length (U64) |
+------------------------------+ +------------------------------+
| Data contents (octet string) | | Data contents (octet string) |
+------------------------------+ +------------------------------+
Figure 12: Format of XFER_SEGMENT Messages Figure 22: Format of XFER_SEGMENT Messages
The fields of the XFER_SEGMENT message are: The fields of the XFER_SEGMENT message are:
Message Flags: A one-octet field of single-bit flags, interpreted Message Flags: A one-octet field of single-bit flags, interpreted
according to the descriptions in Table 6. according to the descriptions in Table 6.
Transfer ID: A 64-bit unsigned integer identifying the transfer Transfer ID: A 64-bit unsigned integer identifying the transfer
being made. being made.
Data length: A 64-bit unsigned integer indicating the number of Data length: A 64-bit unsigned integer indicating the number of
skipping to change at page 29, line 29 skipping to change at page 35, line 29
Although the TCP transport provides reliable transfer of data between Although the TCP transport provides reliable transfer of data between
transport peers, the typical BSD sockets interface provides no means transport peers, the typical BSD sockets interface provides no means
to inform a sending application of when the receiving application has to inform a sending application of when the receiving application has
processed some amount of transmitted data. Thus, after transmitting processed some amount of transmitted data. Thus, after transmitting
some data, the TCPCL needs an additional mechanism to determine some data, the TCPCL needs an additional mechanism to determine
whether the receiving agent has successfully received the segment. whether the receiving agent has successfully received the segment.
To this end, the TCPCL protocol provides feedback messaging whereby a To this end, the TCPCL protocol provides feedback messaging whereby a
receiving node transmits acknowledgments of reception of data receiving node transmits acknowledgments of reception of data
segments. segments.
The format of an XFER_ACK message follows in Figure 13. The format of an XFER_ACK message follows in Figure 23.
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Message Flags (U8) | | Message Flags (U8) |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
| Acknowledged length (U64) | | Acknowledged length (U64) |
+-----------------------------+ +-----------------------------+
Figure 13: Format of XFER_ACK Messages Figure 23: Format of XFER_ACK Messages
The fields of the XFER_ACK message are: The fields of the XFER_ACK message are:
Message Flags: A one-octet field of single-bit flags, interpreted Message Flags: A one-octet field of single-bit flags, interpreted
according to the descriptions in Table 6. according to the descriptions in Table 6.
Transfer ID: A 64-bit unsigned integer identifying the transfer Transfer ID: A 64-bit unsigned integer identifying the transfer
being acknowledged. being acknowledged.
Acknowledged length: A 64-bit unsigned integer indicating the total Acknowledged length: A 64-bit unsigned integer indicating the total
number of octets in the transfer which are being acknowledged. number of octets in the transfer which are being acknowledged.
A receiving TCPCL node SHALL send an XFER_ACK message in response to A receiving TCPCL node SHALL send an XFER_ACK message in response to
each received XFER_SEGMENT message. The flags portion of the each received XFER_SEGMENT message. The flags portion of the
XFER_ACK header SHALL be set to match the corresponding DATA_SEGMENT XFER_ACK header SHALL be set to match the corresponding DATA_SEGMENT
message being acknowledged. The acknowledged length of each XFER_ACK message being acknowledged. The acknowledged length of each XFER_ACK
contains the sum of the data length fields of all XFER_SEGMENT contains the sum of the data length fields of all XFER_SEGMENT
messages received so far in the course of the indicated transfer. messages received so far in the course of the indicated transfer.
The sending node MAY transmit multiple XFER_SEGMENT messages without The sending node MAY transmit multiple XFER_SEGMENT messages without
necessarily waiting for the corresponding XFER_ACK responses. This necessarily waiting for the corresponding XFER_ACK responses. This
enables pipelining of messages on a channel. enables pipelining of messages on a transfer stream.
For example, suppose the sending node transmits four segments of For example, suppose the sending node transmits four segments of
bundle data with lengths 100, 200, 500, and 1000, respectively. bundle data with lengths 100, 200, 500, and 1000, respectively.
After receiving the first segment, the node sends an acknowledgment After receiving the first segment, the node sends an acknowledgment
of length 100. After the second segment is received, the node sends of length 100. After the second segment is received, the node sends
an acknowledgment of length 300. The third and fourth an acknowledgment of length 300. The third and fourth
acknowledgments are of length 800 and 1800, respectively. acknowledgments are of length 800 and 1800, respectively.
5.2.5. Transfer Refusal (XFER_REFUSE) 5.2.5. Transfer Refusal (XFER_REFUSE)
skipping to change at page 30, line 48 skipping to change at page 36, line 48
XFER_REFUSE can be used in cases where the agent's bundle storage is XFER_REFUSE can be used in cases where the agent's bundle storage is
temporarily depleted or somehow constrained. A XFER_REFUSE can also temporarily depleted or somehow constrained. A XFER_REFUSE can also
be used after the bundle header or any bundle data is inspected by an be used after the bundle header or any bundle data is inspected by an
agent and determined to be unacceptable. agent and determined to be unacceptable.
A receiver MAY send an XFER_REFUSE message as soon as it receives a A receiver MAY send an XFER_REFUSE message as soon as it receives a
XFER_INIT message without waiting for the next XFER_SEGMENT message. XFER_INIT message without waiting for the next XFER_SEGMENT message.
The sender MUST be prepared for this and MUST associate the refusal The sender MUST be prepared for this and MUST associate the refusal
with the correct bundle via the Transfer ID fields. with the correct bundle via the Transfer ID fields.
The format of the XFER_REFUSE message is as follows in Figure 14. The format of the XFER_REFUSE message is as follows in Figure 24.
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Reason Code (U8) | | Reason Code (U8) |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
Figure 14: Format of XFER_REFUSE Messages Figure 24: Format of XFER_REFUSE Messages
The fields of the XFER_REFUSE message are: The fields of the XFER_REFUSE message are:
Reason Code: A one-octet refusal reason code interpreted according Reason Code: A one-octet refusal reason code interpreted according
to the descriptions in Table 7. to the descriptions in Table 7.
Transfer ID: A 64-bit unsigned integer identifying the transfer Transfer ID: A 64-bit unsigned integer identifying the transfer
being refused. being refused.
+------------+------------------------------------------------------+ +------------+------------------------------------------------------+
| Name | Semantics | | Name | Semantics |
+------------+------------------------------------------------------+ +------------+------------------------------------------------------+
| Unknown | Reason for refusal is unknown or not specified. | | Unknown | Reason for refusal is unknown or not specified. |
| | | | | |
| Extension | A failure processing the Transfer Extension Items ha |
| Failure | occurred. |
| | |
| Completed | The receiver already has the complete bundle. The | | Completed | The receiver already has the complete bundle. The |
| | sender MAY consider the bundle as completely | | | sender MAY consider the bundle as completely |
| | received. | | | received. |
| | | | | |
| No | The receiver's resources are exhausted. The sender | | No | The receiver's resources are exhausted. The sender |
| Resources | SHOULD apply reactive bundle fragmentation before | | Resources | SHOULD apply reactive bundle fragmentation before |
| | retrying. | | | retrying. |
| | | | | |
| Retransmit | The receiver has encountered a problem that requires | | Retransmit | The receiver has encountered a problem that requires |
| | the bundle to be retransmitted in its entirety. | | | the bundle to be retransmitted in its entirety. |
skipping to change at page 32, line 46 skipping to change at page 38, line 49
SESS_TERM message an entity MAY immediately close the associated TCP SESS_TERM message an entity MAY immediately close the associated TCP
connection. When performing an unclean shutdown, a receiving node connection. When performing an unclean shutdown, a receiving node
SHOULD acknowledge all received data segments before closing the TCP SHOULD acknowledge all received data segments before closing the TCP
connection. When performing an unclean shutodwn, a transmitting node connection. When performing an unclean shutodwn, a transmitting node
SHALL treat either sending or receiving a SESS_TERM message (i.e. SHALL treat either sending or receiving a SESS_TERM message (i.e.
before the final acknowledgment) as a failure of the transfer. Any before the final acknowledgment) as a failure of the transfer. Any
delay between request to terminate the TCP connection and actual delay between request to terminate the TCP connection and actual
closing of the connection (a "half-closed" state) MAY be ignored by closing of the connection (a "half-closed" state) MAY be ignored by
the TCPCL node. the TCPCL node.
The format of the SESS_TERM message is as follows in Figure 15. The format of the SESS_TERM message is as follows in Figure 25.
+-----------------------------------+ +-----------------------------------+
| Message Header | | Message Header |
+-----------------------------------+ +-----------------------------------+
| Message Flags (U8) | | Message Flags (U8) |
+-----------------------------------+ +-----------------------------------+
| Reason Code (optional U8) | | Reason Code (optional U8) |
+-----------------------------------+ +-----------------------------------+
Figure 15: Format of SESS_TERM Messages Figure 25: Format of SESS_TERM Messages
The fields of the SESS_TERM message are: The fields of the SESS_TERM message are:
Message Flags: A one-octet field of single-bit flags, interpreted Message Flags: A one-octet field of single-bit flags, interpreted
according to the descriptions in Table 8. according to the descriptions in Table 8.
Reason Code: A one-octet refusal reason code interpreted according Reason Code: A one-octet refusal reason code interpreted according
to the descriptions in Table 9. The Reason Code is present or to the descriptions in Table 9. The Reason Code is present or
absent as indicated by one of the flags. absent as indicated by one of the flags.
skipping to change at page 34, line 19 skipping to change at page 40, line 19
| | | | | |
| Version | The node cannot conform to the specified TCPCL | | Version | The node cannot conform to the specified TCPCL |
| mismatch | protocol version. | | mismatch | protocol version. |
| | | | | |
| Busy | The node is too busy to handle the current | | Busy | The node is too busy to handle the current |
| | session. | | | session. |
| | | | | |
| Contact | The node cannot interpret or negotiate contact | | Contact | The node cannot interpret or negotiate contact |
| Failure | header option. | | Failure | header option. |
| | | | | |
| TLS Failure | The node failed to negotiate TLS session and |
| | cannot continue the session. |
| | |
| Resource | The node has run into some resource limit and | | Resource | The node has run into some resource limit and |
| Exhaustion | cannot continue the session. | | Exhaustion | cannot continue the session. |
+---------------+---------------------------------------------------+ +---------------+---------------------------------------------------+
Table 9: SESS_TERM Reason Codes Table 9: SESS_TERM Reason Codes
A session shutdown MAY occur immediately after transmission of a A session shutdown MAY occur immediately after transmission of a
contact header (and prior to any further message transmit). This contact header (and prior to any further message transmit). This
MAY, for example, be used to notify that the node is currently not MAY, for example, be used to notify that the node is currently not
able or willing to communicate. However, an entity MUST always send able or willing to communicate. However, an entity MUST always send
skipping to change at page 37, line 10 skipping to change at page 43, line 7
service on other, well-behaving sessions. There is also nothing to service on other, well-behaving sessions. There is also nothing to
prevent a malicious entity from continually establishing sessions and prevent a malicious entity from continually establishing sessions and
repeatedly trying to send copious amounts of bundle data. A repeatedly trying to send copious amounts of bundle data. A
listening entity MAY take countermeasures such as ignoring TCP SYN listening entity MAY take countermeasures such as ignoring TCP SYN
messages, closing TCP connections as soon as they are established, messages, closing TCP connections as soon as they are established,
waiting before sending the contact header, sending a SESS_TERM waiting before sending the contact header, sending a SESS_TERM
message quickly or with a delay, etc. message quickly or with a delay, etc.
9. IANA Considerations 9. IANA Considerations
In this section, registration procedures are as defined in [RFC5226]. In this section, registration procedures are as defined in [RFC8126].
Some of the registries below are created new for TCPCLv4 but share Some of the registries below are created new for TCPCLv4 but share
code values with TCPCLv3. This was done to disambiguate the use of code values with TCPCLv3. This was done to disambiguate the use of
these values between TCPCLv3 and TCPCLv4 while preserving the these values between TCPCLv3 and TCPCLv4 while preserving the
semantics of some values. semantics of some values.
9.1. Port Number 9.1. Port Number
Port number 4556 has been previously assigned as the default port for Port number 4556 has been previously assigned as the default port for
the TCP convergence layer in [RFC7242]. This assignment is unchanged the TCP convergence layer in [RFC7242]. This assignment is unchanged
skipping to change at page 41, line 10 skipping to change at page 47, line 10
IANA will create, under the "Bundle Protocol" registry, a sub- IANA will create, under the "Bundle Protocol" registry, a sub-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
XFER_REFUSE Reason Codes" and initialize it with the contents of XFER_REFUSE Reason Codes" and initialize it with the contents of
Table 14. The registration procedure is RFC Required. Table 14. The registration procedure is RFC Required.
+----------+---------------------------+ +----------+---------------------------+
| Code | Refusal Reason | | Code | Refusal Reason |
+----------+---------------------------+ +----------+---------------------------+
| 0x0 | Unknown | | 0x0 | Unknown |
| | | | | |
| 0x1 | Completed | | 0x1 | Extension Failure |
| | | | | |
| 0x2 | No Resources | | 0x2 | Completed |
| | | | | |
| 0x3 | Retransmit | | 0x3 | No Resources |
| | | | | |
| 0x4--0x7 | Unassigned | | 0x4 | Retransmit |
| | |
| 0x5--0x7 | Unassigned |
| | | | | |
| 0x8--0xf | Reserved for future usage | | 0x8--0xf | Reserved for future usage |
+----------+---------------------------+ +----------+---------------------------+
Table 14: XFER_REFUSE Reason Codes Table 14: XFER_REFUSE Reason Codes
9.7. SESS_TERM Reason Codes 9.7. SESS_TERM Reason Codes
EDITOR NOTE: sub-registry to-be-created upon publication of this EDITOR NOTE: sub-registry to-be-created upon publication of this
specification. specification.
skipping to change at page 41, line 44 skipping to change at page 47, line 46
| Code | Shutdown Reason | | Code | Shutdown Reason |
+------------+---------------------+ +------------+---------------------+
| 0x00 | Idle timeout | | 0x00 | Idle timeout |
| | | | | |
| 0x01 | Version mismatch | | 0x01 | Version mismatch |
| | | | | |
| 0x02 | Busy | | 0x02 | Busy |
| | | | | |
| 0x03 | Contact Failure | | 0x03 | Contact Failure |
| | | | | |
| 0x04 | TLS failure | | 0x04 | Resource Exhaustion |
| | |
| 0x05 | Resource Exhaustion |
| | | | | |
| 0x06--0xFF | Unassigned | | 0x05--0xFF | Unassigned |
+------------+---------------------+ +------------+---------------------+
Table 15: SESS_TERM Reason Codes Table 15: SESS_TERM Reason Codes
9.8. MSG_REJECT Reason Codes 9.8. MSG_REJECT Reason Codes
EDITOR NOTE: sub-registry to-be-created upon publication of this EDITOR NOTE: sub-registry to-be-created upon publication of this
specification. specification.
IANA will create, under the "Bundle Protocol" registry, a sub- IANA will create, under the "Bundle Protocol" registry, a sub-
skipping to change at page 42, line 42 skipping to change at page 48, line 42
This specification is based on comments on implementation of This specification is based on comments on implementation of
[RFC7242] provided from Scott Burleigh. [RFC7242] provided from Scott Burleigh.
11. References 11. References
11.1. Normative References 11.1. Normative References
[I-D.ietf-dtn-bpbis] [I-D.ietf-dtn-bpbis]
Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol Burleigh, S., Fall, K., and E. Birrane, "Bundle Protocol
Version 7", draft-ietf-dtn-bpbis-10 (work in progress), Version 7", draft-ietf-dtn-bpbis-11 (work in progress),
November 2017. May 2018.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981, RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>. <https://www.rfc-editor.org/info/rfc793>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts - [RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989, DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>. <https://www.rfc-editor.org/info/rfc1122>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol
Specification", RFC 5050, DOI 10.17487/RFC5050, November
2007, <https://www.rfc-editor.org/info/rfc5050>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>. 2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
11.2. Informative References 11.2. Informative References
[github-dtn-bpbis-tcpcl] [github-dtn-bpbis-tcpcl]
Sipos, B., "TCPCL Example Implementation", Sipos, B., "TCPCL Example Implementation",
<https://github.com/BSipos-RKF/dtn-bpbis-tcpcl/tree/ <https://github.com/BSipos-RKF/dtn-bpbis-tcpcl/tree/
develop>. develop>.
[I-D.ietf-dtn-bpsec] [I-D.ietf-dtn-bpsec]
Birrane, E. and K. McKeever, "Bundle Protocol Security Birrane, E. and K. McKeever, "Bundle Protocol Security
Specification", draft-ietf-dtn-bpsec-06 (work in Specification", draft-ietf-dtn-bpsec-06 (work in
skipping to change at page 44, line 5 skipping to change at page 49, line 47
[RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP", [RFC2595] Newman, C., "Using TLS with IMAP, POP3 and ACAP",
RFC 2595, DOI 10.17487/RFC2595, June 1999, RFC 2595, DOI 10.17487/RFC2595, June 1999,
<https://www.rfc-editor.org/info/rfc2595>. <https://www.rfc-editor.org/info/rfc2595>.
[RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst,
R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant
Networking Architecture", RFC 4838, DOI 10.17487/RFC4838, Networking Architecture", RFC 4838, DOI 10.17487/RFC4838,
April 2007, <https://www.rfc-editor.org/info/rfc4838>. April 2007, <https://www.rfc-editor.org/info/rfc4838>.
[RFC5050] Scott, K. and S. Burleigh, "Bundle Protocol
Specification", RFC 5050, DOI 10.17487/RFC5050, November
2007, <https://www.rfc-editor.org/info/rfc5050>.
[RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell, [RFC6257] Symington, S., Farrell, S., Weiss, H., and P. Lovell,
"Bundle Security Protocol Specification", RFC 6257, "Bundle Security Protocol Specification", RFC 6257,
DOI 10.17487/RFC6257, May 2011, DOI 10.17487/RFC6257, May 2011,
<https://www.rfc-editor.org/info/rfc6257>. <https://www.rfc-editor.org/info/rfc6257>.
[RFC7242] Demmer, M., Ott, J., and S. Perreault, "Delay-Tolerant [RFC7242] Demmer, M., Ott, J., and S. Perreault, "Delay-Tolerant
Networking TCP Convergence-Layer Protocol", RFC 7242, Networking TCP Convergence-Layer Protocol", RFC 7242,
DOI 10.17487/RFC7242, June 2014, DOI 10.17487/RFC7242, June 2014,
<https://www.rfc-editor.org/info/rfc7242>. <https://www.rfc-editor.org/info/rfc7242>.
skipping to change at page 44, line 26 skipping to change at page 50, line 26
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
Appendix A. Significant changes from RFC7242 Appendix A. Significant changes from RFC7242
The areas in which changes from [RFC7242] have been made to existing The areas in which changes from [RFC7242] have been made to existing
headers and messages are: headers and messages are:
o Split contact header into pre-TLS protocol negotiation and o Split contact header into pre-TLS protocol negotiation and
SESS_INIT parameter negotiation. SESS_INIT parameter negotiation. The contact header is now fixed-
length.
o Changed contact header content to limit number of negotiated o Changed contact header content to limit number of negotiated
options. options.
o Added contact option to negotiate maximum segment size (per each o Added contact option to negotiate maximum segment size (per each
direction). direction).
o Added session extension capability. o Added session extension capability.
o Added transfer extension capability. o Added transfer extension capability.
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The areas in which extensions from [RFC7242] have been made as new The areas in which extensions from [RFC7242] have been made as new
messages and codes are: messages and codes are:
o Added contact negotiation failure SESS_TERM reason code. o Added contact negotiation failure SESS_TERM reason code.
o Added MSG_REJECT message to indicate an unknown or unhandled o Added MSG_REJECT message to indicate an unknown or unhandled
message was received. message was received.
o Added TLS session security mechanism. o Added TLS session security mechanism.
o Added TLS failure and Resource Exhaustion SESS_TERM reason code. o Added Resource Exhaustion SESS_TERM reason code.
Authors' Addresses Authors' Addresses
Brian Sipos Brian Sipos
RKF Engineering Solutions, LLC RKF Engineering Solutions, LLC
7500 Old Georgetown Road 7500 Old Georgetown Road
Suite 1275 Suite 1275
Bethesda, MD 20814-6198 Bethesda, MD 20814-6198
US United States of America
Email: BSipos@rkf-eng.com Email: BSipos@rkf-eng.com
Michael Demmer Michael Demmer
University of California, Berkeley University of California, Berkeley
Computer Science Division Computer Science Division
445 Soda Hall 445 Soda Hall
Berkeley, CA 94720-1776 Berkeley, CA 94720-1776
US United States of America
Email: demmer@cs.berkeley.edu Email: demmer@cs.berkeley.edu
Joerg Ott Joerg Ott
Aalto University Aalto University
Department of Communications and Networking Department of Communications and Networking
PO Box 13000 PO Box 13000
Aalto 02015 Aalto 02015
Finland Finland
 End of changes. 73 change blocks. 
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