draft-ietf-dtn-tcpclv4-05.txt   draft-ietf-dtn-tcpclv4-06.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: June 17, 2018 J. Ott Expires: August 1, 2018 J. Ott
Aalto University Aalto University
S. Perreault S. Perreault
December 14, 2017 January 28, 2018
Delay-Tolerant Networking TCP Convergence Layer Protocol Version 4 Delay-Tolerant Networking TCP Convergence Layer Protocol Version 4
draft-ietf-dtn-tcpclv4-05 draft-ietf-dtn-tcpclv4-06
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 and updates to the Bundle Protocol contents,
encodings, and convergence layer requirements in Bundle Protocol encodings, and convergence layer requirements in Bundle Protocol
Version 7. Specifically, the TCPCLv4 uses CBOR-encoded BPv7 bundles Version 7. Specifically, the TCPCLv4 uses CBOR-encoded BPv7 bundles
as its service data unit being transported and provides a reliable as its service data unit being transported and provides a reliable
skipping to change at page 1, line 43 skipping to change at page 1, line 43
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 June 17, 2018. This Internet-Draft will expire on August 1, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 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.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 1.1. Convergence Layer Services . . . . . . . . . . . . . . . 4
2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 4 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6
3. General Protocol Description . . . . . . . . . . . . . . . . 6 2.1. Definitions Specific to the TCPCL Protocol . . . . . . . 6
3.1. TCPCL Session Overview . . . . . . . . . . . . . . . . . 6 3. General Protocol Description . . . . . . . . . . . . . . . . 7
3.2. Example Message Exchange . . . . . . . . . . . . . . . . 7 3.1. TCPCL Session Overview . . . . . . . . . . . . . . . . . 7
3.2. Example Message Exchange . . . . . . . . . . . . . . . . 8
4. Session Establishment . . . . . . . . . . . . . . . . . . . . 9 4. Session Establishment . . . . . . . . . . . . . . . . . . . . 9
4.1. Contact Header . . . . . . . . . . . . . . . . . . . . . 10 4.1. TCP Connection . . . . . . . . . . . . . . . . . . . . . 10
4.1.1. Header Extension Items . . . . . . . . . . . . . . . 12 4.2. Contact Header . . . . . . . . . . . . . . . . . . . . . 10
4.2. Validation and Parameter Negotiation . . . . . . . . . . 13 4.2.1. Header Extension Items . . . . . . . . . . . . . . . 13
4.3. Session Security . . . . . . . . . . . . . . . . . . . . 15 4.3. Validation and Parameter Negotiation . . . . . . . . . . 14
4.3.1. TLS Handshake Result . . . . . . . . . . . . . . . . 15 4.4. Session Security . . . . . . . . . . . . . . . . . . . . 15
4.3.2. Example TLS Initiation . . . . . . . . . . . . . . . 15 4.4.1. TLS Handshake Result . . . . . . . . . . . . . . . . 16
5. Established Session Operation . . . . . . . . . . . . . . . . 16 4.4.2. Example TLS Initiation . . . . . . . . . . . . . . . 16
5.1. Message Type Codes . . . . . . . . . . . . . . . . . . . 16 5. Established Session Operation . . . . . . . . . . . . . . . . 17
5.2. Upkeep and Status Messages . . . . . . . . . . . . . . . 17 5.1. Message Type Codes . . . . . . . . . . . . . . . . . . . 17
5.2.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 17 5.2. Upkeep and Status Messages . . . . . . . . . . . . . . . 18
5.2.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 18 5.2.1. Session Upkeep (KEEPALIVE) . . . . . . . . . . . . . 18
5.3. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 19 5.2.2. Message Rejection (MSG_REJECT) . . . . . . . . . . . 19
5.3.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 19 5.3. Bundle Transfer . . . . . . . . . . . . . . . . . . . . . 20
5.3.2. Transfer Initialization (XFER_INIT) . . . . . . . . . 20 5.3.1. Bundle Transfer ID . . . . . . . . . . . . . . . . . 21
5.3.3. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 21 5.3.2. Transfer Initialization (XFER_INIT) . . . . . . . . . 21
5.3.4. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 22 5.3.3. Data Transmission (XFER_SEGMENT) . . . . . . . . . . 22
5.3.5. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 23 5.3.4. Data Acknowledgments (XFER_ACK) . . . . . . . . . . . 24
6. Session Termination . . . . . . . . . . . . . . . . . . . . . 25 5.3.5. Transfer Refusal (XFER_REFUSE) . . . . . . . . . . . 25
6.1. Shutdown Message (SHUTDOWN) . . . . . . . . . . . . . . . 25 6. Session Termination . . . . . . . . . . . . . . . . . . . . . 27
6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 28 6.1. Shutdown Message (SHUTDOWN) . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 28 6.2. Idle Session Shutdown . . . . . . . . . . . . . . . . . . 29
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
8.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 30 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
8.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 30 8.1. Port Number . . . . . . . . . . . . . . . . . . . . . . . 31
8.3. Header Extension Types . . . . . . . . . . . . . . . . . 31 8.2. Protocol Versions . . . . . . . . . . . . . . . . . . . . 31
8.4. Message Types . . . . . . . . . . . . . . . . . . . . . . 31 8.3. Header Extension Types . . . . . . . . . . . . . . . . . 32
8.5. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 32 8.4. Message Types . . . . . . . . . . . . . . . . . . . . . . 33
8.6. SHUTDOWN Reason Codes . . . . . . . . . . . . . . . . . . 33 8.5. XFER_REFUSE Reason Codes . . . . . . . . . . . . . . . . 33
8.7. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 34 8.6. SHUTDOWN Reason Codes . . . . . . . . . . . . . . . . . . 34
8.7. MSG_REJECT Reason Codes . . . . . . . . . . . . . . . . . 35
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 35
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
10.1. Normative References . . . . . . . . . . . . . . . . . . 34 10.1. Normative References . . . . . . . . . . . . . . . . . . 35
10.2. Informative References . . . . . . . . . . . . . . . . . 35 10.2. Informative References . . . . . . . . . . . . . . . . . 36
Appendix A. Significant changes from RFC7242 . . . . . . . . . . 36 Appendix A. Significant changes from RFC7242 . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38
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"
[RFC4838]. [RFC4838].
An important goal of the DTN architecture is to accommodate a wide An important goal of the DTN architecture is to accommodate a wide
range of networking technologies and environments. The protocol used range of networking technologies and environments. The protocol used
for DTN communications is the revised Bundle Protocol (BP) for DTN communications is the Bundle Protocol Version 7 (BPv7)
[I-D.ietf-dtn-bpbis], an application-layer protocol that is used to [I-D.ietf-dtn-bpbis], an application-layer protocol that is used to
construct a store-and- forward overlay network. As described in the construct a store-and-forward overlay network. BPv7 requires the
Bundle Protocol specification [I-D.ietf-dtn-bpbis], it requires the services of a "convergence-layer adapter" (CLA) to send and receive
services of a "convergence- layer adapter" (CLA) to send and receive
bundles using the service of some "native" link, network, or Internet bundles using the service of some "native" link, network, or Internet
protocol. This document describes one such convergence-layer adapter protocol. This document describes one such convergence-layer adapter
that uses the well-known Transmission Control Protocol (TCP). This that uses the well-known Transmission Control Protocol (TCP). This
convergence layer is referred to as TCPCL. convergence layer is referred to as TCP Convergence Layer Version 4
(TCPCLv4). For the remainder of this document, the abbreviation "BP"
without the version suffix refers to BPv7. For the remainder of this
document, the abbreviation "TCPCL" without the version suffix refers
to TCPCLv4.
The locations of the TCPCL and the BP in the Internet model protocol The locations of the TCPCL and the BP in the Internet model protocol
stack (described in [RFC1122]) are shown in Figure 1. In particular, stack (described in [RFC1122]) are shown in Figure 1. In particular,
when BP is using TCP as its bearer with TCPCL as its convergence when BP is using TCP as its bearer with TCPCL as its convergence
layer, both BP and TCPCL reside at the application layer of the layer, both BP and TCPCL reside at the application layer of the
Internet model. Internet model.
+-------------------------+ +-------------------------+
| DTN Application | -\ | DTN Application | -\
+-------------------------| | +-------------------------| |
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document does not address: document does not address:
o The format of protocol data units of the Bundle Protocol, as those o The format of protocol data units of the Bundle Protocol, as those
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 nodes within o Mechanisms for locating or identifying other bundle nodes within
an internet. an internet.
1.1. Convergence Layer Services
This version of the TCPCL provides the following services to support
the overlaying Bundle Protocol agent:
Attempt Session The TCPCL allows a BP agent to pre-emptively attempt
to establish a TCPCL session with a peer node. Each session
attempt can send a different set of contact header parameters as
directed by the BP agent.
Session Started The TCPCL supports indication when a new TCP
connection has been started (as either client or server) before
the TCPCL handshake has begun.
Session Established The TCPCL supports indication when a new session
has been fully established and is ready for its first transfer.
Session Shutdown The TCPCL supports indication when an established
session has been ended by normal exchange of SHUTDOWN messages
with all transfers completed.
Session Failed The TCPCL supports indication when a session fails,
either during contact negotiation, TLS negotiation, or after
establishement for any reason other than normal shutdown.
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
bundle has been fully transferred to a peer node.
Transmission Intermediate Progress The TCPCL supports positive
indication of intermediate progress of transferr to a peer node.
This intermediate progress is at the granularity of each
transferred segment.
Transmission Failure The TCPCL supports positive indication of
certain reasons for bundle transmission failure, notably when the
peer node rejects the bundle or when a TCPCL session ends before
transferr success. The TCPCL itself does not have a notion of
transfer timeout.
Reception Interruption The TCPCL allows a BP agent to interrupt an
individual transfer before it has fully completed (successfully or
not).
Reception Success The TCPCL supports positive indication when a
bundle has been fully transferred from a peer node.
Reception Intermediate Progress The TCPCL supports positive
indication of intermediate progress of transfer from the peer
node. This intermediate progress is at the granularity of each
transferred segment. Intermediate reception indication allows a
BP agent the chance to inspect bundle header contents before the
entire bundle is available, and thus supports the "Reception
Interruption" capability.
Reception Failure The TCPCL supports positive indication of certain
reasons for reception failure, notably when the local node rejects
an attempted transfer for some local policy reason or when a TCPCL
session ends before transfer success. The TCPCL itself does not
have a notion of transfer timeout.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2.1. Definitions Specific to the TCPCL Protocol 2.1. Definitions Specific to the TCPCL Protocol
This section contains definitions that are interpreted to be specific This section contains definitions specific to the TCPCL protocol.
to the operation of the TCPCL protocol, as described below.
TCPCL Node: A TCPCL node refers to either side of an negotiating or TCPCL Node: This term refers to either side of a negotiating or in-
in-service TCPCL Session. For most TCPCL behavior, the two nodes service TCPCL Session. For most TCPCL behavior, the two nodes are
are symmetric and there is no protocol distinction between them. symmetric and there is no protocol distinction between them. Some
Some specific behavior, particularly during negotiation, specific behavior, particularly during negotiation, distinguishes
distinguishes between the connecting node and the connected-to between the connecting node and the connected-to node. For the
node. For the remainder of this document, the term "node" without remainder of this document, the term "node" without the prefix
the prefix "TCPCL" refers to a TCPCL node. "TCPCL" refers to a TCPCL node.
TCP Connection: A TCP connection refers to a transport connection TCP Connection: This term refers to a transport connection using TCP
using TCP as the transport protocol. as the transport protocol.
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 bundle nodes. The TCPCL communication relationship between two bundle nodes. The
lifetime of a TCPCL session is bound to the lifetime of an lifetime of a TCPCL session is bound to the lifetime of an
underlying TCP connection. Therefore, a TCPCL session is underlying TCP connection. A TCPCL session is terminated when the
initiated after a bundle node establishes a TCP connection to for TCP connection ends, due either to one or both nodes actively
the purposes of bundle communication. A TCPCL session is terminating the TCP connection or due to network errors causing a
terminated when the TCP connection ends, due either to one or both failure of the TCP connection. For the remainder of this
nodes actively terminating the TCP connection or due to network document, the term "session" without the prefix "TCPCL" refers to
errors causing a failure of the TCP connection. For the remainder a TCPCL session.
of this document, the term "session" without the prefix "TCPCL"
refers to a TCPCL session.
Session parameters: The session parameters are a set of values used Session parameters: These are a set of values used to affect the
to affect the operation of the TCPCL for a given session. The operation of the TCPCL for a given session. The manner in which
manner in which these parameters are conveyed to the bundle node these parameters are conveyed to the bundle node and thereby to
and thereby to the TCPCL is implementation dependent. However, the TCPCL is implementation dependent. However, the mechanism by
the mechanism by which two bundle nodes exchange and negotiate the which two bundle nodes exchange and negotiate the values to be
values to be used for a given session is described in Section 4.2. used for a given session is described in Section 4.3.
Transfer: Transfer refers to the procedures and mechanisms Transfer: This refers to the procedures and mechanisms for
(described below) for conveyance of an individual bundle from one conveyance of an individual bundle from one node to another. Each
node to another. Each transfer within TCPCLv4 is identified by a transfer within TCPCL is identified by a Transfer ID number which
Transfer ID number which is unique only to a single direction is unique only to a single direction within a single Session.
within a single Session.
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.
Lively Session: A TCPCL session is lively while any messages are Live Session: A TCPCL session is live while any messages are being
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. This limits reasons for individual failure/error message types.
the expressiveness of TCPCL error encodings, but simplifies the
encoding of errors and allows an application policy to attempt
recovery from expected 'failure' modes (e.g. if a Session cannot
be established with USE_TLS disabled because of a Contact Failure
shutdown, a re-attempt can be made with USE_TLS enabled).
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
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exchanged in both directions to set parameters of the TCPCL session exchanged in both directions to set parameters of the TCPCL session
and exchange a singleton endpoint identifier for each node (not the and exchange a singleton endpoint identifier for each node (not the
singleton Endpoint Identifier (EID) of any application running on the singleton Endpoint Identifier (EID) of any application running on the
node) to denote the bundle-layer identity of each DTN node. This is 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 used to assist in routing and forwarding messages (e.g. to prevent
loops). loops).
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. The more logical segments of data within an XFER_SEGMENT message.
choice of the length to use for segments is an implementation matter, Multiple bundles can be transmitted consecutively on a single TCPCL
but each segment must be no larger than the receiving node's maximum connection. Segments from different bundles are never interleaved.
receive unit (MRU) (see the field "Segment MRU" of Section 4.1). The Bundle interleaving can be accomplished by fragmentation at the BP
first segment for a bundle MUST set the 'START' flag, and the last layer or by establishing multiple TCPCL sessions between the same
one MUST set the 'end' flag in the XFER_SEGMENT message flags. peers.
If multiple bundles are transmitted on a single TCPCL connection,
they MUST be transmitted consecutively. Interleaving data segments
from different bundles is not allowed. Bundle interleaving can be
accomplished by fragmentation at the BP layer or by establishing
multiple TCPCL sessions.
A feature of this protocol is for the receiving node to send A feature of this protocol is for the receiving node to send
acknowledgments as bundle data segments arrive (XFER_ACK). The acknowledgment (XFER_ACK) messages as bundle data segments arrive .
rationale behind these acknowledgments is to enable the sender node The rationale behind these acknowledgments is to enable the sender
to determine how much of the bundle has been received, so that in node to determine how much of the bundle has been received, so that
case the session is interrupted, it can perform reactive in case the session is interrupted, it can perform reactive
fragmentation to avoid re-sending the already transmitted part of the fragmentation to avoid re-sending the already transmitted part of the
bundle. For each data segment that is received, the receiving node bundle. In addition, there is no explicit flow control on the TCPCL
sends an XFER_ACK message containing the cumulative length of the layer.
bundle that has been received. The sending node MAY transmit
multiple XFER_SEGMENT messages without necessarily waiting for the
corresponding XFER_ACK responses. This enables pipelining of
messages on a channel. In addition, there is no explicit flow
control on the TCPCL layer.
Another feature is that a receiver MAY interrupt the transmission of A TCPCL receiver can interrupt the transmission of a bundle at any
a bundle at any point in time by replying with a XFER_REFUSE message, point in time by replying with a XFER_REFUSE message, which causes
which causes the sender to stop transmission of the current bundle, the sender to stop transmission of the associated bundle (if it
after completing transmission of a partially sent data segment. hasn't already finished transmission) Note: This enables a cross-
Note: This enables a cross-layer optimization in that it allows a layer optimization in that it allows a receiver that detects that it
receiver that detects that it already has received a certain bundle already has received a certain bundle to interrupt transmission as
to interrupt transmission as early as possible and thus save early as possible and thus save transmission capacity for other
transmission capacity for other bundles. bundles.
For sessions that are idle, a KEEPALIVE message is sent at a For sessions that are idle, a KEEPALIVE message is sent at a
negotiated interval. This is used to convey node liveliqness negotiated interval. This is used to convey node live-ness
information during otherwise message-less time intervals. information during otherwise message-less time intervals.
Finally, before sessions close, a SHUTDOWN message is sent to the A SHUTDOWN message is used to start the closing of a TCPCL session
session peer (see Section 6.1). After sending a SHUTDOWN message, (see Section 6.1). During shutdown sequencing, in-progress transfers
the peer can not initiate any further transfers and the session can be completed but no new transfers can be initiated. A SHUTDOWN
enters a closing-down phase. After receiving a SHUTDOWN message and message can also be used to refuse a session setup by a peer (see
when no transfers are in-progress (i.e. have pending or Section 4.3). It is an implementation matter to determine whether or
unacknowledged segments), the receiving peer can close the session not to close a TCPCL session while there are no transfers queued or
without chance of lost transfers. A SHUTDOWN message can also be in-progress.
used to refuse a session setup by a peer (see Section 4.2). It is an
implementation matter to determine whether or not to close a TCPCL
session while there are no transfers queued or in-progress.
There are specific messages for sending and receiving operations (in TCPCL is a symmetric protocol between the peers of a session. Both
addition to session setup/teardown). TCPCL is symmetric, i.e., both
sides can start sending data segments in a session, and one side's sides can start sending data segments in a session, and one side's
bundle transfer does not have to complete before the other side can bundle transfer does not have to complete before the other side can
start sending data segments on its own. Hence, the protocol allows start sending data segments on its own. Hence, the protocol allows
for a bi-directional mode of communication. Note that in the case of for a bi-directional mode of communication. Note that in the case of
concurrent bidirectional transmission, acknowledgment segments MAY be concurrent bidirectional transmission, acknowledgment segments MAY be
interleaved with data segments. interleaved with data segments.
3.2. Example Message Exchange 3.2. Example Message Exchange
The following figure depicts the protocol exchange for a simple The following figure depicts the protocol exchange for a simple
skipping to change at page 9, line 10 skipping to change at page 10, line 4
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
Figure 2: An Example of the Flow of Protocol Messages on a Single TCP Figure 2: An Example of the Flow of Protocol Messages on a Single TCP
Session between Two Nodes (A and B) Session between Two Nodes (A and B)
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 nodes. It is up to MUST first be established between communicating nodes. It is up to
the implementation to decide how and when session setup is triggered. the implementation to decide how and when session setup is triggered.
For example, some sessions MAY be opened proactively and maintained For example, some sessions MAY be opened proactively and maintained
for as long as is possible given the network conditions, while other for as long as is possible given the network conditions, while other
sessions MAY be opened only when there is a bundle that is queued for sessions MAY be opened only when there is a bundle that is queued for
transmission and the routing algorithm selects a certain next-hop transmission and the routing algorithm selects a certain next-hop
node. node.
4.1. TCP Connection
To establish a TCPCL session, a node MUST first establish a TCP To establish a TCPCL session, a node MUST first establish a TCP
connection with the intended peer node, typically by using the connection with the intended peer node, typically by using the
services provided by the operating system. Destination port number services provided by the operating system. Destination port number
4556 has been assigned by IANA as the Registered Port number for the 4556 has been assigned by IANA as the Registered Port number for the
TCP convergence layer. Other destination port numbers MAY be used TCP convergence layer. Other destination port numbers MAY be used
per local configuration. Determining a peer's destination port per local configuration. Determining a peer's destination port
number (if different from the registered TCPCL port number) is up to number (if different from the registered TCPCL port number) is up to
the implementation. Any source port number MAY be used for TCPCL the implementation. Any source port number MAY be used for TCPCL
sessions. Typically an operating system assigned number in the TCP sessions. Typically an operating system assigned number in the TCP
Ephemeral range (49152--65535) is used. Ephemeral range (49152-65535) is used.
If the node is unable to establish a TCP connection for any reason, If the node is unable to establish a TCP connection for any reason,
then it is an implementation matter to determine how to handle the then it is an implementation matter to determine how to handle the
connection failure. A node MAY decide to re-attempt to establish the connection failure. A node MAY decide to re-attempt to establish the
connection. If it does so, it MUST NOT overwhelm its target with connection. If it does so, it MUST NOT overwhelm its target with
repeated connection attempts. Therefore, the node MUST retry the repeated connection attempts. Therefore, the node MUST retry the
connection setup only after some delay (a 1-second minimum is connection setup no earlier than some delay time from the last
RECOMMENDED), and it SHOULD use a (binary) exponential backoff attempt, and it SHOULD use a (binary) exponential backoff mechanism
mechanism to increase this delay in case of repeated failures. In to increase this delay in case of repeated failures. In case a
case a SHUTDOWN message specifying a reconnection delay is received, SHUTDOWN message specifying a reconnection delay is received, that
that delay is used as the initial delay. The default initial delay delay is used as the initial delay. The default initial re-attempt
SHOULD be at least 1 second but SHOULD be configurable since it will delay SHOULD be no shorter than 1 second and SHOULD be configurable
be application and network type dependent. since it will be application and network type dependent.
The node MAY declare failure after one or more connection attempts
and MAY attempt to find an alternate route for bundle data. Such
decisions are up to the higher layer (i.e., the BP).
Once a TCP connection is established, each node MUST immediately Once a TCP connection is established, each node MUST immediately
transmit a contact header over the TCP connection. The format of the transmit a contact header over the TCP connection. The format of the
contact header is described in Section 4.1. contact header is described in Section 4.2.
Upon receipt of the contact header, both nodes perform the validation
and negotiation procedures defined in Section 4.2
After receiving the contact header from the other node, either node
MAY also refuse the session by sending a SHUTDOWN message. If
session setup is refused, a reason MUST be included in the SHUTDOWN
message.
4.1. Contact Header 4.2. Contact Header
Once a TCP connection is established, both parties exchange a contact Once a TCP connection is established, both parties exchange a contact
header. This section describes the format of the contact header and header. This section describes the format of the contact header and
the meaning of its fields. the meaning of its fields.
Upon receipt of the contact header, both nodes perform the validation
and negotiation procedures defined in Section 4.3. After receiving
the contact header from the other node, either node MAY refuse the
session by sending a SHUTDOWN message with an appropriate reason
code.
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 | Keepalive Interval | | Version | Flags | Keepalive Interval |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Segment MRU... | | Segment MRU... |
skipping to change at page 10, line 43 skipping to change at page 11, line 35
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Header Extension Length... | | Header Extension Length... |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| contd. | | contd. |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Header Extension Items... | | Header Extension Items... |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
Figure 3: Contact Header Format Figure 3: Contact Header Format
See Section 4.2 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).
Flags: A one-octet field of single-bit flags, interpreted according Flags: A one-octet field of single-bit flags, interpreted according
skipping to change at page 11, line 24 skipping to change at page 12, line 16
Segment MRU: A 64-bit unsigned integer indicating the largest Segment MRU: A 64-bit unsigned integer indicating the largest
allowable single-segment data payload size to be received in this allowable single-segment data payload size to be received in this
session. Any XFER_SEGMENT sent to this peer SHALL have a data session. Any XFER_SEGMENT sent to this peer SHALL have a data
payload no longer than the peer's Segment MRU. The two nodes of a payload no longer than the peer's Segment MRU. The two nodes of a
single session MAY have different Segment MRUs, and no relation single session MAY have different Segment MRUs, and no relation
between the two is required. between the two is required.
Transfer MRU: A 64-bit unsigned integer indicating the largest Transfer MRU: A 64-bit unsigned integer indicating the largest
allowable total-bundle data size to be received in this session. allowable total-bundle data size to be received in this session.
Any bundle transfer sent to this peer SHALL have a Total bundle Any bundle transfer sent to this peer SHALL have a Total Bundle
data payload no longer than the peer's Transfer MRU. This value Length payload no longer than the peer's Transfer MRU. This value
can be used to perform proactive bundle fragmentation. The two can be used to perform proactive bundle fragmentation. The two
nodes of a single session MAY have different Transfer MRUs, and no nodes of a single session MAY have different Transfer MRUs, and no
relation between the two is required. relation between the two is required.
EID Length and EID Data: Together these fields represent a variable- EID Length and EID Data: Together these fields represent a variable-
length text string. The EID Length is a 16-bit unsigned integer length text string. The EID Length is a 16-bit unsigned integer
indicating the number of octets of EID Data to follow. A zero EID indicating the number of octets of EID Data to follow. A zero EID
Length SHALL be used to indicate the lack of EID rather than a Length SHALL be used to indicate the lack of EID rather than a
truly empty EID. This case allows an node to avoid exposing EID truly empty EID. This case allows a node to avoid exposing EID
information on an untrusted network. A non-zero-length EID Data information on an untrusted network. A non-zero-length EID Data
SHALL contain the UTF-8 encoded EID of some singleton endpoint in SHALL contain the UTF-8 encoded EID of some singleton endpoint in
which the sending node is a member, in the canonical format of which the sending node is a member, in the canonical format of
<scheme name>:<scheme-specific part>. This EID encoding is <scheme name>:<scheme-specific part>. This EID encoding is
consistent with [I-D.ietf-dtn-bpbis]. consistent with [I-D.ietf-dtn-bpbis].
Header Extension Length Header Extension Items: Together these Header Extension Length and Header Extension Items: Together these
fields represent protocol extension data not defined by this fields represent protocol extension data not defined by this
specification. The Header Extension Length is the total number of specification. The Header Extension Length is the total number of
octets to follow which are used to encode the Header Extension octets to follow which are used to encode the Header Extension
Item list. The encoding of each Header Extension Item is Item list. The encoding of each Header Extension Item is within a
identical form as described in Section 4.1.1. consistent data container as described in Section 4.2.1.
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| Name | Code | Description | | Name | Code | Description |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| CAN_TLS | 0x01 | If bit is set, indicates that the sending | | CAN_TLS | 0x01 | If bit is set, indicates that the sending |
| | | peer is capable of TLS security. | | | | peer is capable of TLS security. |
| | | | | | | |
| Reserved | others | | Reserved | others |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
Table 1: Contact Header Flags Table 1: Contact Header Flags
4.1.1. Header Extension Items 4.2.1. Header Extension Items
Each of the Header Extension items SHALL be encoded in an identical Each of the Header Extension Items SHALL be encoded in an identical
Type-Length-Value (TLV) container form as indicated in Figure 4. The Type-Length-Value (TLV) container form as indicated in Figure 4. The
fields of the header extension item are: fields of the Header 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 2. If a TCPCL node receives an Item, which are listed in Table 2. If a TCPCL node receives a
extension item with an unknown Item Type and the CRITICAL flag Header Extension Item with an unknown Item Type and the CRITICAL
set, the node SHALL close the TCPCL session with SHUTDOWN reason flag set, the node SHALL close the TCPCL session with SHUTDOWN
code of "Contact Failure". If the CRITICAL flag is not set, an reason code of "Contact Failure". If the CRITICAL flag is not
node SHALL skip over and ignore any item with an unknown Item set, a node SHALL skip over and ignore any item with an unknown
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 8.3). such codes (see Section 8.3).
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.
Item Value: A variable-length data field which is interpreted Item Value: A variable-length data field which is interpreted
according to the associated Item Type. This specification places according to the associated Item Type. This specification places
no restrictions on an extensions use of available Item Value data. no restrictions on an extension's use of available Item Value
Extension specification SHOULD avoid the use of large data data. Extension specification SHOULD avoid the use of large data
exchanges within the TCPCLv4 contact header as no bundle transfers exchanges within the TCPCL contact header as no bundle transfers
can begin until the a full contact exchange and negotiation has can begin until the full contact exchange and negotiation has been
been completed. completed.
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 4: Header Extention Item Format Figure 4: Header 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 2: Header Extension Item Flags Table 2: Header Extension Item Flags
4.2. Validation and Parameter Negotiation 4.3. Validation and Parameter Negotiation
Upon reception of the contact header, each node follows the following Upon reception of the contact header, each node follows the following
procedures to ensure the validity of the TCPCL session and to procedures to ensure the validity of the TCPCL session and to
negotiate values for the session parameters. negotiate values for the session parameters.
If the magic string is not present or is not valid, the connection If the magic string is not present or is not valid, the connection
MUST be terminated. The intent of the magic string is to provide MUST be terminated. The intent of the magic string is to provide
some protection against an inadvertent TCP connection by a different some protection against an inadvertent TCP connection by a different
protocol than the one described in this document. To prevent a flood protocol than the one described in this document. To prevent a flood
of repeated connections from a misconfigured application, a node MAY of repeated connections from a misconfigured application, a node MAY
skipping to change at page 14, line 6 skipping to change at page 14, line 43
node MAY attempt further TCPCL sessions with the peer using earlier node MAY attempt further TCPCL sessions with the peer using earlier
protocol version numbers in decreasing order. Managing multi-TCPCL- protocol version numbers in decreasing order. Managing multi-TCPCL-
session state such as this is an implementation matter. session state such as this is an implementation matter.
If a node receives a contact header containing a version that is If a node receives a contact header containing a version that is
greater than the current version of the protocol that the node greater than the current version of the protocol that the node
implements, then the node SHALL shutdown the session with a reason implements, then the node SHALL shutdown the session with a reason
code of "Version mismatch". If a node receives a contact header with code of "Version mismatch". If a node receives a contact header with
a version that is lower than the version of the protocol that the a version that is lower than the version of the protocol that the
node implements, the node MAY either terminate the session (with a node implements, the node MAY either terminate the session (with a
reason code of "Version mismatch"). Otherwise, the node MAY adapt reason code of "Version mismatch") or the node MAY adapt its
its 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.
A node calculates the parameters for a TCPCL session by negotiating A node calculates the parameters for a TCPCL session by negotiating
the values from its own preferences (conveyed by the contact header the values from its own preferences (conveyed by the contact header
it sent to the peer) with the preferences of the peer node (expressed it sent to the peer) with the preferences of the peer node (expressed
in the contact header that it received from the peer). The in the contact header that it received from the peer). The
negotiated parameters defined by this specification are described in negotiated parameters defined by this specification are described in
the following paragraphs. the following paragraphs.
Transfer MTU and Segment MTU: The maximum transmit unit (MTU) for
whole transfers and individual segments are idententical to the
Transfer MRU and Segment MRU, respectively, of the recevied
contact header. A transmitting peer can send individual segments
with any size smaller than the Segment MTU, depending on local
policy, dynamic network conditions, etc. Determining the size of
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. If the negotiated Session Keepalive is zero Keepalive Interval. The Session Keepalive interval is a parameter
(i.e. one or both contact headers contains a zero Keepalive for the behavior described in Section 5.2.1.
Interval), then the keepalive feature (described in Section 5.2.1)
is disabled. There is no logical minimum value for the keepalive
interval, but when used for many sessions on an open, shared
network a short interval could lead to excessive traffic. For
shared network use, nodes SHOULD choose a keepalive interval no
shorter than 30 seconds. There is no logical maximum value for
the keepalive interval, but an idle TCP connection is liable for
closure by the host operating system if the keepalive time is
longer than tens-of-minutes. Nodes SHOULD choose a keepalive
interval no longer than 10 minutes (600 seconds).
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.
If the negotiated Enable TLS value is true then TLS negotiation A local security policy is then applied to determine of the
feature (described in Section 4.3) begins immediately following negotated value of Enable TLS is acceptable. If not, the node
the contact header exchange. The security policy on either node SHALL shutdown the session with a reason code of "Contact
MAY forbid the establishment of a TCPCL session for any Enable TLS Failure". Note that this contact failure is different than a "TLS
result (or for any combination of local or peer CAN_TLS flag), in Failure" after an agreed-upon and acceptable Enable TLS state. If
which case the node SHALL shutdown the session with a reason code the negotiated Enable TLS value is true and acceptable then TLS
of "Contact Failure". For example, one node may disallow TCPCL negotiation feature (described in Section 4.4) begins immediately
sessions without TLS, while a second node may disallow sessions following the contact header exchange.
with TLS. Also note that this Contact Failure (of the header
negotiation) is different than a TLS Failure (after an agreed-upon
Enable TLS state).
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.
4.3. 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. Security (TLS) session within an existing TCP connection. When TLS
Negotiation of whether or not to initiate TLS within a TCPCL session is used within the TCPCL it affects the entire session. Once
is part of the contact header as described in Section 4.2. The TLS established, there is no mechanism available to downgrade a TCPCL
handshake, if it occurs, is considered to be part of the contact session to non-TLS operation. If this is desired, the entire TCPCL
negotiation before the TCPCL session itself is established. session MUST be shutdown and a new non-TLS-negotiated session
Specifics about sensitive data exposure are discussed in Section 7. established.
When TLS is used within the TCPCL it affects the entire session. By The use of TLS is negotated using the Contact Header as described in
convention, this protocol uses the node which initiated the Section 4.3. After negotiating an Enable TLS parameter of true, and
underlying TCP connection as the "client" role of the TLS handshake before any other TCPCL messages are sent within the session, the
request. Once a TLS session is established within TCPCL, there is no session nodes SHALL begin a TLS handshake in accordance with
mechanism provided to end the TLS session and downgrade the session. [RFC5246]. The parameters within each TLS negotiation are
If a non-TLS session is desired after a TLS session is started then implementation dependent but any TCPCL node SHOULD follow all
the entire TCPCL session MUST be shutdown first. recommended best practices of [RFC7525]. By convention, this
protocol uses the node which initiated the underlying TCP connection
as the "client" role of the TLS handshake request.
After negotiating an Enable TLS parameter of true, and before any The TLS handshake, if it occurs, is considered to be part of the
other TCPCL messages are sent within the session, the session nodes contact negotiation before the TCPCL session itself is established.
SHALL begin a TLS handshake in accordance with [RFC5246]. The Specifics about sensitive data exposure are discussed in Section 7.
parameters within each TLS nqion are implementation dependent but any
TCPCL node SHOULD follow all recommended best practices of [RFC7525].
4.3.1. TLS Handshake Result 4.4.1. TLS Handshake Result
If a TLS handshake cannot negotiate a TLS session, both nodes of the If a TLS handshake cannot negotiate a TLS session, both nodes of the
TCPCL session SHALL cause a TCPCL shutdown with reason "TLS Failure". TCPCL session SHALL start a TCPCL shutdown with reason "TLS Failure".
After a TLS session is successfully established, both TCPCL nodes After a TLS session is successfully established, both TCPCL nodes
SHALL re-exchange TCPCL Contact Header messages. Any information SHALL re-exchange TCPCL Contact Header messages. Any information
cached from the prior Contact Header exchange SHALL be discarded. cached from the prior Contact Header exchange SHALL be discarded.
This re-exchange avoids man-in-the-middle attack in identical fashion This re-exchange avoids a "man-in-the-middle" attack in identical
to [RFC2595]. Each re-exchange header CAN_TLS flag SHALL be fashion to [RFC2595]. Each re-exchange header CAN_TLS flag SHALL be
identical to the original header CAN_TLS flag from the same node. identical to the original header CAN_TLS flag from the same node.
The CAN_TLS logic (TLS negotiation) SHALL NOT apply during header re- The CAN_TLS logic (TLS negotiation) SHALL NOT apply during header re-
exchange. This reinforces the fact that there is no TLS downgrade exchange. This reinforces the fact that there is no TLS downgrade
mechanism. mechanism.
4.3.2. 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 5 below.
Node A Node B Node A Node B
====== ====== ====== ======
+-------------------------+ +-------------------------+
| Open TCP Connnection | -> | Open TCP Connnection | ->
+-------------------------+ +-------------------------+ +-------------------------+ +-------------------------+
skipping to change at page 18, line 5 skipping to change at page 19, line 5
Table 3: TCPCL Message Types Table 3: TCPCL Message Types
5.2. Upkeep and Status Messages 5.2. Upkeep and Status Messages
5.2.1. Session Upkeep (KEEPALIVE) 5.2.1. Session Upkeep (KEEPALIVE)
The protocol includes a provision for transmission of KEEPALIVE The protocol includes a provision for transmission of KEEPALIVE
messages over the TCPCL session to help determine if the underlying messages over the TCPCL session to help determine if the underlying
TCP connection has been disrupted. TCP connection has been disrupted.
As described in Section 4.1, one of the parameters in the contact As described in Section 4.3, a negotiated parameter of each session
header is the Keepalive Interval. Both sides populate this field is the Session Keepalive interval. If the negotiated Session
with their requested intervals (in seconds) between KEEPALIVE Keepalive is zero (i.e. one or both contact headers contains a zero
messages. Keepalive Interval), then the keepalive feature is disabled. There
is no logical minimum value for the keepalive interval, but when used
for many sessions on an open, shared network a short interval could
lead to excessive traffic. For shared network use, nodes SHOULD
choose a keepalive interval no shorter than 30 seconds. There is no
logical maximum value for the keepalive interval, but an idle TCP
connection is liable for closure by the host operating system if the
keepalive time is longer than tens-of-minutes. Nodes SHOULD choose a
keepalive interval no longer than 10 minutes (600 seconds).
Note: The Keepalive Interval SHOULD NOT be chosen too short as TCP
retransmissions MAY occur in case of packet loss. Those will have to
be triggered by a timeout (TCP retransmission timeout (RTO)), which
is dependent on the measured RTT for the TCP connection so that
KEEPALIVE messages MAY experience noticeable latency.
The format of a KEEPALIVE message is a one-octet message type code of The format of a KEEPALIVE message is a one-octet message type code of
KEEPALIVE (as described in Table 3) with no additional data. Both KEEPALIVE (as described in Table 3) with no additional data. Both
sides SHOULD send a KEEPALIVE message whenever the negotiated sides SHOULD send a KEEPALIVE message whenever the negotiated
interval has elapsed with no transmission of any message (KEEPALIVE interval has elapsed with no transmission of any message (KEEPALIVE
or other). or other).
If no message (KEEPALIVE or other) has been received for at least If no message (KEEPALIVE or other) has been received in a session
twice the Keepalive Interval, then either party MAY terminate the after some implementation-defined time duration, then the node MAY
session by transmitting a one-octet SHUTDOWN message (as described in terminate the session by transmitting a one-octet SHUTDOWN message
Section 6.1) with reason code "Idle Timeout", and by closing the (as described in Section 6.1) with reason code "Idle Timeout.
session.
Note: The Keepalive Interval SHOULD not be chosen too short as TCP
retransmissions MAY occur in case of packet loss. Those will have to
be triggered by a timeout (TCP retransmission timeout (RTO)), which
is dependent on the measured RTT for the TCP connection so that
KEEPALIVE messages MAY experience noticeable latency.
5.2.2. Message Rejection (MSG_REJECT) 5.2.2. 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.
skipping to change at page 19, line 28 skipping to change at page 20, line 43
| | | | | | | |
| Message | 0x03 | A message was received while the session is | | Message | 0x03 | A message was received while the session is |
| Unexpected | | in a state in which the message is not | | Unexpected | | in a state in which the message is not |
| | | expected. | | | | expected. |
+-------------+------+----------------------------------------------+ +-------------+------+----------------------------------------------+
Table 4: MSG_REJECT Reason Codes Table 4: MSG_REJECT Reason Codes
5.3. Bundle Transfer 5.3. Bundle Transfer
All of the message in this section are directly associated with All of the messages in this section are directly associated with
transferring a bundle between TCPCL nodes. transferring a bundle between TCPCL nodes.
A single TCPCL transfer results in a bundle (handled by the A single TCPCL transfer results in a bundle (handled by the
convergence layer as opaque data) being exchanged from one node to convergence layer as opaque data) being exchanged from one node to
the other. In TCPCL a transfer is accomplished by dividing a single the other. In TCPCL a transfer is accomplished by dividing a single
bundle up into "segments" based on the receiving-side Segment MRU bundle up into "segments" based on the receiving-side Segment MRU
(see Section 4.1). (see Section 4.2). The choice of the length to use for segments is
an implementation matter, but each segment MUST be no larger than the
receiving node's maximum receive unit (MRU) (see the field "Segment
MRU" of Section 4.2). The first segment for a bundle MUST set the
'START' flag, and the last one MUST set the 'end' flag in the
XFER_SEGMENT message flags.
A single transfer (and by extension a single segment) SHALL NOT A single transfer (and by extension a single segment) SHALL NOT
contain data of more than a single bundle. This requirement is contain data of more than a single bundle. This requirement is
imposed on the agent using the TCPCL rather than TCPCL itself. imposed on the agent using the TCPCL rather than TCPCL itself.
If multiple bundles are transmitted on a single TCPCL connection,
they MUST be transmitted consecutively without interleaving of
segments from multiple bundles.
5.3.1. Bundle Transfer ID 5.3.1. Bundle Transfer ID
Each of the bundle transfer messages contains a Transfer ID number Each of the bundle transfer messages contains a Transfer ID which is
which is used to correlate messages originating from sender and used to correlate messages (from both sides of a transfer) for each
receiver of a bundle. A Transfer ID does not attempt to address bundle. A Transfer ID does not attempt to address uniqueness of the
uniqueness of the bundle data itself and has no relation to concepts bundle data itself and has no relation to concepts such as bundle
such as bundle fragmentation. Each invocation of TCPCL by the bundle fragmentation. Each invocation of TCPCL by the bundle protocol
protocol agent, requesting transmission of a bundle (fragmentary or agent, requesting transmission of a bundle (fragmentary or
otherwise), results in the initiation of a single TCPCL transfer. otherwise), results in the initiation of a single TCPCL transfer.
Each transfer entails the sending of a XFER_INIT message and some Each transfer entails the sending of a XFER_INIT message and some
number of XFER_SEGMENT and XFER_ACK messages; all are correlated by number of XFER_SEGMENT and XFER_ACK messages; all are correlated by
the same Transfer ID. the same Transfer ID.
Transfer IDs from each node SHALL be unique within a single TCPCL Transfer IDs from each node SHALL be unique within a single TCPCL
session. The initial Transfer ID from each node SHALL have value session. The initial Transfer ID from each node SHALL have value
zero. Subsequent Transfer ID values SHALL be incremented from the zero. Subsequent Transfer ID values SHALL be incremented from the
prior Transfer ID value by one. Upon exhaustion of the entire 64-bit prior Transfer ID value by one. Upon exhaustion of the entire 64-bit
Transfer ID space, the sending node SHALL terminate the session with Transfer ID space, the sending node SHALL terminate the session with
skipping to change at page 20, line 41 skipping to change at page 22, line 18
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: The format of the XFER_INIT message is as follows:
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
| Total bundle length (U64) | | Total Bundle Length (U64) |
+-----------------------------+ +-----------------------------+
Figure 8: Format of XFER_INIT Messages Figure 8: 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.
An XFER_INIT message SHALL be sent immediately before transmission of An XFER_INIT message SHALL be sent as the first message in a transfer
any XFER_SEGMENT messages for each Transfer ID. XFER_INIT messages sequence, before transmission of any XFER_SEGMENT messages for the
MUST NOT be sent unless the next XFER_SEGMENT message has the 'START' same Transfer ID. XFER_INIT messages MUST NOT be sent unless the
bit set to "1" (i.e., just before the start of a new transfer). next XFER_SEGMENT message has the 'START' bit set to "1" (i.e., just
before the start of a new transfer).
A receiver MAY send a BUNDLE_REFUSE message as soon as it receives a
XFER_INIT message without waiting for the next XFER_SEGMENT message.
The sender MUST be prepared for this and MUST associate the refusal
with the correct bundle via the Transfer ID fields.
5.3.3. Data Transmission (XFER_SEGMENT) 5.3.3. 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 9. of a XFER_SEGMENT message follows in Figure 9.
+------------------------------+ +------------------------------+
| Message Header | | Message Header |
+------------------------------+ +------------------------------+
| Message Flags (U8) | | Message Flags (U8) |
skipping to change at page 22, line 40 skipping to change at page 24, line 18
transfers from the same node is possible within a single TCPCL transfers from the same node is possible within a single TCPCL
session. Simultaneous transfers between two nodes MAY be achieved session. Simultaneous transfers between two nodes MAY be achieved
using multiple TCPCL sessions. using multiple TCPCL sessions.
5.3.4. Data Acknowledgments (XFER_ACK) 5.3.4. Data Acknowledgments (XFER_ACK)
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, a Bundle Protocol agent needs an additional mechanism to some data, the TCPCL needs an additional mechanism to determine
determine whether the receiving agent has successfully received the whether the receiving agent has successfully received the segment.
segment. To this end, the TCPCL protocol provides feedback messaging To this end, the TCPCL protocol provides feedback messaging whereby a
whereby a receiving node transmits acknowledgments of reception of receiving node transmits acknowledgments of reception of data
data segments. segments.
The format of an XFER_ACK message follows in Figure 10. The format of an XFER_ACK message follows in Figure 10.
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Message Flags (U8) | | Message Flags (U8) |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
skipping to change at page 23, line 28 skipping to change at page 24, line 49
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 5. according to the descriptions in Table 5.
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 endpoing SHALL send an XFER_ACK message in response A receiving TCPCL node SHALL send an XFER_ACK message in response to
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
necessarily waiting for the corresponding XFER_ACK responses. This
enables pipelining of messages on a channel.
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.
5.3.5. Transfer Refusal (XFER_REFUSE) 5.3.5. Transfer Refusal (XFER_REFUSE)
The TCPCL supports an mechanism by which a receiving node can The TCPCL supports a mechanism by which a receiving node can indicate
indicate to the sender that it does not want to receive the to the sender that it does not want to receive the corresponding
corresponding bundle. To do so, upon receiving a XFER_INIT or bundle. To do so, upon receiving a XFER_INIT or XFER_SEGMENT
XFER_SEGMENT message, the node MAY transmit a XFER_REFUSE message. message, the node MAY transmit a XFER_REFUSE message. As data
As data segments and acknowledgments MAY cross on the wire, the segments and acknowledgments MAY cross on the wire, the bundle that
bundle that is being refused SHALL be identified by the Transfer ID is being refused SHALL be identified by the Transfer ID of the
of the refusal. refusal.
There is no required relation between the Transfer MRU of a TCPCL There is no required relation between the Transfer MRU of a TCPCL
node (which is supposed to represent a firm limitation of what the node (which is supposed to represent a firm limitation of what the
node will accept) and sending of a XFER_REFUSE message. A node will accept) and sending of a XFER_REFUSE message. A
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
XFER_INIT message without waiting for the next XFER_SEGMENT message.
The sender MUST be prepared for this and MUST associate the refusal
with the correct bundle via the Transfer ID fields.
The format of the XFER_REFUSE message is as follows: The format of the XFER_REFUSE message is as follows:
+-----------------------------+ +-----------------------------+
| Message Header | | Message Header |
+-----------------------------+ +-----------------------------+
| Reason Code (U8) | | Reason Code (U8) |
+-----------------------------+ +-----------------------------+
| Transfer ID (U64) | | Transfer ID (U64) |
+-----------------------------+ +-----------------------------+
skipping to change at page 25, line 44 skipping to change at page 27, line 22
transmitted by either node at any point following complete transmitted by either node at any point following complete
transmission of any other message. After sending a SHUTDOWN message, transmission of any other message. After sending a SHUTDOWN message,
the sender of the message MAY send further acknowledgments (XFER_ACK the sender of the message MAY send further acknowledgments (XFER_ACK
or XFER_REFUSE) but no further data messages (XFER_INIT or or XFER_REFUSE) but no further data messages (XFER_INIT or
XFER_SEGMENT). A receiving node SHOULD acknowledge all received data XFER_SEGMENT). A receiving node SHOULD acknowledge all received data
segments before sending a SHUTDOWN message to end the session. A segments before sending a SHUTDOWN message to end the session. A
transmitting node SHALL treat a SHUTDOWN message received mid- transmitting node SHALL treat a SHUTDOWN message received mid-
transfer (i.e. before the final acknowledgment) as a failure of the transfer (i.e. before the final acknowledgment) as a failure of the
transfer. transfer.
After transmitting a SHUTDOWN message, an node MAY immediately close After transmitting a SHUTDOWN message, a node MAY immediately close
the associated TCP connection. Once the SHUTDOWN message is sent, the associated TCP connection. Once the SHUTDOWN message is sent,
any further received data on the TCP connection SHOULD be ignored. any further received data on the TCP connection SHOULD be ignored.
Any delay between request to terminate the TCP connection and actual Any 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 SHUTDOWN message is as follows: The format of the SHUTDOWN message is as follows:
+-----------------------------------+ +-----------------------------------+
| Message Header | | Message Header |
skipping to change at page 26, line 27 skipping to change at page 28, line 6
The fields of the SHUTDOWN message are: The fields of the SHUTDOWN 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 7. according to the descriptions in Table 7.
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 8. The Reason Code is present or to the descriptions in Table 8. The Reason Code is present or
absent as indicated by one of the flags. absent as indicated by one of the flags.
Reconnection Delay: A 16-bit unsigned integer indicating the desired Reconnection Delay: A 16-bit unsigned integer indicating the desired
delay until further TCPCL sessions to the sending node. The delay, in seconds, before re-attepmting a TCPCL session to the
Reconnection Delay is present or absent as indicated by one of the sending node. The Reconnection Delay is present or absent as
flags. indicated by one of the flags.
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| Name | Code | Description | | Name | Code | Description |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
| D | 0x01 | If bit is set, indicates that a Reconnection | | D | 0x01 | If bit is set, indicates that a Reconnection |
| | | Delay field is present. | | | | Delay field is present. |
| | | | | | | |
| R | 0x02 | If bit is set, indicates that a Reason Code | | R | 0x02 | If bit is set, indicates that a Reason Code |
| | | field is present. | | | | field is present. |
| | | | | | | |
| Reserved | others | | Reserved | others |
+----------+--------+-----------------------------------------------+ +----------+--------+-----------------------------------------------+
Table 7: SHUTDOWN Flags Table 7: SHUTDOWN Flags
It is possible for a node to convey additional information regarding It is possible for a node to convey optional information regarding
the reason for session termination. To do so, the node MUST set the the reason for session termination. To do so, the node MUST set the
'R' bit in the message flags and transmit a one-octet reason code 'R' bit in the message flags and transmit a one-octet reason code
immediately following the message header. The specified values of immediately following the message header. The specified values of
the reason code are: the reason code are:
+---------------+---------------------------------------------------+ +---------------+---------------------------------------------------+
| Name | Description | | Name | Description |
+---------------+---------------------------------------------------+ +---------------+---------------------------------------------------+
| Idle timeout | The session is being closed due to idleness. | | Idle timeout | The session is being closed due to idleness. |
| | | | | |
skipping to change at page 27, line 28 skipping to change at page 29, line 5
| | | | | |
| TLS Failure | The node failed to negotiate TLS session and | | TLS Failure | The node failed to negotiate TLS session and |
| | cannot continue the session. | | | 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 8: SHUTDOWN Reason Codes Table 8: SHUTDOWN Reason Codes
It is also possible to convey a requested reconnection delay to If a node does not want its peer to reopen a connection immediately,
indicate how long the other node MUST wait before attempting session it SHALL set the 'D' bit in the flags and include a reconnection
re-establishment. To do so, the node sets the 'D' bit in the message delay to indicate when the peer is allowed to attempt another session
flags and then transmits an 16-bit unsigned integer specifying the setup. The Reconnection Delay value 0 SHALL be interpreted as an
requested delay, in seconds, following the message header (and infinite delay, i.e., that the connecting node MUST NOT re-establish
optionally, the SHUTDOWN reason code). The value 0 SHALL be the session.
interpreted as an infinite delay, i.e., that the connecting node MUST
NOT re-establish the session. In contrast, if the node does not wish
to request a delay, it SHOULD omit the reconnection delay field (and
set the 'D' bit to zero).
A session shutdown MAY occur immediately after TCP connection A session shutdown MAY occur immediately after transmission of a
establishment or reception of a contact header (and prior to any contact header (and prior to any further message transmit). This
further data exchange). This MAY, for example, be used to notify MAY, for example, be used to notify that the node is currently not
that the node is currently not able or willing to communicate. able or willing to communicate. However, a node MUST always send the
However, a node MUST always send the contact header to its peer contact header to its peer before sending a SHUTDOWN message.
before sending a SHUTDOWN message.
If either node terminates a session prematurely in this manner, it If reception of the contact header itself somehow fails (e.g. an
SHOULD send a SHUTDOWN message and MUST indicate a reason code unless invalid "magic string" is recevied), a node SHOULD close the TCP
the incoming connection did not include the magic string. If the connection without sending a SHUTDOWN message. If the content of the
magic string was not present, a node SHOULD close the TCP connection Header Extension Items data disagrees with the Header Extension
without sending a SHUTDOWN message. If a node does not want its peer Length (i.e. the last Item claims to use more octets than are present
to reopen a connection immediately, it SHOULD set the 'D' bit in the in the Header Extension Length), the reception of the contact header
flags and include a reconnection delay to indicate when the peer is is considered to have failed.
allowed to attempt another session setup.
If a session is to be terminated before a protocol message has If a session is to be terminated before a protocol message has
completed being sent, then the node MUST NOT transmit the SHUTDOWN completed being sent, then the node MUST NOT transmit the SHUTDOWN
message but still SHOULD close the TCP connection. Each TCPCL message but still SHOULD close the TCP connection. Each TCPCL
message is contiguous in the octet stream and has no ability to be message is contiguous in the octet stream and has no ability to be
cut short and/or preempted by an other message. This is particularly cut short and/or preempted by an other message. This is particularly
important when large segment sizes are being transmitted; either important when large segment sizes are being transmitted; either
entire XFER_SEGMENT is sent before a SHUTDOWN message or the entire XFER_SEGMENT is sent before a SHUTDOWN message or the
connection is simply terminated mid-XFER_SEGMENT. connection is simply terminated mid-XFER_SEGMENT.
skipping to change at page 28, line 27 skipping to change at page 29, line 46
The protocol includes a provision for clean shutdown of idle The protocol includes a provision for clean shutdown of idle
sessions. Determining the length of time to wait before closing idle sessions. Determining the length of time to wait before closing idle
sessions, if they are to be closed at all, is an implementation and sessions, if they are to be closed at all, is an implementation and
configuration matter. configuration matter.
If there is a configured time to close idle links and if no TCPCL If there is a configured time to close idle links and if no TCPCL
messages (other than KEEPALIVE messages) has been received for at messages (other than KEEPALIVE messages) has been received for at
least that amount of time, then either node MAY terminate the session least that amount of time, then either node MAY terminate the session
by transmitting a SHUTDOWN message indicating the reason code of by transmitting a SHUTDOWN message indicating the reason code of
'Idle timeout' (as described in Table 8). "Idle timeout" (as described in Table 8).
7. Security Considerations 7. Security Considerations
One security consideration for this protocol relates to the fact that One security consideration for this protocol relates to the fact that
nodes present their endpoint identifier as part of the contact header nodes present their endpoint identifier as part of the contact header
exchange. It would be possible for a node to fake this value and exchange. It would be possible for a node to fake this value and
present the identity of a singleton endpoint in which the node is not present the identity of a singleton endpoint in which the node is not
a member, essentially masquerading as another DTN node. If this a member, essentially masquerading as another DTN node. If this
identifier is used outside of a TLS-secured session or without identifier is used outside of a TLS-secured session or without
further verification as a means to determine which bundles are further verification as a means to determine which bundles are
transmitted over the session, then the node that has falsified its transmitted over the session, then the node that has falsified its
identity would be able to obtain bundles that it otherwise would not identity would be able to obtain bundles that it otherwise would not
have. Therefore, a node SHALL NOT use the EID value of an unsecured have. Therefore, a node SHALL NOT use the EID value of an unsecured
contact header to derive a peer node's identity unless it can contact header to derive a peer node's identity unless it can
corroborate it via other means. When TCPCL session security mandated corroborate it via other means. When TCPCL session security is
by a TCPCL peer, that peer SHALL transmit initial unsecured contact mandated by a TCPCL peer, that peer SHALL transmit initial unsecured
header values indicated in Table 9 in order. These values avoid contact header values indicated in Table 9 in order. These values
unnecessarily leaking endpoing parameters and will be ignored when avoid unnecessarily leaking session parameters and will be ignored
secure contact header re-exchange occurs. when secure contact header re-exchange occurs.
+--------------------+---------------------------------------------+ +--------------------+---------------------------------------------+
| Parameter | Value | | Parameter | Value |
+--------------------+---------------------------------------------+ +--------------------+---------------------------------------------+
| Flags | The USE_TLS flag is set. | | Flags | The USE_TLS flag is set. |
| | | | | |
| Keepalive Interval | Zero, indicating no keepalive. | | Keepalive Interval | Zero, indicating no keepalive. |
| | | | | |
| Segment MRU | Zero, indicating all segments are refused. | | Segment MRU | Zero, indicating all segments are refused. |
| | | | | |
skipping to change at page 30, line 37 skipping to change at page 32, line 4
| | | | | |
| Reference: | [RFC7242] | | Reference: | [RFC7242] |
| | | | | |
| Port Number: | 4556 | | Port Number: | 4556 |
+------------------------+-------------------------------------+ +------------------------+-------------------------------------+
8.2. Protocol Versions 8.2. Protocol Versions
IANA has created, under the "Bundle Protocol" registry, a sub- IANA has created, under the "Bundle Protocol" registry, a sub-
registry titled "Bundle Protocol TCP Convergence-Layer Version registry titled "Bundle Protocol TCP Convergence-Layer Version
Numbers" and initialized it with the following table. The Numbers" and initialize it with the following table. The
registration procedure is RFC Required. registration procedure is RFC Required.
+-------+-------------+---------------------+ +-------+-------------+---------------------+
| Value | Description | Reference | | Value | Description | Reference |
+-------+-------------+---------------------+ +-------+-------------+---------------------+
| 0 | Reserved | [RFC7242] | | 0 | Reserved | [RFC7242] |
| | | | | | | |
| 1 | Reserved | [RFC7242] | | 1 | Reserved | [RFC7242] |
| | | | | | | |
| 2 | Reserved | [RFC7242] | | 2 | Reserved | [RFC7242] |
skipping to change at page 31, line 28 skipping to change at page 32, line 30
| 5-255 | Unassigned | | 5-255 | Unassigned |
+-------+-------------+---------------------+ +-------+-------------+---------------------+
8.3. Header Extension Types 8.3. Header Extension Types
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-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
Header Extension Types" and initialized it with the contents of Header Extension Types" and initialize it with the contents of
Table 10. The registration procedure is RFC Required within the Table 10. The registration procedure is RFC Required within the
lower range 0x0001--0x3fff. Values in the range 0x8000--0xffff are lower range 0x0001--0x3fff. Values in the range 0x8000--0xffff are
reserved for use on private networks for functions not published to reserved for use on private networks for functions not published to
the IANA. the IANA.
+----------------+--------------------------+ +----------------+--------------------------+
| Code | Message Type | | Code | Message Type |
+----------------+--------------------------+ +----------------+--------------------------+
| 0x0000 | Reserved | | 0x0000 | Reserved |
| | | | | |
skipping to change at page 32, line 4 skipping to change at page 33, line 12
Table 10: Header Extension Type Codes Table 10: Header Extension Type Codes
8.4. Message Types 8.4. Message Types
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-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
Message Types" and initialized it with the contents of Table 11. The Message Types" and initialize it with the contents of Table 11. The
registration procedure is RFC Required. registration procedure is RFC Required.
+-----------+--------------+ +-----------+--------------+
| Code | Message Type | | Code | Message Type |
+-----------+--------------+ +-----------+--------------+
| 0x00 | Reserved | | 0x00 | Reserved |
| | | | | |
| 0x01 | XFER_SEGMENT | | 0x01 | XFER_SEGMENT |
| | | | | |
| 0x02 | XFER_ACK | | 0x02 | XFER_ACK |
skipping to change at page 32, line 38 skipping to change at page 33, line 46
Table 11: Message Type Codes Table 11: Message Type Codes
8.5. XFER_REFUSE Reason Codes 8.5. XFER_REFUSE 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-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
XFER_REFUSE Reason Codes" and initialized it with the contents of XFER_REFUSE Reason Codes" and initialize it with the contents of
Table 12. The registration procedure is RFC Required. Table 12. The registration procedure is RFC Required.
+----------+---------------------------+ +----------+---------------------------+
| Code | Refusal Reason | | Code | Refusal Reason |
+----------+---------------------------+ +----------+---------------------------+
| 0x0 | Unknown | | 0x0 | Unknown |
| | | | | |
| 0x1 | Completed | | 0x1 | Completed |
| | | | | |
| 0x2 | No Resources | | 0x2 | No Resources |
skipping to change at page 33, line 30 skipping to change at page 34, line 30
Table 12: XFER_REFUSE Reason Codes Table 12: XFER_REFUSE Reason Codes
8.6. SHUTDOWN Reason Codes 8.6. SHUTDOWN 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-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
SHUTDOWN Reason Codes" and initialized it with the contents of SHUTDOWN Reason Codes" and initialize it with the contents of
Table 13. The registration procedure is RFC Required. Table 13. The registration procedure is RFC Required.
+------------+------------------+ +------------+---------------------+
| 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 | TLS failure |
| | | | | |
| 0x05--0xFF | Unassigned | | 0x05 | Resource Exhaustion |
+------------+------------------+ | | |
| 0x06--0xFF | Unassigned |
+------------+---------------------+
Table 13: SHUTDOWN Reason Codes Table 13: SHUTDOWN Reason Codes
8.7. MSG_REJECT Reason Codes 8.7. 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-
registry titled "Bundle Protocol TCP Convergence-Layer Version 4 registry titled "Bundle Protocol TCP Convergence-Layer Version 4
MSG_REJECT Reason Codes" and initialized it with the contents of MSG_REJECT 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 | Rejection Reason | | Code | Rejection Reason |
+-----------+----------------------+ +-----------+----------------------+
| 0x00 | reserved | | 0x00 | reserved |
| | | | | |
| 0x01 | Message Type Unknown | | 0x01 | Message Type Unknown |
| | | | | |
| 0x02 | Message Unsupported | | 0x02 | Message Unsupported |
| | | | | |
| 0x03 | Message Unexpected | | 0x03 | Message Unexpected |
| | | | | |
| 0x04-0xFF | Unassigned | | 0x04-0xFF | Unassigned |
+-----------+----------------------+ +-----------+----------------------+
Table 14: REJECT Reason Codes Table 14: REJECT Reason Codes
9. Acknowledgments 9. Acknowledgments
This memo is based on comments on implementation of [RFC7242] This specification is based on comments on implementation of
provided from Scott Burleigh. [RFC7242] provided from Scott Burleigh.
10. References 10. References
10.1. Normative References 10.1. 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-10 (work in progress),
November 2017. November 2017.
skipping to change at page 36, line 47 skipping to change at page 37, line 47
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 SHUTDOWN reason code. o Added contact negotiation failure SHUTDOWN 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 SHUTDOWN reason code. o Added TLS failure and Resource Exhaustion SHUTDOWN 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 US
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334 lines changed or deleted 388 lines changed or added

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