draft-ietf-idr-bgp-extended-messages-25.txt   draft-ietf-idr-bgp-extended-messages-26.txt 
Network Working Group R. Bush Network Working Group R. Bush
Internet-Draft Internet Initiative Japan Internet-Draft Internet Initiative Japan
Updates: 4271 (if approved) K. Patel Updates: 4271 (if approved) K. Patel
Intended status: Standards Track Arrcus, Inc. Intended status: Standards Track Arrcus, Inc.
Expires: November 22, 2018 D. Ward Expires: December 8, 2018 D. Ward
Cisco Systems Cisco Systems
May 21, 2018 June 6, 2018
Extended Message support for BGP Extended Message support for BGP
draft-ietf-idr-bgp-extended-messages-25 draft-ietf-idr-bgp-extended-messages-26
Abstract Abstract
The BGP specification mandates a maximum BGP message size of 4096 The BGP specification mandates a maximum BGP message size of 4096
octets. As BGP is extended to support newer AFI/SAFIs and other octets. As BGP is extended to support newer AFI/SAFIs and other
features, there is a need to extend the maximum message size beyond features, there is a need to extend the maximum message size beyond
4096 octets. This document updates the BGP specification RFC4271 by 4096 octets. This document updates the BGP specification RFC4271 by
providing an extension to BGP to extend its current maximum message providing an extension to BGP to extend its current maximum message
size from 4096 octets to 65535 octets for all except the OPEN size from 4096 octets to 65535 octets for all except the OPEN
message. message.
skipping to change at page 1, line 47 skipping to change at page 1, line 47
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 22, 2018. This Internet-Draft will expire on December 8, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. BGP Extended Message . . . . . . . . . . . . . . . . . . . . 2 2. BGP Extended Message . . . . . . . . . . . . . . . . . . . . 2
3. Extended message Capability for BGP . . . . . . . . . . . . . 3 3. Extended Message Capability for BGP . . . . . . . . . . . . . 3
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 4 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 4
6. Changes to RFC4271 . . . . . . . . . . . . . . . . . . . . . 4 6. Changes to RFC4271 . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Security Considerations . . . . . . . . . . . . . . . . . . . 4 8. Security Considerations . . . . . . . . . . . . . . . . . . . 4
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
10.1. Normative References . . . . . . . . . . . . . . . . . . 5 10.1. Normative References . . . . . . . . . . . . . . . . . . 5
10.2. Informative References . . . . . . . . . . . . . . . . . 5 10.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
The BGP specification [RFC4271] mandates a maximum BGP message size The BGP specification [RFC4271] mandates a maximum BGP message size
of 4096 octets. As BGP is extended to support newer AFI/SAFIs and of 4096 octets. As BGP is extended to support newer AFI/SAFIs and
newer capabilities (e.g., [I-D.ietf-sidr-bgpsec-protocol]), there is newer capabilities (e.g., [I-D.ietf-sidr-bgpsec-protocol]), there is
a need to extend the maximum message size beyond 4096 octets. This a need to extend the maximum message size beyond 4096 octets. This
draft provides an extension to BGP to extend its current message size draft provides an extension to BGP to extend its current message size
limit from 4096 octets to 65535 octetsfor all except the OPEN limit from 4096 octets to 65535 octets for all except the OPEN
message. message.
2. BGP Extended Message 2. BGP Extended Message
A BGP message over 4096 octets in length is a BGP Extended Message. A BGP message over 4096 octets in length is a BGP Extended Message.
BGP Extended Messages have maximum message size of 65535 octets. The BGP Extended Messages have maximum message size of 65535 octets. The
smallest message that may be sent consists of a BGP header without a smallest message that may be sent consists of a BGP header without a
data portion (19 octets). data portion (19 octets).
3. Extended message Capability for BGP 3. Extended Message Capability for BGP
To advertise the BGP Extended Message Capability to a peer, a BGP To advertise the BGP Extended Message Capability to a peer, a BGP
speaker uses BGP Capabilities Advertisement [RFC5492]. By speaker uses BGP Capabilities Advertisement [RFC5492]. By
advertising the BGP Extended Message Capability to a peer, a BGP advertising the BGP Extended Message Capability to a peer, a BGP
speaker conveys that it is able to send, receive, and properly handle speaker conveys that it is able to send, receive, and properly handle
BGP Extended Messages. BGP Extended Messages.
A peer which does not advertise this capability MUST NOT send BGP A peer which does not advertise this capability MUST NOT send BGP
Extended Messages, and BGP Extended Messages MUST NOT be sent to it. Extended Messages, and BGP Extended Messages MUST NOT be sent to it.
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4. Operation 4. Operation
A BGP speaker that is capable of sending and receiving BGP Extended A BGP speaker that is capable of sending and receiving BGP Extended
Messages SHOULD advertise the BGP Extended Message Capability to the Messages SHOULD advertise the BGP Extended Message Capability to the
peer using BGP Capabilities Advertisement [RFC5492]. A BGP speaker peer using BGP Capabilities Advertisement [RFC5492]. A BGP speaker
MAY send Extended Messages to its peer only if it has received the MAY send Extended Messages to its peer only if it has received the
Extended Message Capability from that peer. Extended Message Capability from that peer.
The Extended Message Capability only applies to all messages except The Extended Message Capability only applies to all messages except
for the OPEN message. This exception is reduce compexity of for the OPEN message. This exception is made to reduce compexity of
providing backward compatibility providing backward compatibility
An implementation that advertises support for BGP Extended Messages An implementation that advertises support for BGP Extended Messages
MUST be capable of receiving a message with a length up to and MUST be capable of receiving a message with a length up to and
including 65535 octets. including 65535 octets.
Applications generating information which might be encapsulated Applications generating information which might be encapsulated
within BGP messages MUST limit the size of their payload to take the within BGP messages MUST limit the size of their payload to take the
maximum message size into account. maximum message size into account.
A BGP announcement will, in the normal case, propagate throughout the A BGP announcement will, in the normal case, propagate throughout the
BGP speaking Internet; and there will undoubtedly be BGP speakers BGP speaking Internet; and there will undoubtedly be BGP speakers
which do not have the Extended Message capability. Therefore putting which do not have the Extended Message capability. Therefore,
an attribute which can not be decomposed to 4096 octets or less in an putting an attribute which can not be decomposed to 4096 octets or
Extended Message is a likely path to routing failure. less in an Extended Message is a likely path to routing failure.
It is RECOMMENDED that BGP protocol developers and implementers are It is RECOMMENDED that BGP protocol developers and implementers are
conservative in their application and use of Extended Messages. conservative in their application and use of Extended Messages.
Future protocol specifications will need to describe how to handle Future protocol specifications will need to describe how to handle
peers which can only accomodate 4096 octet messages. peers which can only accommodate 4096 octet messages.
5. Error Handling 5. Error Handling
A BGP speaker that has the ability to use Extended Messages but has A BGP speaker that has the ability to use Extended Messages but has
not advertised the BGP Extended Messages capability, presumably due not advertised the BGP Extended Messages capability, presumably due
to configuration, SHOULD NOT accept an Extended Message. A speaker to configuration, SHOULD NOT accept an Extended Message. A speaker
MAY implement a more liberal policy and accept Extended Messages, MAY implement a more liberal policy and accept Extended Messages,
even from a peer to which it has not advertised the capability, in even from a peer to which it has not advertised the capability, in
the interest of preserving the BGP session if at all possible. the interest of preserving the BGP session if at all possible.
A BGP speaker that does not advertise the BGP Extended Messages A BGP speaker that does not advertise the BGP Extended Messages
capability might also genuinely not support Extended Messages. Such capability might also genuinely not support Extended Messages. Such
a speaker would be expected to follow the error handling procedures a speaker MUST follow the error handling procedures of [RFC4271] if
of [RFC4271] if it receives an Extended Message. Similarly, any it receives an Extended Message. Similarly, any speaker that treats
speaker that treats an improper Extended Message as a fatal error, an improper Extended Message as a fatal error, MUST treat it
MUST treat it similarly. similarly.
The inconsistency between the local and remote BGP speakers MUST be The inconsistency between the local and remote BGP speakers MUST be
flagged to the network operator through standard operational flagged to the network operator through standard operational
interfaces. The information should include the NLRI and as much interfaces. The information should include the NLRI and as much
relevant information as reasonably possible. relevant information as reasonably possible.
6. Changes to RFC4271 6. Changes to RFC4271
[RFC4271] states "The value of the Length field MUST always be at [RFC4271] states "The value of the Length field MUST always be at
least 19 and no greater than 4096." This document changes the latter least 19 and no greater than 4096." This document changes the latter
number to 65535 for all except the OPEN message. number to 65535 for all except the OPEN message.
[RFC4271] Sec 6.1, specifies raising an error if the length of a [RFC4271] Sec 6.1, specifies raising an error if the length of a
message is over 4096 octets. For all messages except the OPEN message is over 4096 octets. For all messages except the OPEN
message, if the receiver has advertised the capability to receive message, if the receiver has advertised the capability to receive
Extended Messages, this document raises that limit to 65535. Extended Messages, this document raises that limit to 65535.
7. IANA Considerations 7. IANA Considerations
The IANA has made an early allocation for this new BGP BGP Extended The IANA has made an early allocation for this new BGP Extended
Message Capability referring to this document. Message Capability referring to this document.
Registry: BGP Capability Code Registry: BGP Capability Code
Value Description Document Value Description Document
----- ----------------------------------- ------------- ----- ----------------------------------- -------------
6 BGP-Extended Message [this draft] 6 BGP-Extended Message [this draft]
8. Security Considerations 8. Security Considerations
This extension to BGP does not change BGP's underlying security This extension to BGP does not change BGP's underlying security
issues; see [RFC4272]. issues; see [RFC4272].
Section 5 allowed a receiver to accept an Extended Message even Section 5 allowed a receiver to accept an Extended Message even
though they had not advertised the capability. This slippery slope though it had not advertised the capability. This slippery slope
will surely lead to sloppy implementations sending Extended Messages could lead to sloppy implementations sending Extended Messages when
when the receiver is not prepared to deal with them, e.g. to peer the receiver is not prepared to deal with them, e.g. to peer groups.
groups. At best, this will result in errors; at worst, buffer At best, this will result in errors; at worst, buffer overflows.
overflows.
Due to increased (over [RFC4272]) memory requirements for buffering, Due to increased memory requirements for buffering, there may be
there may be increased exposure to resource exhaustion, intentional increased exposure to resource exhaustion, intentional or
or unintentional. unintentional.
9. Acknowledgments 9. Acknowledgments
The authors thank Alvaro Retana, Enke Chen, Susan Hares, John The authors thank Alvaro Retana, Enke Chen, Susan Hares, John
Scudder, John Levine, and Job Snijders for their input; and Oliver Scudder, John Levine, and Job Snijders for their input; and Oliver
Borchert and Kyehwan Lee for their implementations and testing. Borchert and Kyehwan Lee for their implementations and testing.
10. References 10. References
10.1. Normative References 10.1. Normative References
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