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Extended Message support for BGP
draft-ietf-idr-bgp-extended-messages-26

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 8654.
Authors Randy Bush , Keyur Patel , David Ward
Last updated 2018-10-03 (Latest revision 2018-06-06)
Replaces draft-ymbk-bgp-extended-messages
RFC stream Internet Engineering Task Force (IETF)
Formats
Reviews
Additional resources Mailing list discussion
Stream WG state WG Document
Document shepherd Susan Hares
Shepherd write-up Show Last changed 2017-03-06
IESG IESG state Became RFC 8654 (Proposed Standard)
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Alvaro Retana
Send notices to jgs@juniper.net, jie.dong@huawei.com, aretana.ietf@gmail.com
draft-ietf-idr-bgp-extended-messages-26
Network Working Group                                            R. Bush
Internet-Draft                                 Internet Initiative Japan
Updates: 4271 (if approved)                                     K. Patel
Intended status: Standards Track                            Arrcus, Inc.
Expires: December 8, 2018                                        D. Ward
                                                           Cisco Systems
                                                            June 6, 2018

                    Extended Message support for BGP
                draft-ietf-idr-bgp-extended-messages-26

Abstract

   The BGP specification mandates a maximum BGP message size of 4096
   octets.  As BGP is extended to support newer AFI/SAFIs and other
   features, there is a need to extend the maximum message size beyond
   4096 octets.  This document updates the BGP specification RFC4271 by
   providing an extension to BGP to extend its current maximum message
   size from 4096 octets to 65535 octets for all except the OPEN
   message.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
   be interpreted as described in [RFC2119] only when they appear in all
   upper case.  They may also appear in lower or mixed case as English
   words, without normative meaning.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 8, 2018.

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Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  BGP Extended Message  . . . . . . . . . . . . . . . . . . . .   2
   3.  Extended Message Capability for BGP . . . . . . . . . . . . .   3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Changes to RFC4271  . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     10.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The BGP specification [RFC4271] mandates a maximum BGP message size
   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
   a need to extend the maximum message size beyond 4096 octets.  This
   draft provides an extension to BGP to extend its current message size
   limit from 4096 octets to 65535 octets for all except the OPEN
   message.

2.  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
   smallest message that may be sent consists of a BGP header without a
   data portion (19 octets).

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3.  Extended Message Capability for BGP

   To advertise the BGP Extended Message Capability to a peer, a BGP
   speaker uses BGP Capabilities Advertisement [RFC5492].  By
   advertising the BGP Extended Message Capability to a peer, a BGP
   speaker conveys that it is able to send, receive, and properly handle
   BGP Extended Messages.

   A peer which does not advertise this capability MUST NOT send BGP
   Extended Messages, and BGP Extended Messages MUST NOT be sent to it.

   The BGP Extended Message Capability is a new BGP Capability [RFC5492]
   defined with Capability code 6 and Capability length 0.

4.  Operation

   A BGP speaker that is capable of sending and receiving BGP Extended
   Messages SHOULD advertise the BGP Extended Message Capability to the
   peer using BGP Capabilities Advertisement [RFC5492].  A BGP speaker
   MAY send Extended Messages to its peer only if it has received the
   Extended Message Capability from that peer.

   The Extended Message Capability only applies to all messages except
   for the OPEN message.  This exception is made to reduce compexity of
   providing backward compatibility

   An implementation that advertises support for BGP Extended Messages
   MUST be capable of receiving a message with a length up to and
   including 65535 octets.

   Applications generating information which might be encapsulated
   within BGP messages MUST limit the size of their payload to take the
   maximum message size into account.

   A BGP announcement will, in the normal case, propagate throughout the
   BGP speaking Internet; and there will undoubtedly be BGP speakers
   which do not have the Extended Message capability.  Therefore,
   putting an attribute which can not be decomposed to 4096 octets or
   less in an Extended Message is a likely path to routing failure.

   It is RECOMMENDED that BGP protocol developers and implementers are
   conservative in their application and use of Extended Messages.
   Future protocol specifications will need to describe how to handle
   peers which can only accommodate 4096 octet messages.

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5.  Error Handling

   A BGP speaker that has the ability to use Extended Messages but has
   not advertised the BGP Extended Messages capability, presumably due
   to configuration, SHOULD NOT accept an Extended Message.  A speaker
   MAY implement a more liberal policy and accept Extended Messages,
   even from a peer to which it has not advertised the capability, in
   the interest of preserving the BGP session if at all possible.

   A BGP speaker that does not advertise the BGP Extended Messages
   capability might also genuinely not support Extended Messages.  Such
   a speaker MUST follow the error handling procedures of [RFC4271] if
   it receives an Extended Message.  Similarly, any speaker that treats
   an improper Extended Message as a fatal error, MUST treat it
   similarly.

   The inconsistency between the local and remote BGP speakers MUST be
   flagged to the network operator through standard operational
   interfaces.  The information should include the NLRI and as much
   relevant information as reasonably possible.

6.  Changes to RFC4271

   [RFC4271] states "The value of the Length field MUST always be at
   least 19 and no greater than 4096."  This document changes the latter
   number to 65535 for all except the OPEN message.

   [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, if the receiver has advertised the capability to receive
   Extended Messages, this document raises that limit to 65535.

7.  IANA Considerations

   The IANA has made an early allocation for this new BGP Extended
   Message Capability referring to this document.

   Registry:  BGP Capability Code

   Value    Description                               Document
   -----    -----------------------------------       -------------
   6        BGP-Extended Message                      [this draft]

8.  Security Considerations

   This extension to BGP does not change BGP's underlying security
   issues; see [RFC4272].

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   Section 5 allowed a receiver to accept an Extended Message even
   though it had not advertised the capability.  This slippery slope
   could lead to sloppy implementations sending Extended Messages when
   the receiver is not prepared to deal with them, e.g. to peer groups.
   At best, this will result in errors; at worst, buffer overflows.

   Due to increased memory requirements for buffering, there may be
   increased exposure to resource exhaustion, intentional or
   unintentional.

9.  Acknowledgments

   The authors thank Alvaro Retana, Enke Chen, Susan Hares, John
   Scudder, John Levine, and Job Snijders for their input; and Oliver
   Borchert and Kyehwan Lee for their implementations and testing.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, DOI 10.17487/RFC4272, January 2006,
              <http://www.rfc-editor.org/info/rfc4272>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <http://www.rfc-editor.org/info/rfc5492>.

10.2.  Informative References

   [I-D.ietf-sidr-bgpsec-protocol]
              Lepinski, M., "BGPSEC Protocol Specification", draft-ietf-
              sidr-bgpsec-protocol-07 (work in progress), February 2013.

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Authors' Addresses

   Randy Bush
   Internet Initiative Japan
   5147 Crystal Springs
   Bainbridge Island, Washington  98110
   United States of America

   Email: randy@psg.com

   Keyur Patel
   Arrcus, Inc.

   Email: keyur@arrcus.com

   Dave Ward
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   United States of America

   Email: dward@cisco.com

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