Network Working Group                                            R. Bush
Internet-Draft                                 Internet Initiative Japan
Updates: 4271 (if approved)                                     K. Patel
Intended status: Standards Track                            Arrcus, Inc.
Expires: August 20, September 6, 2017                                       D. Ward
                                                           Cisco Systems
                                                       February 16,
                                                           March 5, 2017

                    Extended Message support for BGP
                draft-ietf-idr-bgp-extended-messages-20
                draft-ietf-idr-bgp-extended-messages-21

Abstract

   The BGP specification mandates a maximum BGP message size of 4096
   octets.  As BGP is extended to support newer AFI/SAFIs, there is a
   need to extend the maximum message size beyond 4096 octets.  This
   document updates the BGP specification RFC 4271 RFC4271 by providing an
   extension to BGP to extend its current maximum message size from 4096
   octets to 65535 octets.

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 RFC 2119 [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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 20, September 6, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  BGP Extended Message  . . . . . . . . . . . . . . . . . . . .   2
   3.  Extended message Capability for BGP . . . . . . . . . . . . .   3
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   3
   6.  Acknowledgements  .  Changes to RFC4271  . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     9.1.   5
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   4
     9.2.   5
     10.2.  Informative References . . . . . . . . . . . . . . . . .   4   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The BGP specification RFC4271 [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-overview]), [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.

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).

   Multi-octet fields MUST be in network byte order.

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 TBD 6 and Capability length 0.

4.  Operation

   A BGP speaker that is willing to send and receive BGP Extended
   Messages from its with a peer SHOULD advertise the BGP Extended Message
   Capability to its the peer using BGP Capabilities Advertisement
   [RFC5492].  A BGP speaker MAY send extended messages Extended Messages to its peer only
   if it has received the Extended Message Capability from its that peer.

   Currently, the Extended Message Capability only applies to UPDATE
   messages.

   An implementation that supports the advertises support for BGP Extended Messages
   MUST be
   prepared to receive capable of receiving an UPDATE message that is larger than 4096 bytes. with a length up to
   and including 65535 octets.

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

5.  Error Handling

   A BGP speaker that has the ability to use extended messages Extended Messages but has
   not advertised the BGP Extended Messages capability, presumably due
   to configuration, SHOULD NOT accept an extended message. Extended Message.  A speaker
   MAY implement a more liberal policy and accept extended messages Extended Messages,
   even from a peer that to which it has not advertised the capability.

   However, a 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. Extended Messages.  Such
   a speaker would be expected to follow the error handling procedures
   of [RFC4271], Section 6.1, and reset the session
   with a Bad Message Length NOTIFICATION [RFC4271] if it receives an extended
   message. Extended Message.  Similarly, any
   speaker that treats an improper extended
   message Extended Message as a fatal error,
   MUST do likewise. treat it similarly.

   The inconsistency between the local and remote BGP speakers MUST be
   reported via syslog and/or SNMP.

6.  Acknowledgements
   flagged to the network operator through standard operational
   interfaces.  The authors thank Enke Chen, Susan Hares, John Scudder, John Levine, information should include the NLRI and Job Snijders 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 their input. UPDATE messages.

   [RFC4271] Sec 6.1, specifies raising an error if the length of a
   message is over 4096 octets.  For UPDATE messages, if the receiver
   has advertised the capability to receive Extended Messages, this
   document raises that limit to 65535.

7.  IANA Considerations

   The IANA is requested to register a has made an early allocation for this new BGP Capability Code to be
   named BGP Extended
   Message Capability and referring to this document.

   Registry:  BGP Capability Code

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

8.  Security Considerations

   This extension to BGP does not change BGP's underlying security
   issues.  It does enable large BGPsec BGPSEC_PATHs,
   issues; see
   [I-D.ietf-sidr-bgpsec-protocol] [RFC4272].

   Section 5 allowed a receiver to accept an Extended Message even
   though they had not advertised the capability.  This slippery slope
   will surely 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.

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

9.1.

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis",
              RFC 4272, January 2006.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, February 2009.

9.2.

10.2.  Informative References

   [I-D.ietf-sidr-bgpsec-overview]
              Lepinski, M. and S. Turner, "An Overview of BGPSEC",
              draft-ietf-sidr-bgpsec-overview-02 (work in progress), May
              2012.

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

Authors' Addresses

   Randy Bush
   Internet Initiative Japan
   5147 Crystal Springs
   Bainbridge Island, Washington  98110
   US

   Email: randy@psg.com

   Keyur Patel
   Arrcus, Inc.

   Email: keyur@arrcus.com
   Dave Ward
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: dward@cisco.com