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Versions: (draft-ymbk-bgp-extended-messages) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21

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


                    Extended Message support for BGP
                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 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 [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 http://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 September 6, 2017.






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Copyright Notice

   Copyright (c) 2017 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
   (http://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  . . . . . . . . . . . . . . . . . . . . . . .   3
   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  . . . . . . . . . . . . . . . . . . . . . . .   5

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.

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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   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 6 and Capability length 0.

4.  Operation

   A BGP speaker that is willing to send and receive BGP Extended
   Messages with a peer 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.

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

   An implementation that advertises support for BGP Extended Messages
   MUST be capable of receiving an UPDATE 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 sure path to routing failure.

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,




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   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 would be expected to 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 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 has made an early allocation for this new BGP 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].

   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.



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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, 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.

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.

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








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   Dave Ward
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: dward@cisco.com












































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