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Network Working Group                                            J. Dong
Internet-Draft                                                   M. Chen
Intended status: Standards Track                     Huawei Technologies
Expires: January 5, 2012                                        K. Patel
                                                           Cisco Systems
                                                            July 4, 2011


             BGP End-of-RIB Usage Extension and Negotiation
               draft-dong-idr-end-of-rib-use-extension-00

Abstract

   This document describes the use of BGP End-of-RIB marker in improving
   BGP routing convergence during initial route exchange.  A mechanism
   to negotiate the extension of End-of-RIB usage is also specified.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 January 5, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  BGP Convergence Problem in Initial Route Exchange . . . . . . . 3
   3.  End-of-RIB Usage Extension  . . . . . . . . . . . . . . . . . . 3
   4.  BGP End-of-RIB Capability . . . . . . . . . . . . . . . . . . . 4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 6






























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1.  Introduction

   BGP Graceful Restart (GR) [RFC4724] defines an End-of-RIB marker to
   convey routing convergence information during BGP restart.  It is
   also specified that the generation of such a marker upon completion
   of the initial update would be useful for routing convergence in
   general.

   Currently most of BGP routers neither generate End-of-RIB marker upon
   completion of initial route advertisement nor anticipate the arrival
   of End-of-RIB from peers during initial route exchange.  In addition,
   for some BGP implementations receiving End-of-RIB marker in scenarios
   other than BGP GR may be treated as an error.

   This document describes the benefit of using BGP End-of-RIB marker to
   inform completion of initial BGP route exchange.  A mechanism to
   negotiate the extension of End-of-RIB usage is also specified.


2.  BGP Convergence Problem in Initial Route Exchange

   When a BGP speaker establishes BGP sessions with multiple peers, the
   initial route exchange begins.  Normally whenever a route is received
   from one of the peers, BGP path calculation would be executed and new
   UPDATE message will be advertised to peers immediately.  Since during
   initial route exchange the BGP speaker may consecutively receive
   different routes to the same prefixes from different peers, this
   normal procedure may cause the BGP speaker execute the path
   calculation for some prefixes for multiple times, and would further
   result in advertising non-optimal routes before routing convergence.

   Apparently this is a waste of processing resource and also impacts
   routing convergence and stability of the network.  Some optimization
   has been proposed.  One typical approach is to set a timer for
   initial route exchange, and BGP speaker will not execute path
   calculation and advertise routes to peers until that timer expires.
   The disadvantage of this approach is value of the timer would be
   critical for BGP convergence performance, and since the timer value
   would be fixed once configured, it cannot guarantee best performance
   and convergence time for different cases.


3.  End-of-RIB Usage Extension

   [RFC4724] defines the use of End-of-RIB marker in BGP Graceful
   Restart scenario, and it also specifies that "generation of such a
   marker upon completion of the initial update would be useful for
   routing convergence in general, and thus the practice is



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   recommended".

   Actually End-of-RIB marker should be used as an individual feature
   independent of whether BGP GR is enabled or not.  One example is
   [RFC4684] specifies the use of End-of-RIB for RT Membership
   information advertisement.

   Similar to the use in BGP Graceful Restart, End-of-RIB marker could
   also be used to inform completion of initial route exchange.  Thus
   route calculation and further advertisement would be suspended until
   End-of-RIB marker is received from all or a predefined portion of BGP
   peers.  In addition, a relative large timer could be used as a backup
   trigger to ensure path calculation and advertisement would always be
   executed within a predefined time range.

   Although it is easy to understand the use of End-of-RIB in improving
   initial routing convergence, such benefit may not be obtained
   directly, as currently most of BGP routers neither generate End-of-
   RIB marker upon completion of initial route advertisement nor
   anticipate the arrival of End-of-RIB from peers during initial route
   exchange.  In addition, for some BGP implementations receiving End-
   of-RIB marker in scenarios other than BGP GR may be treated as an
   error.  Thus to use End-of-RIB for initial route exchange scenario,
   some negotiation between the sending and receiving BGP speaker would
   be necessary.


4.  BGP End-of-RIB Capability

   A new BGP capability called End-of-RIB Capability is defined.  The
   Capability code for this capability is to be assigned.  The
   Capability length field is zero.

   By advertising this capability to a peer, a BGP speaker conveys to
   the peer that the speaker support advertising and receiving End-of-
   RIB marker and the related procedures described in this document.

   After capability negotiation, if both the peer speaker and local
   speaker support this capability, then End-of-RIB marker MUST be sent
   to peer after finishing initial route advertisement, and both
   speakers MUST use the End-of-RIB marker received from peer as
   notification of initial exchange completion and trigger of local
   route processing and further advertisement.  If any one of the
   peering speakers does not support this extension, End-of-RIB MUST not
   be used in initial route exchange scenario.

   When End-of-RIB is used for initial exchange, a timer MAY also be
   used to control the maximum initial delay of route processing and



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   UPDATEs advertisement.  The timer value SHOULD be configurable.


5.  IANA Considerations

   A new BGP capability - End-of-RIB Capability is defined in this
   document.  The Capability code needs to be assigned by the IANA.


6.  Security Considerations

   This document does not change the security properties of BGP.


7.  Acknowledgements

   The authors would like to thank John Scudder, Shunwan Zhuang, Qing
   Zeng for their valuable comments and discussions to this document.


8.  References

8.1.  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.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              January 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

8.2.  Informative References

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, November 2006.






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Authors' Addresses

   Jie Dong
   Huawei Technologies
   Huawei Building, No.3 Xinxi Rd
   Beijing,   100085
   China

   Email: jie.dong@huawei.com


   Mach Chen
   Huawei Technologies
   Huawei Building, No.3 Xinxi Rd
   Beijing,   100085
   China

   Email: mach.chen@huawei.com


   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com
























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