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Internet Engineering Task Force (IETF)                          K. PatelRequest for Comments: 7313                                       E. ChenUpdates:2918                                              Cisco SystemsCategory: Standards Track                           B. VenkatachalapathyISSN: 2070-1721                                                July 2014Enhanced Route Refresh Capability for BGP-4Abstract   In this document, we enhance the existing BGP route refresh   mechanisms to provide for the demarcation of the beginning and the   ending of a route refresh.  The enhancement can be used to facilitate   correction of BGP Routing Information Base (RIB) inconsistencies in a   non-disruptive manner.  This document updatesRFC 2918.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7313.Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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.Patel, et al.                Standards Track                    [Page 1]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 2014Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Requirements Language . . . . . . . . . . . . . . . . . . . .23.  Protocol Extensions . . . . . . . . . . . . . . . . . . . . .23.1.  Enhanced Route Refresh Capability . . . . . . . . . . . .33.2.  Subtypes for ROUTE-REFRESH Message  . . . . . . . . . . .34.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .35.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .56.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .67.  Security Considerations . . . . . . . . . . . . . . . . . . .78.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .79.  Normative References  . . . . . . . . . . . . . . . . . . . .71.  Introduction   It is sometimes necessary to perform routing consistency validations   such as checking for possible missing route withdrawals between BGP   speakers [RFC4271].  Currently, such validations typically involve   offline, manual operations that can be tedious and time-consuming.   In this document, we enhance the existing BGP route refresh   mechanisms [RFC2918] to provide for the demarcation of the beginning   and the ending of a route refresh (which refers to the complete   re-advertisement of the Adj-RIB-Out to a peer, subject to routing   policies).  The enhancement can be used to facilitate online, non-   disruptive consistency validation of BGP routing updates.   This document updates [RFC2918] by redefining a field in the ROUTE-   REFRESH message that was previously designated as Reserved.2.  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 [RFC2119] only when   they appear in all upper case.  They may also appear in lower or   mixed case as English words, without any normative meaning.3.  Protocol Extensions   The BGP protocol extensions introduced in this document include the   definition of a new BGP capability, named "Enhanced Route Refresh   Capability", and the specification of the message subtypes for the   ROUTE-REFRESH message.Patel, et al.                Standards Track                    [Page 2]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 20143.1.  Enhanced Route Refresh Capability   The "Enhanced Route Refresh Capability" is a new BGP capability   [RFC5492].  IANA has assigned a Capability Code of 70 for this   capability.  The Capability Length field of this capability is zero.   By advertising this capability to a peer, a BGP speaker conveys to   the peer that the speaker supports the message subtypes for the   ROUTE-REFRESH message and the related procedures described in this   document.3.2.  Subtypes for ROUTE-REFRESH Message   The "Reserved" field of the ROUTE-REFRESH message specified in   [RFC2918] is redefined as the "Message Subtype" with the following   values:             0 - Normal route refresh request [RFC2918]                 with/without Outbound Route Filtering (ORF) [RFC5291]             1 - Demarcation of the beginning of a route refresh                 (BoRR) operation             2 - Demarcation of the ending of a route refresh                 (EoRR) operation           255 - Reserved   The remaining values of the message subtypes are reserved for future   use; seeSection 6 ("IANA Considerations").  The use of the new   message subtypes is described inSection 4 ("Operation").4.  Operation   A BGP speaker that supports the message subtypes for the ROUTE-   REFRESH message and the related procedures SHOULD advertise the   "Enhanced Route Refresh Capability".   The following procedures are applicable only if a BGP speaker has   received the "Enhanced Route Refresh Capability" from a peer.   Before the speaker starts a route refresh that is either initiated   locally, or in response to a "normal route refresh request" from the   peer, the speaker MUST send a BoRR message.  After the speaker   completes the re-advertisement of the entire Adj-RIB-Out to the peer,   it MUST send an EoRR message.   Conceptually, the "entire Adj-RIB-Out" for a peer in this section   refers to all the route entries in the "Adj-RIB-Out" for the peer at   the start of the route refresh operation.  These route entries   comprise both the reachability as well as unreachability information.Patel, et al.                Standards Track                    [Page 3]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 2014   When a route entry in the "Adj-RIB-Out" changes, only the modified   route entry needs to be advertised.   In processing a ROUTE-REFRESH message from a peer, the BGP speaker   MUST examine the "message subtype" field of the message and take the   appropriate actions.  The message processing rules for ROUTE-REFRESH   message with subtype of 0 are described in [RFC2918] and [RFC5291].   A BGP speaker can receive a BoRR message from a peer at any time,   either as a result of a peer responding to a ROUTE-REFRESH message,   or as a result of a peer unilaterally initiating a route refresh.   When a BGP speaker receives a BoRR message from a peer, it MUST mark   all the routes with the given Address Family Identifier and   Subsequent Address Family Identifier, <AFI, SAFI> [RFC2918], from   that peer as stale.  As it receives routes from its peer's subsequent   Adj-RIB-Out re-advertisement, these replace any corresponding stale   routes.  When a BGP speaker receives an EoRR message from a peer, it   MUST immediately remove any routes from the peer that are still   marked as stale for that <AFI, SAFI>.  Such purged routes MAY be   logged for future analysis.  A BGP speaker MAY ignore any EoRR   message received without a prior receipt of an associated BoRR   message.  Such messages MAY be logged for future analysis.   An implementation MAY impose a locally configurable upper bound on   how long it would retain any stale routes.  Once the upper bound is   reached, the implementation MAY remove any routes from the peer that   are still marked as stale for that <AFI, SAFI> without waiting for an   EoRR message.   The following procedures are specified in order to simplify the   interaction with the BGP Graceful Restart [RFC4724].  In particular,   these procedures ensure that End-of-RIB (EoR) defined in Graceful   Restart and EoRR as defined in this specification are kept separate,   thereby avoiding any premature cleanup of stale routes.  For a BGP   speaker that supports the BGP Graceful Restart, it MUST NOT send a   BoRR for an <AFI, SAFI> to a neighbor before it sends the EoR for the   <AFI, SAFI> to the neighbor.  A BGP speaker that has received the   Graceful Restart Capability from its neighbor MUST ignore any BoRRs   for an <AFI, SAFI> from the neighbor before the speaker receives the   EoR for the given <AFI, SAFI> from the neighbor.  The BGP speaker   SHOULD log an error of the condition for further analysis.Patel, et al.                Standards Track                    [Page 4]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 20145.  Error Handling   This document defines a new NOTIFICATION error code:          Error Code   Name              7        ROUTE-REFRESH Message Error   The following error subcode is defined as well:          Subcode      Name             1         Invalid Message Length   The error handling specified in this section is applicable only when   a BGP speaker has received the "Enhanced Route Refresh Capability"   from a peer.   If the length, excluding the fixed-size message header, of the   received ROUTE-REFRESH message with Message Subtype 1 and 2 is not 4,   then the BGP speaker MUST send a NOTIFICATION message with the Error   Code of "ROUTE-REFRESH Message Error" and the subcode of "Invalid   Message Length".  The Data field of the NOTIFICATION message MUST   contain the complete ROUTE-REFRESH message.   When the BGP speaker receives a ROUTE-REFRESH message with a "Message   Subtype" field other than 0, 1, or 2, it MUST ignore the received   ROUTE-REFRESH message.  It SHOULD log an error for further analysis.Patel, et al.                Standards Track                    [Page 5]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 20146.  IANA Considerations   This document defines the Enhanced Route Refresh Capability for BGP.   In the "Capability Codes" registry, IANA has assigned it value 70,   referencing this document.   This document also defines two new subcodes for the Route Refresh   message.  They have been registered with the IANA in a new registry   as follows:           Under "Border Gateway Protocol (BGP) Parameters":           Registry: "BGP Route Refresh Subcodes"           Reference: [RFC7313]           Registration Procedure(s): Values 0-127 Standards Action,             values 128-254 First Come First Served           Value   Code                Reference           0       Route-Refresh       [RFC2918], [RFC5291]           1       BoRR                [RFC7313]           2       EoRR                [RFC7313]           3-254   Unassigned           255     Reserved            [RFC7313]   In addition, this document defines a NOTIFICATION error code and an   error subcode related to the ROUTE-REFRESH message.  IANA has changed   the name of the "BGP Error Codes" to "BGP Error (Notification) Codes"   and added this document as a reference.  IANA has allocated a new   error code from that registry with the name "ROUTE-REFRESH Message   Error", referencing this document.   IANA has created a new registry for the error subcodes as follows:           Under "Border Gateway Protocol (BGP) Parameters",           under "BGP Error Subcodes":           Registry: "BGP ROUTE-REFRESH Message Error subcodes"           Reference: [RFC7313]           Registration Procedure(s): Values 0-127 Standards Action,             values 128-255 First Come First Served           Value   Name                     Reference           0       Reserved                 [RFC7313]           1       Invalid Message Length   [RFC7313]           2-255   UnassignedPatel, et al.                Standards Track                    [Page 6]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 20147.  Security Considerations   Security considerations are given in [RFC4272] , but they do not   cover Route-Refresh and many other BGP extensions.  This document   does not significantly change the underlying security issues   regarding Route-Refresh, although improved error handling may aid   operational security.8.  Acknowledgements   The authors would like to thank Pedro Marques, Pradosh Mohapatra,   Robert Raszuk, Pranav Mehta, Shyam Sethuram, Bruno Decraene, Martin   Djernaes, Jeff Haas, Ilya Varlashkin, Rob Shakir, Paul Jakma, Jie   Dong, Qing Zeng, Albert Tian, Jakob Heitz, and Chris Hall for their   review and comments.  The authors would like to thank John Scudder   for the review and contribution to this document.9.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2918]  Chen, E., "Route Refresh Capability for BGP-4",RFC 2918,              September 2000.   [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",RFC4272, January 2006.   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.              Rekhter, "Graceful Restart Mechanism for BGP",RFC 4724,              January 2007.   [RFC5291]  Chen, E. and Y. Rekhter, "Outbound Route Filtering              Capability for BGP-4",RFC 5291, August 2008.   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement              with BGP-4",RFC 5492, February 2009.Patel, et al.                Standards Track                    [Page 7]

RFC 7313       Enhanced Route Refresh Capability for BGP-4     July 2014Authors' Addresses   Keyur Patel   Cisco Systems   170 W. Tasman Drive   San Jose, CA  95134   USA   EMail: keyupate@cisco.com   Enke Chen   Cisco Systems   170 W. Tasman Drive   San Jose, CA  95134   USA   EMail: enkechen@cisco.com   Balaji Venkatachalapathy   EMail: balaji_pv@hotmail.comPatel, et al.                Standards Track                    [Page 8]