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Network Working Group                                           E. ChenRequest for Comments: 5292                                    S. SangliCategory: Standards Track                                 Cisco Systems                                                            August 2008Address-Prefix-Based Outbound Route Filter for BGP-4Status of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Abstract   This document defines a new Outbound Router Filter (ORF) type for   BGP, termed "Address Prefix Outbound Route Filter", that can be used   to perform address-prefix-based route filtering.  This ORF-type   supports prefix-length- or range-based matching, wild-card-based   address prefix matching, as well as the exact address prefix matching   for address families.1.  Introduction   The Outbound Route Filtering Capability defined in [BGP-ORF] provides   a mechanism for a BGP speaker to send to its BGP peer a set of   Outbound Route Filters (ORFs) that can be used by its peer to filter   its outbound routing updates to the speaker.   This documents defines a new ORF-type for BGP, termed "Address Prefix   Outbound Route Filter (Address Prefix ORF)", that can be used to   perform address-prefix-based route filtering.  The Address Prefix ORF   supports prefix-length- or range-based matching, wild-card-based   address prefix matching, as well as the exact address prefix matching   for address families [BGP-MP].2.  Address Prefix ORF-Type   The Address Prefix ORF-Type allows one to express ORFs in terms of   address prefixes.  That is, it provides address-prefix-based route   filtering, including prefix-length- or range-based matching, as well   as wild-card address prefix matching.   Conceptually, an Address Prefix ORF entry consists of the fields   <Sequence, Match, Length, Prefix, Minlen, Maxlen>.Chen & Sangli               Standards Track                     [Page 1]

RFC 5292           Address-Prefix-Based ORF for BGP-4        August 2008   The "Sequence" field specifies the relative ordering of the entry   among all the Address Prefix ORF entries.   The "Match" field specifies whether this entry is "PERMIT" (value 0)   or "DENY" (value 1).   The "Length" field indicates the length (in bits) of the address   prefix.  A length of zero indicates a prefix that matches all (as   specified by the address family) addresses (with the prefix itself of   zero octets).   The "Prefix" field contains an address prefix of an address family.   The "Minlen" field indicates the minimum prefix length (in bits) that   is required for "matching".  The field is considered unspecified with   a value of 0.   The "Maxlen" field indicates the maximum prefix length (in bits) that   is required for "matching".  The field is considered unspecified with   a value of 0.   The fields "Sequence", "Length", "Minlen", and "Maxlen" are all   unsigned integers.   This document imposes the following requirement on the values of   these fields:         0 <= Length < Minlen <= Maxlen   However, tests related to the "Minlen" or "Maxlen" value should be   omitted when the "Minlen" or "Maxlen" field (respectively) is   unspecified.   In addition, the "Maxlen" value must be no more than the maximum   length (in bits) of a host address for a given address family   [BGP-MP].Chen & Sangli               Standards Track                     [Page 2]

RFC 5292           Address-Prefix-Based ORF for BGP-4        August 20083.  Address Prefix ORF Encoding   The value of the ORF-Type for the Address Prefix ORF-Type is 64.   An Address Prefix ORF entry is encoded as follows.  The "Match" field   of the entry is encoded in the "Match" field of the common part   [BGP-ORF], and the remaining fields of the entry are encoded in the   "Type specific part", as shown in Figure 1.         +--------------------------------+         |   Sequence (4 octets)          |         +--------------------------------+         |   Minlen   (1 octet)           |         +--------------------------------+         |   Maxlen   (1 octet)           |         +--------------------------------+         |   Length   (1 octet)           |         +--------------------------------+         |   Prefix   (variable length)   |         +--------------------------------+         Figure 1: Address Prefix ORF Encoding   Note that the "Prefix" field contains the address prefix followed by   enough trailing bits to make the end of the field fall on an octet   boundary.  The value of the trailing bits is irrelevant.4.  Address Prefix ORF Matching   In addition to the general matching rules defined in [BGP-ORF],   several Address-Prefix-ORF-specific matching rules are defined as   follows.   Consider an Address Prefix ORF entry, and a route maintained by a BGP   speaker with Network Layer Reachability Information (NLRI) in the   form of <Prefix, Length>.   The route is considered as "no match" to the ORF entry if the NLRI is   neither more specific than, nor equal to, the <Prefix, Length> fields   of the ORF entry.   When the NLRI is either more specific than, or equal to, the <Prefix,   Length> fields of the ORF entry, the route is considered as a match   to the ORF entry only if the NLRI match condition as listed in Table   1 is satisfied.Chen & Sangli               Standards Track                     [Page 3]

RFC 5292           Address-Prefix-Based ORF for BGP-4        August 2008             ORF Entry                  NLRI        Minlen      Maxlen         Match Condition      +------------------------------------------------------+      | un-spec.    un-spec.       NLRI.length == ORF.length |      +------------------------------------------------------+      | specified   un-spec.       NLRI.length >= ORF.Minlen |      +------------------------------------------------------+      | un-spec.    specified      NLRI.length <= ORF.Maxlen |      +------------------------------------------------------+      | specified   specified      NLRI.length >= ORF.Minlen |      |                        AND NLRI.length <= ORF.Maxlen |      +------------------------------------------------------+      Table 1: Address Prefix ORF Matching   When more than one Address Prefix ORF entry matches the NLRI of the   route, the "first-match" rule applies.  That is, the ORF entry with   the smallest sequence number (among all the matching ORF entries) is   considered as the sole match, and it would determine whether the   route should be advertised.   The assignment of the sequence numbers is a local matter for the BGP   speaker that sends the Address Prefix ORF entries.5.  IANA Considerations   This document specifies a new Outbound Route Filtering (ORF) type,   Address Prefix ORF.  The value of the ORF-type is 64.6.  Security Considerations   This extension to BGP does not change the underlying security issues   in [BGP-4].7.  Normative References   [BGP-4]   Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border             Gateway Protocol 4 (BGP-4)",RFC 4271, January 2006.   [BGP-MP]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,             "Multiprotocol Extensions for BGP-4",RFC 4760, January             2007.   [BGP-ORF] Chen, E., and Y. Rekhter, "Outbound Route Filtering             Capability for BGP-4",RFC 5291, August 2008.Chen & Sangli               Standards Track                     [Page 4]

RFC 5292           Address-Prefix-Based ORF for BGP-4        August 2008Authors' Addresses   Enke Chen   Cisco Systems, Inc.   170 W. Tasman Dr.   San Jose, CA 95134   EMail: enkechen@cisco.com   Srihari R. Sangli   Cisco Systems, Inc.   170 W. Tasman Dr.   San Jose, CA 95134   EMail: rsrihari@cisco.comChen & Sangli               Standards Track                     [Page 5]

RFC 5292           Address-Prefix-Based ORF for BGP-4        August 2008Full Copyright Statement   Copyright (C) The IETF Trust (2008).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Chen & Sangli               Standards Track                     [Page 6]