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IDR                                                             S. Hares
Internet-Draft                                                    Huawei
Intended status: Standards Track                                K. Patel
Expires: June 22, 2017                                             Cisco
                                                       December 19, 2016


             AS Path Based Outbound Route Filter for BGP-4
                    draft-ietf-idr-aspath-orf-13.txt

Abstract

   This document defines a new Outbound Router Filter type for BGP,
   termed "Aspath Outbound Route Filter", that can be used to perform
   aspath based route filtering.  This ORF-type supports aspath based
   route filtering as well as regular expression based matching, for
   address groups.

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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   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 June 22, 2017.

Copyright Notice

   Copyright (c) 2016 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
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  ASpath ORF-Type . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  ASpath ORF encoding . . . . . . . . . . . . . . . . . . . . .   3
   4.  Capability Specification for Cooperative route filtering with
       ASpath  . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  ASpath ORF Matching . . . . . . . . . . . . . . . . . . . . .   6
   6.  Error handling  . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   10. Security Considerations . . . . . . . . . . . . . . . . . . .   7
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The Cooperative Outbound Route Filtering Capability defined in
   [RFC5292] 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 "ASpath
   Outbound Route Filter (ASpath ORF)", that can be used to perform AS
   Path based route filtering.  The ASpath ORF supports AS path route
   filtering as well as the regular expression based matching for
   address groups.

2.  ASpath ORF-Type

   The ASpath ORF-Type allows one to express ORFs in terms of regular
   expression and AS path numbers.  That is, it provides AS path based
   route filtering, including regular expression based matching.

   Conceptually an ASpath ORF entry consists of the fields <Sequence,
   Match, Length, Aspath>.

      The "Sequence" field is a number that specifies the relative
      ordering of the entry.

      The "Match" field specifies whether this entry is "PERMIT" (value
      0), or "DENY" (value 1).





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      The "Length" field indicates the length of AS path regular
      expression string.

      The "aspath" field contains an AS path regular expression of an
      address group.

      The field "Sequence" is an unsigned 32 bit value.  The field
      "Length" is an unsigned 16 bit value.  The field "aspath" is a
      variable length hexadecimal string.  The field "aspath" will be
      followed by enough trailing bits to make end of field fall on an
      octet boundary.  Note that the value of trailing bits is
      irrelevant.

3.  ASpath ORF encoding

   The value of the ORF-Type for the ASpath ORF-Type is <TBD>.

   An ASpath ORF entry is encoded as follows.  The "Match" field of the
   entry is encoded in the "Match" field of the common part [RFC5292],
   and the remaining fields of the entry is encoded in the "Type
   specific part" as follows:


        +--------------------------------+
        |   Sequence (4 octets)          |
        +--------------------------------+
        |   Length   (2 octet)           |
        +--------------------------------+
        |   Aspath   ( variable length)  |
        +--------------------------------+

   Note the aspath is a variable length hexadecimal string whose length
   is defined by Length field.

4.  Capability Specification for Cooperative route filtering with ASpath

   As specified in Cooperative Route Filter[RFC5292], a BGP speaker that
   is willing to receive ORF entries from its peer, or a BGP speaker
   that would like to send ORF entries to its peer advertises this to
   the peer by using the Cooperative Route Filtering Capability uses a
   new BGP capability [RFC3392] defined as follows:

      Capability code: 3

      Capability length: variable

      Capability value: one or more of the following entries:




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      +--------------------------------------------------+
      | Address Family Identifier (2 octets)             |
      +--------------------------------------------------+
      | Reserved (1 octet)                               |
      +--------------------------------------------------+
      | Subsequent Address Family Identifier (1 octet)   |
      +--------------------------------------------------+
      | Number of ORFs (1 octet)                         |
      +--------------------------------------------------+
      | ORF Type (1 octet)                               |
      +--------------------------------------------------+
      | Send/Receive (1 octet)                           |
      +--------------------------------------------------+
      | ...                                              |
      +--------------------------------------------------+
      | ORF Type (1 octet)                               |
      +--------------------------------------------------+
      | Send/Receive (1 octet)                           |
      +--------------------------------------------------+

               Fig 4. Capability encoding


   The use and meaning of these fields are as follows:

      Address Family Identifier (AFI)

         This field carries the identity of the address family for the
         Network Layer protocol associated with the Network Address that
         follows.

      Subsequent Address Family Identifier (SAFI):

         This field provides additional information about the type of
         the Network Layer Reachability Information carried in the
         attribute.

      Number of ORF Types

         This field contains the number of Filter Types to be listed in
         the following fields.

      ORF Type

         This field contains the value of an ORF Type.

      Send/Receive




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         This field indicates whether the sender is (a) willing to
         receive ORF entries from its peer (value 1), (b) would like to
         send ORF entries to its peer (value 2), or (c) both (value 3)
         for the ORF Type that follows.

         In the upper bits of the Send/Receive byte the top three bits
         have the following encoding: [FFFKKKSR] where bit 0 is the left
         most bit.

         where:

            S = Send ORF for ASpath

            R = Receive ORF for ASpath

            KKK = a 3 bit field reserved for future expansion of regular
            expression differences in ORF.

            FFF = 3 bits.

               Bit 0 is the left most bit, and indicates anchoring
               status.

                  Bit 0 = 0 - implies full length regular express
                  (regex), that is implicit anchoring of ASPath as in
                  "^ASPath$"

                     anchoring--non-anchoring

                     ^X --------> X .*

                     ^X$ --------> X

                     X -----------> .* X .*

                  Bit 0 = 1 - implies partial aspath regex, regex may or
                  may not have anchors

               Bit 1 is the middle bit, and it is the "." wildcard
               operator.  [Collating Element]

                  Bit 1 = 0 -- indicates traditional application of "."
                  as wildcard, ie: "." matches any single character of
                  the set [0-9 ].

                  Bit 1 = 1 -- indicates "." matches an AS-path token/
                  term, regex "." == traditional regex "[0-9]+"




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               Bit 2 is the right most bit, and indicates the "[]"
               operator where:

                  Bit 2 = 0 - indicates not supported

                  Bit 2 = 1 - indicates support, e.g. [0-9]

5.  ASpath ORF Matching

   In addition to the general matching rules defined in [RFC5292],
   several ASpath ORF specific matching rules are defined as follows.

   It is possible that the speaker would have more than one ASpath ORF
   entry that matches the route.  In that case 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.

   If any speaker does not support capabilities specified by the
   receiver but still decide to establish the connection, the receiver
   is expected to translate the AS path regular expressions to the its
   (receiver's) interpretation of regular expressions as indicated in
   the capability announcement.

6.  Error handling

   ORFs provide information that guides future sending, but any
   malformed ORF is simply missed filtering information.  If ASpath ORF
   is malformed, the attribute shall simply be discarded.

7.  Security Considerations

   This extension to BGP does not change the underlying security issues.

8.  Acknowledgements

   We express our thanks to Andrew Partan, Avneesh Sachdev, Alec
   Peterson, Enke Chen, John Heasley, Dorian Kim and Bruce Cole for
   their comments.

9.  IANA Considerations

   No IANA exist for this document.








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10.  Security Considerations

   No security considerations are involved with a gap analysis.

11.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3392]  Chandra, R. and J. Scudder, "Capabilities Advertisement
              with BGP-4", RFC 3392, DOI 10.17487/RFC3392, November
              2002, <http://www.rfc-editor.org/info/rfc3392>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC5292]  Chen, E. and S. Sangli, "Address-Prefix-Based Outbound
              Route Filter for BGP-4", RFC 5292, DOI 10.17487/RFC5292,
              August 2008, <http://www.rfc-editor.org/info/rfc5292>.

Authors' Addresses

   Susan Hares
   Huawei
   7453 Hickory Hill
   Saline, MI  48176
   USA

   Email: shares@ndzh.com


   Keyur Patel
   Cisco
   Milipitas, CA  95035

   Email: keyupate@cisco.com











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