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Versions: 00 07

Network Working Group                                              Z. Li
Internet-Draft                                                    Huawei
Intended status: Standards Track                                   L. Ou
Expires: February 4, 2021                                         Y. Luo
                                                  China Telcom Co., Ltd.
                                                                   S. Lu
                                                                 Tencent
                                                               G. Mishra
                                                            Verizon Inc.
                                                                 H. Chen
                                                               Futurewei
                                                               S. Zhuang
                                                                 H. Wang
                                                                  Huawei
                                                          August 3, 2020


          BGP Extensions for Routing Policy Distribution (RPD)
                         draft-ietf-idr-rpd-07

Abstract

   It is hard to adjust traffic and optimize traffic paths in a
   traditional IP network from time to time through manual
   configurations.  It is desirable to have a mechanism for setting up
   routing policies, which adjusts traffic and optimizes traffic paths
   automatically.  This document describes BGP Extensions for Routing
   Policy Distribution (BGP RPD) to support this.

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] [RFC8174]
   when, and only when, they appear in all capitals, as shown here.

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 https://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



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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 February 4, 2021.

Copyright Notice

   Copyright (c) 2020 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
   (https://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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Inbound Traffic Control . . . . . . . . . . . . . . . . .   4
     3.2.  Outbound Traffic Control  . . . . . . . . . . . . . . . .   4
   4.  Protocol Extensions . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Using a New AFI and SAFI  . . . . . . . . . . . . . . . .   5
     4.2.  BGP Wide Community and Atoms  . . . . . . . . . . . . . .   6
       4.2.1.  RouteAttr TLV/sub-TLV . . . . . . . . . . . . . . . .   7
       4.2.2.  Sub-TLVs of the Parameters TLV  . . . . . . . . . . .  10
     4.3.  Capability Negotiation  . . . . . . . . . . . . . . . . .  12
   5.  Routing Policy Considerations . . . . . . . . . . . . . . . .  13
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  14
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Existing Assignments  . . . . . . . . . . . . . . . . . .  14
     9.2.  Routing Policy Type Registry  . . . . . . . . . . . . . .  14
     9.3.  RouteAttr Atom Type . . . . . . . . . . . . . . . . . . .  15
     9.4.  Route Attributes Sub-TLV Registry . . . . . . . . . . . .  15
     9.5.  Attribute Change Sub-TLV Registry . . . . . . . . . . . .  16
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informative References . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17




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1.  Introduction

   It is difficult to optimize traffic paths in a traditional IP network
   because of the following:

   o  Heavy and error prone configuration.  Traffic can only be adjusted
      device by device.  All routers that the traffic traverses need to
      be configured.  The configuration workload is heavy.  The
      operation is not only time consuming but also prone to
      misconfiguration for Service Providers.

   o  Complex.  The routing policies used to control network routes are
      complex, posing difficulties to subsequent maintenance.  High
      maintenance skills are required.

   It is desirable to have an automatic mechanism for setting up routing
   policies, which can simplify routing policy configuration.  This
   document describes extensions to BGP for Routing Policy Distribution
   to resolve these issues.

2.  Terminology

   The following terminology is used in this document.

   o  ACL: Access Control List

   o  BGP: Border Gateway Protocol [RFC4271]

   o  FS: Flow Specification

   o  NLRI: Network Layer Reachability Information [RFC4271]

   o  PBR: Policy-Based Routing

   o  RPD: Routing Policy Distribution

   o  VPN: Virtual Private Network

3.  Problem Statement

   Providers have the requirement to adjust their business traffic
   routing policies from time to time because of the following:

   o  Business development or network failure introduces link congestion
      and overload.

   o  Business changes or network additions produce unused resources
      such as idle links.



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   o  Network transmission quality is decreased as the result of delay,
      loss and they need to adjust traffic to other paths.

   o  To control OPEX and CPEX, they may prefer the transit provider
      with lower price.

3.1.  Inbound Traffic Control

   In Figure 1, for the reasons above, the provider P of AS100 may wish
   the inbound traffic from AS200 to enter AS100 through link L3 instead
   of the others.  Since P doesn't have any administrative control over
   AS200, there is no way for P to directly modify the route selection
   criteria inside AS200.

                  Traffic from PE1 to Prefix1
             ----------------------------------->

   +-----------------+            +-------------------------+
   |     +---------+ |        L1  | +----+      +----------+|
   |     |Speaker1 | +------------+ |IGW1|      |policy    ||
   |     +---------+ |**      L2**| +----+      |controller||
   |                 |  **    **  |             +----------+|
   | +---+           |    ****    |                         |
   | |PE1|           |    ****    |                         |
   | +---+           |  **    **  |                         |
   |     +---------+ |**      L3**| +----+                  |
   |     |Speaker2 | +------------+ |IGW2|      AS100       |
   |     +---------+ |        L4  | +----+                  |
   |                 |            |                         |
   |    AS200        |            |                         |
   |                 |            |  ...                    |
   |                 |            |                         |
   |     +---------+ |            | +----+      +-------+   |
   |     |Speakern | |            | |IGWn|      |Prefix1|   |
   |     +---------+ |            | +----+      +-------+   |
   +-----------------+            +-------------------------+

               Prefix1 advertised from AS100 to AS200
             <----------------------------------------

                  Figure 1: Inbound Traffic Control case

3.2.  Outbound Traffic Control

   In Figure 2, the provider P of AS100 prefers link L3 for the traffic
   to the destination Prefix2 among multiple exits and links to AS200.
   This preference can be dynamic and might change frequently because of




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   the reasons above.  So, provider P expects an efficient and
   convenient solution.

                  Traffic from PE2 to Prefix2
             ----------------------------------->
   +-------------------------+            +-----------------+
   |+----------+      +----+ |L1          | +---------+     |
   ||policy    |      |IGW1| +------------+ |Speaker1 |     |
   ||controller|      +----+ |**        **| +---------+     |
   |+----------+             |L2**    **  |        +-------+|
   |                         |    ****    |        |Prefix2||
   |                         |    ****    |        +-------+|
   |                         |L3**    **  |                 |
   |      AS100       +----+ |**        **| +---------+     |
   |                  |IGW2| +------------+ |Speaker2 |     |
   |                  +----+ |L4          | +---------+     |
   |                         |            |                 |
   |+---+                    |            |    AS200        |
   ||PE2|              ...   |            |                 |
   |+---+                    |            |                 |
   |                  +----+ |            | +---------+     |
   |                  |IGWn| |            | |Speakern |     |
   |                  +----+ |            | +---------+     |
   +-------------------------+            +-----------------+

               Prefix2 advertised from AS200 to AS100
             <----------------------------------------

                  Figure 2: Outbound Traffic Control case

4.  Protocol Extensions

   This document specifies a solution using a new AFI and SAFI with the
   BGP Wide Community for encoding a routing policy.

4.1.  Using a New AFI and SAFI

   A new AFI and SAFI are defined: the Routing Policy AFI whose
   codepoint 16398 has been assigned by IANA, and SAFI whose codepoint
   75 has been assigned by IANA.

   The AFI and SAFI pair uses a new NLRI, which is defined as follows:









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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+
   |  NLRI Length  |
   +-+-+-+-+-+-+-+-+
   |  Policy Type  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Distinguisher (4 octets)                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Peer IP (4/16 octets)                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

     NLRI Length:  1 octet represents the length of NLRI.  If the Length
      is anything other than 9 or 21, the NLRI is corrupt and the
      enclosing UPDATE message is ignored.

     Policy Type:  1 octet indicates the type of a policy.  1 is for
      export policy. 2 is for import policy.  If the Policy Type is any
      other value, the NLRI is corrupt and the enclosing UPDATE message
      is ignored.

     Distinguisher:  4 octet value uniquely identifies the policy in the
      peer.

     Peer IP:  4/16 octet value indicates an IPv4/IPv6 peer.

   The NLRI containing the Routing Policy is carried in MP_Reach_NLRI
   and MP_UNREACH_NLRI path attributes in a BGP UPDATE message, which
   MUST also contain the BGP mandatory attributes and MAY contain some
   BGP optional attributes.

   When receiving a BGP UPDATE message with routing policy, a BGP
   speaker processes it only if the peer IP address in the NLRI is 0 or
   the IP address of the BGP speaker.

   The content of the Routing Policy is encoded in a BGP Wide Community.

4.2.  BGP Wide Community and Atoms

   The BGP wide community is defined in
   [I-D.ietf-idr-wide-bgp-communities].  It can be used to facilitate
   the delivery of new network services and be extended easily for
   distributing different kinds of routing policies.

   A wide community Atom is a TLV (or sub-TLV), which may be included in
   a BGP wide community container (or BGP wide community for short)



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   containing some BGP Wide Community TLVs.  Three BGP Wide Community
   TLVs are defined in [I-D.ietf-idr-wide-bgp-communities], which are
   BGP Wide Community Target(s) TLV, Exclude Target(s) TLV, and
   Parameter(s) TLV.  The value of each of these TLVs comprises a series
   of Atoms, each of which is a TLV (or sub-TLV).  A new wide community
   Atom is defined for BGP Wide Community Target(s) TLV and a few new
   Atoms are defined for BGP Wide Community Parameter(s) TLV.  For your
   reference, the format of the TLV is illustrated below:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |             Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Value (variable)                      ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Format of Wide Community Atom TLV

4.2.1.  RouteAttr TLV/sub-TLV

   A RouteAttr Atom TLV (or RouteAttr TLV/sub-TLV for short) is defined
   and may be included in a Target TLV.  It has the following format.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type (TBD1)  |        Length (variable)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          sub-TLVs                             ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Format of RouteAttr Atom TLV

   The Type for RouteAttr is TBD1.  In RouteAttr TLV, four sub-TLVs are
   defined: IPv4 Prefix, IPv6 Prefix, AS-Path, and Community sub-TLV.

   An IP prefix sub-TLV gives matching criteria on IPv4 prefixes.  Its
   format is illustrated below:












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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type  1      |         Length (N x 8)        |M-Type | Flags |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          IPv4 Address                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |     GeMask    |     LeMask    |M-Type | Flags |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~       . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          IPv4 Address                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |     GeMask    |     LeMask    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Format of IPv4 Prefix sub-TLV

   Type:  1 for IPv4 Prefix.

   Length:  N x 8, where N is the number of tuples <M-Type, Flags, IPv4
      Address, Mask, GeMask, LeMask>.  If Length is not a multiple of 8,
      the Atom is corrupt and the enclosing UPDATE message MUST be
      ignored.

   M-Type:  4 bits for match types, four of which are defined:

      M-Type = 0:  Exact match.

      M-Type = 1:  Match prefix greater and equal to the given masks.

      M-Type = 2:  Match prefix less and equal to the given masks.

      M-Type = 3:  Match prefix within the range of the given masks.

   Flags:  4 bits.  No flags are currently defined.

   IPv4 Address:  4 octets for an IPv4 address.

   Mask:  1 octet for the mask length.

   GeMask:  1 octet for match range, must be less than Mask or be 0.

   LeMask:  1 octet for match range, must be greater than Mask or be 0.

   For example, tuple <M-Type=0, Flags=0, IPv4 Address = 1.1.0.0, Mask =
   22, GeMask = 0, LeMask = 0> represents an exact IP prefix match for
   1.1.0.0/22.



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   <M-Type=1, Flags=0, IPv4 Address = 16.1.0.0, Mask = 24, GeMask = 24,
   LeMask = 0> represents match IP prefix 1.1.0.0/24 greater-equal 24.

   <M-Type=2, Flags=0, IPv4 Address = 17.1.0.0, Mask = 24, GeMask = 0,
   LeMask = 26> represents match IP prefix 17.1.0.0/24 less-equal 26.

   <M-Type=3, Flags=0, IPv4 Address = 18.1.0.0, Mask = 24, GeMask = 24,
   LeMask = 32> represents match IP prefix 18.1.0.0/24 greater-equal to
   24 and less-equal 32.

   Similarly, an IPv6 Prefix sub-TLV represents match criteria on IPv6
   prefixes.  Its format is illustrated below:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type  4     |         Length (N x 20)       |M-Type | Flags |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     IPv6 Address (16 octets)                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |     GeMask    |     LeMask    |M-Type | Flags |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~       . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      IPv6 Address (16 octets                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Mask      |     GeMask    |     LeMask    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Format of IPv6 Prefix sub-TLV

   An AS-Path sub-TLV represents a match criteria in a regular
   expression string.  Its format is illustrated below:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type  2      |      Length (Variable)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    AS-Path Regex String                       |
   :                                                               :
   |                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Format of AS Path sub-TLV

   Type:  2 for AS-Path.




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   Length:  Variable, maximum is 1024.

   AS-Path Regex String:  AS-Path regular expression string.

   A community sub-TLV represents a list of communities to be matched
   all.  Its format is illustrated below:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type  3      |        Length (N x 4 + 1)       |    Flags    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Community 1 Value                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                              . . .                            ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Community N Value                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Format of Community sub-TLV

   Type:  3 for Community.

   Length:  N x 4 + 1, where N is the number of communities.  If Length
      is not a multiple of 4 plus 1, the Atom is corrupt and the
      enclosing UPDATE MUST be ignored.

   Flags:  1 octet.  No flags are currently defined.  These bits MUST be
      sent as zero and ignored on receipt.

4.2.2.  Sub-TLVs of the Parameters TLV

   For the Parameter(s) TLV, two action sub-TLVs are defined: MED change
   sub-TLV and AS-Path change sub-TLV.  When the community in the
   container is MATCH AND SET ATTR, the Parameter(s) TLV can include
   these sub-TLVs.  When the community is MATCH AND NOT ADVERTISE, the
   Parameter(s) TLV's value is empty.

   A MED change sub-TLV indicates an action to change the MED.  Its
   format is illustrated below:











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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type  1      |          Length (5)           |      OP       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Value                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Format of MED Change sub-TLV

   Type:  1 for MED Change.

   Length:  5.  If Length is any other value, the sub-TLV is corrupt and
      the enclosing UPDATE MUST be ignored.

   OP:  1 octet.  Three are defined:

      OP = 0:  assign the Value to the existing MED.

      OP = 1:  add the Value to the existing MED.  If the sum is greater
         than the maximum value for MED, assign the maximum value to
         MED.

      OP = 2:  subtract the Value from the existing MED.  If the
         existing MED minus the Value is less than 0, assign 0 to MED.

      If OP is any other value, the sub-TLV is ignored.

   Value:  4 octets.

   An AS-Path change sub-TLV indicates an action to change the AS-Path.
   Its format is illustrated below:



















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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Type  2      |        Length (n x 5)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             AS1                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Count1     |
   +-+-+-+-+-+-+-+-+
   ~       . . .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             ASn                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Countn     |
   +-+-+-+-+-+-+-+-+

                         Format of AS-Path Change sub-TLV

   Type:  2 for AS-Path Change.

   Length:  n x 5.  If Length is not a multiple of 5, the sub-TLV is
      corrupt and the enclosing UPDATE MUST be ignored.

   ASi:  4 octet.  An AS number.

   Counti:  1 octet.  ASi repeats Counti times.

   The sequence of AS numbers are added to the existing AS Path.

4.3.  Capability Negotiation

   It is necessary to negotiate the capability to support BGP Extensions
   for Routing Policy Distribution (RPD).  The BGP RPD Capability is a
   new BGP capability [RFC5492].  The Capability Code for this
   capability is 72 assigned by the IANA.  The Capability Length field
   of this capability is variable.  The Capability Value field consists
   of one or more of the following tuples:

           +--------------------------------------------------+
           |  Address Family Identifier (2 octets)            |
           +--------------------------------------------------+
           |  Subsequent Address Family Identifier (1 octet)  |
           +--------------------------------------------------+
           |  Send/Receive (1 octet)                          |
           +--------------------------------------------------+

                          BGP RPD Capability




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   The meaning and use of the fields are as follows:

   Address Family Identifier (AFI): This field is the same as the one
   used in [RFC4760].

   Subsequent Address Family Identifier (SAFI): This field is the same
   as the one used in [RFC4760].

   Send/Receive: This field indicates whether the sender is (a) willing
   to receive Routing Policies from its peer (value 1), (b) would like
   to send Routing Policies to its peer (value 2), or (c) both (value 3)
   for the <AFI, SAFI>.  If Send/Receive is any other value, that tuple
   is ignored but any other tuples present are still used.

5.  Routing Policy Considerations

   Routing policies are used to filter routes and control how routes are
   received and advertised.  If route attributes, such as reachability,
   are changed, the path along which network traffic passes changes
   accordingly.

   When advertising, receiving, and importing routes, the router
   implements certain policies based on actual networking requirements
   to filter routes and change the attributes of the routes.  Routing
   policies serve the following purposes:

   o  Control route advertising: Only routes that match the rules
      specified in a policy are advertised.

   o  Control route receiving: Only the required and valid routes are
      received.  This reduces the size of the routing table and improves
      network security.

   o  Filter and control imported routes: A routing protocol may import
      routes discovered by other routing protocols.  Only routes that
      satisfy certain conditions are imported to meet the requirements
      of the protocol.

   o  Modify attributes of specified routes Attributes of the routes:
      that are filtered by a routing policy are modified to meet the
      requirements of the local device.

   o  Configure fast reroute (FRR): If a backup next hop and a backup
      outbound interface are configured for the routes that match a
      routing policy, IP FRR, VPN FRR, and IP+VPN FRR can be
      implemented.

   Routing policies are implemented using the following procedures:



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   1.  Define rules: Define features of routes to which routing policies
       are applied.  Users define a set of matching rules based on
       different attributes of routes, such as the destination address
       and the address of the router that advertises the routes.

   2.  Implement the rules: Apply the matching rules to routing policies
       for advertising, receiving, and importing routes.

6.  Contributors

   The following people have substantially contributed to the definition
   of the BGP-FS RPD and to the editing of this document:

   Peng Zhou
   Huawei
   Email: Jewpon.zhou@huawei.com

7.  Security Considerations

   Protocol extensions defined in this document do not affect BGP
   security other than as discussed in the Security Considerations
   section of [RFC5575].

8.  Acknowledgements

   The authors would like to thank Acee Lindem, Jeff Haas, Jie Dong,
   Lucy Yong, Qiandeng Liang, Zhenqiang Li, and Donald Eastlake for
   their comments to this work.

9.  IANA Considerations

9.1.  Existing Assignments

   IANA has assigned a new AFI of value 16398 from the registry "Address
   Family Numbers" for Routing Policy.

   IANA has assigned a new SAFI of value 75 from the registry
   "Subsequent Address Family Identifiers (SAFI) Parameters" for Routing
   Policy.

   IANA has assigned a new Code Point of value 72 from the registry
   "Capability Codes" for Routing Policy Distribution.

9.2.  Routing Policy Type Registry

   IANA is requested to create a new registry called "Routing Policy
   Type".  The allocation policy of this registry is "First Come First
   Served (FCFS)".



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   The initial code points are as follows:

      +-------------+-----------------------------------+-------------+
      | Code Point  | Description                       | Reference   |
      +-------------+-----------------------------------+-------------+
      |     0       |  Reserved                         |             |
      +-------------+-----------------------------------+-------------+
      |     1       | Export Policy                     |This document|
      +-------------+-----------------------------------+-------------+
      |     2       | Import Policy                     |This document|
      +-------------+-----------------------------------+-------------+
      |   3 - 255   |  Available                        |             |
      +-------------+-----------------------------------+-------------+

9.3.  RouteAttr Atom Type

   IANA is requested to assign a code-point from the registry "BGP
   Community Container Atom Types" as follows:

    +---------------------+------------------------------+-------------+
    | TLV Code Point      | Description                  | Reference   |
    +---------------------+------------------------------+-------------+
    | TBD1 (48 suggested) | RouteAttr Atom               |This document|
    +---------------------+------------------------------+-------------+

9.4.  Route Attributes Sub-TLV Registry

   IANA is requested to create a new registry called "Route Attributes
   Sub-TLV" under RouteAttr Atom TLV.  The allocation policy of this
   registry is "First Come First Served (FCFS)".

   The initial code points are as follows:

      +-------------+-----------------------------------+-------------+
      | Code Point  | Description                       | Reference   |
      +-------------+-----------------------------------+-------------+
      |      0      |  Reserved                         |             |
      +-------------+-----------------------------------+-------------+
      |      1      |  IPv4 Prefix Sub-TLV              |This document|
      +-------------+-----------------------------------+-------------+
      |      2      |  AS-Path Sub-TLV                  |This document|
      +-------------+-----------------------------------+-------------+
      |      3      |  Community Sub-TLV                |This document|
      +-------------+-----------------------------------+-------------+
      |      4      |  IPv6 Prefix Sub-TLV              |This document|
      +-------------+-----------------------------------+-------------+
      |   5 - 255   |  Available                        |             |
      +-------------+-----------------------------------+-------------+



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9.5.  Attribute Change Sub-TLV Registry

   IANA is requested to create a new registry called "Attribute Change
   Sub-TLV" under Parameter(s) TLV.  The allocation policy of this
   registry is "First Come First Served (FCFS)".

   Initial code points are as follows:

      +-------------+-----------------------------------+-------------+
      | Code Point  | Description                       | Reference   |
      +-------------+-----------------------------------+-------------+
      |      0      |  Reserved                         |             |
      +-------------+-----------------------------------+-------------+
      |      1      |  MED Change Sub-TLV               |This document|
      +-------------+-----------------------------------+-------------+
      |      2      |  AS-Path Change Sub-TLV           |This document|
      +-------------+-----------------------------------+-------------+
      |   3 - 255   |  Available                        |             |
      +-------------+-----------------------------------+-------------+

10.  References

10.1.  Normative References

   [I-D.ietf-idr-wide-bgp-communities]
              Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S.,
              and P. Jakma, "BGP Community Container Attribute", draft-
              ietf-idr-wide-bgp-communities-05 (work in progress), July
              2018.

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
              <https://www.rfc-editor.org/info/rfc1997>.

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

   [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,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.



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   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <https://www.rfc-editor.org/info/rfc5492>.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
              <https://www.rfc-editor.org/info/rfc5575>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

10.2.  Informative References

   [I-D.ietf-idr-registered-wide-bgp-communities]
              Raszuk, R. and J. Haas, "Registered Wide BGP Community
              Values", draft-ietf-idr-registered-wide-bgp-communities-02
              (work in progress), May 2016.

Authors' Addresses

   Zhenbin Li
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Liang Ou
   China Telcom Co., Ltd.
   109 West Zhongshan Ave,Tianhe District
   Guangzhou  510630
   China

   Email: ouliang@chinatelecom.cn








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   Yujia Luo
   China Telcom Co., Ltd.
   109 West Zhongshan Ave,Tianhe District
   Guangzhou  510630
   China

   Email: luoyuj@sdu.edu.cn


   Sujian Lu
   Tencent
   Tengyun Building,Tower A ,No. 397 Tianlin Road
   Shanghai, Xuhui District  200233
   China

   Email: jasonlu@tencent.com


   Gyan S. Mishra
   Verizon Inc.
   13101 Columbia Pike
   Silver Spring  MD 20904
   USA

   Phone:  301 502-1347
   Email: gyan.s.mishra@verizon.com


   Huaimo Chen
   Futurewei
   Boston, MA
   USA

   Email: Huaimo.chen@futurewei.com


   Shunwan Zhuang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: zhuangshunwan@huawei.com








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   Haibo Wang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: rainsword.wang@huawei.com












































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