[Search] [txt|xml|pdf|bibtex] [Tracker] [Email] [Nits]

Versions: 00                                                            
IDR Working Group                                                 Y. Liu
Internet-Draft                                              Shaofu. Peng
Intended status: Standards Track                         ZTE Corporation
Expires: September 30, 2021                               March 29, 2021


                   Advertisement of Algorithm in BGP
                     draft-lp-lsr-bgp-algorithm-00

Abstract

   This document proposes extensions to BGP to support algorithm-based
   end-to-end path establishment.

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
   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 September 30, 2021.

Copyright Notice

   Copyright (c) 2021 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.






Liu & Peng             Expires September 30, 2021               [Page 1]


Internet-Draft              Algorithm in BGP                  March 2021


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   2
     2.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   3.  Algorithm Extended Community  . . . . . . . . . . . . . . . .   2
   4.  Algo-based Inter-domain Path  . . . . . . . . . . . . . . . .   3
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [I-D.ietf-lsr-flex-algo] proposes a solution that allows IGPs
   themselves to compute constraint-based paths over the SR network.
   [I-D.ietf-lsr-ip-flexalgo] allows flex-algo to be deployed in any IP
   network, even in the absence of SR-MPLS and SRv6.

   However, the algorithm-based path can only be used in the IGP domain.
   In the BGP-based inter-domain scenario, end-to-end path based on
   algorithms cannot be supported.

   This document proposes extensions to BGP to support algorithm-based
   end-to-end path establishment.

2.  Conventions used in this document

2.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Algorithm Extended Community

   This document defines a new transitive BGP Extended Communities
   Attribute[RFC4360].  This new Extended Community has the following
   encoding, where:








Liu & Peng             Expires September 30, 2021               [Page 2]


Internet-Draft              Algorithm in BGP                  March 2021


    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=0x03    | Sub-Type=TBA1 |     Flags     |   Algorithm   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                         Reserved (4 Octets)                   ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 1: Algorithm Extended Community

      Type: 1 octet.  The value is 0x03.

      Sub-Type: 1 octet.  TBA1

      Flags: 1 octet.  Unused, MUST be set to 0 and ingored on receipt.

      Algorithm: 1 octet specifying IGP Algorithm Types.  Value from 0
      to 255.

      Reserved: 4 Octets.  MUST be set to 0, ignored at reception

4.  Algo-based Inter-domain Path


   +----------------------+             +----------------------+
   |         | 2 |        |             |        | 6 |         |
   |         +---+        |             |        +---+         |
   |                      |             |                      |
   |    Flex-algo 128     |             |    Flex-algo 128     |
   |                      |             |                      |
   |---+                +---+         +---+                +---|
   | 1 |----------------| 4 |---------| 5 |----------------| 8 |
   |---+                +---+         +---+                +---|
   |                      |             |                      |
   |    Flex-algo 129     |             |    Flex-algo 129     |
   |                      |             |                      |
   |         +---+        |             |        +---+         |
   |         | 3 |        |             |        | 7 |         |
   +----------------------+             +----------------------+
   |<-----IGP Domain1---->|             |<-----IGP Domain2---->|


                  Figure 2: Algo-based Inter-domain Path

   As shown in Figure 2, node 8 is configured with two loopback
   addresses, loopback-1 and loopback-2, they belong to the flex-algo
   128 plane and the flex-algo 129 plane respectively.  In IGP domain 2,



Liu & Peng             Expires September 30, 2021               [Page 3]


Internet-Draft              Algorithm in BGP                  March 2021


   the routes to loopback-1 will be generated on the nodes (e.g, node
   5,6,8) in the Flex-algo 128 plane and the routes to loopback-2 will
   be generated on the nodes (e.g, node 5,7,8) in the Flex-algo 129
   plane.

   Node 5 can advertise prefix loopback-1 and prefix loopback-2 to node
   4 through BGP[RFC2545][RFC4271].  Node 4 can import the BGP routes
   into IGP and continue to advertise the routes to its neighbors in IGP
   domain1.  Or, node 4 directly advertises the routes to node 1 through
   BGP.

   In both cases, the corresponding algorithm information from IGP
   domain2 is lost during the advertisement.  As a result, node 4 does
   not know which Flex-algo plane to import loopback-1 or loopback-2
   into IGP domain 1.

   With the Algorithm Extended Community, the algorithm information can
   be carried in the BGP route of loopbacks advertised from node 5 to
   node 4.

   The administrator can configure algorithms in each IGP domain in the
   network.  A simple configuration method is that algorithms in each
   IGP domain are consistent.  If the algorithm configurations in each
   IGP domain are inconsistent, the ASBR needs to know the mapping
   relationship of the algorithms and carry the converted algorithm
   information in Algorithm Extended Community when advertising the BGP
   route.

   A BGP speaker can advertise multiple paths for the same address
   prefix, each path is identified by a Path Identifier in addition to
   the address prefix [RFC7911].  By leveraging add-path, multiple
   loopbacks on the egress node can be avoided.

   Same approach is applicable for BGP Prefix SID advertisement[RFC8669]
   and BGP Labeled Unicast(BGP-LU)[RFC8227].  If any Router Reflector
   existed in the network, it SHOULD support this new Extended
   Community.

5.  Security Considerations

   TBD

6.  IANA Considerations

   IANA is requested to allocate the sub-type TBA1 for "Algorithm
   Extended Community" under the "BGP Transitive Opaque Extended
   Community"




Liu & Peng             Expires September 30, 2021               [Page 4]


Internet-Draft              Algorithm in BGP                  March 2021


7.  References

7.1.  Normative References

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-13 (work in progress), October 2020.

   [I-D.ietf-lsr-ip-flexalgo]
              Britto, W., Hegde, S., Kaneriya, P., Shetty, R., Bonica,
              R., and P. Psenak, "IGP Flexible Algorithms (Flex-
              Algorithm) In IP Networks", draft-ietf-lsr-ip-flexalgo-00
              (work in progress), December 2020.

   [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>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [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>.

   [RFC8227]  Cheng, W., Wang, L., Li, H., van Helvoort, H., and J.
              Dong, "MPLS-TP Shared-Ring Protection (MSRP) Mechanism for
              Ring Topology", RFC 8227, DOI 10.17487/RFC8227, August
              2017, <https://www.rfc-editor.org/info/rfc8227>.

   [RFC8669]  Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
              A., and H. Gredler, "Segment Routing Prefix Segment
              Identifier Extensions for BGP", RFC 8669,
              DOI 10.17487/RFC8669, December 2019,
              <https://www.rfc-editor.org/info/rfc8669>.

7.2.  Informative References

   [I-D.zhou-idr-inter-domain-lcu]
              Chen, R., Dai, C., and S. Peng, "Inter-domain Network
              Slicing via BGP-LU", draft-zhou-idr-inter-domain-lcu-02
              (work in progress), January 2021.






Liu & Peng             Expires September 30, 2021               [Page 5]


Internet-Draft              Algorithm in BGP                  March 2021


Authors' Addresses

   Liu Yao
   ZTE Corporation

   Email: liu.yao71@zte.com.cn


   Peng Shaofu
   ZTE Corporation

   Email: peng.shaofu@zte.com.cn







































Liu & Peng             Expires September 30, 2021               [Page 6]