[Search] [txt|pdfized|bibtex] [Tracker] [Email] [Diff1] [Diff2] [Nits]
Versions: 00 01 02 03 04                                                
IDR Working Group                                                          Louis Chan
Intended status: Experimental                                        Juniper Networks
Expires: Oct 15, 2020                                                    Apr 16, 2020

                        Color Operation with BGP Label Unicast


      This document specifies how to carry colored path advertisement via an enhancement
      to the existing protocol BGP Label Unicast. It would allow backward compatibility
      with RFC8277.

      The targeted solution is to use stack of labels advertised via BGP Label Unicast
      2.0 for end to end traffic steering across multiple IGP domains. The operation is
      similar to Segment Routing.

      This proposed protocol will convey the necessary reachability information to the
      ingress PE node to construct an end to end path

   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

      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 Oct 15, 2020.

   Copyright Notice

      Copyright (c) 2017 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 (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

   Chan                     Expires Oct 15, 2020                    [Page 1]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

      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...................................................2
      2. Conventions used in this document..............................3
      3. Carrying Label Mapping Information with Color and Label Stack..4
         3.1. Color extended community for BGP Labeled Unicast..........4
         3.2. Color extended community for service prefixes.............5
      4. Uniqueness of path entries.....................................5
      5. AIGP consideration.............................................5
      6. Explicit Withdraw of a <color, prefix>.........................6
      7. Error Handling Procedure.......................................6
      8. Controller Compatibility.......................................6
      9. Security Considerations........................................6
      10. IANA Considerations...........................................6
      11. References....................................................7
         11.1. Normative References.....................................7
         11.2. Informative References...................................7
      12. Acknowledgments...............................................8

   1. Introduction

      The proposed protocol is aimed to solve interdomain traffic steering, with
      different transport services in mind. One application is low latency service across
      multiple IGP domains, which could scale up to 100k routers network.

      BGP is a flexible protocol. With additional of color attribute to BGP Label
      Unicast, a path with specific color would be given a meaning in application - a low
      latency path, a fully protected path, or a path for diversity.

      The stack of labels would mean an end to end path across domains through each ABR
      or ASBR. Each ABR or ASBR will take one label from the stack, and hence pick the
      forwarding path to next ABR, ASBR, or the final destination.

      And the label in the stack may be derived from any of the below

      - Prefix SID
      - Binding SID for RSVP LSP
      - Binding SID for SR-TE LSP
      - Local assigned label

      The enhancement to the original RFC8277 is to add color extended community, with
      multiple advertisement allowed. The result is similar to multi-topology BGP-LU with
      different colors.

      A new [BGP-CAP] should be required to enable such slicing.

      On the other hand, to enable the service prefixes to be mapped accordingly, the
      L3VPN, L2VPN, EVPN and prefix with BGP signaling, the color extended community is

   Chan                     Expires Oct 15, 2020                    [Page 2]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

      also added there. In the PE node, the service prefixes with color will be matched
      to a transport tunnel with the same color.

      The following is an example. Between PE1 and PE2, there is a VPN service running
      with label 16, which is associated with color 100.


      PE1 will send the following labels with a color 100 path plus VPN label

      [2001 13001 801 16], where

      2001 - SR label to reach ABR1

      13001 - a Binding-SID label for ABR1-ABR2 tunnel. Underlying tunnel type is RSVP-TE

      801 - a Binding-SID label for ABR2-PE2 tunnel. Underlying tunnel type is SR-TE

      16 - a VPN label, which is signaled via other means

      [2001 13001 801]  denotes the label stack for this color 100 path to reach PE2

      The document here is going to describe how PE1 gains enough information to build
      this label stack across routing domains.

      If PE1 wants to reach PE2 with another colored path, say color 200, the label stack
      could be different.

      At the same time, this architecture is also controller friendly, since all the
      notation is Segment Routing compatible, like use of Binding-SID.

   2. Conventions used in this document

      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 RFC 2119 [RFC2119].

      In this document, these words will appear with that interpretation   only when in
      ALL CAPS. Lower case uses of these words are not to be    interpreted as carrying
      significance described in RFC 2119.

   Chan                     Expires Oct 15, 2020                    [Page 3]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

   3. Carrying Label Mapping Information with Color and Label Stack

   3.1. Color extended community for BGP Labeled Unicast

      The addition of Color Extended Community is an opaque extended community from
      RFC4360 and RFC5512. The draft allows multiple color values advertisement.

                   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
                  |       0x03    |     0x0b      |C|O|        Reserved     |X|X|X|
                  |                          Color Value                          ~
                  ~       0x03    |     0x0b      |C|O|        Reserved     |X|X|X|
                  |                          Color Value                          |

                            Figure 1: Color value advertisement format
      Both in BGP update and MP_UNREACH_NLRI message, multiple color extended communities
      could be included. It means that multiple colors, indicating different kind of
      services, could share the same label stack.

      If only one color extended community is specified, only prefix with that color
      value is updated or withdrawn.

      If a MP_UNREACH_NLRI message without any color specified is received for a given
      prefix, that prefix with color(s) should not be affected.

      If color extended community is not present in a BGP update message, it would be
      treated as normal BGP-LU without any color.

      3 bits of XXX is reserved here for the draft.

      The meaning for XXX is interpreted as sub-slice of color, with 0 to 7 in decimal,
      or 000b and 111b in binary. These sub-slice could be used in either of the
      following case.

      a) Primary path and fallback paths in order of preference
        0  primary path
        1  first and most preferred backup path

        7  least preferred backup path

      b) ECMP paths up to 8, since all paths should be active in forwarding plane.

      Color value 0 is reserved for future interoperability purpose.

      Color value 1 - 31 are not recommended to use, and this range is reserved for
      future use.

   Chan                     Expires Oct 15, 2020                    [Page 4]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

   3.2. Color extended community for service prefixes

      The same format of color extended community is advertised with service prefixes.
      The order of the color extended community could be interpreted as

      - Order of primary and fallback colors
      - Or, ECMP of equal split between color paths

      The above would be interpreted by the receiving PE upon its local configuration.

      It is optional to enable sub-slice notation.

      But if sub-slice bits are used, it will be used to map directly to each of the sub-
      slice path. If sub-slice path is not available for mapping, it should just fallback
      to resolving by color.

   4. Uniqueness of path entries

      a) Use of color can be considered to slice into multiple BGP Label Unicast RIB.
      Therefore, it should be treated as unique entries for the <color, prefix>.

      e.g. <color, prefix>, [labels]

      <1,>, [100 200]

      <2,>, [100 200]

      <null,>, [100 200]

      All these 3 NLRI are considered different but valid entries for different color

      b) With sub-slice notation
        <color-sub, prefix>, [labels]

        <1-0,>, [100 200]

        <1-1,>, [101 300]

        <1-7,>, [102 400]

        These 3 NLRI are distinct, and the second and third NLRI could be used for
        backup or ECMP purpose.

   5. AIGP consideration

      AIGP (RFC7311) would be also used in here to embed certain metric across.

   Chan                     Expires Oct 15, 2020                    [Page 5]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

   6. Explicit Withdraw of a <color, prefix>
      According to RFC8277, MP_UNREACH_NLRI can be used to remove binding of a <color,

      Compatibility is set to 0xC00000 to specify the use of color. Multiple color
      extended communities could be applied here.

            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
           |    Length     |        Compatibility                          |
           |                          Prefix                               ~
           ~                                                               |
                        Figure 2: NLRI for Withdrawal

   7. Error Handling Procedure

      If BGP receiver could not handle the NLRI, it should silently discard with error

   8. Controller Compatibility

      The proposed architecture is compatible with controller for end to end
      provisioning. Persistent label, like Binding-SIS is recommended to be used. Hence,
      controller could learn these labels from the network, and program specific end to
      end path.

      Controller could also be deployed based on domain by domain perspective. e.g.
      Optimizing latency of a RSVP LSP, or maintain the bandwidth and loading between SR-
      TE LSPs.

   9. Security Considerations

   10. IANA Considerations

      TBD. It will require a new BGP capability code to enable such color operation.

      New SAFI might be required as well.

   Chan                     Expires Oct 15, 2020                    [Page 6]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

   11. References

   11.1. Normative References

      [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
              BCP 14, RFC 2119, March 1997.

   11.2. Informative References

      [RFC3107] Rekhter, Y. and E. Rosen, "Carrying Label Information in BGP-4", RFC
              3107, DOI 10.17487/RFC3107, May 2001,


      [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006


      [RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation Subsequent Address
              Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC
              5512, April 2009.


      [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,

      [RFC7311] Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro,
                "The Accumulated IGP Metric Attribute for BGP", RFC 7311,
                DOI 10.17487/RFC7311, August 2014,


      [RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder, "Advertisement of
              Multiple Paths in BGP", RFC 7911, DOI 10.17487/RFC7911, July 2016,


      [RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address Prefixes", RFC 8277,
              DOI 10.17487/RFC8277, October 2017,


      [BGP-CAP] Chandra, R. and J. Scudder, "Capabilities Advertisement

                with BGP-4", RFC 2842, May 2000.

   Chan                     Expires Oct 15, 2020                    [Page 7]

   Internet-Draft          draft-chan-idr-bgp-lu2-01.txt               April 2020

   12. Acknowledgments

           The following people have contributed to this document:

           Jeff Haas, Juniper Networks

           Shraddha Hedge, Juniper Networks

           Santosh Kolenchery, Juniper Networks

           Shihari Sangli, Juniper Networks

           Krzysztof Szarkowicz, Juniper Networks

           Yimin Shen, Juniper Networks

        Authors Addresses

        Louis Chan (editor)
           Juniper Networks
           2604, Cityplaza One, 1111 King's Road
           Taikoo Shing
           Hong Kong

           Phone: +85225876659
           Email: louisc@juniper.net

   Chan                     Expires Oct 15, 2020                    [Page 8]