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Distribution of Service Metadata in BGP-LS
draft-ls-idr-bgp-ls-service-metadata-03

Document Type Active Internet-Draft (individual)
Authors Cheng Li , Hang Shi , Tao He , Ran Pang , Guofeng Qian
Last updated 2024-05-05
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draft-ls-idr-bgp-ls-service-metadata-03
Inter-Domain Routing                                          C. Li, Ed.
Internet-Draft                                               H. Shi, Ed.
Intended status: Standards Track                     Huawei Technologies
Expires: 7 November 2024                                           T. He
                                                                 R. Pang
                                                            China Unicom
                                                                 G. Qian
                                                     Huawei Technologies
                                                              6 May 2024

               Distribution of Service Metadata in BGP-LS
                draft-ls-idr-bgp-ls-service-metadata-03

Abstract

   In edge computing, a service may be deployed on multiple instances
   within one or more sites, called edge service.  The edge service is
   associated with an ANYCAST address in the IP layer, and the route of
   it with potential service metadata will be distributed to the
   network.  The Edge Service Metadata can be used by ingress routers to
   make path selections not only based on the routing cost but also the
   running environment of the edge services.

   The service route with metadata can be collected by a PCE(Path
   Compute Element) or an analyzer for calculating the best path to the
   best site/instance.  This draft describes a mechanism to collect
   information of the service routes and related service metadata in
   BGP-LS.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at
   https://VMatrix1900.github.io/draft-service-metadata-in-BGP-LS/draft-
   ls-idr-bgp-ls-service-metadata.html.  Status information for this
   document may be found at https://datatracker.ietf.org/doc/draft-ls-
   idr-bgp-ls-service-metadata/.

   Discussion of this document takes place on the Inter-Domain Routing
   Working Group mailing list (mailto:idr@ietf.org), which is archived
   at https://mailarchive.ietf.org/arch/browse/idr/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/idr/.

   Source for this draft and an issue tracker can be found at
   https://github.com/VMatrix1900/draft-service-metadata-in-BGP-LS.

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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
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   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 7 November 2024.

Copyright Notice

   Copyright (c) 2024 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
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   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  BGP-LS Extension for Service in a Site  . . . . . . . . . . .   3
     2.1.  Prefix NLRI . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Attributes  . . . . . . . . . . . . . . . . . . . . . . .   4
       2.2.1.  Metadata Path Attribute TLV . . . . . . . . . . . . .   5
     2.3.  Prefix SID Attribute TLV  . . . . . . . . . . . . . . . .   6
       2.3.1.  Color Attribute TLV . . . . . . . . . . . . . . . . .   6
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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1.  Introduction

   Many services deploy their service instances in multiple sites to get
   better response time and resource utilization.  These sites are often
   geographically distributed to serve the user demand.  For some
   services such as VR/AR and intelligent transportation, the QoE will
   depend on both the network metrics and the compute metrics.  For
   example, if the nearest site is overloaded due to the demand
   fluctuation, then steering the user traffic to another light-loaded
   site may improve the QoE.

   [I-D.ietf-idr-5g-edge-service-metadata] describes the BGP extension
   of distributing service route with network and computing-related
   metrics.  The router connected to the site will receive the service
   routes and service metadata sent from devices inside the edge site,
   and then generate the corresponding routes and distribute them to
   ingress routers.  However, the route with service metadata on the
   router connected to the site can be also collected by a central
   Controller for calculating the best path to the best site.

   This document defines an extension of BGP-LS to carry the service
   metadata along with the service route.  Using the service metadata
   and the service route, the controller can calculate the best site for
   the traffic, giving each user the best QoE.

1.1.  Terminology

1.2.  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.

2.  BGP-LS Extension for Service in a Site

   The goal of the BGP-LS extension is to collect information of the
   service prefix and metadata of the service, such as network metrics
   and compute metrics.  A service is identified by a prefix, and this
   information is carried by the existing prefix NLRI TLV.  Other
   information including service metadata is carried by attributes TLVs.

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2.1.  Prefix NLRI

   A service is identified by a prefix, and the Prefix NLRI defined in
   the [RFC7752] is used to collect the prefix information of the
   service.  The format of the Prefix NLRI is shown in Figure 1 for
   better understanding.

        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
       +-+-+-+-+-+-+-+-+
       |  Protocol-ID  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           Identifier                          |
       |                            (64 bits)                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //              Local Node Descriptors (variable)              //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //                Prefix Descriptors (variable)                //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: The IPv4/IPv6 Topology Prefix NLRI Format

   Specifically, the service prefix is carried by the IP Reachability
   Information TLV(Figure 2) inside the Prefix Descriptor field.  The
   Prefix Length field contains the length of the prefix in bits.  The
   IP Prefix field contains the most significant octets of the prefix.

        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            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Prefix Length | IP Prefix (variable)                         //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 2: IP Reachability Information TLV Format

2.2.  Attributes

   The following three prefix attribute TLVs are used to carry the
   metadata of a service instance:

   1.  Metadata Path Attribute TLV carries the computing metric of the
       service instances such as site preference, capacity index, and
       load measurement defined in
       [I-D.ietf-idr-5g-edge-service-metadata].

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   2.  Prefix SID TLV carries a Prefix SID associated with the edge
       site.

   3.  Color Attribute TLV carries the service requirement level
       information of the service

2.2.1.  Metadata Path Attribute TLV

   The Metadata Path Attribute TLV is an optional attribute to carry the
   Edge Service Metadata defined in the
   [I-D.ietf-idr-5g-edge-service-metadata].  It contains multiple sub-
   TLVs, with each sub-TLV containing a specific metric of the Edge
   Service Metadata.  This document defines a new TLV in BGP-LS, which
   reuses the name and the format of Metadata Path Attribute TLV.

        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 (multiple Metadata sub-TLVs)               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 3: Metadata Path Attribute TLV format

   *  Type: identify the Metadata Path Attribute, to be assigned by
      IANA.

   *  Length: the total number of octets of the value field.

   *  Value: contains multiple sub-TLVs.

   There are three types of Edge Service Metadata sub-TLVs defined in
   [I-D.ietf-idr-5g-edge-service-metadata]:

   1.  Site Preference Index indicates the preference to choose the
       site.

   2.  Capacity Index indicates the capability of a site.  One Edge Site
       can be at full capacity, reduced capacity, or completely out of
       service.

   3.  Load Measurement indicates the load level of the site.

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   To collect this information, this document defines TLVs reusing the
   name and format of the TLVs defined in
   [I-D.ietf-idr-5g-edge-service-metadata].

2.3.  Prefix SID Attribute TLV

   In some cases, there may be multiple sites connected to one
   Edge(egress) router through different interfaces.  Generally, an
   overlay tunnel will be used between the ingress router and the egress
   for steering the traffic to the best site correctly.  In SR-MPLS
   networks or SRv6 networks, a prefix SID is needed.  For example, some
   SRv6 Endpoint Behaviors such as End.DX6, End.X can be encoded for
   each site so that the egress router can steer the traffic to the
   corresponding site.  The Prefix SID TLV defined [RFC9085] can be used
   to collect this information.

   The Prefix SID TLV is an optional TLV to carry the Prefix SID
   associated with the edge site.  The TLV format is illustrated in
   Figure 4.

        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 (Prefix SID sub-TLV)                    |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 4: Prefix-SID TLV format

   *  Type: 1158, identify the Prefix SID Attribute.

   *  Length: the total number of octets of the value field.

   *  Value: contains Prefix SID sub-TLV.

2.3.1.  Color Attribute TLV

   Color is used to indicate the service level.  For example, different
   sites may have different levels of service capability which is taken
   into account by the controller when calculating the path to the
   egress router.  More details can be added in the future revision.

   The TLV format(shown in Figure 5) is similar to the BGP Color
   Extended Community defined in [RFC9012].

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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             |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             Flags             |          Color Value          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Color Value          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 5: Color Attribute TLV format

   *  Type: identify the Color Attribute, to be assigned by IANA.

   *  Length: 6, length of Flags + Color Value.

   *  Flags and Color are the same as defined in [RFC9012].  Color
      Value: 32 bit value of color.

3.  Security Considerations

   TBD

4.  IANA Considerations

   This document requires IANA to assign the following code points from
   the registry called "BGP-LS Node Descriptor, Link Descriptor, Prefix
   Descriptor, and Attribute TLVs":

         +=======+==============================+===============+
         | Value | Description                  | Reference     |
         +=======+==============================+===============+
         | TBD1  | Metadata Path Attribute Type | Section 2.2.1 |
         +-------+------------------------------+---------------+
         | TBD2  | Site Preference Sub-Type     | Section 2.2.1 |
         +-------+------------------------------+---------------+
         | TBD3  | Capacity Sub-Type            | Section 2.2.1 |
         +-------+------------------------------+---------------+
         | TBD4  | Load Measurement Sub-Type1:  | Section 2.2.1 |
         |       | Aggregated-Cost              |               |
         +-------+------------------------------+---------------+
         | TBD5  | Load Measurement Sub-Type2:  | Section 2.2.1 |
         |       | Raw-Measurements             |               |
         +-------+------------------------------+---------------+
         | TBD6  | Color Attribute Type         | Section 2.3.1 |
         +-------+------------------------------+---------------+

                                 Table 1

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5.  Contributors

   Xiangfeng Ding

   email: dingxiangfeng@huawei.com

6.  Normative References

   [I-D.ietf-idr-5g-edge-service-metadata]
              Dunbar, L., Majumdar, K., Li, C., Mishra, G. S., and Z.
              Du, "BGP Extension for 5G Edge Service Metadata", Work in
              Progress, Internet-Draft, draft-ietf-idr-5g-edge-service-
              metadata-18, 25 April 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-5g-
              edge-service-metadata-18>.

   [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/rfc/rfc2119>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/rfc/rfc7752>.

   [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/rfc/rfc8174>.

   [RFC9012]  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", RFC 9012,
              DOI 10.17487/RFC9012, April 2021,
              <https://www.rfc-editor.org/rfc/rfc9012>.

   [RFC9085]  Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
              H., and M. Chen, "Border Gateway Protocol - Link State
              (BGP-LS) Extensions for Segment Routing", RFC 9085,
              DOI 10.17487/RFC9085, August 2021,
              <https://www.rfc-editor.org/rfc/rfc9085>.

   [RFC9252]  Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
              B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
              Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
              DOI 10.17487/RFC9252, July 2022,
              <https://www.rfc-editor.org/rfc/rfc9252>.

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Appendix A.  Acknowledgements

   The authors would like to thank Haibo Wang, Lili Wang, Jianwei Mao
   for their help.

Authors' Addresses

   Cheng Li (editor)
   Huawei Technologies
   Beijing
   China
   Email: c.l@huawei.com

   Hang Shi (editor)
   Huawei Technologies
   Beijing
   China
   Email: shihang9@huawei.com

   Tao He
   China Unicom
   Beijing
   China
   Email: het21@chinaunicom.cn

   Ran Pang
   China Unicom
   Beijing
   China
   Email: pangran@chinaunicom.cn

   Guofeng Qian
   Huawei Technologies
   Beijing
   China
   Email: qianguofeng@huawei.com

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