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BGP SPF for Network Resource Partitions
draft-dong-lsvr-bgp-spf-nrp-02

Document Type Active Internet-Draft (individual)
Authors Jie Dong , Zhenbin Li , Haibo Wang , Jian Ge
Last updated 2023-10-20
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draft-dong-lsvr-bgp-spf-nrp-02
LSVR Working Group                                               J. Dong
Internet-Draft                                                     Z. Li
Intended status: Standards Track                                 H. Wang
Expires: 22 April 2024                               Huawei Technologies
                                                                   J. Ge
              China Academy of Information and Communications Technology
                                                         20 October 2023

                BGP SPF for Network Resource Partitions
                     draft-dong-lsvr-bgp-spf-nrp-02

Abstract

   A VTN is a virtual underlay network which has customized network
   topology and a set of dedicated or shared network resources.  Network
   Resource Partition (NRP) refers to a set of network resources that
   are available to carry traffic and meet the SLOs and SLEs.  Multiple
   NRPs can be created in a network to provide different Virtual
   Transport Networks (VTN) to meet the requirements of different
   services or different service groups.

   As the number of NRP increases, there can be scalability concerns
   about using Interial Gateway Protocols (IGP) to distribute the NRP
   information in the network.  In networks where BGP Shortest Path
   First (SPF) can used as the underlay routing mechanism to distribute
   the link-state information among network nodes, the information of
   NRPs needs to be distributed along with the basic network
   information.  This document specifies the BGP SPF mechanisms with
   necessary extensions to distribute the NRP information and perform
   NRP-specific path computation.

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 22 April 2024.

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Copyright Notice

   Copyright (c) 2023 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 Revised BSD License text as
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Applicability of NRP related BGP-LS Extensions to BGP SPF . .   3
     2.1.  Reuse of BGP-LS TLVs for BGP SPF VTN  . . . . . . . . . .   3
     2.2.  NRP Topology and Resource Distribution  . . . . . . . . .   5
   3.  SPF Calculation for NRPs  . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The concept of Virtual Transport Network (VTN) is introduced in
   [I-D.ietf-teas-enhanced-vpn].  A VTN is a virtual underlay network
   which has customized network topology and a set of dedicated or
   shared network resources.  In a network, different VTNs may be
   created to meet different service requirements, and services can be
   mapped to the same or different VTNs.

   [I-D.ietf-teas-ietf-network-slices] introduces the concept Network
   Resource Partition (NRP) as a set of network resources that are
   available to carry traffic and meet the SLOs and SLEs.  In the
   context of network slicing, an NRP can be used to instantiate a VTN
   for one or a group of IETF network slice services.  In the context of
   network slicing, an NRP can be used to instantiate a VTN for one or a
   group of IETF network slice services.

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   [I-D.ietf-spring-sr-for-enhanced-vpn] describes the use of resource-
   aware segments [I-D.ietf-spring-resource-aware-segments] to build SR
   based NRPs.  The SIDs of each NRP and the associated topology and
   resource attributes need to be distributed using the control plane.
   [I-D.dong-lsr-sr-enhanced-vpn] specifies the IGP mechanism and
   extensions to build a relatively large number of SR based NRPs.
   [I-D.dong-idr-bgpls-sr-enhanced-vpn] further specifies the BGP-LS
   mechanisms and extensions to advertise the NRP information within
   each domain and the NRP information on the inter-domain links to the
   network controller, so that the controller could use the collected
   information to obtain the view of the inter-domain SR NRPs .

   As the number of NRP increases, there can be scalability concerns
   about using IGP to distribute the NRP information in the network.  In
   networks where BGP SPF is used to distribute the link-state
   information among network nodes, the NRP information needs to be
   distributed along with the basic network link state and TE
   information.  Comparing with the Internal Gateway Protocols (IGPs),
   BGP SPF may have some advantage in supporting a relatively large
   number of NRPs.  This document specifies the BGP SPF mechanisms with
   necessary extensions to advertise the information of NRPs.  The
   proposed mechanism is applicable to segment routing with MPLS data
   plane (SR-MPLS), segment routing with IPv6 data plane (SRv6), and
   native IPv6 data plane.

1.1.  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
   BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

2.  Applicability of NRP related BGP-LS Extensions to BGP SPF

2.1.  Reuse of BGP-LS TLVs for BGP SPF VTN

   As described in [I-D.ietf-lsvr-bgp-spf], the NLRI and TLVs of BGP-LS
   can be reused by BGP SPF, this section describes the TLVs which are
   defined in BGP-LS and can be reused in BGP SPF for the distribution
   of NRP related information.

   According to [I-D.ietf-teas-enhanced-vpn], a virtual transport
   network (VTN) has a customized network topology and a set of
   dedicated or shared network resources.  Thus a VTN can be defined as
   the combination of a set of network attributes, including the
   topology attribute and the network resource attribute.  As the

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   instantiation of VTN, an NRP is associated with a Multi-Topology ID
   (MT-ID) and/or an Algorithm ID which are used to define the NRP
   topology and path computation constraints.  In some cases, each NRP
   can be associated with a separate MT-ID or a Flex-Algo ID.  When the
   amount of NRPs in a network is large, as described in
   [I-D.ietf-teas-nrp-scalability], multiple NRPs may be associated with
   the same topology and/or algorithm, so that the amount of topology-
   specific path computation can be shared by a group of NRPs, this
   could help to reduce the computation overhead in the control plane.

   [I-D.ietf-lsvr-bgp-spf] does not cover the usage of Multi-Topology or
   Flex-Algo with BGP SPF.  This document proposes to use Multi-Topology
   [RFC4915][RFC5120] or Flex-Algo [RFC9350] with BGP SPF for topology
   and/or algorithm -specific link-state information distribution and
   path computation.  For this purpose, the Multi-topology TLV as
   defined in [I-D.ietf-idr-rfc7752bis], the SR Algorithm TLV as defined
   [RFC9085], and the Flex-Algo Definition TLV as defined in
   [I-D.ietf-idr-bgp-ls-flex-algo] are reused for BGP SPF.

   [I-D.ietf-lsvr-bgp-spf] does not explicitly describe the usage with
   Segment Routing data plane.  To build SR based NRPs, the SR-MPLS and
   SRv6 TLVs as defined in [RFC9085] and [I-D.ietf-idr-bgpls-srv6-ext]
   are reused for BGP SPF.

   The NRP extensions to BGP-LS as defined in
   [I-D.dong-idr-bgpls-sr-enhanced-vpn] applies to BGP SPF as well.
   This section lists the TLVs which are reused by BGP SPF, the detailed
   format of the TLVs are described in
   [I-D.dong-idr-bgpls-sr-enhanced-vpn].

   The BGP-LS Attribute TLVs which are defined in
   [I-D.dong-idr-bgpls-sr-enhanced-vpn] and reused with BGP-LS-SPF SAFI
   are listed as below:

   *  NRP Definition (NRPD) TLV: This is used to advertise the
      association between the NRP and the topology ID and/or algorithm
      ID.  It can be carried in BGP-LS attribute associated with a Node
      NLRI.

   *  NRP IDs TLV: This is used to describe the identifiers of one or
      more NRPs which are associated with a specific set of network
      resources.  It can be carried in BGP-LS attribute which is
      associated with a Link NLRI, or it could be carried as a sub-TLV
      in the L2 Bundle Member Attribute TLV or the NRP-specific TE
      attribute TLV.

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   *  Link Attribute Flags TLV: This is used to specify the
      characteristics of a link, its functionality is similar to the IS-
      IS Link Attribute sub-TLV defined in [RFC5029].  It can be carried
      in BGP-LS attribute which is associated with a Link NLRI, or it
      could be carried as a sub-TLV in the L2 Bundle Member Attribute
      TLV.

   *  NRP-specific prefix-SID TLV: This is used to advertise the prefix-
      SID and its associated NRP.  It can be carried in BGP-LS attribute
      which is associated with a Prefix NLRI.

   *  NRP-specific Adj-SID TLV: This is used to advertise the adj-SID
      and its associated NRP.  It can be carried in BGP-LS attribute of
      the associated Link NLRI.

   *  NRP Locator-block sub-TLV: This is used to advertise the SRv6
      locator block and its associated NRP.  It can be carried in the
      SRv6 Locator TLV of the associated Prefix NLRI.

   *  NRP ID Sub-TLV.  This is used to advertise the relationship
      between SRv6 End.X SIDs and its associated NRP.

   Further BGP-LS TLVs may be defined in
   [I-D.dong-idr-bgpls-sr-enhanced-vpn], their usage with BGP SPF will
   be specified in a future version of this document.

2.2.  NRP Topology and Resource Distribution

   In network scenarios where each NRP is associated with a unique MT-
   ID, The BGP-LS mechanisms used to distribute the NRP topology and
   resource information to the network controller are described in
   [I-D.ietf-idr-bgpls-sr-vtn-mt].  Such mechanism can be reused for the
   distribution of NRP information with BGP SPF.

   In network scenarios where each NRP is associated with a unique Flex-
   Algo ID, The BGP-LS mechanisms used to distribute the NRP topology
   and resource information to the network controller are described in
   [I-D.zhu-idr-bgpls-sr-vtn-flexalgo].  Such mechanism can be reused
   for the distribution of NRP information with BGP SPF.

   In network scenarios where multiple NRPs are associated with the same
   <topology, algorithm> tuple, while each NRP has different resource
   attributes, the BGP-LS mechanisms which can be used to distribute the
   NRP topology and resource information to the network controller are
   described in [I-D.dong-idr-bgpls-sr-enhanced-vpn].  Such mechanism
   can be reused for the distribution of NRP information with BGP SPF.

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   The Sequence Number TLV as defined in [I-D.ietf-lsvr-bgp-spf] MUST be
   carried in the BGP-LS attribute associated with the BGP-LS-SPF NLRI.
   If the Sequence-Number TLV is not received then the corresponding
   Link NLRI is considered as malformed and MUST be handled as 'Treat-
   as- withdraw'.  An implementation MAY log an error for further
   analysis.

3.  SPF Calculation for NRPs

   [I-D.ietf-lsvr-bgp-spf] describes the mechanisms of using the BGP-LS-
   SPF Node, Link, and Prefix NLRIs for shortest path computation.  With
   the introduction of NRP, the same mechanism is used for the shortest
   path computation of each NRP.  The path computation for a NRP is
   based on the topology attributes and the constraints specified with
   the MT-ID and/or Algorithm ID associated with the NRP.  When multiple
   NRPs are associated with the same <topology, algorithm> tuple, the
   result of the shortest path computation based on that <topology,
   algorithm> could be shared by these NRPs.

4.  Security Considerations

   This document introduces no additional security vulnerabilities to
   BGP SPF.

   The mechanism proposed in this document is subject to the same
   vulnerabilities as any other protocol that relies on BGP SPF.

5.  IANA Considerations

   This document request no IANA actions.

6.  Acknowledgments

   TBD

7.  References

7.1.  Normative References

   [I-D.dong-idr-bgpls-sr-enhanced-vpn]
              Dong, J., Hu, Z., Li, Z., Tang, X., and R. Pang, "BGP-LS
              Extensions for Scalable Segment Routing based Enhanced
              VPN", Work in Progress, Internet-Draft, draft-dong-idr-
              bgpls-sr-enhanced-vpn-04, 4 March 2022,
              <https://datatracker.ietf.org/doc/html/draft-dong-idr-
              bgpls-sr-enhanced-vpn-04>.

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   [I-D.ietf-idr-bgp-ls-flex-algo]
              Talaulikar, K., Psenak, P., Zandi, S., and G. Dawra,
              "Flexible Algorithm Advertisement using BGP Link-State",
              Work in Progress, Internet-Draft, draft-ietf-idr-bgp-ls-
              flex-algo-12, 24 August 2022,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
              ls-flex-algo-12>.

   [I-D.ietf-idr-bgpls-srv6-ext]
              Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
              Bernier, D., and B. Decraene, "BGP Link State Extensions
              for SRv6", Work in Progress, Internet-Draft, draft-ietf-
              idr-bgpls-srv6-ext-14, 17 February 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              bgpls-srv6-ext-14>.

   [I-D.ietf-idr-rfc7752bis]
              Talaulikar, K., "Distribution of Link-State and Traffic
              Engineering Information Using BGP", Work in Progress,
              Internet-Draft, draft-ietf-idr-rfc7752bis-17, 25 August
              2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
              idr-rfc7752bis-17>.

   [I-D.ietf-lsvr-bgp-spf]
              Patel, K., Lindem, A., Zandi, S., and W. Henderickx, "BGP
              Link-State Shortest Path First (SPF) Routing", Work in
              Progress, Internet-Draft, draft-ietf-lsvr-bgp-spf-28, 29
              August 2023, <https://datatracker.ietf.org/doc/html/draft-
              ietf-lsvr-bgp-spf-28>.

   [I-D.ietf-spring-resource-aware-segments]
              Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
              Z., and F. Clad, "Introducing Resource Awareness to SR
              Segments", Work in Progress, Internet-Draft, draft-ietf-
              spring-resource-aware-segments-07, 31 May 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              resource-aware-segments-07>.

   [I-D.ietf-teas-enhanced-vpn]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Network (VPN+)",
              Work in Progress, Internet-Draft, draft-ietf-teas-
              enhanced-vpn-14, 28 July 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              enhanced-vpn-14>.

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   [I-D.ietf-teas-ietf-network-slices]
              Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
              K., Contreras, L. M., and J. Tantsura, "A Framework for
              Network Slices in Networks Built from IETF Technologies",
              Work in Progress, Internet-Draft, draft-ietf-teas-ietf-
              network-slices-25, 14 September 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              ietf-network-slices-25>.

   [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>.

   [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>.

   [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/info/rfc9085>.

7.2.  Informative References

   [I-D.dong-lsr-sr-enhanced-vpn]
              Dong, J., Hu, Z., Li, Z., Tang, X., Pang, R., and S.
              Bryant, "IGP Extensions for Scalable Segment Routing based
              Virtual Transport Network (VTN)", Work in Progress,
              Internet-Draft, draft-dong-lsr-sr-enhanced-vpn-09, 10 July
              2023, <https://datatracker.ietf.org/doc/html/draft-dong-
              lsr-sr-enhanced-vpn-09>.

   [I-D.ietf-idr-bgpls-sr-vtn-mt]
              Xie, C., Li, C., Dong, J., and Z. Li, "BGP-LS with Multi-
              topology for Segment Routing based Virtual Transport
              Networks", Work in Progress, Internet-Draft, draft-ietf-
              idr-bgpls-sr-vtn-mt-03, 10 September 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              bgpls-sr-vtn-mt-03>.

   [I-D.ietf-spring-sr-for-enhanced-vpn]
              Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
              Z., and F. Clad, "Segment Routing based Virtual Transport
              Network (VTN) for Enhanced VPN", 12 February 2021,
              <https://tools.ietf.org/html/draft-ietf-spring-sr-for-
              enhanced-vpn>.

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   [I-D.ietf-teas-nrp-scalability]
              Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J.,
              Mishra, G. S., Qin, F., Saad, T., and V. P. Beeram,
              "Scalability Considerations for Network Resource
              Partition", Work in Progress, Internet-Draft, draft-ietf-
              teas-nrp-scalability-02, 2 June 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              nrp-scalability-02>.

   [I-D.zhu-idr-bgpls-sr-vtn-flexalgo]
              Zhu, Y., Dong, J., and Z. Hu, "BGP-LS with Flex-Algo for
              Segment Routing based Virtual Transport Networks", Work in
              Progress, Internet-Draft, draft-zhu-idr-bgpls-sr-vtn-
              flexalgo-01, 22 February 2021,
              <https://datatracker.ietf.org/doc/html/draft-zhu-idr-
              bgpls-sr-vtn-flexalgo-01>.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC5029]  Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link
              Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029,
              September 2007, <https://www.rfc-editor.org/info/rfc5029>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC9350]  Psenak, P., Ed., Hegde, S., Filsfils, C., Talaulikar, K.,
              and A. Gulko, "IGP Flexible Algorithm", RFC 9350,
              DOI 10.17487/RFC9350, February 2023,
              <https://www.rfc-editor.org/info/rfc9350>.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing
   100095
   China
   Email: jie.dong@huawei.com

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   Zhenbin Li
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing
   100095
   China
   Email: lizhenbin@huawei.com

   Haibo Wang
   Huawei Technologies
   Huawei Campus, No. 156 Beiqing Road
   Beijing
   100095
   China
   Email: rainsword.wang@huawei.com

   Jian Ge
   China Academy of Information and Communications Technology
   China
   Email: gejian@caict.ac.cn

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