LSR Working Group                                                J. Dong
Internet-Draft                                                     Z. Hu
Intended status: Standards Track                                   Z. Li
Expires: 12 January 2023                             Huawei Technologies
                                                                 X. Tang
                                                                 R. Pang
                                                            China Unicom
                                                               S. Bryant
                                                    University of Surrey
                                                            11 July 2022


     IGP Extensions for Scalable Segment Routing based Enhanced VPN
                   draft-dong-lsr-sr-enhanced-vpn-08

Abstract

   Enhanced VPN (VPN+) aims to provide enhanced VPN services to support
   some application's needs of enhanced isolation and stringent
   performance requirements.  VPN+ requires integration between the
   overlay VPN connectivity and the characteristics provided by the
   underlay network.  A Virtual Transport Network (VTN) is a virtual
   underlay network which has a customized network topology and a set of
   network resources allocated from the physical network.  A VTN could
   be used to support one or a group of VPN+ services.  In the context
   of network slicing, a VTN could be instantiated as a network resource
   partition (NRP).

   This document specifies the IGP mechanisms with necessary extensions
   to advertise the associated topology and resource attributes for
   scalable Segment Routing (SR) based NRPs.  Each NRP can have a
   customized topology and a set of network resources allocated from the
   physical network.  Multiple NRPs may shared the same topology, and
   multiple NRPs may share the same set of network resources on some
   network segments.  This allows flexible combination of the network
   topology and network resource attributes to build a relatively large
   number of NRPs with a relatively small number of logical topologies.
   A group of resource-aware SIDs and SRv6 Locators can be assigned to
   each NRP.  The proposed mechanism is applicable to both Segment
   Routing with MPLS data plane (SR-MPLS) and Segment Routing with IPv6
   data plane (SRv6).  This document also describes the mechanism of
   using dedicated NRP ID in the data plane instead of the per-NRP
   resource-aware SIDs and SRv6 Locators to further reduce the control
   plane and data plane overhead of maintaining a large number of NRPs.







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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
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   This Internet-Draft will expire on 12 January 2023.

Copyright Notice

   Copyright (c) 2022 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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Advertisement of NRP Definition . . . . . . . . . . . . . . .   5
   3.  Advertisement of NRP Topology Attribute . . . . . . . . . . .   6
     3.1.  MTR based Topology Advertisement  . . . . . . . . . . . .   6
     3.2.  Flex-Algo based Topology Advertisement  . . . . . . . . .   7
   4.  Advertisement of NRP Resource Attribute . . . . . . . . . . .   8
     4.1.  Option 1: L2 Bundle based Approach  . . . . . . . . . . .   8
     4.2.  Option 2: Per-NRP Link TE Attributes  . . . . . . . . . .  10
   5.  Advertisement of NRP specific Data Plane Identifiers  . . . .  12
     5.1.  Advertisement of NRP-specific SR-MPLS SIDs  . . . . . . .  12
     5.2.  Advertisement of NRP-specific SRv6 Locators and SIDs  . .  15
       5.2.1.  NRP-specific SRv6 Locators and End SIDs . . . . . . .  15
       5.2.2.  NRP-specific SRv6 End.X SIDs  . . . . . . . . . . . .  18
     5.3.  Advertisement of Dedicated Data Plane NRP ID  . . . . . .  18



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   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  20
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  20
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  20
     10.2.  Informative References . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   Enhanced VPN (VPN+) is an enhancement to VPN services to support the
   needs of new applications, particularly the applications that are
   associated with 5G services.  These applications require enhanced
   isolation and have more stringent performance requirements than that
   can be provided with traditional overlay VPNs.  These properties
   require integration between the underlay and the overlay networks.
   [I-D.ietf-teas-enhanced-vpn] specifies the framework of enhanced VPN
   and describes the candidate component technologies in different
   network planes and layers.  An enhanced VPN can be used for 5G
   network slicing, and will also be of use in more generic scenarios.

   To meet the requirement of different enhanced VPN services, a number
   of virtual underlay networks need to be created, each with a
   customized network topology and a set of network resources allocated
   from the physical network to meet the requirement of one or a group
   of VPN+ services.  Such a virtual underlay network is called Virtual
   Transport Network (VTN) in [I-D.ietf-teas-enhanced-vpn].

   [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 order to
   allocate network resources to an NRP, the NRP is associated with a
   network topology to define the set of links and nodes.  Thus VTN and
   NRP are similar concepts, and NRP can be seen as an instantiation of
   VTN in the context of network slicing.  For clarity, the rest of this
   document uses NRP in the description of the proposed mechanisms and
   protocol extensions.

   [I-D.ietf-spring-resource-aware-segments] introduces resource-aware
   segments by associating existing type of SIDs with network resource
   attributes (e.g. bandwidth, processing or storage resources).  These
   resource-aware SIDs retain their original functionality, with the
   additional semantics of identifying the set of network resources
   available for the packet processing
   action.[I-D.ietf-spring-sr-for-enhanced-vpn] describes the use of
   resource-aware segments to build SR based NRPs.  To allow the network
   controller and network nodes to perform NRP-specific explicit path



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   computation and/or shortest path computation, the group of resource-
   aware SIDs allocated by network nodes to each NRP and the associated
   topology and resource attributes need to be distributed using the
   control plane.

   [I-D.ietf-teas-nrp-scalability] analyzes the scalability requirements
   and the control plane and data plane scalability considerations of
   NRP.  In order to support a relatively large number of NRPs in the
   network, one proposed approach is to separate the topology and
   resource attributes of the NRP in control plane, so that the
   advertisement and processing of each type of attribute could be
   decoupled.  Multiple NRPs may shared the same topology, and multiple
   NRPs may share the same set of network resources on some network
   segments, while the difference in either the topology or resource
   attributes makes them different NRPs.  This allows flexible
   combination of network topology and network resource attributes to
   build a large number of NRPs with a relatively small number of
   logical topologies.

   This document specifies the IGP control plane mechanisms with
   necessary extensions for scalable SR based NRPs.  A group of
   resource-aware SIDs and SRv6 Locators can be assigned to each NRP.
   The proposed mechanism is applicable to both segment routing with
   MPLS data plane (SR-MPLS) and segment routing with IPv6 data plane
   (SRv6).  This document also describes the mechanisms of using
   dedicated NRP ID in the data plane instead of the per-NRP resource-
   aware SIDs to further reduce the control plane and data plane
   overhead of maintaining a large number of NRPs.

   In general this approach applies to both IS-IS and OSPF, while the
   specific protocol extensions and encodings are different.  In the
   current version of this document, the required IS-IS extensions are
   described.  The required OSPF extensions will be described in a
   future version or in a separate document.

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 BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.









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2.  Advertisement of NRP Definition

   According to [I-D.ietf-teas-ietf-network-slices], an NRP is a
   collection of network resources allocated in the underlay network,
   and is associated with a network topology.  Thus an NRP can be
   defined as the combination of a set of network attributes, which
   include the topology attribute, the resource attributes, and other
   possible attributes.

   The IS-IS Network Resource Partition Definition (NRPD) sub-TLV is
   used to advertise the definition of a NRP.  It is a sub-TLV of the
   IS-IS Router-Capability TLV 242 as defined in [RFC7981].

   The format of IS-IS NRPD sub-TLV is as 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     |           NRP ID              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       NRP ID (Continue)       |           MT-ID               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Algorithm  |     Flags     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~                         Sub-sub-TLVs                          ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the included sub-TLVs.

   *  NRP ID: A domain significant 32-bit identifier which is used to
      identify an NRP.

   *  MT-ID: 16-bit field which indicates the multi-topology identifier
      as defined in [RFC5120].  The first 4-bit are set to zero.

   *  Algorithm: 8-bit identifier which indicates the algorithm which
      applies to this NRP.  It can be either a normal algorithm
      [RFC8402] or a Flexible Algorithm [I-D.ietf-lsr-flex-algo].






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   *  Flags: 8-bit flags.  Currently all the flags are reserved for
      future use.  They SHOULD be set to zero on transmission and MUST
      be ignored on receipt.

   *  Sub-sub-TLVs: optional sub-sub-TLVs to specify the additional
      attributes of an NRP.  Currently no sub-sub-TLV is defined in this
      document.

   The NRPD Sub-TLV MAY be advertised in an LSP of any number.  A node
   MUST NOT advertise more than one NRPD Sub-TLV for a given NRP ID.

3.  Advertisement of NRP Topology Attribute

   This section describes the mechanisms used to advertise the topology
   attribute associated with SR based NRPs.  Basically the topology of
   an NRP can be determined by the MT-ID and/or the algorithm ID
   included in the NRP definition.  In practice, it could be described
   using two optional approaches.

   The first approach is to use Multi-Topology Routing (MTR) [RFC4915]
   [RFC5120] with the segment routing extensions to advertise the
   topology associated with the SR based NRPs.  Different algorithms MAY
   be used to further specify the computation algorithm or the metric
   type used for path computation within the topology.  Multiple NRPs
   can be associated with the same <topology, algorithm>, and the IGP
   computation with the <topology, algorithm> tuple can be shared by
   these NRPs.

   The second approach is to use Flex-Algo [I-D.ietf-lsr-flex-algo] to
   describe the topological constraints of SR based NRPs on a shared
   network topology (e.g. the default topology).  Multiple NRPs can be
   associated with the same Flex-Algo, and the IGP computation with this
   Flex-Algo can be shared by these NRPs.

3.1.  MTR based Topology Advertisement

   Multi-Topology Routing (MTR) has been defined in [RFC4915] and
   [RFC5120] to create different network topologies in one network.  It
   also has the capability of specifying customized attributes for each
   topology.  The traditional use cases of multi-topology are to
   maintain separate topologies for unicast and multicast services, or
   to create different topologies for IPv4 and IPv6 in a network.  There
   are some limitations when MTR is used with native IP forwarding, the
   considerations about MT based IP forwarding are described in
   [RFC5120].






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   MTR can be used with SR-MPLS data plane.  [RFC8667] specifies the IS-
   IS extensions to support SR-MPLS data plane, in which the Prefix-SID
   sub-TLVs can be carried in IS-IS TLV 235 (MT IP Reachability) and TLV
   237 (MT IPv6 IP Reachability), and the Adj-SID sub-TLVs can be
   carried in IS-IS TLV 222 (MT-ISN) and TLV 223 (MT IS Neighbor
   Attribute).

   MTR can also be used with SRv6 data plane.
   [I-D.ietf-lsr-isis-srv6-extensions] specifies the IS-IS extensions to
   support SRv6 data plane, in which the MT-ID is carried in the SRv6
   Locator TLV.  The SRv6 End SIDs are carried as sub-TLVs in the SRv6
   Locator TLV, and inherit the topology/algorithm from the parent
   locator.  The SRv6 End.X SIDs are carried as sub-TLVs in the IS-IS
   TLV 222 (MT-ISN) and TLV 223 (MT IS Neighbor Attribute), and inherit
   the topology/algorithm from the parent locator.

   These IGP extensions for SR-MPLS and SRv6 can be used to advertise
   and build the topology for a group of SR based NRPs.

   An algorithm ID MAY be used to further specify the computation
   algorithm or the metric type used for path computation within the
   topology.

3.2.  Flex-Algo based Topology Advertisement

   [I-D.ietf-lsr-flex-algo] specifies the mechanisms to provide
   distributed computation of constraint-based paths, and how the SR-
   MPLS prefix-SIDs and SRv6 locators can be used to steer packets along
   the constraint-based paths.

   The Flex-Algo Definition (FAD) can be used to describe the
   topological constraints for path computation on a network topology.
   According to the network nodes' participation of a Flex-Algo, and the
   rules of including or excluding specific Administrative Groups
   (colors) and the Shared Risk Link Groups (SRLGs), the topology of an
   NRP can be determined using the associated Flex-Algo on a particular
   topology (e.g. the default topology).

   With the mechanisms defined in[RFC8667] [I-D.ietf-lsr-flex-algo],
   prefix-SID advertisement can be associated with a <topology,
   algorithm> tuple, in which the algorithm can be a Flex-Algo.  This
   allows network nodes to use the prefix-SID to steer traffic along
   distributed computed paths according to the identified Flex-Algo in
   the topology.

   [I-D.ietf-lsr-isis-srv6-extensions] specifies the IS-IS extensions to
   support SRv6 data plane, in which the SRv6 locators advertisement can
   be associated with a specific topology and a specific algorithm,



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   which can be a Flex-Algo.  With the mechanism defined in
   [I-D.ietf-lsr-flex-algo], The SRv6 locator can be used to steer
   traffic along distributed computed paths according to the identified
   Flex-Algo in the topology.  In addition, topology/algorithm specific
   SRv6 End SID and End.X SID can be used to enforce traffic over the
   LFA computed backup path.

   Multiple Flex-Algos MAY be defined to describe the topological
   constraints on a shared network topology (e.g. the default topology).

4.  Advertisement of NRP Resource Attribute

   This section specifies the mechanisms to advertise the network
   resource attributes associated with the NRPs.  The mechanism of
   advertising the link resources and attributes associated with NRPs is
   described.  The mechanism of advertising node resources and
   attributes associated with NRPs are for further study.  Two optional
   approaches are described in the following sub-sections: the first
   option is the L2 Bundle [RFC8668] based approach, the second option
   is to extend IGP to advertise per-NRP link TE attributes.

4.1.  Option 1: L2 Bundle based Approach

   On a Layer-3 interface, each NRP can be allocated with a subset of
   link resources (e.g. bandwidth).  A subset of link resources may be
   dedicated to an NRP, or may be shared by a group of NRPs.  Each
   subset of link resource can be represented as a virtual layer-2
   member link under the Layer-3 interface, and the Layer-3 interface is
   considered as a virtual Layer-2 bundle.  The Layer-3 interface may
   also be a physical Layer 2 link bundle, in this case a subset of link
   resources allocated to an NRP may be provided by one of the physical
   Layer-2 member links.

   [RFC8668] describes the IS-IS extensions to advertise the link
   attributes of the Layer 2 member links which comprise a Layer 3
   interface.  Such mechanism can be extended to advertise the
   attributes of each physical or virtual member links, and its
   associated NRPs.

   A new flag "E" (Exclusive) is defined in the flag field of the Parent
   L3 Neighbor Descriptor in the L2 Bundle Member Attributes TLV (25).

                0 1 2 3 4 5 6 7
               +-+-+-+-+-+-+-+-+
               |P|E|           |
               +-+-+-+-+-+-+-+-+





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   E flag: When the E flag is set, it indicates each member link under
   the Parent L3 link are used exclusively for one or a specific group
   of NRPs, and load sharing among the member links is not allowed.
   When the E flag is clear, it indicates load balancing and sharing
   among the member links are allowed.

   A new NRP IDs sub-TLV is carried under the L2 Bundle Attribute
   Descriptors to describe the mapping relationship between the NRPs and
   the virtual or physical member links.  As one or more NRPs may use
   the same set of link resource on a specific network segment, these
   NRP IDs will be advertised under the same virtual or physical member
   link.

   The format of the NRP IDs Sub-TLV is as 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     |            Flags              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           NRP ID #1                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                              ...                              ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           NRP ID #n                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the number of NRP IDs included.

   *  Flags: 16 bit flags.  All the bits are reserved for future use,
      which SHOULD be set to 0 on transmission and MUST be ignored on
      receipt.

   *  NRP IDs: One or more 32-bit identifiers to identify the NRPs this
      member link belongs to.

   Each physical or virtual member link MAY be associated with a
   different group of NRPs.  Thus each L2 Bundle Attribute Descriptor
   may carry the link local identifier and attributes of only one Layer
   2 member link.  Multiple L2 Bundle Attribute Descriptors will be used
   to carry the attributes and the associated NRP IDs of all the Layer 2
   member links.




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   The TE attributes of each virtual or physical member link, such as
   the bandwidth attributes and the SR SIDs, can be advertised using the
   mechanism as defined in [RFC8668].

4.2.  Option 2: Per-NRP Link TE Attributes

   A Layer-3 interface can participate in multiple NRPs, each of which
   is allocated with a subset of the forwarding resources of the
   interface.  For each NRP, the associated resources can be described
   using per-NRP TE attributes.  A new NRP-specific TE attribute sub-TLV
   is defined to advertise the link attributes associated with an NRP.
   This sub-TLV MAY be advertised as a sub-TLV of the following TLVs:

     TLV-22 (Extended IS reachability) [RFC5305]

     TLV-23 (IS Neighbor Attribute) [RFC5311]

     TLV-141 (Inter-AS Reachability Information) [RFC5316]

     TLV-222 (MT ISN) [RFC5120]

     TLV-223 (MT IS Neighbor Attribute) [RFC5311]

   The format of the sub-TLV is shown as 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     |     Flags     |    Reserved   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      NRP ID Sub-sub-TLV                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                      Other Sub-sub-TLVs                       ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the length of the Sub-sub-TLVs field.

   *  Flags: 8-bit flags.  All the 8 bits are reserved for future use,
      which SHOULD be set to 0 on transmission and MUST be ignored on
      receipt.

   *  Reserved: 8-bit field reserved for future use, SHOULD be set to 0
      on transmission and MUST be ignored on receipt.



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   *  NRP ID Sub-sub-TLV: contains one or more NRP IDs which is
      associated with the same group of TE attributes.

   *  Other Sub-sub-TLVs: the TLVs which carry the TE attributes
      associated with the NRPs.

   The format of the NRP ID sub-sub-TLV is shown as 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     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           NRP ID #1                           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                              ...                              ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-sub-TLV.  It is
      the number of the NRP IDs in the TLV multiplied by 4.

   *  NRP ID: A 32-bit identifier which is used to identify an NRP.

   One sub-sub-TLV "NRP bandwidth sub-sub-TLV" is defined in this
   document.  Its format is shown as 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     |     Flags     |    Reserved   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          Bandwidth                            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-sub-TLV.  It is
      set to 6.

   *  Flags: 8-bit flags.  All the 8 bits are reserved for future use,
      which SHOULD be set to 0 on transmission and MUST be ignored on
      receipt.



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   *  Reserved: 8-bit field reserved for future use, SHOULD be set to 0
      on transmission and MUST be ignored on receipt.

   *  Bandwidth: The bandwidth allocated to the NRP, encoded in 32 bits
      in IEEE floating point format.

   The NRP Bandwidth sub-sub-TLV is optional.  This sub-sub-TLV SHOULD
   appear once at most in each NRP-specific TE attribute sub-TLV.

5.  Advertisement of NRP specific Data Plane Identifiers

   In order to steer packets to the NRP-specific paths which are
   computed taking the topology and network resources of the NRP as the
   constraints, some fields in the data packet needs to be used to infer
   or identify the NRP the packet belongs to.  As multiple NRPs may
   share the same topology or Flex-Algo, the topology/Flex-Algo specific
   SR SIDs or Locators cannot be used to distinguish the packets which
   belong to different NRPs.  Some additional data plane identifiers
   would be needed to identify the NRP a packet belongs to.

   This section describes the mechanisms to advertise the NRP
   identifiers in different data plane encapsulations.

5.1.  Advertisement of NRP-specific SR-MPLS SIDs

   With SR-MPLS data plane, the NRP identification information can be
   implicitly carried in the NRP-specific SIDs.  Each node SHOULD
   allocate a unique Prefix-SID for each NRP it participates in.  On a
   Layer-3 interface, if each Layer 2 member link is associated with
   only one NRP, the adj-SIDs of the L2 member links could also identify
   the NRPs.  If a member link is associated with multiple NRPs, NRP-
   specific adj-SIDs MAY need to be allocated to help the NRP-specific
   local protection.

   A new NRP-specific prefix-SID sub-TLV is defined to advertise the
   prefix-SID and its associated NRP.  This sub-TLV MAY be advertised as
   a sub-TLV of the following TLVs:

     TLV-135 (Extended IPv4 Reachability) defined in [RFC5305].

     TLV-235 (MT IP Reachability) defined in [RFC5120].

     TLV-236 (IPv6 IP Reachability) defined in [RFC5308].

     TLV-237 (MT IPv6 IP Reachability) defined in [RFC5120].

   The format of the sub-TLV is shown as 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     |    Length     |              Flags            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            NRP ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  SID/Index/Label(Variable)                    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the length of the SID/Index/Label field.

   *  Flags: 16-bit flags.  The high-order 8 bits are the same as in the
      Prefix-SID sub-TLV defined in [RFC8667].  The lower-order 8 bits
      are reserved for future use, which SHOULD be set to 0 on
      transmission and MUST be ignored on receipt.

   *  NRP ID: A 32-bit identifier to identify the NRP this prefix-SID
      associates with.

   *  SID/Index/Label: The same as defined in [RFC8667].

   One or more of NRP-specific Prefix-SID sub-TLVs MAY be carried in the
   Multi-topology IP Reachability TLVs (TLV 235 or TLV 237), the MT-ID
   of the TLV SHOULD be the same as the MT-ID in the definition of these
   NRPs.

   A new NRP-specific Adj-SID sub-TLV is defined to advertise the adj-
   SID and its associated NRP.  This sub-TLV may be advertised as a sub-
   TLV of the following TLVs:

     TLV-22 (Extended IS reachability) [RFC5305]

     TLV-23 (IS Neighbor Attribute) [RFC5311]

     TLV-25 (L2 Bundle Member Attributes) [RFC8668]

     TLV-141 (Inter-AS Reachability Information) [RFC5316]

     TLV-222 (MT ISN) [RFC5120]

     TLV-223 (MT IS Neighbor Attribute) [RFC5311]




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   The format of the sub-TLV is shown as 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     |           Flags               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            NRP ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      SID/Index/Label(Variable)                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the length of the SID/Index/Label field.

   *  Flags: 16-bit flags.  The high-order 8 bits are the same as in the
      Adj-SID sub-TLV defined in [RFC8667].  The lower-order 8 bits are
      reserved for future use, which SHOULD be set to 0 on transmission
      and MUST be ignored on receipt.

   *  NRP ID: A 32-bit global identifier to identify the NRP this Adj-
      SID associates with.

   *  SID/Index/Label: The same as defined in [RFC8667].

   One or more NRP-specific Adj-SID sub-TLV MAY be carried in the Multi-
   topology ISN or Multi-topology IS Attribute TLVs (TLV 222 or TLV
   223), the MT-ID of the TLV SHOULD be the same as the MT-ID in the
   definition of these NRPs.

   A new NRP-specific LAN Adj-SID sub-TLV is defined to advertise the
   adj-SID and its associated NRP for each neighbor on a LAN interface.
   This sub-TLV may be advertised as a sub-TLV of the following TLVs:

     TLV-22 (Extended IS reachability) [RFC5305]

     TLV-23 (IS Neighbor Attribute) [RFC5311]

     TLV-222 (MT ISN) [RFC5120]

     TLV-223 (MT IS Neighbor Attribute) [RFC5311]

   The format of the sub-TLV is shown as 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     |    Length     |           Flags               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            NRP ID                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                 Neighbor System-ID  (ID length octets)        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      SID/Index/Label(Variable)                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the length of the SID/Index/Label field.

   *  Flags: 16-bit flags.  The high-order 8 bits are the same as in the
      Adj-SID sub-TLV defined in [RFC8667].  The lower-order 8 bits are
      reserved for future use, which SHOULD be set to 0 on transmission
      and MUST be ignored on receipt.

   *  NRP ID: A 32-bit global identifier to identify the NRP this Adj-
      SID associates with.

   *  Neighbor System-ID: IS-IS System-ID of length "ID Length" as
      defined in [ISO10589].

   *  SID/Index/Label: The same as defined in [RFC8667].

   One or more NRP-specific LAN Adj-SID sub-TLV MAY be carried in the
   Multi-topology ISN or Multi-topology IS Attribute TLVs (TLV 222 or
   TLV 223), the MT-ID of the TLV SHOULD be the same as the MT-ID in the
   definition of these NRPs.

5.2.  Advertisement of NRP-specific SRv6 Locators and SIDs


5.2.1.  NRP-specific SRv6 Locators and End SIDs

   With SRv6 data plane, the NRP identification information can be
   implicitly or explicitly carried in the SRv6 Locator of the
   corresponding NRP, this is to ensure that all network nodes
   (including both the end nodes and the transit nodes) can identify the
   NRP to which a packet belongs to.  Network nodes SHOULD allocate NRP-
   specific Locators for each NRP it participates in.  The NRP-specific



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   Locators are used as the covering prefix of NRP-specific SRv6 End
   SIDs, End.X SIDs and other types of SIDs.

   In one possible approach, each NRP-specific Locator is advertised in
   a separate TLV called "NRP specific SRv6 Locator TLV".  Its format is
   shown as 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    |R|R|R|R|    MT ID              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                   Locator Entries . . .                       |

   Where:

   *  Type: TBD

   *  The semantics of the Length field, the R bits and the MT ID field
      are the same as those defined in
      [I-D.ietf-lsr-isis-srv6-extensions].

   Followed by one or more locator entries of the form:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Metric                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Flags      |  Algorithm    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            NRP ID                             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Loc Size   |
       +-+-+-+-+-+-+-+-+

       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //              Locator (continued, variable)                  //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Sub-TLV-len  |         Sub-TLVs (variable) . . .             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  NRP ID: A 32-bit identifier to identify the NRP this Locator is
      associated with.





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   *  All the other fields are the same as those defined in
      [I-D.ietf-lsr-isis-srv6-extensions].

   The NRP-specific SRv6 End SIDs are carried in the NRP-specific SRv6
   Locator TLV, and inherits the topology, algorithm and NRP from the
   parent NRP-specific Locator.

   In another possible approach, when a group of NRPs share the same
   topology/algorithm, the topology/algorithm specific Locator is the
   covering prefix of a group of NRP-specific Locators.  Then the
   advertisement of NRP-specific locators can be optimized to reduce the
   amount of Locator TLVs advertised in the control plane.

   A new NRP locator-block sub-TLV under the SRv6 Locator TLV is defined
   to advertise a set of sub-blocks which follows the topology/algorithm
   specific Locator.  Each NRP locator-block value is assigned to one of
   the NRPs which share the same topology/algorithm.

      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     | Number of NRPs|  Block Length |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            NRP ID #1                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                       Locator Block Value                     ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                               ...                             ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                            NRP ID #n                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~                       Locator Block Value                     ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD

   *  Length: The length of the value field of the sub-TLV.  It is
      variable dependent on the number of NRPs and the Block Length.

   *  Number of NRPs: The number of NRPs which share the same topology/
      algorithm specific Locator as the covering prefix.

   *  Block Length: The length of the NRP locator-block which follows
      the length of the topology/algorithm specific Locator.





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   *  NRP ID: A 32-bit identifier to identify the NRP the locator-block
      is associates with.

   *  Block Value: The value of the NRP locator-block for each NRP.

   With the NRP locator-block sub-TLV, the NRP-specific Locator can be
   obtained by concatenating the topology/algorithm specific locator and
   the locator-block value advertised for the NRP.

   The NRP-specific SRv6 End SIDs inherit the topology, algorithm and
   the NRP from the parent NRP-specific Locator.

5.2.2.  NRP-specific SRv6 End.X SIDs

   The SRv6 End.X SIDs are advertised as sub-TLVs of TLV 22, 23, 25,
   141, 222, and 223.  In order to distinguish the End.X SIDs which
   belong to different NRPs, a new "NRP ID sub-sub-TLV" is introduced
   under the SRv6 End.X SID sub-TLV and SRv6 LAN End.X SID sub-TLV
   defined in [I-D.ietf-lsr-isis-srv6-extensions].  Its format is shown
   as 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    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           NRP ID                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Where:

   *  Type: TBD.

   *  Length: the length of the Value field of the TLV.  It is set to 4.

   *  NRP ID: A 32-bit identifier to identify the NRP this End.X SID
      associates with.

5.3.  Advertisement of Dedicated Data Plane NRP ID

   As the number of NRPs increases, with the mechanism described in
   [I-D.ietf-spring-sr-for-enhanced-vpn], the number of SR SIDs and SRv6
   Locators allocated for different NRPs would also increase.  In
   network scenarios where the number of SIDs or Locators becomes a
   concern, some data plane optimization may be needed to reduce the
   amount of SR SIDs and Locators allocated.  As described in
   [I-D.ietf-teas-nrp-scalability], one approach is to decouple the data
   plane identifiers used for topology based forwarding and the



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   identifiers used for the NRP-specific processing.  Thus a dedicated
   data plane NRP ID could be encapsulated in the packet.  One possible
   encapsulation of NRP ID in IPv6 data plane is proposed in
   [I-D.ietf-6man-enhanced-vpn-vtn-id].  One possible encapsulation of
   NRP ID in MPLS data plane is proposed in
   [I-D.li-mpls-enhanced-vpn-vtn-id].

   In that case, the NRP ID encapsulated in data plane can have the same
   value as the NRP ID in control plane, so that the overhead of
   advertising the mapping between the control plane NRP IDs and the
   corresponding data plane identifiers could be saved.

6.  Security Considerations

   This document introduces no additional security vulnerabilities to
   IS-IS.

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

7.  IANA Considerations

   IANA is requested to assign a new code point in the "sub-TLVs for TLV
   242 registry".

   Type: TBD1
   Description: Network Resource Partition Definition

   IANA is requested to assign four new code points in the "sub-TLVs for
   TLVs 22, 23, 25, 141, 222, and 223 registry".

   Type: TBD2
   Description: Network Resource Partition Identifiers sub-TLV

   Type: TBD3
   Description: NRP-specific TE attribute sub-TLV

   Type: TBD4
   Description: NRP-specific Adj-SID

   Type: TBD5
   Description: NRP-specific LAN Adj-SID

   IANA is requested to assign two new code points in the "Sub-TLVs for
   TLVs 27, 135, 235, 236 and 237 registry".






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   Type: TBD6
   Description: NRP-specific Prefix-SID

   Type: TBD7
   Description: NRP locator-block

   IANA is requested to assign a new code point in the "IS-IS TLV
   Codepoints registry".

   Type: TBD8
   Description: NRP-specific SRv6 Locator TLV

   IANA is requested to assign a new code point in the "sub-sub-TLVs for
   SRv6 End SID and SRv6 End.X SID registry".

   Type: TBD9
   Description: NRP ID Sub-sub-TLV

8.  Contributors

   TBD

9.  Acknowledgments

   The authors would like to thank Mach Chen, Dean Cheng, Lee JooHeon,
   Hongjie Yang and Guoqi Xu for their review and discussion of this
   document.

10.  References

10.1.  Normative References

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", Work in Progress,
              Internet-Draft, draft-ietf-lsr-flex-algo-20, 18 May 2022,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-
              20.txt>.

   [I-D.ietf-lsr-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extensions to Support Segment Routing over
              IPv6 Dataplane", Work in Progress, Internet-Draft, draft-
              ietf-lsr-isis-srv6-extensions-18, 20 October 2021,
              <https://www.ietf.org/archive/id/draft-ietf-lsr-isis-srv6-
              extensions-18.txt>.





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   [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-04, 5 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-spring-
              resource-aware-segments-04.txt>.

   [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", Work in Progress,
              Internet-Draft, draft-ietf-spring-sr-for-enhanced-vpn-02,
              5 March 2022, <https://www.ietf.org/archive/id/draft-ietf-
              spring-sr-for-enhanced-vpn-02.txt>.

   [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+)
              Services", Work in Progress, Internet-Draft, draft-ietf-
              teas-enhanced-vpn-10, 6 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-enhanced-
              vpn-10.txt>.

   [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>.

   [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>.

   [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>.

   [RFC7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/info/rfc7981>.

   [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>.



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   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8667]  Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C.,
              Bashandy, A., Gredler, H., and B. Decraene, "IS-IS
              Extensions for Segment Routing", RFC 8667,
              DOI 10.17487/RFC8667, December 2019,
              <https://www.rfc-editor.org/info/rfc8667>.

   [RFC8668]  Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
              M., and E. Aries, "Advertising Layer 2 Bundle Member Link
              Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
              December 2019, <https://www.rfc-editor.org/info/rfc8668>.

10.2.  Informative References

   [I-D.ietf-6man-enhanced-vpn-vtn-id]
              Dong, J., Li, Z., Xie, C., Ma, C., and G. Mishra,
              "Carrying Virtual Transport Network (VTN) Identifier in
              IPv6 Extension Header", Work in Progress, Internet-Draft,
              draft-ietf-6man-enhanced-vpn-vtn-id-00, 5 March 2022,
              <https://www.ietf.org/archive/id/draft-ietf-6man-enhanced-
              vpn-vtn-id-00.txt>.

   [I-D.ietf-teas-ietf-network-slices]
              Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
              K., Contreras, L. M., and J. Tantsura, "Framework for IETF
              Network Slices", Work in Progress, Internet-Draft, draft-
              ietf-teas-ietf-network-slices-12, 30 June 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-ietf-
              network-slices-12.txt>.

   [I-D.ietf-teas-nrp-scalability]
              Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J. N.,
              Mishra, G., Qin, F., Saad, T., and V. P. Beeram,
              "Scalability Considerations for Network Resource
              Partition", Work in Progress, Internet-Draft, draft-ietf-
              teas-nrp-scalability-00, 11 July 2022,
              <https://www.ietf.org/archive/id/draft-ietf-teas-nrp-
              scalability-00.txt>.









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   [I-D.li-mpls-enhanced-vpn-vtn-id]
              Li, Z. and J. Dong, "Carrying Virtual Transport Network
              Identifier in MPLS Packet", Work in Progress, Internet-
              Draft, draft-li-mpls-enhanced-vpn-vtn-id-02, 7 March 2022,
              <https://www.ietf.org/archive/id/draft-li-mpls-enhanced-
              vpn-vtn-id-02.txt>.

Authors' Addresses

   Jie Dong
   Huawei Technologies
   Email: jie.dong@huawei.com


   Zhibo Hu
   Huawei Technologies
   Email: huzhibo@huawei.com


   Zhenbin Li
   Huawei Technologies
   Email: lizhenbin@huawei.com


   Xiongyan Tang
   China Unicom
   Email: tangxy@chinaunicom.cn


   Ran Pang
   China Unicom
   Email: pangran@chinaunicom.cn


   Stewart Bryant
   University of Surrey
   Email: stewart.bryant@gmail.com














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