SPRING Working Group                                           W. Jiang
Internet Draft                                             China Mobile
Intended status: Standards Track                                 C. Lin
Expires: December 20, 2024                         New H3C Technologies
                                                                R. Chen
                                                        ZTE Corporation
                                                          June 21, 2024

                 Segment Routing Policy Extension for NRP



                    draft-jiang-spring-sr-policy-nrp-01


Abstract

   Network Resource Partition (NRP), which is a subset of the resources
   and associated policies in the underlay network. In networks with
   multiple NRPs, an SR Policy can be associated with a particular NRP.
   This document describes how the SR Policy extension for associated
   NRP and the operational mechanisms function together.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on December 20, 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents

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   carefully, as they describe your rights and restrictions with
   respect to this document. Code Components extracted from this
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   warranty as described in the Simplified BSD License.

Table of Contents


   1. Introduction...................................................3
      1.1. Requirements Language.....................................3
   2. Solution.......................................................4
   3. SR Policy Extension for NRP....................................5
      3.1. NRP ID of a Candidate Path................................5
      3.2. Candidate Path Validity Verification......................6
      3.3. Summary...................................................7
   4. Steering into an SR Policy with NRP............................8
   5. Manageability Considerations...................................8
   6. Security Considerations........................................8
   7. IANA Considerations............................................8
   8. References.....................................................8
      8.1. Normative References......................................8
      8.2. Informative References....................................9
   Acknowledgements.................................................10
   Authors' Addresses...............................................11


























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1. Introduction

   A Segment Routing Policy (SR Policy) [RFC9256] is an ordered list of
   segments (i.e., instructions) that represent a source-routed policy.
   The headend node is said to steer a flow into an SR Policy. The
   packets steered into an SR Policy have an ordered list of segments
   associated with that SR Policy written into them. [RFC8660]
   describes the representation and processing of this ordered list of
   segments as an MPLS label stack for SR-MPLS, while [RFC8754] and
   [RFC8986] describe the same for Segment Routing over IPv6 (SRv6)
   with the use of the Segment Routing Header (SRH).

   [RFC9543] provides the definition of IETF network slice for use
   within the IETF and discusses the general framework for requesting
   and operating IETF Network Slices, their characteristics, and the
   necessary system components and interfaces.It also introduces the
   concept Network Resource Partition (NRP), which is a subset of the
   resources and associated policies in the underlay network.

   As described in [I-D.ietf-teas-nrp-scalability], one scalable data
   plane approach to support network slicing is to carry a dedicated
   NRP ID in the data packet to identify the NRP the packet belongs to,
   so that the packet can be processed and forwarded using the subset
   of network resources allocated to the NRP.

   In networks with multiple NRPs, an SR Policy can be associated with
   a particular NRP. This document describes how the SR Policy
   extension for associated NRP and the operational mechanisms function
   together.

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. Solution

      ----------------------------------------
     ( |PE|.............|PE|.............|PE| )
     (  --   SR Policy-1  --  SR Policy-1 --  )<---------+
      ----------------------------------------           |
       SR Policy-1 with NRP 1                            |
                                                         |
      ----------------------------------------           |
     ( |PE|..............................|PE| )          |
     (  --           SR Policy-2            --  )<-------+
      ----------------------------------------           |
       SR Policy-2 with NRP 2                            |
                                                         |
      ----------------------------------------------     |
     ( |PE|.....-.....|PE|......    |PE|.......|PE| )    |
    (   --     |P|     --      :-...:--     -..:--   )   |
   (    :       -:.............|P|.........|P|        )--+
   (    -......................:-:..-       -         )
    (  |P|.........................|P|......:        )
     (  -                           -               )
      ----------------------------------------------
       Underlay Network

   Figure 1: Solution of SR Policy Extension for NRP


   In each NRP for network slices, the connectivity among PEs is
   achieved by SR Policies. The segment lists of these SR Policies
   composed with segments associated with the corresponding NRPs.
   Traffics are steered into the SR Policies, so that the corresponding
   NRPs will be used for forwarding.
















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               Physical Interface 1
   +---------------------------------------+
   |                                       |
   |  Layer-3 Sub-interface 1-1: 1Gbps     |
   |=======================================|
   |>>>>>> Queue 1-1: NRP-1, 100Mbps >>>>>>|
   |>>>>>> Queue 1-2: NRP-2, 200Mbps >>>>>>|
   |>>>>>>              ...          >>>>>>|
   |=======================================|
   |                                       |
   |  Layer-3 Sub-interface 1-2: 2Gbps     |
   |====================================== |
   |>>>>>> Queue 1-1: NRP-1, 100Mbps >>>>>>|
   |>>>>>> Queue 1-2: NRP-2, 200Mbps >>>>>>|
   |>>>>>>              ...          >>>>>>|
   |=======================================|
   |                                       |
   +---------------------------------------+

   Figure 2: Network Resource Partition

   As shown in Figure 2, the bandwidth resource of a physical interface
   is partitioned in two NRPs.

   The NRPs are sliced by HQoS queues with dedicated bandwidth under
   the layer-3 sub-interface. NRP needs to be identified by using an
   extra dimension. On both MPLS-SR and SRv6 data plane, there are
   several options for realizing NRP-ID, such as [I-D.ietf-6man-
   enhanced-vpn-vtn-id], [I-D.cheng-spring-srv6-encoding-network-
   sliceid], [I-D.decraene-mpls-slid-encoded-entropy-label-id], and [I-
   D.li-mpls-enhanced-vpn-vtn-id]. As mentioned above, the traffics of
   network slice are forwarded according to the segment list of SR
   Policy. Firstly, the outgoing interface associated segment will be
   the layer-3 sub-interface. Then, the HQoS queue will be selected
   according to the NRP-ID carried in the packets, and the bandwidth
   resource of NRP will be used.

3. SR Policy Extension for NRP

   The SR Policy determines the path that packets will traverse, while
   NRP reserves resources along the path designated by the SR Policy.
   Through the integration of SR Policy and NRP, it ensures both the
   forwarding path and resource reservation along the path.

3.1. NRP ID of a Candidate Path

   The NRP ID of a candidate path is utilized to identify the resources
   corresponding to the forwarding paths of all segment lists within an

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   SR Policy. It is a 32-bit value serving as an identifier for the
   Network Resource Partition. The NRP ID associated with a candidate
   path of an SR Policy from a specific Protocol-Origin as specified
   below:

   o When provisioning is via configuration, it is specific to the
      implementation's configuration model.

   o When signaling is via PCEP, the method to uniquely signal an
      individual candidate path along with its NRP ID is described in
      [I-D.draft-dong-pce-pcep-nrp].

   o When signaling is via BGP SR Policy, the method to uniquely
      signal an individual candidate path along with its NRP ID is
      described in [I-D.ietf-idr-sr-policy-nrp].It can be collected via
      BGP-LS [I-D.draft-chen-idr-bgp-ls-sr-policy-nrp].

   Under the same Candidate Path, all segment lists must share the same
   NRP ID. While different Candidate Paths can have identical NRP IDs,
   it is advisable for each candidate path within an SR Policy to
   possess a unique NRP ID.

   By associating NRP IDs with Candidate Paths, the assurance of both
   the SR Policy's path and its resources is achieved. The process
   involves the following steps:

   o Planning the network topology resources and assigning NRP IDs.

   o At the headend node, performing path arrangement. During the path
      planning process of the SR Policy, resources are considered for
      different candidate paths, and NRP IDs are configured under each
      Candidate path to establish the association between the path and
      resources.

3.2. Candidate Path Validity Verification

   A candidate path is considered usable when it is valid, with the
   validation rules outlined in Section 5 of [RFC9256]. When a
   Candidate Path contains an NRP ID, a segment list of a candidate
   path may be declared invalid if the resources corresponding to the
   NRP ID on the segment list path do not exist. Additionally, if the
   head-end is unable to perform path resolution for the first SID into
   one or more outgoing interfaces and next-hops, along with the
   corresponding NRP ID resources, the status of that segment list is
   set to invalid.

   When running fast detection protocols, such as Bidirectional
   Forwarding Detection (BFD), the headend may compute and validate

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   backup candidate paths and provision them into the forwarding plane
   as a backup for the active path. In such cases, it is necessary to
   include NRP encapsulation to detect the NRP resources along the
   path, ensuring the availability of both the path and resources.

3.3. Summary

   In summary, the information model is the following:

   SR Policy POL1

            Candidate Path CP1

               Preference 200

               NRP-ID 100

               Segment List 1 <SID11...SID1i>, Weight 1

               Segment List 2 <SID21...SID2j>, Weight 1

               Segment List 3 <SID31...SID3k>, Weight 1

            Candidate Path CP2

            Preference 100

            NRP-ID 200

               Segment List 4 <SID41...SID4i>, Weight 1

               Segment List 5 <SID51...SID5j>, Weight 1

               Segment List 6 <SID61...SID6k>, Weight 1



   SR Policy POL1 has two Candidate Paths, CP1 and CP2. CP1 is the
   active candidate path (valid and with the highest Preference). NRP-
   ID 100 is configured under CP1, while NRP-ID 200 is configured under
   CP2. The three segment lists of CP1 with NRP-ID 100 are installed as
   the forwarding instantiation of SR Policy POL1. NRP-ID 100 needs to
   be configured and resources reserved on the paths traversed by
   segment list 1, segment list 2, and segment list 3. When traffic is
   steered on POL1 and flow-based hashed on segment list
   <SID11...SID1i>, NRP-100 is added, and forwarding is based on the
   resources pointed to by NRP-100.


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4. Steering into an SR Policy with NRP

   The method of traffic steering aligns with the description in
   Section 8 of [RFC9256]. When an SR policy's active path contains an
   NRP ID, specific handling is necessary, as follows:

   o when steering traffic to the SR policy through Per-Destination
      Steering or Policy-Based Routing, after adding the corresponding
      segment list encapsulation for the SR policy, NRP encapsulation
      is also required. The specific NRP encapsulation details are
      outside the scope of this document.

   o Similarly, When steering traffic to the SR policy via the
      BindingSID, after adding the segment list encapsulation for the
      SR policy, NRP encapsulation is required. The specific NRP
      encapsulation details are outside the scope of this document.

5. Manageability Considerations

   This document specifies the detailed construction of the SR Policy
   with NRP-ID and its operational mechanisms. Therefore, the
   manageability considerations of [RFC9256] apply.

6. Security Considerations

   The security considerations described in [RFC9256] also apply to
   this document.

   This document does not introduce any new security consideration.

7. IANA Considerations

   This document has no IANA actions.

8. References

8.1. Normative References

   [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>.



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   [RFC9256] Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
             P. Mattes, "Segment Routing Policy Architecture", BCP 14,
             RFC 9256, DOI 10.17487/RFC9256, July 2022, <
             https://www.rfc-editor.org/info/rfc9256 >.

      [I-D.ietf-teas-nrp-scalability]Dong, J., Li, Z., Gong, L., Yang,
             G., Mishra, G. S., and F. Qin, "Scalability Considerations
             for Network Resource Partition", Work in Progress,
             Internet-Draft, draft-ietf-teas-nrp-scalability-03, 21
             October 2023,<https://datatracker.ietf.org/doc/html/draft-
             ietf-teas-nrp-scalability-03>.

8.2. Informative References

   [I-D.ietf-teas-nrp-scalability] Dong, J., Li, Z., Gong, L., Yang,
             G., Mishra, G. S., and F. Qin, "Scalability Considerations
             for Network Resource Partition", Work in Progress,
             Internet-Draft, draft-ietf-teas-nrp-scalability-03, 21
             October 2023,<https://datatracker.ietf.org/doc/html/draft-
             ietf-teas-nrp-scalability-03>.

   [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, <http://www.ietf.org/internet-
             drafts/draft-ietf-6man-enhanced-vpn-vtn-id-00.txt>.

   [I-D.cheng-spring-srv6-encoding-network-sliceid] Cheng, W., Lin, C.,
             Gong, L., Zadok, S., and X. Wang, "Encoding Network Slice
             Identification for SRv6", Work in Progress, Internet-
             Draft, draft-cheng-spring-srv6-encoding-network-sliceid-
             04, 8 July 2022, <http://www.ietf.org/internet-
             drafts/draft-cheng-spring-srv6-encoding-network-sliceid-
             04.txt>.

   [I-D.decraene-mpls-slid-encoded-entropy-label-id] Decraene B.,
             Filsfils, C., Henderickx W., Saad T., Beeram V., "Using
             Entropy Label for Network Slice Identification in MPLS
             networks", Work in Progress, Internet-Draft, draft-
             decraene-mpls-slid-encoded-entropy-label-id-04, 14 June
             2022, <http://www.ietf.org/internet-drafts/draft-decraene-
             mpls-slid-encoded-entropy-label-id-04.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, <http://www.ietf.org/internet-
             drafts/draft-li-mpls-enhanced-vpn-vtn-id-02.txt>.

   [I-D. draft-dong-pce-pcep-nrp] Dong, J.,S. Fang,Q. Xiong,S. Peng,L.
             Han, "Path Computation Element Communication Protocol
             (PCEP) Extensions for Network Resource Partition (NRP)",
             Work in Progress, Internet-Draft, draft-dong-pce-pcep-nrp-
             01, 23 October 2023,
             <https://www.ietf.org/archive/id/draft-dong-pce-pcep-nrp-
             01.txt>.

   [I-D.ietf-idr-sr-policy-nrp] Dong, J., Hu, Z., and R. Pang, "BGP SR
             Policy Extensions for Network Resource Partition", Work in
             Progress,Internet-Draft, draft-ietf-idr-sr-policy-nrp-00,
             17 December 2023, <https://datatracker.ietf.org/doc/html/
             draft-ietf-idr-sr-policy-nrp-00>.

   [I-D.draft-chen-idr-bgp-ls-sr-policy-nrp] R. Chen, J. Dong, D. Zhao,
             L. Gong, Y. Zhu and R. Pang, "SR Policies Extensions for
             Network Resource Partition in BGP-LS", Work in
             Progress,Internet-Draft, draft-chen-idr-bgp-ls-sr-policy-
             nrp-08,18 May 2024,<https://www.ietf.org/archive/id/draft-
             chen-idr-bgp-ls-sr-policy-nrp-08.txt>.



Acknowledgements

   TBD
















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Authors' Addresses


   Wenying Jiang
   China Mobile
   Beijing
   China
   Email: jiangwenying@chinamobile.com

   Changwang Lin
   New H3C Technologies
   Beijing
   China
   Email: linchangwang.04414@h3c.com

   Ran Chen
   ZTE Corporation
   Email: chen.ran@zte.com.cn


























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