Internet DRAFT - draft-dong-idr-sr-policy-nrp

draft-dong-idr-sr-policy-nrp







IDR Working Group                                                J. Dong
Internet-Draft                                                     Z. Hu
Intended status: Standards Track                     Huawei Technologies
Expires: 25 April 2024                                           R. Pang
                                                            China Unicom
                                                         23 October 2023


        BGP SR Policy Extensions for Network Resource Partition
                    draft-dong-idr-sr-policy-nrp-04

Abstract

   Segment Routing (SR) Policy is a set of candidate paths, each
   consisting of one or more segment lists and the associated
   information.  The header of a packet steered in an SR Policy is
   augmented with an ordered list of segments associated with that SR
   Policy.  A Network Resource Partition (NRP) is a subset of network
   resources allocated in the underlay network which can be used to
   support one or a group of RFC XXXX network slice services.

   In networks where there are multiple NRPs, an SR Policy may be
   associated with a particular NRP.  The association between SR Policy
   and NRP needs to be specified, so that for service traffic which is
   steered into the SR Policy, the header of the packets can be
   augmented with the information associated with the NRP.  An SR Policy
   candidate path can be distributed using BGP SR Policy.  This document
   defines the extensions to BGP SR policy to specify the NRP which the
   SR Policy candidate path is associated with.

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
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   This Internet-Draft will expire on 25 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
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  NRP Identifier of SR Policy . . . . . . . . . . . . . . . . .   3
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Scalability Considerations  . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   RFC Editor Note: Please replace "RFC XXXX" in this document with the
   RFC number assigned to [I-D.ietf-teas-ietf-network-slices], and
   remove this note.

   The concept of Segment Routing (SR) policy is defined in [RFC9256].
   An SR Policy is a set of candidate paths, each consisting of one or
   more segment lists.  The head end of an SR Policy may learn multiple
   candidate paths for an SR Policy.  The header of a packet steered in
   an SR Policy is augmented with an ordered list of segments associated
   with that SR Policy.  The BGP extensions to distribute SR Policy
   candidate paths is defined in
   [I-D.ietf-idr-segment-routing-te-policy].

   [I-D.ietf-teas-ietf-network-slices] introduces the concept and the
   characteristics of RFC XXXX network slice, and describes a general
   framework for RFC XXXX network slice management and operation.  It
   also introduces the concept Network Resource Partition (NRP), which



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   is a subset of the resources and associated policies in the underlay
   network.  RFC XXXX network slice can be realized by mapping one or
   more connectivity constructs to an NRP.  [I-D.ietf-teas-enhanced-vpn]
   describes the framework and the candidate component technologies for
   providing enhanced VPN (VPN+) services based on VPN and Traffic
   Engineering (TE) technologies.  Enhanced VPN (VPN+) can be used for
   the realization of RFC XXXX network slices.  In the context of
   network slicing, an NRP is considered as an instantiation of the VTN
   as defined in [I-D.ietf-teas-enhanced-vpn].

   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 where there are multiple NRPs, an SR Policy may be
   associated with a particular NRP.  The association between SR Policy
   and NRP needs to be specified, so that for service traffic which is
   steered into the SR Policy, the header of the packets can be
   augmented with the information associated with the NRP.  An SR Policy
   candidate path can be distributed using BGP SR Policy.  This document
   defines the extensions to BGP SR policy to specify the NRP which the
   SR Policy candidate path is associated with.

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

2.  NRP Identifier of SR Policy

   In order to specify the NRP the candidate path of SR policy is
   associated with, a new sub-TLV called "NRP sub-TLV" is defined in the
   BGP Tunnel Encapsulation Attribute [RFC9012].  The NRP sub-TLV can be
   carried in the BGP Tunnel Encapsulation Attribute with the tunnel
   type set to SR Policy.

   The NRP sub-TLV is optional and MUST NOT appear more than once for
   one SR Policy candidate path.  If the NRP sub-TLV appears more than
   once, the associated BGP SR Policy NLRI is considered malformed and
   the "treat-as-withdraw" strategy of [RFC7606] is applied.

   The NRP sub-TLV has the following format:




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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     |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         NRP ID (4 octets)                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 1. NRP Sub-TLV

   where:

   *  Type: 123

   *  Length: 6

   *  Flags: 1-octet flag field.  None is defined at this stage.  The
      flags SHOULD be set to zero on transmission and MUST be ignored on
      receipt.

   *  RESERVED: 1 octet of reserved bits.  It SHOULD be set to zero on
      transmission and MUST be ignored on receipt.

   *  NRP ID: A 32-bit domain significant identifier which is used to
      identify an NRP.  Value 0 and 0xFFFFFFFF are reserved.

   The encoding structure of BGP SR Policy with the NRP sub-TLV is
   expressed as below:

            SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
            Attributes:
               Tunnel Encaps Attribute (23)
                  Tunnel Type: SR Policy (15)
                      Binding SID
                      SRv6 Binding SID
                      Preference
                      Priority
                      Policy Name
                      Policy Candidate Path Name
                      Explicit NULL Label Policy (ENLP)
                      NRP
                      Segment List
                          Weight
                          Segment
                          Segment
                          ...
                      ...
                Figure 2. SR Policy Encoding with NRP sub-TLV




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3.  Procedures

   When a candidate path of SR Policy is instantiated with a specific
   NRP, the originating node of SR Policy SHOULD include the NRP sub-TLV
   in the BGP Tunnel Encapsulation Attribute of the BGP SR Policy.  The
   setting of other fields and attributes in BGP SR Policy SHOULD follow
   the mechanism as defined in [I-D.ietf-idr-segment-routing-te-policy].

   On reception of an SR Policy NLRI, a BGP speaker determines if it is
   acceptable and usable according to the rules defined in Section 4.2
   of [I-D.ietf-idr-segment-routing-te-policy].  If the SR Policy
   candidate path selected as the best candidate path is associated with
   an NRP, the headend node of the SR Policy SHOULD encapsulate the NRP
   ID and the segment list of the selected candidate path in the header
   of packets which are steered to the SR Policy.  For SR Policy with
   IPv6 data plane, the approach to encapsulate the NRP ID in IPv6 Hop-
   by-Hop Options header is defined in
   [I-D.ietf-6man-enhanced-vpn-vtn-id].  For SR Policy with MPLS data
   plane, one approach to encapsulate the NRP ID to the packet is
   defined in [I-D.li-mpls-enhanced-vpn-vtn-id].

   Although the proposed mechanism allows that different candidate paths
   in one SR policy be associated with different NRPs, in normal network
   scenarios it is considered that the association between an SR Policy
   and NRP is consistent, in such case all candidate paths of one SR
   policy SHOULD be associated with the same NRP.

4.  Scalability Considerations

   The mechanism specified in this document adds additional information
   to the SR Policy candidate paths.  In order to steer traffic into
   different NRPs using SR Policy, the SR Policies used for different
   NRPs need to be different.  As the number of NRP increases, the
   number of SR Policies would also increase accordingly.  When BGP is
   used for distributing SR Policy candidate paths, the amount of
   control plane information exchanged between the network controller
   and the headend nodes would also increase.  However, since the SR
   Policies candidate paths distributed in BGP are only installed by the
   corresponding headend nodes, the impacts to the BGP control plane are
   considered acceptable.

5.  Security Considerations

   The security considerations of BGP [RFC4271] and BGP SR policy
   [I-D.ietf-idr-segment-routing-te-policy] apply to this document.






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6.  IANA Considerations

   IANA has assigned the sub-TLV type as defined in Section 2 from "BGP
   Tunnel Encapsulation Attribute sub-TLVs" registry.

              Value     Description                     Reference
              ----------------------------------------------------
               123        NRP                         This document

7.  Acknowledgments

   The authors would like to thank Guoqi Xu, Lei Bao, Haibo Wang and
   Shunwan Zhuang for their review and discussion of this document.

8.  References

8.1.  Normative References

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
              D. Jain, "Advertising Segment Routing Policies in BGP",
              Work in Progress, Internet-Draft, draft-ietf-idr-segment-
              routing-te-policy-25, 26 September 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              segment-routing-te-policy-25>.

   [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>.

   [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>.




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   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

   [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>.

   [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/info/rfc9012>.

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

8.2.  Informative References

   [I-D.ietf-6man-enhanced-vpn-vtn-id]
              Dong, J., Li, Z., Xie, C., Ma, C., and G. S. Mishra,
              "Carrying Virtual Transport Network (VTN) Information in
              IPv6 Extension Header", Work in Progress, Internet-Draft,
              draft-ietf-6man-enhanced-vpn-vtn-id-05, 6 July 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-6man-
              enhanced-vpn-vtn-id-05>.

   [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>.









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   [I-D.li-mpls-enhanced-vpn-vtn-id]
              Li, Z. and J. Dong, "Carrying Virtual Transport Network
              (VTN) Information in MPLS Packet", Work in Progress,
              Internet-Draft, draft-li-mpls-enhanced-vpn-vtn-id-03, 16
              October 2022, <https://datatracker.ietf.org/doc/html/
              draft-li-mpls-enhanced-vpn-vtn-id-03>.

Authors' Addresses

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


   Zhibo Hu
   Huawei Technologies
   Email: huzhibo@huawei.com


   Ran Pang
   China Unicom
   Email: pangran@chinaunicom.cn





























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