IDR                                                             F. Yang
Internet Draft                                             China Mobile
Intended status: Standards Track                                 C. Lin
Expires: June 30, 2025                             New H3C Technologies
                                                      December 30, 2024



              BGP SR Policy Extensions for Weight Time Range
               draft-yang-idr-sr-policy-weight-timerange-01


Abstract

   Segment Routing is a source routing paradigm that explicitly
   indicates the forwarding path for packets at the ingress node. An SR
   Policy is a set of candidate paths, each consisting of one or more
   segment lists.

   In the scenario where there are multiple segment list paths, traffic
   load balancing can be achieved based on the weight value assigned to
   each path. Typically, the weight value for each path is fixed. This
   document defines an extension of BGP SR Policy for setting the
   weight value for each path based on time range.

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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   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 June 30, 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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. Weight Time Range in SR Policy.................................3
      2.1. Weight Time Range Sub-TLV.................................4
   3. Security Considerations........................................7
   4. IANA Considerations............................................7
   5. References.....................................................7
      5.1. Normative References......................................7
      5.2. Informative References....................................8
   Authors' Addresses................................................9

1. Introduction

   Segment routing (SR) [RFC8402] is a source routing paradigm that
   explicitly indicates the forwarding path for packets at the ingress
   node. The ingress node steers packets into a specific path according
   to the Segment Routing Policy (SR Policy) as defined in [RFC9256].
   In order to distribute SR policies to the headend, [I-D.ietf-idr-sr-
   policy-safi] specifies a mechanism by using BGP.

   In the scenario where there are multiple segment list paths, traffic
   load balancing can be achieved based on the weight value assigned to
   each path. Typically, the weight value for each path is fixed.

   The load on network paths typically exhibits periodic variations
   throughout the day. In order to effectively utilize network
   bandwidth, it is important for the weight parameter in SR Policy-
   based traffic forwarding to be adjustable over time rather than
   remaining constant.

   This document introduces a BGP SR Policy extension to enable the
   setting of forwarding weight values for each path based on time,
   allowing for time-based adjustments of traffic forwarding paths.



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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.

2. Weight Time Range in SR Policy

   As defined in [I-D.ietf-idr-sr-policy-safi], the SR policy encoding
   structure is as follows:

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

   SR policy with Weight Time Range is expressed as below:
















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      SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
      Attributes:
         Tunnel Encaps Attribute (23)
            Tunnel Type: SR Policy
                Binding SID
                SRv6 Binding SID
                Preference
                Priority
                Policy Name
                Policy Candidate Path Name
                Explicit NULL Label Policy (ENLP)
                Segment List
                    Weight Time Range
                    Segment
                    Segment
                    ...
                ...

   The Weight Time Range can be advertised using the Weight Time Range
   sub-TLV, as defined in Section 2.1.

   Within the Segment List sub-TLV, an optional single Weight sub-TLV
   and zero or more Weight Time Range sub-TLVs can be carried. If both
   the Weight Sub-TLV and Weight Time Range Sub-TLV are present, the
   weight value specified in the Weight Time Range sub-TLV takes effect
   during the defined time range. For the remaining time, the weight
   value specified in the Weight Sub-TLV takes effect.

2.1. Weight Time Range Sub-TLV

   The Weight Time Range sub-TLV is used to indicate the Weight Based
   on Time Range of the Segment List.

   The Weight Time Range sub-TLV is optional and it can appear more
   than once inside the Segment List sub-TLV.

   The Weight Time Range 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    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Weight                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | TimeRangeType |             RESERVED                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Start                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             End                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Weight                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | TimeRangeType |             RESERVED                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Start                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             End                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             ...                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   where:

   o Type: TBD.

   o Length: 2 + Weight Number * (one TimeRange Weight Length).

   o Flags: 1 octet of flags. None are defined at this stage. Flags
      SHOULD be set to zero on transmission and MUST be ignored on
      receipt.

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

   o TimeRangeType: 1 octet. Type 1: Absolute Time

                              Type 2: Period Day Time

                              Type 3: Period Week Time

                              Type 4: Perion Month Time


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   o start/end: The format varies depending on the TimeRangeType.
      Please refer to the detailed description below for the specific
      format.



   Absolute Time format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             StartTime                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  StartYear                    |  StartMonth   |   StartDay    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             EndTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  EndYear                      |  EndMonth     |   EndDay      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   StartTime/EndTime: 4 octets.
   hour(1octet)+Minute(1octet)+Second(1octet)+Reserved(1octet)


   Period Day Time format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             StartTime                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             EndTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   StartTime/EndTime: 4 octets.
   hour(1octet)+Minute(1octet)+Second(1octet)+Reserved(1octet)


   Period Week Time format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             StartTime                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  StartDay     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             EndTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  EndDay       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   StartTime/EndTime: 4 octets.
   hour(1octet)+Minute(1octet)+Second(1octet)+Reserved(1octet)
   StartDay/EndDay: 1 octet, 0-6



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   Period Month Time format:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             StartTime                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  StartDay     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             EndTime                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  EndDay       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   StartTime/EndTime: 4 octets.
   hour(1octet)+Minute(1octet)+Second(1octet)+Reserved(1octet)
   StartDay/EndDay: 1 octet, 1-31


3. Security Considerations

   The security requirements and mechanisms described in [I-D.ietf-idr-
   sr-policy-safi] also apply to this document.

   This document does not introduce any new security consideration.

4. IANA Considerations

   This document defines a new Sub-TLV in the registry "SR Policy
   Weight Time Range Sub-TLVs" [I-D.ietf-idr-sr-policy-safi]:

   Value    Description                         Reference
   -------------------------------------------------------
   TBA      Weight Time Range sub-TLV           This document

5. References

5.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, May 2017

   [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>.



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   [I-D.ietf-idr-sr-policy-safi] 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-sr-policy-safi-04, 30 April 2024,
             <https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-
             policy-safi-04>.

5.2. Informative References

   [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>.

   [I-D.ietf-pce-multipath] Koldychev, M., Sivabalan, S., Saad, T.,
             Beeram, V. P., Bidgoli, H., Yadav, B., Peng, S., and G. S.
             Mishra, "PCEP Extensions for Signaling Multipath
             Information", Work in Progress, Internet-Draft, draft-
             ietf-pce-multipath-09, 24 July 2023,
             <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
             multipath-09>.



























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Authors' Addresses

   Feng Yang
   China Mobile
   Beijing
   China
   Email: yangfeng@chinamobile.com


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



































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