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Versions: 00 01 02                                                      
SPRING                                                         R. Bonica
Internet-Draft                                                   Juniper
Intended status: Informational                                  W. Cheng
Expires: January 9, 2022                                    China Mobile
                                                           D. Dukes, Ed.
                                                           Cisco Systems
                                                           W. Henderickx
                                                                   Nokia
                                                                   C. Li
                                                                  Huawei
                                                               P. Shaofu
                                                                     ZTE
                                                                  C. Xie
                                                           China Telecom
                                                           July 08, 2021


                   Compressed SRv6 SID List Analysis
            draft-srcompdt-spring-compression-analysis-02

Abstract

   Several mechanisms have been proposed to compress the SRv6 SID list.
   This document analyzes each mechanism with regard to the requirements
   stated in the companion requirements document.

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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 9, 2022.

Copyright Notice

   Copyright (c) 2021 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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  SRv6 Compression Requirements . . . . . . . . . . . . . . . .   3
     2.1.  Encapsulation Header Size . . . . . . . . . . . . . . . .   4
       2.1.1.  Reference Scenarios . . . . . . . . . . . . . . . . .   4
     2.2.  Forwarding Efficiency . . . . . . . . . . . . . . . . . .   5
       2.2.1.  Headers Parsed  . . . . . . . . . . . . . . . . . . .   5
       2.2.2.  Lookups Performed (LKU) . . . . . . . . . . . . . . .   7
     2.3.  State Efficiency  . . . . . . . . . . . . . . . . . . . .   8
   3.  SRv6 Specific Requirements  . . . . . . . . . . . . . . . . .  10
     3.1.  SRv6 Based  . . . . . . . . . . . . . . . . . . . . . . .  10
     3.2.  Functional Requirements . . . . . . . . . . . . . . . . .  11
       3.2.1.  SRv6 Functionality  . . . . . . . . . . . . . . . . .  11
       3.2.2.  Heterogeneous SID Lists . . . . . . . . . . . . . . .  14
       3.2.3.  SID List Length . . . . . . . . . . . . . . . . . . .  15
       3.2.4.  SID Summarization . . . . . . . . . . . . . . . . . .  15
     3.3.  Operational Requirements  . . . . . . . . . . . . . . . .  15
       3.3.1.  Lossless Compression  . . . . . . . . . . . . . . . .  16
       3.3.2.  Preservation of non-routing information . . . . . . .  16
       3.3.3.  Address Planning  . . . . . . . . . . . . . . . . . .  16
     3.4.  Scalability Requirements  . . . . . . . . . . . . . . . .  17
       3.4.1.  Compression Levels  . . . . . . . . . . . . . . . . .  18
   4.  Protocol Design Requirements  . . . . . . . . . . . . . . . .  18
     4.1.  SRv6 Base Coexistence . . . . . . . . . . . . . . . . . .  18
   5.  Security Requirements . . . . . . . . . . . . . . . . . . . .  19
     5.1.  Security Mechanisms . . . . . . . . . . . . . . . . . . .  19
     5.2.  SR Domain Protection  . . . . . . . . . . . . . . . . . .  19
   6.  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . .  19
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  21
   Appendix A.  Encapsulation analysis . . . . . . . . . . . . . . .  24
     A.1.  CRH note  . . . . . . . . . . . . . . . . . . . . . . . .  24
     A.2.  Analysis results  . . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  27







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1.  Introduction

   The following mechanisms are proposed to compress the SRv6 SID list:

   o  CSID - [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc] - Describes
      two new SRv6 SID flavors, a combination of SID flavors from
      [I-D.filsfils-spring-net-pgm-extension-srv6-usid] and
      [I-D.cl-spring-generalized-srv6-for-cmpr]
   o  CRH - [I-D.bonica-6man-comp-rtg-hdr] - Requires two new routing
      header types and a label mapping technique.
   o  VSID - [I-D.decraene-spring-srv6-vlsid] - Defines a set of SID
      behaviors to access smaller SIDs within the SR header.
   o  UIDSR - [I-D.mirsky-6man-unified-id-sr] - Extends the SRH to carry
      MPLS labels or IPv6 addresses.

   This document analyzes each mechanism against the requirements stated
   in [I-D.srcompdt-spring-compression-requirement].  Each section of
   this document corresponds to a similarly named section in
   [I-D.srcompdt-spring-compression-requirement].  Each section
   reiterates corresponding requirements and analyzes each proposal
   against the those requirements.

   The terms compression mechanism, compression solution, and
   compression proposal are used interchangeably within this document.

2.  SRv6 Compression Requirements

   An SR domain consisting of 3 sub-domains is shown to illustrate the
   scenarios associated with encapsulation header size, forwarding
   efficiency and state efficiency.

        + * * * * * * * * * * * * * * * * * * * * * * * * * * +
        *                                                     *
        * - - - - - - - - + - - - - - - - - + - - - - - - - - *
        *                 |                 |                 *
        *   [M1_0]      [B5]  [C_0]       [B7]  [M2_0]        *
[H1]--[E3]                |                 |                [E4]---[H2]
        *        [M1_i] [B6]        [C_j] [B8]       [M2_k]   *
        *                 |                 |                 *
        *     Metro 1     |      Core       |     Metro 2     *
        *- - - - - - - - - - - - - - - - - - - - - - - - - - -*
        *                                                     *
        *                      SR domain                      *
        + * * * * * * * * * * * * * * * * * * * * * * * * * * +

                        Figure 1: Sample SR Domain

   o  H1 and H2 are hosts outside the SR domain



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   o  E3 and E4 are SR domain edge routers
   o  Metro 1, Core and Metro 2 are sub-domains with independent IGP
      instances
   o  B5 and B6 are border routers between the Metro 1 and Core
   o  B7 and B8 are border routers between the Metro 2 and Core
   o  M1_1..M1_i are routers in Metro 1
   o  C_1..C_j are routers in Core
   o  M2_1..M2_k are routers in Metro 2
   o  If Metro and Core are different AS's the border routers (B5 to B8)
      may be replaced by pairs of ASBRs
   o  Flexible algorithms may be deployed within each sub-domain

2.1.  Encapsulation Header Size

   The compression proposal MUST reduce the size of the SRv6
   encapsulation header.

   Encapsulation header size is evaluated against a set of reference
   scenarios.

2.1.1.  Reference Scenarios

   A service provider offers a VPN service with underlay optimization in
   the SR domain.

   o  Hosts H1 and H2 are located in two different sites of a VPN
      customer.
   o  Edge nodes E3 and E4 encapsulate/decapsulate traffic between H1
      and H2 to provide the VPN service.
   o  The encapsulation consists of a VPN SID (V) (eg END.DT etc) and an
      SR policy with between 0 and 15 transport segments (T) (eg END or
      END.X)
   o  The SR domain has a block size (B) of 48 bits
   o  These independent variables are used to uniquely identify each
      scenario.  For example

      *  A scenario with 48bit block size, 3 transport segments and a
         VPN segment is named 48B.3T.V

   Proposals are evaluated against the set of scenarios to calculate the
   encapsulation in octets (E) and the encapsulation savings (ES) as a
   fraction of the SRv6 base encapsulation in octets.

   E and ES were evaluated for:

   o  each proposal in two variants

      *  16-bit SID



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      *  32-bit SID
   o  48-bit SRv6 block, 0 to 15 transport segments and a VPN segment
      (expressed in short form as 48B.0-15T.V)

   The average encapsulation savings for each proposal is shown below.
   The complete analysis is recorded in Appendix:

         +-------------+-------+-------+---------+-------+-------+
         | 16-bit SIDs | CSID  | CRH   | CRH+TPF | VSID  | UIDSR |
         +-------------+-------+-------+---------+-------+-------+
         | Average ES  | 54.3% | 54.2% | 50.4%   | 51.6% | 49.2% |
         +-------------+-------+-------+---------+-------+-------+

               Table 1: Average ES, 16-bit SIDs, 48B.0-15T.V

         +-------------+-------+-------+---------+-------+-------+
         | 32-bit SIDs | CSID  | CRH   | CRH+TPF | VSID  | UIDSR |
         +-------------+-------+-------+---------+-------+-------+
         | Average ES  | 42.5% | 45.5% | 43.2%   | 45.5% | 42.5% |
         +-------------+-------+-------+---------+-------+-------+

               Table 2: Average ES, 32-bit SIDs, 48B.0-15T.V

   E and ES are also evaluated for 32bit and 64bit SRv6 block sizes.
   The CSID 16-bit ES averages 57.4% for 32-bit blocks and 49.9% for
   64-bit blocks, other proposals are unchanged.

   Conclusion: All proposals meet the requirement to reduce the size of
   the SRv6 encapsulation header.  Variances between proposals are
   negligible.

2.2.  Forwarding Efficiency

   The compression proposal SHOULD minimize the number of required
   hardware resources accessed to process a segment.

2.2.1.  Headers Parsed

   Forwarding efficiency is calculated against the reference scenarios
   above, recording and summarizing the differences in header parsing
   for different segment lists.

   The following tables indicate the number of headers parsed for each
   proposal.







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       +-------------------+------+------+---------+------+-------+
       | 16-bit            | CSID | CRH  | CRH+TPF | VSID | UIDSR |
       +-------------------+------+------+---------+------+-------+
       | PRS(48B.0T).V)    | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   |      |      |         |      |       |
       | PRS(48B.1-4T).V)  | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   |      | CRH  | CRH     | SRH  | SRH   |
       |                   |      |      |         |      |       |
       | PRS(48B.5-15T).V) | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   | SRH  | CRH  | CRH     | SRH  | SRH   |
       |                   |      |      |         |      |       |
       +-------------------+------+------+---------+------+-------+

     Table 3: Headers parsed on non-decapsulating SR segment endpoint
                      nodes, 16-bit SIDs, 48B.0-15T.V

       +-------------------+------+------+---------+------+-------+
       | 16-bit            | CSID | CRH  | CRH+TPF | VSID | UIDSR |
       +-------------------+------+------+---------+------+-------+
       | PRS(48B.0T).V)    | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   |      |      |         |      |       |
       | PRS(48B.1-4T).V)  | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   |      | CRH  | CRH     | SRH  | SRH   |
       |                   |      |      | TPF     |      |       |
       |                   |      |      |         |      |       |
       | PRS(48B.5-15T).V) | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
       |                   | SRH  | CRH  | CRH     | SRH  | SRH   |
       |                   |      |      | TPF     |      |       |
       +-------------------+------+------+---------+------+-------+

    Table 4: Headers parsed on decapsulating SR segment endpoint nodes,
                         16-bit SIDs, 48B.0-15T.V

        +------------------+------+------+---------+------+-------+
        | 32-bit           | CSID | CRH  | CRH+TPF | VSID | UIDSR |
        +------------------+------+------+---------+------+-------+
        | PRS(48B.0T.V)    | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
        |                  |      |      |         |      |       |
        | PRS(48B.1-15T.V) | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
        |                  | SRH  | CRH  | CRH     | SRH  | SRH   |
        +------------------+------+------+---------+------+-------+

     Table 5: Headers parsed on non-decapsulating SR segment endpoint
                      nodes, 32-bit SIDs, 48B.0-15T.V







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        +------------------+------+------+---------+------+-------+
        | 32-bit           | CSID | CRH  | CRH+TPF | VSID | UIDSR |
        +------------------+------+------+---------+------+-------+
        | PRS(48B.0T.V)    | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
        |                  |      |      |         |      |       |
        | PRS(48B.1-15T.V) | IPv6 | IPv6 | IPv6    | IPv6 | IPv6  |
        |                  | SRH  | CRH  | CRH     | SRH  | SRH   |
        |                  |      |      | TPF     |      |       |
        +------------------+------+------+---------+------+-------+

    Table 6: Headers parsed on decapsulating SR segment endpoint nodes,
                         32-bit SIDs, 48B.0-15T.V

   Conclusion: Overall, the CSID parses the fewest headers.  When per
   packet state is processed per segment, CSID, VSID and UIDSR proposals
   may include it in the routing header, CRH may include it in a
   destination option preceding the CRH.

2.2.2.  Lookups Performed (LKU)

   Some proposals require a different number of lookups per packet,
   depending on the active segment in a segment list.

   An implementation may perform lookups as longest prefix match (LPM)
   or exact match (EM).  CSID, VSID and UIDSR describe SRv6 SID lookup
   from the IPv6 destination address as an LPM, however an
   implementation may use either an LPM or EM lookup for SRv6 SIDs.  CRH
   implementations must always uses an exact match for CRH SID lookups.

   The following table describes the number of lookups per proposal per
   segment type.

       +-----------------+---------+----------+---------+---------+
       |                 | CSID    | CRH      | VSID    | UIDSR   |
       +-----------------+---------+----------+---------+---------+
       | Adjacency and   | LPM (a) | LPM (a)  | LPM (a) | LPM (a) |
       | VPN Segments    |         | EM (b)   |         |         |
       |                 |         | EM (b,c) |         |         |
       |                 |         |          |         |         |
       | Prefix Segments | LPM (a) | LPM (a)  | LPM (a) | LPM (a) |
       |                 | LPM (d) | EM (b)   | LPM (d) | LPM (d) |
       |                 |         |          |         |         |
       +-----------------+---------+----------+---------+---------+

                             Table 7: Lookups

   o  [a] On active SID, appearing in the IPv6 Destination address
   o  [b] On SID in CRH header



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   o  [c] This lookup is required only when the IPv6 next hop node is
      not non-CRH aware
   o  [d] On next SID, appearing in the IPv6 destination address

   Note: [I-D.filsfils-spring-net-pgm-extension-srv6-usid] Section 5
   describes an optional local implementation to reduce CSID 16-bit
   lookups, in some cases, by adding local forwarding state.  The
   analysis of this implementation option is not included in this
   version of the document.

   Conclusion: CSID, VSID, and UIDSR require a single lookup to process
   an adjacency or VPN segment.  CRH always requires 2 lookups for VPN
   segments, and 2 and sometimes 3 lookups for adjacency segments.  All
   proposals require two lookups to process a prefix segment and the
   next segment.

2.3.  State Efficiency

   The compression proposal SHOULD minimize the amount of additional
   forwarding state stored at a node.

   State efficiency is analyzed in a sub-domain of the SR domain, with
   the following parameters:

   o  N: the number of SRv6 nodes in the sub-domain
   o  I: the number of IGP algorithms [I-D.ietf-lsr-flex-algo]
      configured
   o  A: the number of local adjacency SIDs at a node
   o  D: the number of attached SR sub-domains at a border node
   o  V: the number of VPN services at edge nodes

   For a sub-domain consisting of:

   o  1000 SRv6 nodes (N=1000) with some number of non-SRv6 nodes
   o  2 IGP algorithms (I=2)
   o  100 adjacencies per SRv6 node (A=100)
   o  up to 10 attached sub-domains per border node (D=10)
   o  1000 VPN service segments per edge (V=1000)

   The number of forwarding entries at a node is calculated for any
   node, a border node, and an edge node.

   UIDSR, CSID and VSID require the following entries:

   o  a FIB entry for the node's prefix segment (1), per algorithm
      (I=2).
   o  a FIB entry per local adjacency SID (A=100) **Note1
   o  At border nodes (or any SRv6 nodes) either:



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      *  A.1) a FIB entry per domain (D=10) to swap the IPv6 destination
         address prefix.
      *  A.2) no additional FIB entries, and the SR source places a
         128-bit SID in the segment list of a packet if needed.
   o  At edge nodes, a FIB entry per VPN segment (V=1000)

   CRH requires:

   o  a CFIB entry per CRH node per IGP algorithm for local and remote
      prefix segments (N*I=2000)
   o  a CFIB entry per local adjacency segment (A=100) **Note1

      *  When non-CRH adjacent nodes are present, additional state is
         required for CRH as per [I-D.bonica-6man-comp-rtg-hdr]
         Appendix B (note, only the second option in the appendix is
         considered feasible due to state explosion)

         +  B.1) Up to one CFIB entry per next endpoint and an
            additional CFIB entry per adjacency to support non-CRH
            adjacent endpoints, assuming IP flex algo is not implemented
            on non-CRH nodes (I=1) ((N+A)*I=1200).
   o  At border nodes, assuming two inter-domain links per adjacent
      domain for redundancy, additional state is required as per
      [I-D.bonica-6man-comp-rtg-hdr] Appendix B (note, only the second
      option in the appendix is considered feasible due to state
      explosion):

      *  C.1) In a common CRH network topology, the remote sub-domain
         borders support CRH: a CFIB entry per CRH node per IGP
         algorithm for local and remote prefix segments (N*I) plus a
         CFIB entry per local adjacency segment (A) plus a CFIB entry
         per connected remote border router (20) (N*I+A+20=2120).
      *  C.2) In a poorly designed CRH network topology, the remote sub-
         domain borders do not support CRH: a CFIB entry per unique
         endpoint (N*D*I), plus a CFIB entry per local adjacency segment
         (A), assuming IP flex algo is not implemented on non-CRH border
         domain (I=1), plus inter-domain adjacency (20) (N*D*I+2=10120).
   o  At edge nodes, V=1000 entries for SRv6 based VPN SIDs and another
      V=1000 entries for CFIB and TPF VPN SIDs.

   **Note1: there may be additional adjacency SIDs for protected,
   unprotected, and per algorithm adjacencies, resulting in some
   multiple of A.  This is common for all compression proposals.








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    +----------------------+---------+-----------+---------+---------+
    | 16-bit and 32-bit    | CSID    | CRH       | VSID    | UIDSR   |
    +----------------------+---------+-----------+---------+---------+
    | S(N1000,I2,A100,D10) | 102     | 2100      | 102     | 102     |
    |                      | A.1:112 |           | A.1:112 | A.1:112 |
    |                      | A.2:102 |           | A.2:102 | A.2:102 |
    |                      |         | B.1:3300  |         |         |
    |                      |         | C.1:2120  |         |         |
    |                      |         | C.2:10120 |         |         |
    |                      |         |           |         |         |
    | S(V1000)             | 1000    | 2000      | 1000    | 1000    |
    +----------------------+---------+-----------+---------+---------+

                   Table 8: Forwarding State Maintained

   Conclusion: CSID, VSID and UIDSR minimize forwarding state stored at
   a node.  CRH moves per segment state from the packet to the FIB.

3.  SRv6 Specific Requirements

3.1.  SRv6 Based

   A solution to compress SRv6 SID Lists SHOULD be based on the SRv6
   architecture, control plane and data plane.  The compression solution
   MAY be based on a different data plane and control plane, provided
   that it derives sufficient benefit.

   This section records the use of SRv6 standards for compression.























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   +-----------+------+---------------+---------------+----------------+
   |           | CSID | CRH           | VSID          | UIDSR          |
   +-----------+------+---------------+---------------+----------------+
   | U.RFC8402 | Yes  | Yes - update  | Yes           | Yes            |
   |           |      | required for  |               |                |
   |           |      | SRv6 data     |               |                |
   |           |      | plane         |               |                |
   | U.RFC8754 | Yes  | No            | Yes - update  | Yes - update   |
   |           |      |               | required for  | for flags and  |
   |           |      |               | segments left | segments left  |
   | U.PGM     | Yes  | No            | Yes - update  | Yes            |
   |           |      |               | required for  |                |
   |           |      |               | SID behaviors |                |
   | U.IGP     | Yes  | No            | Yes           | Yes -          |
   |           |      |               |               | additional     |
   |           |      |               |               | extensions     |
   | U.BGP     | Yes  | No            | Yes           | Yes            |
   | U.POL     | Yes  | No            | Yes           | Yes            |
   | U.BLS     | Yes  | No            | Yes           | Yes -          |
   |           |      |               |               | additional     |
   |           |      |               |               | extensions     |
   | U.SVC     | Yes  | No            | Yes           | Yes            |
   | U.ALG     | Yes  | Yes - Adds IP | Yes           | Yes            |
   |           |      | flex Algo     |               |                |
   | U.OAM     | Yes  | No            | Yes           | Yes            |
   +-----------+------+---------------+---------------+----------------+

                            Table 9: SRv6 Based

   Conclusion: CSID is SRv6 based, requiring no updates to existing SRv6
   standards, VSID and UIDSR require updates.  CRH is not strictly based
   on SRv6 but is able to provide equivalent functionality.

3.2.  Functional Requirements

3.2.1.  SRv6 Functionality

   A solution to compress an SRv6 SID list MUST support the
   functionality of SRv6.  This requirement ensures no SRv6
   functionality is lost.  It is particularly important to understand
   how a proposal, as evaluated in section "SRv6 Based", provides this
   functionality.

   Functional requirements and the drafts defining how a proposal
   provides the functionality are documented in the table below.






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         +-------------------------------------------------------+
         | Draft reference Abbreviations                         |
         +-------------------------------------------------------+
         | RFC8986: [RFC8986]                                    |
         | SRV6POL: [I-D.ietf-spring-segment-routing-policy]     |
         | SRV6EXT: [I-D.ietf-lsr-isis-srv6-extensions]          |
         | SRV6BGPSVC: [I-D.ietf-bess-srv6-services]             |
         | SRV6BGPLS: [I-D.ietf-idr-bgpls-srv6-ext]              |
         | SRV6SVCP: [I-D.ietf-spring-sr-service-programming]    |
         | SRV6OAM: [I-D.ietf-6man-spring-srv6-oam]              |
         | SRV6FLEXALG: [I-D.ietf-lsr-flex-algo]                 |
         | SRV6TILFA: [I-D.ietf-rtgwg-segment-routing-ti-lfa]    |
         | RFC8402: [RFC8402]                                    |
         | RFC8754: [RFC8754]                                    |
         | CRH: [I-D.bonica-6man-comp-rtg-hdr]                   |
         | VSID: [I-D.decraene-spring-srv6-vlsid]                |
         | UIDSR: [I-D.mirsky-6man-unified-id-sr]                |
         | IPFLEXALG: [I-D.ietf-lsr-ip-flexalgo]                 |
         | CRHEXT: [I-D.bonica-lsr-crh-isis-extensions]          |
         | SRM6BGPSVC: [I-D.ssangli-bess-bgp-vpn-srm6]           |
         | CSID: [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc] |
         +-------------------------------------------------------+

                               Abbreviations

   +--------+-------------+----------------+-------------+-------------+
   |        | CSID        | CRH            | VSID        | UIDSR       |
   +--------+-------------+----------------+-------------+-------------+
   | F.SID  | RFC8402     | CRH            | RFC8402     | RFC8402 1   |
   | F.Scop | RFC8402     | CRH            | RFC8402     | RFC8402 1   |
   | e      |             |                |             |             |
   | F.PFX  | RFC8402,    | CRH            | RFC8402,    | RFC8402,    |
   |        | RFC8986,    |                | RFC8986,    | RFC8986     |
   |        | CSID adds   |                | VSID        | with new    |
   |        | an END SID  |                | updates the | flavor 1    |
   |        | flavor      |                | End         |             |
   |        |             |                | behavior    |             |
   | F.ADJ  | RFC8402,    | CRH            | RFC8402,    | RFC8402,    |
   |        | RFC8986,    |                | RFC8986,    | RFC8986     |
   |        | CSID adds   |                | VSID        | with new    |
   |        | an END.X    |                | updates the | flavor 1    |
   |        | flavor      |                | End.X       |             |
   |        |             |                | behavior    |             |
   | F.BIND | RFC8402,    | CRH            | RFC8402,    | RFC8402,    |
   |        | RFC8986     |                | RFC8986,    | RFC8986     |
   |        |             |                | VSID        | with new    |
   |        |             |                | updates the | flavor 1    |
   |        |             |                | End.B       |             |



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   |        |             |                | behaviors   |             |
   | F.PEER | RFC8402,    | CRH            | RFC8402,    | RFC8402,    |
   |        | RFC8986,    |                | RFC8986,    | RFC8986     |
   |        | CSID adds   |                | VSID        | with new    |
   |        | an END.X.   |                | updates the | flavor 1,2  |
   |        | flavor      |                | End.X       |             |
   |        |             |                | behaviors   |             |
   | F.SVC  | RFC8986     | CRH            | RFC8986,    | RFC8986 1   |
   |        |             |                | VSID        |             |
   |        |             |                | updates the |             |
   |        |             |                | service     |             |
   |        |             |                | segment     |             |
   |        |             |                | behaviors   |             |
   | F.ALG  | SRV6FLEXALG | IPFLEXALG      | SRV6FLEXALG | SRV6FLEXALG |
   | F.TILF | SRV6TILFA   | SRV6TILFA      | SRV6TILFA   | SRV6TILFA 3 |
   | A      |             |                |             |             |
   | F.SEC  | RFC8754     | CRH            | RFC8754     | RFC8754     |
   | F.IGP  | SRV6EXT     | CRH-EXT        | SRV6EXT     | SRV6EXT 1,4 |
   | F.BGP  | SRV6BGPSVC  | SRM6BGPSVC     | SRV6BGPSVC  | SRV6BGPSVC  |
   |        |             |                |             | 1           |
   | F.POL  | SRV6SRPOL   | SRV6SRPOL      | SRV6SRPOL   | SRV6SRPOL   |
   |        |             | update         |             |             |
   |        |             | required       |             |             |
   | F.BLS  | SRV6BGPLS   | (specification | SRV6BGPLS   | SRV6BGPLS 5 |
   |        |             | required)      | and         |             |
   |        |             |                | addition    |             |
   |        |             |                | for VSID    |             |
   |        |             |                | Length      |             |
   | F.SFC  | SRV6SVCP    | CRH            | SRV6SVC     | SRV6SVCP 1  |
   | F.PING | SRV6OAM     | CRH            | SRV6OAM     | SRv6OAM     |
   +--------+-------------+----------------+-------------+-------------+

                       Table 10: SRv6 Functionality

   1.  UIDSR with Global Container SID + local index enhancement
   2.  draft-peng-spring-truncates-sid-inter-domain
   3.  For protections described in section 6.1.2.1, 6.1.2.2, and 6.2,
       to get next-next SID from SRH with the help of draft-pl-spring-
       compr-path-recover.
   4.  Need more extensions to advertise the capability of U-SID
       compression (32bits, 16bits, etc.).  Note: Global Container SID +
       local index enhancement.
   5.  IGP extensions

   Conclusion: CSID supports SRv6 functionality.  CRH VSID and UID
   support SRv6 functionality or equivalent with some new
   specifications.




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3.2.2.  Heterogeneous SID Lists

   The compression proposal SHOULD support a combination of compressed
   and non-compressed segments in a single path.  As an example, a
   solution may satisfy this requirement without being SRv6 based by
   using a binding SID to impose an additional SRv6 header (IPv6 header
   plus optional SRH) with non-compressed SID.

          +-------------------------+------+-----+------+-------+
          |                         | CSID | CRH | VSID | UIDSR |
          +-------------------------+------+-----+------+-------+
          | Heterogeneous SID Lists | Yes  | Yes | Yes  | Yes   |
          +-------------------------+------+-----+------+-------+

                          Heterogeneous SID Lists

   VSID require a binding SID with an additional SRv6 encapsulation to
   encode non-compressed segments in a single path.  VSID changes the
   interpretation of the SRH Segments Left field, which makes it capable
   of carrying only compressed segments.

   The CRH can include a binding SID that imposes a new IPv6 header with
   an SRH.  This is required when the next segment endpoint in the path
   can process the SRH, but not the CRH.  The next segment endpoint or a
   subsequent endpoint can execute decapsulation, removing the new IPv6
   header and exposing the old one with its CRH.  This is required
   because an IPv6 packet can carry only one routing header.

   CSID and UIDSR permit the encoding of, and processing of, any
   combination of compressed or non-compressed segments in a segment
   list of an SRH.

   CSID makes use of the SRH, without modification, to encode CSIDs as
   128 bits, supporting the use of non-compressed segments within the
   SRH.

   UIDSR modifies the interpretation of the SRH Segments Left field at
   segment endpoint nodes to allow variable segment lengths within a
   segment list.

   Conclusion: All proposals support heterogeneous SID lists.  CSID and
   UIDSR support heterogeneous SID lists in the SRH, while CRH and VSID
   require installation of binding SIDs at midpoint nodes.








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3.2.3.  SID List Length

   The compression proposal MUST be able to represent SR paths that
   contain up to 16 segments.

                +-------------+------+-----+------+-------+
                |             | CSID | CRH | VSID | UIDSR |
                +-------------+------+-----+------+-------+
                | 16 Segments | Yes  | Yes | Yes  | Yes   |
                +-------------+------+-----+------+-------+

                              SID List Length

   Conclusion: All proposals support segment lists of at least 16
   segments.

3.2.4.  SID Summarization

   The solution MUST be compatible with segment summarization.

   In inter sub-domain deployments with summarization:

   o  Any node can reach any other node in another sub-domain via a
      prefix segment.
   o  Prefixes are summarized for advertisement between domains.

   Without summarization, border router SIDs must be leaked:

   o  An additional global prefix segment is required for each domain
      border to be traversed.

             +-------------------+------+-----+------+-------+
             |                   | CSID | CRH | VSID | UIDSR |
             +-------------------+------+-----+------+-------+
             | SID Summarization | Yes  | No  | Yes  | Yes   |
             +-------------------+------+-----+------+-------+

                             SID Summarization

   Conclusion: CSID, VSID and UIDSR support segment summarization, CRH
   does not.

3.3.  Operational Requirements








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3.3.1.  Lossless Compression

   A path traversed using a compressed SID list MUST always be the same
   as the path traversed using the uncompressed SID list if no
   compression was applied.

           +----------------------+------+-----+------+-------+
           |                      | CSID | CRH | VSID | UIDSR |
           +----------------------+------+-----+------+-------+
           | Lossless Compression | Yes  | Yes | Yes  | Yes   |
           +----------------------+------+-----+------+-------+

                           Lossless Compression

   Conclusion: All proposals provide lossless compression.

3.3.2.  Preservation of non-routing information

   The compression mechanism MUST NOT cause the loss of non-routing
   information when delivering a packet from the SR ingress node to the
   egress/penultimate SR node

   +-----------------------+----------+----------+----------+----------+
   |                       | CSID     | CRH      | VSID     | UIDSR    |
   +-----------------------+----------+----------+----------+----------+
   | Preserves Non-Routing | Complies | Complies | Complies | Complies |
   | Information           |          |          |          |          |
   +-----------------------+----------+----------+----------+----------+

                  Preservation of non-routing information

   Conclusion: All proposals preserve non-routing information.

3.3.3.  Address Planning

   Description: Network operators require addressing plan flexibility,
   The compression mechanism MUST support flexible IPv6 address
   planning, it MUST support deployment by using GUA from different
   address blocks.

         +---------------------------+------+-----+------+-------+
         |                           | CSID | CRH | VSID | UIDSR |
         +---------------------------+------+-----+------+-------+
         | Flexible Address Planning | Yes  | Yes | Yes  | Yes   |
         +---------------------------+------+-----+------+-------+

                             Address Planning




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   All compression mechanisms provide the encapsulation savings
   described in Tables 1 and 2.  CRH provides these encapsulation
   savings regardless of the IPv6 addressing scheme.  CSID adds a CSID
   container, or one compressed SID (END.X with XPS behavior), for each
   change in locator block in a segment list.  VSID (via XPS behavior)
   and UIDSR add one compressed SID for each change in locator block in
   the segment list.

   The XPS behavior draws the new address block from the control plane.
   At the time of publication, this control plane behavior is undefined.
   Therefore XPS impact on the control plane is not entirely understood.
   While it may be possible to define these mechanisms without impacting
   the control plane, specifications are not yet available.

   Conclusion: All proposals support flexible IPv6 planning.

3.4.  Scalability Requirements

   The compression proposal MUST be capable of representing 65000
   adjacency segments per node.

   The compression proposal MUST be capable of representing 1 million
   prefix segments per SID numbering space.

   The compression proposal MUST be capable of representing 1 million
   services per node.

       +-------------------------------+------+-----+------+-------+
       |                               | CSID | CRH | VSID | UIDSR |
       +-------------------------------+------+-----+------+-------+
       | Adjacency Segment Scale 65000 | Yes  | Yes | Yes  | Yes   |
       | Prefix Segment Scale 1000000  | Yes  | Yes | Yes  | Yes   |
       | Service Scale 1000000         | Yes  | Yes | Yes  | Yes   |
       +-------------------------------+------+-----+------+-------+

                       Table 11: Scale Requirements

   The 32-bit variants of all proposals support this scale of prefix,
   adjacency and services at a node.

   Each proposals 16-bit variant supports a lesser scale.  All proposals
   can encode 2^16 prefix, adjacency and service segments.  However,
   each proposal has various ways of supporting some larger scale per
   node if required.

   CRH 16-bit proposes the encoding of the ultimate segment in a TPF
   destination option instead of the CRH.  This supports 2^32 service
   segments per node.



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   VSID proposes the combination of multiple vSIDs, by copying multiple
   SIDs to a destination address or looking up the next segment in the
   segment list.  This supports more than 2^16 adjacency and service
   segments per node.

   CSID 16-bit variant uses a LIB for adjacency and service segments,
   the LIB allows local definition of SIDs longer than 16-bits when
   needed.  This supports more than 2^16 adjacency and service segments
   per node.

   UIDSR defines a segment type that modifies the value of SRH segments
   left field to support variable segment sizes within the segment list.
   This supports 2^32 adjacency and service segments per node.

   Conclusion: All proposals meet scalability requirements.

3.4.1.  Compression Levels

   The compression proposal SHOULD be able to support multiple levels of
   compression.

        +-----------------------------+------+-----+------+-------+
        |                             | CSID | CRH | VSID | UIDSR |
        +-----------------------------+------+-----+------+-------+
        | Multiple compression Levels | Yes  | Yes | Yes  | Yes   |
        +-----------------------------+------+-----+------+-------+

                            Compression Levels

   Conclusion: All proposals support 16-bit and 32-bit SID variants.

4.  Protocol Design Requirements

4.1.  SRv6 Base Coexistence

   The compression proposal MUST support deployment in SRv6 networks.

           +-----------------------+------+-----+------+-------+
           |                       | CSID | CRH | VSID | UIDSR |
           +-----------------------+------+-----+------+-------+
           | SRv6 Base Coexistence | Yes  | Yes | Yes  | Yes   |
           +-----------------------+------+-----+------+-------+

                           SRv6 Base Coexistence

   Conclusion: All proposals can be deployed simultaneously with the
   SRv6 base solution.




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5.  Security Requirements

5.1.  Security Mechanisms

   The compression solution SHOULD be able to address security issues
   that it introduces, using existing security mechanisms.

            +---------------------+------+-----+------+-------+
            |                     | CSID | CRH | VSID | UIDSR |
            +---------------------+------+-----+------+-------+
            | Security Mechanisms | Yes  | Yes | Yes  | Yes   |
            +---------------------+------+-----+------+-------+

                            Security Mechanisms

   Conclusion: All proposals address security issues they may introduce
   with existing security mechanisms.

5.2.  SR Domain Protection

   A compression solution must not require nodes outside the SR domain
   to know SID values within the SR domain, and it must provide the
   ability to block nodes outside an SR domain from accessing SIDS.

           +----------------------+------+-----+------+-------+
           |                      | CSID | CRH | VSID | UIDSR |
           +----------------------+------+-----+------+-------+
           | SR Domain Protection | Yes  | Yes | Yes  | Yes   |
           +----------------------+------+-----+------+-------+

                           SR Domain Protection

   Conclusion: All proposals protect SIDs within the SR domain.

6.  Conclusions

   Encapsulation Header Size

   o  All proposals meet the requirement to reduce the size of the SRv6
      encapsulation header.  Variances between proposals are negligible.

   Forwarding Efficiency

   o  Overall, the CSID parses the fewest headers.  When per packet
      state is processed per segment, CSID, VSID and UIDSR proposals may
      include it in the routing header, CRH may include it in a
      destination option preceding the CRH.




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   o  CSID, VSID, and UIDSR require a single lookup to process an
      adjacency or VPN segment.  CRH always requires 2 lookups for VPN
      segments, and 2 and sometimes 3 lookups for adjacency segments.
      All proposals require two lookups to process a prefix segment and
      the next segment.

   State Efficiency

   o  CSID, VSID and UIDSR minimize forwarding state stored at a node.
      CRH moves per segment state from the packet to the FIB.

   SRv6 Based

   o  CSID is SRv6 based, requiring no updates to existing SRv6
      standards, VSID and UIDSR require updates.  CRH is not strictly
      based on SRv6 but is able to provide equivalent functionality.

   SRv6 Functionality

   o  CSID supports SRv6 functionality.  CRH VSID and UID support SRv6
      functionality or equivalent with some new specifications.

   Heterogeneous SID lists

   o  All proposals support heterogeneous SID lists.  CSID and UIDSR
      support heterogeneous SID lists in the SRH, while CRH and VSID
      require installation of binding SIDs at midpoint nodes.

   SID List Length

   o  All proposals support segment lists of at least 16 segments.

   SID Summarization

   o  VSID, CSID and UIDSR support segment summarization, CRH does not.

   Operational Requirements

   o  All proposals provide lossless compression.
   o  All proposals preserve non-routing information.
   o  All proposals support flexible IPv6 planning.

   Scalability Requirements

   o  All proposals meet scalability requirements.
   o  All proposals support 16-bit and 32-bit SID variants.

   Protocol Design Requirements



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   o  All proposals can be deployed simultaneously with the SRv6 base
      solution.

   Security Requirements

   o  All proposals address security issues they may introduce with
      existing security mechanisms.
   o  All proposals protect SIDs within the SR domain.

7.  Normative References

   [I-D.bonica-6man-comp-rtg-hdr]
              Bonica, R., Kamite, Y., Alston, A., Henriques, D., and L.
              Jalil, "The IPv6 Compact Routing Header (CRH)", draft-
              bonica-6man-comp-rtg-hdr-24 (work in progress), January
              2021.

   [I-D.bonica-6man-vpn-dest-opt]
              Bonica, R., Kamite, Y., Jalil, L., Zhou, Y., and G. Chen,
              "The IPv6 Tunnel Payload Forwarding (TPF) Option", draft-
              bonica-6man-vpn-dest-opt-15 (work in progress), February
              2021.

   [I-D.bonica-lsr-crh-isis-extensions]
              Kaneriya, P., Shetty, R., Hegde, S., and R. Bonica, "IS-IS
              Extensions To Support The IPv6 Compressed Routing Header
              (CRH)", draft-bonica-lsr-crh-isis-extensions-04 (work in
              progress), March 2021.

   [I-D.cl-spring-generalized-srv6-for-cmpr]
              Cheng, W., Li, Z., Li, C., Clad, F., Liu, A., Xie, C.,
              Liu, Y., and S. Zadok, "Generalized SRv6 Network
              Programming for SRv6 Compression", draft-cl-spring-
              generalized-srv6-for-cmpr-03 (work in progress), April
              2021.

   [I-D.decraene-spring-srv6-vlsid]
              Decraene, B., Raszuk, R., Li, Z., and C. Li, "SRv6 vSID:
              Network Programming extension for variable length SIDs",
              draft-decraene-spring-srv6-vlsid-05 (work in progress),
              February 2021.










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   [I-D.filsfils-spring-net-pgm-extension-srv6-usid]
              Filsfils, C., Garvia, P. C., Cai, D., Voyer, D., Meilik,
              I., Patel, K., Henderickx, W., Jonnalagadda, P., Melman,
              D., Liu, Y., and J. Guichard, "Network Programming
              extension: SRv6 uSID instruction", draft-filsfils-spring-
              net-pgm-extension-srv6-usid-10 (work in progress), March
              2021.

   [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc]
              Cheng, W., Filsfils, C., Li, Z., Cai, D., Voyer, D., Clad,
              F., Zadok, S., Guichard, J. N., and L. Aihua, "Compressed
              SRv6 Segment List Encoding in SRH", draft-filsfilscheng-
              spring-srv6-srh-comp-sl-enc-02 (work in progress),
              November 2020.

   [I-D.ietf-6man-spring-srv6-oam]
              Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
              Chen, "Operations, Administration, and Maintenance (OAM)
              in Segment Routing Networks with IPv6 Data plane (SRv6)",
              draft-ietf-6man-spring-srv6-oam-10 (work in progress),
              April 2021.

   [I-D.ietf-bess-srv6-services]
              Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R.,
              Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based
              Overlay Services", draft-ietf-bess-srv6-services-07 (work
              in progress), April 2021.

   [I-D.ietf-idr-bgpls-srv6-ext]
              Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
              Bernier, D., and B. Decraene, "BGP Link State Extensions
              for SRv6", draft-ietf-idr-bgpls-srv6-ext-07 (work in
              progress), March 2021.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-15 (work in progress), April 2021.

   [I-D.ietf-lsr-ip-flexalgo]
              Britto, W., Hegde, S., Kaneriya, P., Shetty, R., Bonica,
              R., and P. Psenak, "IGP Flexible Algorithms (Flex-
              Algorithm) In IP Networks", draft-ietf-lsr-ip-flexalgo-02
              (work in progress), April 2021.







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   [I-D.ietf-lsr-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extension to Support Segment Routing over
              IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-14
              (work in progress), April 2021.

   [I-D.ietf-rtgwg-segment-routing-ti-lfa]
              Litkowski, S., Bashandy, A., Filsfils, C., Francois, P.,
              Decraene, B., and D. Voyer, "Topology Independent Fast
              Reroute using Segment Routing", draft-ietf-rtgwg-segment-
              routing-ti-lfa-06 (work in progress), February 2021.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-11 (work in progress),
              April 2021.

   [I-D.ietf-spring-sr-service-programming]
              Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C.,
              Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and
              S. Salsano, "Service Programming with Segment Routing",
              draft-ietf-spring-sr-service-programming-04 (work in
              progress), March 2021.

   [I-D.mirsky-6man-unified-id-sr]
              Weiqiang, C., Mirsky, G., Shaofu, P., Aihua, L., and G. S.
              Mishra, "Unified Identifier in IPv6 Segment Routing
              Networks", draft-mirsky-6man-unified-id-sr-09 (work in
              progress), March 2021.

   [I-D.srcompdt-spring-compression-requirement]
              Cheng, W., Xie, C., Bonica, R., Dukes, D., Li, C., Shaofu,
              P., and W. Henderickx, "Compressed SRv6 SID List
              Requirements", draft-srcompdt-spring-compression-
              requirement-06 (work in progress), March 2021.

   [I-D.ssangli-bess-bgp-vpn-srm6]
              Sangli, S. and R. Bonica, "BGP based Virtual Private
              Network (VPN) Services over SRm6 enabled IPv6 networks",
              draft-ssangli-bess-bgp-vpn-srm6-02 (work in progress),
              September 2020.

   [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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   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

   [RFC8986]  Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
              D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
              (SRv6) Network Programming", RFC 8986,
              DOI 10.17487/RFC8986, February 2021,
              <https://www.rfc-editor.org/info/rfc8986>.

Appendix A.  Encapsulation analysis

A.1.  CRH note

   CRH compression efficiency statistics are derived as follows:

   If an SR path contains no transport segments and a VPN segment, the
   SR path is encoded in a single IPv6 header (40 bytes).  The
   destination address in the IPv6 header is a classic SRv6 SID (e.g.,
   END.DT4, END.DT6).

   If the SR path contains T transport segments and a VPN segment, and T
   is greater than 0, the SR path can be encoded:

   o  With an IPv6 Tunnel Payload Function (TPF) Option
      [I-D.bonica-6man-vpn-dest-opt]
   o  Without a TPF Option

   If the SR path is encoded with a TPF Option, the packet includes a
   single IPv6 Header (40 bytes), a CRH (variable length), and a
   Destination Options header (8 bytes).  The destination address in the
   IPv6 header represents the IPv6 address of an interface on the first
   transport segment endpoint.  The CRH must be large enough to contain
   the subsequent T segments.

   If the SR path is encoded without a TPF Option, the packet includes a
   single IPv6 Header (40 bytes) plus a CRH (variable length).  The
   destination address in the IPv6 header represents the IPv6 address of
   an interface on the first transport segment endpoin . The CRH must be
   large enough to contain T+1 segments.  In the CRH, SID[1] maps to the
   IPv6 address of the PE router.  SID[0] maps to a classic SRv6 SID
   (e.g., END.DT4) that is instantiated on the PE router.

   In some deployment scenarios, each encoding strategy yields better
   compression.





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A.2.  Analysis results

   The detailed encapsulation and encapsulation savings per proposal
   with one VPN segment and "T" transport segments:

               +----+------+-----+---------+------+-------+
               | T  | CSID | CRH | CRH+TPF | VSID | UIDSR |
               +----+------+-----+---------+------+-------+
               | 0  | 40   | 40  | 40      | 40   | 40    |
               | 1  | 40   | 48  | 56      | 56   | 64    |
               | 2  | 40   | 56  | 56      | 56   | 64    |
               | 3  | 40   | 56  | 64      | 56   | 64    |
               | 4  | 64   | 56  | 64      | 64   | 64    |
               | 5  | 64   | 56  | 64      | 64   | 64    |
               | 6  | 64   | 64  | 64      | 64   | 64    |
               | 7  | 64   | 64  | 72      | 64   | 64    |
               | 8  | 64   | 64  | 72      | 72   | 64    |
               | 9  | 80   | 64  | 72      | 72   | 80    |
               | 10 | 80   | 72  | 72      | 72   | 80    |
               | 11 | 80   | 72  | 80      | 72   | 80    |
               | 12 | 80   | 72  | 80      | 80   | 80    |
               | 13 | 80   | 72  | 80      | 80   | 80    |
               | 14 | 96   | 80  | 80      | 80   | 80    |
               | 15 | 96   | 80  | 88      | 80   | 80    |
               +----+------+-----+---------+------+-------+

        Table 12: Encapsulation (E) octets, 16bit SIDS, 48B.0-15T.V
























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             +----+-------+-------+---------+-------+-------+
             | T  | CSID  | CRH   | CRH+TPF | VSID  | UIDSR |
             +----+-------+-------+---------+-------+-------+
             | 0  | 0.0%  | 0.0%  | 0.0%    | 0.0%  | 0.0%  |
             | 1  | 37.5% | 25.0% | 12.5%   | 12.5% | 0.0%  |
             | 2  | 50.0% | 30.0% | 30.0%   | 30.0% | 20.0% |
             | 3  | 58.3% | 41.7% | 33.3%   | 41.7% | 33.3% |
             | 4  | 42.9% | 50.0% | 42.9%   | 42.9% | 42.9% |
             | 5  | 50.0% | 56.3% | 50.0%   | 50.0% | 50.0% |
             | 6  | 55.6% | 55.6% | 55.6%   | 55.6% | 55.6% |
             | 7  | 60.0% | 60.0% | 55.0%   | 60.0% | 60.0% |
             | 8  | 63.6% | 63.6% | 59.1%   | 59.1% | 63.6% |
             | 9  | 58.3% | 66.7% | 62.5%   | 62.5% | 58.3% |
             | 10 | 61.5% | 65.4% | 65.4%   | 65.4% | 61.5% |
             | 11 | 64.3% | 67.9% | 64.3%   | 67.9% | 64.3% |
             | 12 | 66.7% | 70.0% | 66.7%   | 66.7% | 66.7% |
             | 13 | 68.8% | 71.9% | 68.8%   | 68.8% | 68.8% |
             | 14 | 64.7% | 70.6% | 70.6%   | 70.6% | 70.6% |
             | 15 | 66.7% | 72.2% | 69.4%   | 72.2% | 72.2% |
             +----+-------+-------+---------+-------+-------+

       Table 13: Encapsulation Savings (ES), 16bit SIDS, 48B.0-15T.V

               +----+------+-----+---------+------+-------+
               | T  | CSID | CRH | CRH+TPF | VSID | UIDSR |
               +----+------+-----+---------+------+-------+
               | 0  | 40   | 40  | 40      | 40   | 40    |
               | 1  | 64   | 56  | 56      | 56   | 64    |
               | 2  | 64   | 56  | 64      | 56   | 64    |
               | 3  | 64   | 64  | 64      | 64   | 64    |
               | 4  | 64   | 64  | 72      | 64   | 64    |
               | 5  | 80   | 72  | 72      | 72   | 80    |
               | 6  | 80   | 72  | 80      | 72   | 80    |
               | 7  | 80   | 80  | 80      | 80   | 80    |
               | 8  | 80   | 80  | 88      | 80   | 80    |
               | 9  | 96   | 88  | 88      | 88   | 96    |
               | 10 | 96   | 88  | 96      | 88   | 96    |
               | 11 | 96   | 96  | 96      | 96   | 96    |
               | 12 | 96   | 96  | 104     | 96   | 96    |
               | 13 | 112  | 104 | 104     | 104  | 112   |
               | 14 | 112  | 104 | 112     | 104  | 112   |
               | 15 | 112  | 112 | 112     | 112  | 112   |
               +----+------+-----+---------+------+-------+

        Table 14: Encapsulation (E) octets, 32bit SIDS, 48B.0-15T.V






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             +----+-------+-------+---------+-------+-------+
             | T  | CSID  | CRH   | CRH+TPF | VSID  | UIDSR |
             +----+-------+-------+---------+-------+-------+
             | 0  | 0.0%  | 0.0%  | 0.0%    | 0.0%  | 0.0%  |
             | 1  | 0.0%  | 12.5% | 12.5%   | 12.5% | 0.0%  |
             | 2  | 20.0% | 30.0% | 20.0%   | 30.0% | 20.0% |
             | 3  | 33.3% | 33.3% | 33.3%   | 33.3% | 33.3% |
             | 4  | 42.9% | 42.9% | 35.7%   | 42.9% | 42.9% |
             | 5  | 37.5% | 43.8% | 43.8%   | 43.8% | 37.5% |
             | 6  | 44.4% | 50.0% | 44.4%   | 50.0% | 44.4% |
             | 7  | 50.0% | 50.0% | 50.0%   | 50.0% | 50.0% |
             | 8  | 54.5% | 54.5% | 50.0%   | 54.5% | 54.5% |
             | 9  | 50.0% | 54.2% | 54.2%   | 54.2% | 50.0% |
             | 10 | 53.8% | 57.7% | 53.8%   | 57.7% | 53.8% |
             | 11 | 57.1% | 57.1% | 57.1%   | 57.1% | 57.1% |
             | 12 | 60.0% | 60.0% | 56.7%   | 60.0% | 60.0% |
             | 13 | 56.3% | 59.4% | 59.4%   | 59.4% | 56.3% |
             | 14 | 58.8% | 61.8% | 58.8%   | 61.8% | 58.8% |
             | 15 | 61.1% | 61.1% | 61.1%   | 61.1% | 61.1% |
             +----+-------+-------+---------+-------+-------+

       Table 15: Encapsulation Savings (ES), 32bit SIDS, 48B.0-15T.V

Authors' Addresses

   Ron Bonica
   Juniper

   Email: rbonica@juniper.net


   Weiqiang Cheng
   China Mobile

   Email: chengweiqiang@chinamobile.com


   Darren Dukes (editor)
   Cisco Systems

   Email: ddukes@cisco.com


   Wim Henderickx
   Nokia

   Email: wim.henderickx@nokia.com




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Internet-Draft             SRCOMP Requirements                 July 2021


   Cheng Li
   Huawei

   Email: c.l@huawei.com


   Peng Shaofu
   ZTE

   Email: peng.shaofu@zte.com.cn


   Chongfeng Xie
   China Telecom

   Email: xiechf@chinatelecom.cn



































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