Network Programming extension: SRv6 uSID instruction
draft-filsfils-spring-net-pgm-extension-srv6-usid-08

The information below is for an old version of the document
Document Type Active Internet-Draft (individual)
Authors Clarence Filsfils  , Pablo Camarillo  , Dezhong Cai  , Dani Voyer  , Israel Meilik  , Keyur Patel  , Wim Henderickx  , Prem Jonnalagadda  , David Melman  , Yisong Liu  , Jim Guichard 
Last updated 2020-11-02 (latest revision 2020-05-19)
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SPRING                                                  C. Filsfils, Ed.
Internet-Draft                                         P. Camarillo, Ed.
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: May 6, 2021                                              D. Cai
                                                                 Alibaba
                                                                D. Voyer
                                                             Bell Canada
                                                               I. Meilik
                                                                Broadcom
                                                                K. Patel
                                                            Arrcus, Inc.
                                                           W. Henderickx
                                                                   Nokia
                                                         P. Jonnalagadda
                                                       Barefoot Networks
                                                               D. Melman
                                                                 Marvell
                                                                  Y. Liu
                                                            China Mobile
                                                             J. Guichard
                                                               Futurewei
                                                        November 2, 2020

          Network Programming extension: SRv6 uSID instruction
          draft-filsfils-spring-net-pgm-extension-srv6-usid-08

Abstract

   The SRv6 "micro segment" (SRv6 uSID or uSID for short) instruction is
   a straightforward extension of the SRv6 Network Programming model:

   o  The SRv6 Control Plane is leveraged without any change

   o  The SRH dataplane encapsulation is leveraged without any change

   o  Any SID in the SID list can carry micro segments

   o  Based on the Compressed SRv6 Segment List Encoding in SRH
      [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc] framework

   This enables:

   o  ultra-scale (e.g. multi-domain 5G deployments)

   o  minimum MTU overhead

   o  installed-base reuse

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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.

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

   This Internet-Draft will expire on May 6, 2021.

Copyright Notice

   Copyright (c) 2020 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  uSID Allocation within a uSID Block . . . . . . . . . . . . .   6
     3.1.  GIB, LIB, global uSID and local uSID  . . . . . . . . . .   6
       3.1.1.  Global uSID . . . . . . . . . . . . . . . . . . . . .   6
       3.1.2.  Local uSID  . . . . . . . . . . . . . . . . . . . . .   6

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       3.1.3.  Reference Illustration  . . . . . . . . . . . . . . .   6
   4.  SRv6 behaviors associated with a uSID . . . . . . . . . . . .   8
     4.1.  uSID behaviors related to the IGP . . . . . . . . . . . .   8
       4.1.1.  uN  . . . . . . . . . . . . . . . . . . . . . . . . .   8
       4.1.2.  uA  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.2.  uSID Behaviors related to BGP . . . . . . . . . . . . . .  10
       4.2.1.  uDT . . . . . . . . . . . . . . . . . . . . . . . . .  10
       4.2.2.  uDX . . . . . . . . . . . . . . . . . . . . . . . . .  10
   5.  FIB entry at originating node for performant support of
       global-local sequence . . . . . . . . . . . . . . . . . . . .  11
   6.  Routing . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
   8.  Running code  . . . . . . . . . . . . . . . . . . . . . . . .  14
   9.  Security  . . . . . . . . . . . . . . . . . . . . . . . . . .  14
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   12. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  15
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  19
     13.2.  Informative References . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

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1.  Introduction

   SRv6 Network Programming [I-D.ietf-spring-srv6-network-programming]
   defines a mechanism to build a network program with topological and
   service segments.  It leverages the SRH [RFC8754] to encode a network
   program together with optional metadata shared among the different
   SIDs.

   This draft extends SRv6 Network Programming with a new type of SRv6
   SID behaviors: SRv6 uN, uA, uDT, uDX.

   This extension fully leverages the SRv6 network programming solution:

   o  The SRv6 Control Plane is leveraged without any change

   o  The SRH dataplane encapsulation is leveraged without any change

   o  Any SID in the SID list can carry micro segments

   o  Based on the Compressed SRv6 Segment List Encoding in SRH
      [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc] framework

   This enables:

   o  ultra-scale (e.g. multi-domain 5G deployments)

   o  minimum MTU overhead

   o  installed-base reuse

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2.  Terminology

   The SRv6 Network Programming, SRH and Compressed SRv6 Segment List
   Encoding in SRH terminology is leveraged and extended with the
   following terms:

   +-----------+-------------------------------------------------------+
   | Term      | Definition                                            |
   +-----------+-------------------------------------------------------+
   | uSID      | A block of uSID's. It can be any IPv6 prefix          |
   | block     | available to the provider.                            |
   +-----------+-------------------------------------------------------+
   | uSID      | A Compressed-SID. In this document a 16-bit ID. A     |
   |           | different uSID length may be used.                    |
   +-----------+-------------------------------------------------------+
   | Active    | First uSID after the uSID block.                      |
   | uSID      |                                                       |
   +-----------+-------------------------------------------------------+
   | Next uSID | Next uSID after the Active uSID.                      |
   +-----------+-------------------------------------------------------+
   | Last uSID | From left to right, the last uSID before the first    |
   |           | End-of-Container uSID.                                |
   +-----------+-------------------------------------------------------+
   | End-of-   | Reserved uSID used to mark the end of a uSID          |
   | Container | container. The value 0000 is selected as End-of-      |
   |           | Container. All of the empty uSID container positions  |
   |           | must be filled with the End-of-Container ID. Hence,   |
   |           | the End-of-Container can be present more than once in |
   |           | a uSID container.                                     |
   +-----------+-------------------------------------------------------+
   | uSID      | A CSID container. A 128bit SRv6 SID of format         |
   | container | <uSID-Block><Active-uSID><Next-uSID>...<Last-         |
   |           | uSID><End-of-Container>...<End-of-Container>.         |
   |           | A uSID container can be encoded in the Destination    |
   |           | Address of an IPv6 header or at any position in the   |
   |           | Segment List of an SRH.                               |
   +-----------+-------------------------------------------------------+

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3.  uSID Allocation within a uSID Block

3.1.  GIB, LIB, global uSID and local uSID

   GIB: The set of IDs available for global uSID allocation.

   LIB: The set of IDs available for local uSID allocation.

3.1.1.  Global uSID

   A uSID from the GIB.

   A Global uSID typically identifies a shortest-path to a node in the
   SR domain.  An IP route (e.g., /64) is advertised by the parent node
   to each of its global uSID's, under the associated uSID block.  The
   parent node executes a variant of the END behavior.

   A node can have multiple global uSID's under the same uSID blocks
   (e.g. one per IGP flex-algorithm).  Multiple nodes may share the same
   global uSID (anycast).

3.1.2.  Local uSID

   A uSID from the LIB.

   A local uSID may identify a cross-connect to a direct neighbor over a
   specific interface or a VPN context.

   No IP route is advertised by a parent node for its local uSID'.

   If N1 and N2 are two different physical nodes of the uSID domain and
   I is a local uSID value, then N1 and N2 may bind two different
   behaviors to I.

3.1.3.  Reference Illustration

   For illustration simplicity, we will use:

   o  uSID block length: 48 bits

   o  uSID block: 2001:db8:0::/48

   o  uSID length: 16 bits

   o  uSID: 2001:db8:0:XYZW::/64

   o  GIB: nibble X from hexa(0) to hexa(D)

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   o  LIB: nibble X hexa(E) or hexa(F)

   Leveraging our reference illustration,

   o  A uSID 2001:db8:0:XYZW::/64 is said to be allocated from its block
      (2001:db8:0::/48).

   o  More specifically, a uSID is allocated from the GIB or LIB of
      block 2001:db8:0::/48 depending on the value of the "X" nibble:
      0-D for GIB, and E-F for LIB.

   o  With the above allocation scheme, the uSID Block 2001:db8:0::/48
      supports up to 57k global uSID's (e.g. routers) while each router
      would support up to 8k local uSID's.

   Another illustration could assume a 32-bit uSID length and a LIB
   restricted to the uSIDs with the first byte set to FF.  In this
   context, the network as a whole would support 2^32-2^24 global uSID's
   (e.g. routers) while each router would support up to 2^24 local
   uSID's.

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4.  SRv6 behaviors associated with a uSID

   The SRv6 SRH encapsulation and its network programming model are
   extended with the following functions:

4.1.  uSID behaviors related to the IGP

4.1.1.  uN

   The uN is a short notation for the End behavior with NEXT-CSID, PSP
   and USD flavors as defined in
   [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc].

   As a reminder the pseudo-code of the End behavior with NEXT-CSID
   flavor, when applied to a 48b uSID block and a 16b uSID length is as
   follows:

   2001:db8:0:0N00::/64 bound to the pseudocode shift-and-lookup:
       1.   Copy DA[64..127] into DA[48..111]                  ;; Ref1
       2.   Set DA[112..127] to 0x0000
       3.   Forward the packet to the new DA

   2001:db8:0:0N00::/80 bound to the End behavior with PSP & USD flavors

   Ref 1: DA[X..Y] refers to the bits from position X to Y (included) in
   the IPv6 Destination Address of the received packet.  The bit 0 is
   the MSB, while the bit 127 is the LSB.

4.1.1.1.  Control-plane representation

   In ISIS [I-D.ietf-lsr-isis-srv6-extensions], a uN is advertised with
   the following information:

   o  Value = 2001:db8:0:0N00::

   o  Behavior = uN

   o  Structure =

      *  LBL = 48

      *  LNL = 16

      *  FL = 0

      *  AL = 64

   o  Algorithm = 0 (or other)

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4.1.2.  uA

   The uA local behavior is a short notation for the End.X behavior with
   NEXT-CSID, PSP and USD flavors
   [I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc].

   An instance of the uA SRv6 uSID behavior is associated with a set, J,
   of one or more Layer-3 adjacencies.

   As a reminder the pseudo-code of the End.X behavior with NEXT-CSID
   flavor, when applied to a 48b uSID block and a 16b uSID length is as
   follows:

   2001:db8:0:FNAJ::/64 bound to the pseudocode shift-and-xconnect:
       1.   Copy DA[64..127] into DA[48..111]                  ;; Ref1
       2.   Set DA[112..127] to 0x0000
       3.   Forward to layer-3 adjacency J

   2001:db8:0:FNAJ::/80 bound to the End.X behavior w PSP & USD flavors

   Ref 1: DA[X..Y] refers to the bits from position X to Y (included) in
   the IPv6 Destination Address of the received packet.  The bit 0 is
   the MSB, while the bit 127 is the LSB.

4.1.2.1.  Control-plane representation

   In ISIS [I-D.ietf-lsr-isis-srv6-extensions], a uA is advertised with
   the following information:

   o  Value = 2001:db8:0:0N00:FNAJ::

   o  Behavior = uA

   o  Structure =

      *  LBL = 48

      *  LNL = 16

      *  FL = 16

      *  AL = 48

   o  Algorithm = 0 (or other)

   Note: From a formal viewpoint, a uA SID of node N is defined by the
   local FIB entry B:uA/64 of N (i.e. this definition is independent
   from any uN SID of node N).  In order to signal in ISIS a container

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   SID with the same routable semantics as End.X, the ISIS advertisement
   of a uA SID is done as uN+uA. uN provides the global route to the
   node like the End behavior. uA provides the cross-connect function
   like the "X" of the End.X.

4.2.  uSID Behaviors related to BGP

4.2.1.  uDT

   A local uDT behavior of Node D 2001:db8:0:FNVT:: is defined by the
   following single FIB entry and pseudo-code:

   2001:db8:0:FNVT::/80 bound to the same pseudocode as End.DT4/End.DT6/
   End.DT2*

4.2.1.1.  Control-plane representation

   In BGP [I-D.ietf-bess-srv6-services], a uDT is advertised with the
   following information:

   o  Value = 2001:db8:0:0N00:FNVT::

   o  Behavior = uDT

   o  Structure =

      *  LBL = 48

      *  LNL = 16

      *  FL = 16

      *  AL = 0

      *  TL = 16

      *  TO = 64

   o  Algorithm = 0 (or other)

   Note: the advertised SID value includes the uN SRv6 uSID of the
   parent.

4.2.2.  uDX

   A local uDX behavior of Node D 2001:db8:0:FNXJ:: is defined by the
   following single FIB entry and pseudo-code:

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   2001:db8:0:FNXJ::/80 bound to the same pseudocode as End.DX4/End.DX6/
   End.DX2

4.2.2.1.  Control-plane representation

   In BGP [I-D.ietf-bess-srv6-services], a uDX is advertised with the
   following information:

   o  Value = 2001:db8:0:0N00:FNXJ::

   o  Behavior = uDX

   o  Structure =

      *  LBL = 48

      *  LNL = 16

      *  FL = 16

      *  AL = 0

      *  TL = 16

      *  TO = 64

   o  Algorithm = 0 (or other)

   Note: the advertised SID value includes the uN SRv6 uSID of the
   parent.

5.  FIB entry at originating node for performant support of global-local
    sequence

   Any originating parent node may install the sequence of <Global,
   Local> uSID to perform more efficient processing given the LPM
   lookup.

   For example, a parent node N that has the following FIB entries:

   o  2001:db8:0:0N00::/64 bound to the pseudocode shift-and-lookup

   o  2001:db8:0:0N00:0000::/80 bound to the End behavior with PSP&USD
      flavors

   o  2001:db8:0:FNAJ::/64 bound to the pseudocode shift-and-xconnect

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   o  2001:db8:0:FNAJ:0000:/80 bound to the End.X behavior with PSP&USD
      flavors

   may install the following additional FIB entries:

   o  2001:db8:0:0N00:FNAJ::/80 bound to the pseudocode shift-and-
      xconnect (with 32b shifting)

   o  2001:db8:0:0N00:FNAJ:0000::/96 bound to the End.X behavior with
      PSP&USD flavors

6.  Routing

   If Node 1 is configured with a uN SID 2001:db8:0:0100::/64 then the
   operator must ensure that Node 1 advertises 2001:db8:0:0100::/64 in
   the routing protocol.

7.  Benefits

   o  Leverages SRv6 Network Programming with NO change

      *  SRv6 uSID is a flavor of the SRv6 network programming model

   o  Leverages SRv6 dataplane (SRH) with NO change

      *  Any SID in DA or SRH can be an SRv6 uSID container

   o  Leverages SRv6 Control-Plane with NO change

   o  Ultra-Scale

      *  6 uSID's per uSID container

      *  18 source routing waypoints in only 40bytes of overhead

         +  H.Encaps.Red with an SRH of 40 bytes (8 fixed + 2 * 16
            bytes)

         +  6 uSID's in DA and 12 in SRH

   o  Lowest MTU overhead

      *  In apple to apple comparison, the SRv6 solution outperforms any
         alternative (VxLAN with SR-MPLS, CRH).

   o  Scalable number of globally unique nodes in the domain

      *  16-bit uSID: 65k uSIDs per domain block

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      *  32-bit uSID: 4.3M uSIDs per domain block

   o  Proven Hardware-friendliness

      *  Leverages mature hardware capabilities (Inline DA edit, DA
         longest match)

      *  Avoids any extra lookup in indexed mapping table

      *  Demonstrated by the number of linerate interoperable hardware
         implementations at the first Interop report in February 2020,
         less than 9 months after the first public version of this
         document.

      *  Public operator report of leverage of installed base

      *  A micro-program which requires less than 6 uSID's only requires
         legacy IPinIP encapsulation behavior

   o  Scalable Control-Plane

      *  No indexed mapping table is required

      *  Summarization at area/domain boundary provides massive scaling
         advantage

      *  No routing extension is required: a simple prefix advertisement
         suffices

   o  Seamless Deployment

      *  A uSID may be used as a SID: i.e. the container holds a single
         uSID

      *  The inner structure of an SR Policy can stay opaque to the
         source: i.e. a container with uSID's is just seen as a SID by
         the policy headend

   o  Security

      *  Leverages SRv6's native SR domain security

   o  Large-Scale DC

      *  SID's may be used to address applications on hosts (scale in
         2^128)

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      *  Hardware friendliness of uSID's may be used to specify billions
         of waypoints in cost/power-optimized DC fabric

8.  Running code

   The hardware and software platforms listed below have demonstrated
   support for the uN instruction defined in this document.

   Further on, all these implementations have participated in a joint
   interoperability testing [NANOG78].

   Hardware implementations (in alphabetical order):

   o  Arrcus ArcOS (based on Broadcom Jericho2)

   o  Barefoot Tofino P4-programmable Ethernet switch ASIC

   o  Cisco 8000 Series Routers (based on Cisco Silicon One Q100)

   o  Cisco ASR9000 platform (with 3rd gen Tomahawk and 4th gen
      Lightspeed line-cards)

   o  Cisco NCS5500 platform (based on Broadcom Jericho/Jericho+)

   o  Marvell Prestera Packet Processor

   Software open-source implementations (in alphabetical order):

   o  FD.io VPP

   o  Linux Kernel

9.  Security

   The security rules defined in Section 7 of
   [I-D.ietf-spring-srv6-network-programming], protect intra-domain
   deployments that includes SRv6 uSID.

10.  IANA Considerations

   This document requests IANA to allocate the following codepoints
   within the "SRv6 Endpoint Behaviors" sub-registry under the top-level
   "Segment Routing Parameters" registry.

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        +-------+--------+----------------------------+-----------+
        | Value |  Hex   |     Endpoint behavior      | Reference |
        +-------+--------+----------------------------+-----------+
        | 42    | 0x002A |             uN             | [This.ID] |
        | 43    | 0x002B |        uN (S&L+End)        | [This.ID] |
        | 44    | 0x002C |      uN (S&L+End PSP)      | [This.ID] |
        | 45    | 0x002D |      uN (S&L+End USP)      | [This.ID] |
        | 46    | 0x002E |    uN (S&L+End PSP/USP)    | [This.ID] |
        | 47    | 0x002F |      uN (S&L+End USD)      | [This.ID] |
        | 48    | 0x0030 |    uN (S&L+End PSP/USD)    | [This.ID] |
        | 49    | 0x0031 |    uN (S&L+End USP/USD)    | [This.ID] |
        | 50    | 0x0032 |  uN (S&L+End PSP/USP/USD)  | [This.ID] |
        | 51    | 0x0033 |             uA             | [This.ID] |
        | 52    | 0x0034 |       uA (S&X+End.X)       | [This.ID] |
        | 53    | 0x0035 |     uA (S&X+End.X PSP)     | [This.ID] |
        | 54    | 0x0036 |     uA (S&X+End.X USP)     | [This.ID] |
        | 55    | 0x0037 |   uA (S&X+End.X PSP/USP)   | [This.ID] |
        | 56    | 0x0038 |     uA (S&X+End.X USD)     | [This.ID] |
        | 57    | 0x0039 |   uA (S&X+End.X PSP/USD)   | [This.ID] |
        | 58    | 0x003A |   uA (S&X+End.X USP/USD)   | [This.ID] |
        | 59    | 0x003B | uA (S&X+End.X PSP/USP/USD) | [This.ID] |
        | 60    | 0x003C |            uDX6            | [This.ID] |
        | 61    | 0x003D |            uDX4            | [This.ID] |
        | 62    | 0x003E |            uDT6            | [This.ID] |
        | 63    | 0x003F |            uDT4            | [This.ID] |
        | 64    | 0x0040 |           uDT46            | [This.ID] |
        | 65    | 0x0041 |            uDX2            | [This.ID] |
        +-------+--------+----------------------------+-----------+

                  Table 1: IETF - SRv6 Endpoint Behaviors

11.  Acknowledgements

   The authors would like to acknowledge Francois Clad, Peter Psenak,
   Ketan Talaulikar, Jakub Horn, Swadesh Agrawal, Zafar Ali, Darren
   Dukes, Kiran Sasidharan, Junaid Israr, Lakshmanan Srikanth, Asif
   Islam, Saleem Hafeez, Michael MacKenzie, Sushek Shekar, YuanChao Su,
   Alexander Preusche, Alberto Donzelli, Miya Kohno, David Smith, Ianik
   Semco, Bertrand Duvivier, Frederic Trate, Kris Michielsen, Eyal
   Dagan, Eli Stein, Ofer Iny, Elad Naor, Guy Caspari, Mel Tsai, Anand
   Sridharan, Aviad Behar, Joseph Chin.

12.  Contributors

   Jisu Bhattacharyaa
   Cisco Systems, Inc.
   United States of America

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   Email: jisu@cisco.com

   Kamran Raza
   Cisco Systems, Inc.
   Canada

   Email: skraza@cisco.com

   John Bettink
   Cisco Systems, Inc.
   United States of America

   Email: jbettink@cisco.com

   Tomonobu Niwa
   KDDI
   Japan

   Email: to-niwa@kddi.com

   Luay Jalil
   Verizon
   United States of America

   Email: luay.jalil@one.verizon.com

   Zhichun Jiang
   Tencent
   China

   Email: zcjiang@tencent.com

   Ahmed Shawky
   Saudi Telecom Company
   Saudi Arabia

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   Email: ashawky@stc.com.sa

   Nic Leymann
   Deutsche Telekom
   Germany

   Email: N.Leymann@telekom.de

   Dirk Steinberg
   Lapishills Consulting Limited
   Cyprus

   Email: dirk@lapishills.com

   Shawn Zandi
   LinkedIn
   United States of America

   Email: szandi@linkedin.com

   Gaurav Dawra
   LinkedIn
   United States of America

   Email: gdawra@linkedin.com

   Jim Uttaro
   AT&T
   United States of America

   Email: ju1738@att.com

   Ning So
   Reliance
   United States of America

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   Email: Ning.So@ril.com

   Michael Fiumano
   Sprint
   United States of America

   Email: michael.f.fiumano@sprint.com

   Mazen Khaddam
   Cox
   United States of America

   Email: Mazen.Khaddam@cox.com

   Jichun Ma
   China Unicom
   China

   Email: majc16@chinaunicom.cn

   Satoru Matsushima
   Softbank
   Japan

   Email: satoru.matsushima@g.softbank.co.jp

   Francis Ferguson
   CenturyLink
   United States of America

   Email: Francis.Ferguson@centurylink.com

   Takuya Miyasaka
   KDDI
   Japan

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   Email: ta-miyasaka@kddi.com

   Kentaro Ebisawa
   Toyota Motor Corporation
   Japan

   Email: ebisawa@toyota-tokyo.tech

   Yukito Ueno
   NTT Communications Corporation
   Japan

   Email: yukito.ueno@ntt.com

13.  References

13.1.  Normative References

   [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., and L. Aihua, "Compressed
              SRv6 Segment List Encoding in SRH", draft-filsfilscheng-
              spring-srv6-srh-comp-sl-enc-01 (work in progress), May
              2020.

   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-24 (work in
              progress), October 2020.

   [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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   [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>.

13.2.  Informative References

   [I-D.ietf-bess-srv6-services]
              Dawra, G., Filsfils, C., Raszuk, R., Decraene, B., Zhuang,
              S., and J. Rabadan, "SRv6 BGP based Overlay services",
              draft-ietf-bess-srv6-services-04 (work in progress), July
              2020.

   [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-11
              (work in progress), October 2020.

   [NANOG78]  Filsfils, C., "SRv6 Technology and Deployment Use-cases",
              NANOG78 , February 2020, <https://storage.googleapis.com/
              site-media-prod/meetings/NANOG78/2097/20200212_Mcdougall_S
              rv6_Technology_And_v1.pdf>.

Authors' Addresses

   Clarence Filsfils (editor)
   Cisco Systems, Inc.
   Belgium

   Email: cf@cisco.com

   Pablo Camarillo Garvia (editor)
   Cisco Systems, Inc.
   Spain

   Email: pcamaril@cisco.com

   Dennis Cai
   Alibaba
   China

   Email: d.cai@alibaba-inc.com

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   Daniel Voyer
   Bell Canada
   Canada

   Email: daniel.voyer@bell.ca

   Israel Meilik
   Broadcom
   Israel

   Email: israel.meilik@broadcom.com

   Keyur Patel
   Arrcus, Inc.
   United States of America

   Email: keyur@arrcus.com

   Wim Henderickx
   Nokia
   Belgium

   Email: wim.henderickx@nokia.com

   Prem Jonnalagadda
   Barefoot Networks
   United States of America

   Email: prem@barefootnetworks.com

   David Melman
   Marvell
   Israel

   Email: davidme@marvell.com

   Yisong Liu
   China Mobile
   China

   Email: liuyisong@chinamobile.com

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   James Guichard
   Futurewei
   United States of America

   Email: james.n.guichard@futurewei.com

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