



BESS Working Group                                             G. Mishra
Internet-Draft                                              Verizon Inc.
Intended status: Standards Track                              S. Madhavi
Expires: 23 April 2026                            Juniper Networks, Inc.
                                                              A. Simpson
                                                                   Nokia
                                                               M. Mishra
                                                           Cisco Systems
                                                             J. Tantsura
                                                         Microsoft, Inc.
                                                                 S. Chen
                                                     Huawei Technologies
                                                         20 October 2025


           IPv4-Only and IPv6-Only PE Design DESIGN ALL SAFI
                  draft-ietf-bess-v4-v6-pe-all-safi-03

Abstract

   As Enterprises and Service Providers upgrade their brown field or
   green field MPLS/SR core to an IPv6 transport, Multiprotocol BGP (MP-
   BGP)now plays an important role in the transition of their Provider
   (P) core network as well as Provider Edge (PE) Inter-AS peering
   network from IPv4 to IPv6.  Operators must have flexiblity to
   continue to support IPv4 customers when both the Core and Edge
   networks migrate to IPv6.  As well as must be able to support IPv6
   networks in cases where operators decide to remain on an IPv4 network
   or during transition.

   This document details the External BGP (eBGP) PE-PE Inter-AS and PE-
   CE Edge peering IPv4-Only PE design where both IPv4 and IPv6 all
   supported SAFI NLRI can be advertised over a single IPv4 peer and
   IPv6-Only PE Design where all supported SAFI NLRI can be advertised
   over a single IPv6 peer.

   This document also defines a new IPv4 BGP next hop encoding standard
   that uses an IPv4 address as the next hop and not an IPv4 mapped IPv6
   address.

   This document also provides vendor specific test cases for the
   IPv4-Only peering design and IPv6-Only PE design as well as test
   results for the four major vendors stakeholders in the routing and
   switching indusrty, Cisco, Juniper, Nokia and Huawei.  With the test
   results provided for the IPv6-Only Edge peering design, the goal is
   that all other vendors around the world that have not been tested
   will begin to adopt and implement the design.




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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 23 April 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   8
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   8
   4.  Problem Statement . . . . . . . . . . . . . . . . . . . . . .   9
   5.  IPv6-Only PE-CE Design ALL SAFI Solution  . . . . . . . . . .  10
   6.  IPv4-Only PE-CE Design ALL SAFI Solution  . . . . . . . . . .  12
   7.  IPv6-Only Edge Peering Design ALL SAFI  . . . . . . . . . . .  15
     7.1.  IPv6-Only Edge Peering Packet Walk ALL SAFI . . . . . . .  15
     7.2.  IPv6-Only PE Design ALL SAFI over IPv4-Only Core Packet
           Walk  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     7.3.  IPv6-Only PE Design ALL SAFI over IPv6-Only Core Packet
           Walk  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
   8.  IPv4-Only Edge Peering Design . . . . . . . . . . . . . . . .  20
     8.1.  IPv4-Only Edge Peering Packet Walk ALL SAFI . . . . . . .  20




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     8.2.  IPv4-Only PE Design ALL SAFI over IPv4-Only Core Packet
           Walk  . . . . . . . . . . . . . . . . . . . . . . . . . .  20
     8.3.  IPv4-Only PE Design ALL SAFI over IPv6-Only Core Packet
           Walk  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
   9.  IPv4 Next Hop Encoding  . . . . . . . . . . . . . . . . . . .  25
   10. IPv6-Only PE Design / IPv6-Only PE Design Test Results  . . .  26
   11. IPv6-Only PE Design Testing Details . . . . . . . . . . . . .  28
     11.1.  Test-1 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) . . . . . . . . .  28
     11.2.  Test-2 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv4-Only Core . . . . . . . . . . . . . . . .  29
     11.3.  Test-3 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv6-Only Core (4PE)  . . . . . . . .  29
     11.4.  Test-4 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv6-Only Core . . . . . . . . . . . . . . . .  30
     11.5.  Test-5 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) - Inter-AS
             Option-B  . . . . . . . . . . . . . . . . . . . . . . .  30
     11.6.  Test-6 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) - Inter-AS
             Option-C  . . . . . . . . . . . . . . . . . . . . . . .  31
     11.7.  Test-7 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv4-Only - Inter-AS Option-B  . . . . . . . .  31
     11.8.  Test-8 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv4-Only Core - Inter-AS Option-C . . . . . .  32
     11.9.  Test-9 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv6-Only Core - Inter-AS Option-B  .  32
     11.10. Test-10 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             Global Table over IPv6-Only Core - Inter-AS Option-C  .  33
     11.11. Test-11 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv6-Only Core - Inter-AS Option-B . . . . . .  33
     11.12. Test-12 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE,
             VPN over IPv6-Only Core - Inter-AS Option-C . . . . . .  34
     11.13. IPv6-Only PE-CE Operational Considerations Testing . . .  34
   12. IPv4-Only PE Design Testing Details . . . . . . . . . . . . .  35
     12.1.  Test-1 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) . . . . . . . . .  35
     12.2.  Test-2 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv4-Only Core . . . . . . . . . . . . . . . .  36
     12.3.  Test-3 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv6-Only Core (4PE)  . . . . . . . .  36
     12.4.  Test-4 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv6-Only Core . . . . . . . . . . . . . . . .  37
     12.5.  Test-5 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) - Inter-AS
             Option-B  . . . . . . . . . . . . . . . . . . . . . . .  37





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     12.6.  Test-6 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv4-Only Core(6PE) - Inter-AS
             Option-C  . . . . . . . . . . . . . . . . . . . . . . .  37
     12.7.  Test-7 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv4-Only - Inter-AS Option-B  . . . . . . . .  38
     12.8.  Test-8 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv4-Only Core - Inter-AS Option-C . . . . . .  38
     12.9.  Test-9 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv6-Only Core - Inter-AS Option-B  .  39
     12.10. Test-10 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             Global Table over IPv6-Only Core - Inter-AS Option-C  .  39
     12.11. Test-11 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv6-Only Core - Inter-AS Option-B . . . . . .  40
     12.12. Test-12 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE,
             VPN over IPv6-Only Core - Inter-AS Option-C . . . . . .  40
     12.13. IPv4-Only PE-CE Operational Considerations Testing . . .  41
   13. SRv6 Applicability to IPv6 Only PE Design . . . . . . . . . .  41
   14. Typed and Untyped SAFI  . . . . . . . . . . . . . . . . . . .  43
   15. IPv4-Only PE Design and IPv6-Only PE Design ALL AFI/SFI
           Operational Considerations  . . . . . . . . . . . . . . .  43
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  44
   17. Security Considerations . . . . . . . . . . . . . . . . . . .  45
   18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  45
   19. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  45
   20. References  . . . . . . . . . . . . . . . . . . . . . . . . .  45
     20.1.  Normative References . . . . . . . . . . . . . . . . . .  45
     20.2.  Informative References . . . . . . . . . . . . . . . . .  49
   Appendix A.  SAFI LIST FOR PE-CE Edge Scenario  . . . . . . . . .  51
   Appendix B.  SAFI LIST FOR Inter-AS PE-PE Scenario  . . . . . . .  51
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  54

1.  Introduction

   As Enterprises and Service Providers upgrade their brown field or
   green field MPLS/SR core to an IPv6 transport such as MPLS LDPv6, SR-
   MPLSv6 or SRv6, Multiprotocol BGP (MP-BGP) now plays an important
   role in the transition of the Provider (P) core networks and Provider
   Edge (PE) edge networks from IPv4 to IPv6.

   IXP are also facing IPv4 address depletion at their peering points,
   which are large Layer 2 transit backbones that service providers peer
   and exchange IPv4 and IPv6 Network Layer Reachability Information
   (NLRI).  Today, these transit exchange points are Dual Stacked.  With
   this IPv6-only BGP peering design, only IPv6 MUST be configured on
   the PE-PE inter-as peering interface, the Inter-AS Provider Edge (PE)
   - Provider Edge (PE), the IPv6 BGP peer is now used to carry IPv4
   (Network Layer Reachability Information) NLRI over an IPv6 next hop
   using IPv6 next hop encoding defined in [RFC8950], while continuing



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   to forward both IPv4 and IPv6 packets.  With this IPv6-Only PE
   Design, ASBRs providing Inter-AS options peering PE to PE extending
   L3 VPN services is now no longer Dual Stacked and as well can support
   ALL AFI/SAFI.

   This document also provides a solution for use cases where operators
   are not yet ready to migrate to IPv6 or SRv6 core and would like to
   stay on IPv4-Only Core short to long term and maybe even
   indefinitely.  With this design, operators can now remain with an
   IPv4-Only Core and do not have to migrate to an IPv6-Only Core.  From
   a technical standpoint the underlay can remain IPv4 and still
   transport IPv6 NLRI to support IPv6 customers, and so does not need
   to be migrated to IPv6-Only underlay.  With this IPv4-Only PE Design
   solution , IPv4 addressing only needs to be provisioned for the
   IPv4-Only PE-CE eBGP Edge peering design, thereby eliminating IPv6
   provisioning at the Edge.  This core and edge IPv4-Only peering
   design can apply to any eBGP peering, public internet or private,
   which can be either Core networks, Data Center networks, Access
   networks or can be any eBGP peering scenario.

   MP-BGP specifies that the set of usable next-hop address families is
   determined by the Address Family Identifier (AFI) and the Subsequent
   Address Family Identifier (SAFI).  Historically the AFI/SAFI
   definitions for the IPv4 address family only have provisions for
   advertising a Next Hop address that belongs to the IPv4 protocol when
   advertising IPv4 or VPN-IPv4.  [RFC8950] specifies the extensions
   necessary to allow advertising IPv4 NLRI, Virtual Private Network
   Unicast (VPN-IPv4) NLRI, Multicast Virtual Private Network (MVPN-
   IPv4) NLRI with a Next Hop address that belongs to the IPv6 protocol.
   This comprises of an extended next hop encoding MP-REACH BGP
   capability exchange to allow the address of the Next Hop for IPv4
   NLRI, VPN-IPv4 NLRI and MVPN-IPv4 NLRI to also belong to the IPv6
   Protocol.  [RFC8950] defines the encoding of the Next Hop to
   determine which of the protocols the address actually belongs to, and
   a new BGP Capability allowing MP-BGP Peers to discover dynamically
   whether they can exchange IPv4 NLRI and VPN-IPv4 NLRI with an IPv6
   Next Hop.

   With the new extensions defined in [RFC8950] supporting NLRI and next
   hop address family mismatch, the BGP peer session can now be treated
   as a pure TCP transport and carry both IPv4 and IPv6 NLRI at the
   Provider Edge (PE) - Customer Edge (CE) over a single IPv6 TCP
   session.  This allows for the elimination of dual stack from the PE-
   PE Inter-AS peering point, and now enable the Inter-AS peering to be
   IPv6-ONLY.  The elimination of IPv4 Inter Provider ASBR tie point,
   PE-PE Inter-AS peering points translates into OPEX expenditure
   savings of point-to-point infrastructure links as well as /31 address
   space savings and administration and network management of both IPv4



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   and IPv6 BGP peers.  This reduction decreases the number of PE-PE
   Inter-AS options BGP peers by fifty percent, which is a tremendous
   cost savings for operators.

   This document details an important External BGP (eBGP) PE-CE Edge and
   PE-PE Inter-AS IPv4-Only PE Design and IPv6-Only PE Peering Design
   that leverages the MP-BGP capability exchange by using single IPv4
   peering or IPv6 peering as pure transport, allowing all IPv4 Network
   Layer Reachability Information (NLRI) and IPv6 Network Layer
   Reachability Information (NLRI)to be carried over the same (Border
   Gateway Protocol) BGP TCP session for all supported Subsequent
   Address Family Identifiers(SAFI).

   The design change provides two new alternative to traditional Dual
   Stacking implemnted today while providing the same Dual Stacking
   functionality and capabilities that exists today with separate IPv4
   and IPv6 BGP sessions, but now with this paradigm shift now only
   requires a single IPv4 transport peer "IPv4-Only PE Design" or single
   IPv6 transport peer "IPv6-Only PE Design".

   IPv6-Only PE Design entails that an IPv4 address MUST not be
   configured on the PE-CE or PE-PE interface and with the IPv6-Only PE
   Design an IPv4 address must not be configured on the PE-CE or PE-PE
   interface.

   IPv4-Only PE Design entails that an IPv6 address MUST not be
   configured on the PE-CE or PE-PE interface and with the IPv4-Only PE
   Design an IPv6 address must not be configured on the PE-CE or PE-PE
   interface.

   From a control plane perspective with the IPv6-Only PE design a
   single IPv6-Only peer is required for both IPv4 and IPv6 routing
   updates and from a data plane forwarindg perspective an IPv6 address
   need only be configured on the PE-CE Edge or PE-PE Inter-AS peering
   interface for both IPv4 and IPv6 packet forwarding.

   From a control plane perspective with the IPv4-Only PE design a
   single IPv4-Only peer is required for both IPv4 and IPv6 routing
   updates and from a data plane forwarindg perspective an IPv4 address
   need only be configured on the PE-CE Edge or PE-PE Inter-AS peering
   interface for both IPv4 and IPv6 packet forwarding.

   This document defines the IPv6-Only PE Design and IPv4-Only PE Design
   as a new PE-CE Edge and ASBR-ASBR PE-PE Inter-AS BGP peering Standard
   to support all IPv4 and IPv6 AFI AFI and corresponding SAFI
   ubiquitously.  As service providers migrate to Segment Routing
   architecture SR-MPLS and SRv6, VPN overlay exsits as well, and thus
   Inter-AS options Option-A, Option-B, Option-AB and Option-C are still



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   applicable and thus this pardigm shift to IPv4-Only or IPv6-Only
   peering architecure is still very relevant to Segment Routing
   architecture both SR-MPLS and SRv6.

   With both the IPv4-Only PE Design and IPv6-Only PE Design, while the
   savings exists at the Edge eBGP PE-PE Inter-AS peering, on the core
   side iBGP PE to Route Reflector (RR) peering carrying <AFI/SAFI> IPv4
   <1/1>, VPN-IPV4 <1/128>, and Multicasat VPN <1/129>, there is no
   savings as the Provider (P) Core is IPv6 Only or IPv4-Only, thus can
   only have an IPv6 peer and must use [RFC8950] extended next hop
   encoding to carrying IPv4 NLRI IPV4 <2/1>, VPN-IPV4 <2/128>, and
   Multicast VPN <2/129> over an IPv4 or IPv6 next hop.

   The IPv4-Only PE Design and IPv6-Only PE ALL SAFI Design supports the
   following IPv4 and IPv6 AFI and their corresponding SAFI below: <AFI/
   SAFI>, NLRI Multi-Segment Pseudowires [RFC7267] <1/6>, BGP Tunnel
   Encapsulation SAFI [RFC9012] <1/7>, Tunnel SAFI
   [I-D.nalawade-kapoor-tunnel-safi] <1/6>, BGP MDT SAFI [RFC6037]
   <1/66>, BGP 4to6 SAFI [RFC5747] <1/67>, BGP 6to4 SAFI draft xx <1/8>,
   Layer 1 VPN Auto-Discovery [RFC5195] <1/69>, SR-TE Policy SAFI draft
   <1/73>, BGP 6to4 SAFI draft <1/8>, SDN WAN Capabilities draft <1/74>,
   Classful-Transport SAFI draftxx <1/76>, Tunneled Traffic FlowSpec
   draftxx <1/77>, MCAST-TREE SAFI draft xx <1/78>, Route Target
   Constraints [RFC4684] <1/132>, Dissemination of Flow Specification
   Rules [RFC8955] <1/133>, L3 VPN Dissemination of Flow Specification
   Rules [RFC8955] <1/1344>, VPN Auto-Discovery SAFI draftxx <1/140>

   This document provides proof of concept test results for the
   IPv4-Only PE Design and IPv6-Only PE design for 12 of the most common
   use cases with 3 of the most commonly used SAFI <AFI/SAFI> IPv4
   <1/1>, VPN-IPV4 <1/128>, and Multicasat VPN <1/129>, with four major
   vendors stakeholders in the routing and switching indusrty, Cisco,
   Juniper, Nokia and Huawei.  With the test results provided for the
   IPv6-Only Edge peering design, the goal is that all other vendors
   around the world that have not been tested will begin to adopt and
   implement this new best practice for eBGP IPv6-Only Edge peering.
   This will give confidence to operators to start the proliferation of
   the IPv4-Only PE Design and IPv6-Only PE design worldwide.  This
   document provides a detalied analysis of all IPv4 and IPv6 address
   family and related SAFI that is supported with the IPv4-Only PE
   Design and IPv6-Only PE Design in Section 4.  Thus this draft
   provides a test use case basis with the three SAFI tested, giving
   extensibility to all of the other SAFI that are supported for future
   testing and deployment by operators.

   This document also defines a new IPv4 next hop encoding for IPv6 NLRI
   over IPv4 Next Hop to uses 4 byte IPv4 address for the next hop and
   not a IPv4 mapped IPv6 address as the new standard.  Today the IPv4



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   next hop encoding has mix of 4 octet IPv4 address for the next hop as
   well as IPv4 mapped IPv6 address.  This is discussed in detail in
   section 10.

   The Major benefit from the IPv4-Only PE design is IPv6 address space
   savings and the ability to support IPv6 NLRI without configuring an
   IPv6 address at the PE-CE edge and PE-PE inter-as boundary and avoid
   having to upgrade to support IPv6 as well elimination of provisioning
   of IPv6 addressing and Network Operations and monitoring costs of
   tradditional Dual Stacked interfaces with IPv4 and IPv6 BGP peering
   which now translating into CAPEX and OPEX Savings.

   The Major benefit from the IPv6-Only PE design is IPv4 address space
   savings solving IPv4 address depletion issues and the ability to
   support IPv4 NLRI without configuring an IPv4 address at the PE-CE
   edge and PE-PE inter-as boundary, as well elimination of provisioning
   of IPv4 address and Network Operations and monitoring costs of
   traditional Dual Stacked interfaces with IPv4 and IPv6 BGP peering
   which now translates into CAPEX and OPEX Savings.

2.  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.

3.  Terminology

   Terminolgoy used in defining the IPv6-Only Edge specification.

   AFBR: Address Family Border Router Provider Edge (PE).

   Edge: PE-CE Edge Network Provider Edge - Customer Edge

   Core: P Core Network Provider (P)

   4to6 Softwire : IPv4 edge over an IPv6-Only core

   6to4 Softwire: IPv6 edge over an IPv4-Only core

   E2E: End to End








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4.  Problem Statement

   This specification addresses a real issue that has been discussed at
   many operator with extremely large core networks around the world
   related migration to IPv6 underlay transport which can now be put off
   indefinitely.  Operators around the world are clamoring for a
   solution as well that can help solve issues related to IPv4 address
   depletion at these large IXP peering points.


                                          Problem Statement

                        Dual Stacked            Dual Stacked
                             CE                      PE

                          +-------+ IPv4 BGP Peer +-------+
                          |       |---------------|       |
                          |   CE  | IPv6 BGP Peer |  PE   |
                          |       |---------------|       |
                          +-------+               +-------+
                         IPv4 forwarding            IPv4 forwarding
                         IPv6 forwarding            IPv6 forwarding


              Figure 1: Problem Statement - Dual Stack Peering


                               ________
    Dual Stacked     _____    /        \                Dual Stacked
      PE / CE       /     \__/          \___              PE / CE
  +----+  +----+   /                        \        +------+   +-----+
  |    |  |    |  |0====VPN Overlay Tunnel ==0|      |      |   |     |
  |    |  |    |  |                             \    |      |   |     |
  | CE |--| PE |--\         IPv6-Only Core      |----|  PE  |---|  CE |
  |    |  |    |    \0=========Underlay =======0|    |      |   |     |
  +----+  +----+     \                        __/    +------+   +-----+
  IPv4 IPv6 BGP peer  \ IP / MPLS / SR domain /     IPv4 and IPv6 BGP peer
  IPv4 forwarding      \__         __       /          IPv4 forwarding
  IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




          Figure 2: Problem Statement - E2E Dual Stack Edge







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5.  IPv6-Only PE-CE Design ALL SAFI Solution

   The IPv6-Only Edge design solution applies to ALL IPv4 Network Layer
   Reachability Information (NLRI) and IPv6 Network Layer Reachability
   Information (NLRI) over an IPv6-Only BGP Peering session.

   IPv6-Only PE Design is applicable to infrastructure networks such as
   Core networks, DC networks, Access networks as well as any PE-CE
   public or private network can now utilize this IPv6-Only Edge
   solution and reap the benefits immediately on IPv6 address space
   saving and CAPEX and OPEX savings.

   Six Groupings of AFI/SAFI Use Case Scenario for the IPv6-Only PE
   Design ALL SAFI

   *  Group-1 PE-CE

   *  Group-2 PE-PE Inter-AS

   *  Group-3 L1 and L2 VPN

   *  Group-4 Multicast

   *  Group-5 Tunnel

   *  Group-6 BGP, BGP Flowspec, BGP Misc Policy

   Group-1 Edge Customer IPv4/IPv6 NLRI PE-CE AFI / SAFI grouping (CP-
   DP) - "UNICAST"

   *  AFI/SAFI 1/1 IPv4 Unicast 2/1 IPv6 Unicast

   Group-1 Edge Customer IPv4/IPv6 NLRI PE-CE AFI / SAFI grouping (CP-
   DP) - "MULTICAST"

   *  AFI/SAFI 1/2 IPv4 Multicast 2/2 IPv6 Multicast

   *  AFI/SAFI 1/78 IPv4 MCAST-TREE SAFI 2/78 MCAST-TREE SAFI

   Group-2 ASBR-ASBR Inter-AS Customer IPv4/IPv6 NLRI AFI/SAFI grouping
   (CP-DP) - "UNICAST"

   Global Table

   *  AFI/SAFI 1/4 4PE

   L3 VPN




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   *  AFI/SAFI 1/128 IPv4 VPN 2/128 IPv6 VPN

   *  AFI/SAFI 1/132 IPv4 RTC 2/132 IPv6 RTC

   *  AFI/SAFI 1/140 IPv4 VPN Auto Discovery 2/140 IPv6 VPN Auto
      Discovery

   Group-2 ASBR-ASBR Inter-AS Customer IPv4/IPv6 NLRI AFI/SAFI grouping
   (CP-DP) - "MULTICAST"

   Global Table

   *  AFI/SAFI 1/2 IPv4 Multicast 2/2 IPv6 Multicast

   L3 VPN

   *  AFI/SAFI 1/5 IPv4 MCAST-VPN 2/5 IPv6 MCAST-VPN

   *  AFI/SAFI 1/66 IPv4 BGP MDT SAFI 2/66 IPv6 BGP MDT SAFI

   *  AFI/SAFI 1/78 IPv4 MCAST-TREE SAFI 2/78 MCAST-TREE SAFI

   Group-3 - L1 and L2 VPN

   *  L2 VPN related NLRI control plane in BGP

   *  AFI/SAFI 1/6 IPv4 Multi Segment PW 2/6 IPv6 Multi Segment PW

   *  AFI/SAFI 1/69 L1 VPN Auto Discovery 2/69 L1 VPN Auto Discovery

   Group-4 - Tunnel

   *  AFI/SAFI 1/64 Tunnel-SAFI 2/64 Tunnel-SAFI

   *  AFI/SAFI 1/67 BGP 4over6 Tunnel SAFI 2/67 BGP 4over6 Tunnel SAFI

   *  AFI/SAFI 1/68 BGP 6over4 Tunnel SAFI 2/68 BGP 6over4 Tunnel SAFI

   Group-5 - BGP, BGP Flowspec, BGP Misc Policy

   *  AFI/SAFI 1/73 SR-TE Policy SAFI 2/73 SR-TE Policy SAFI

   *  AFI/SAFI 1/74 SD-WAN Capabilities 2/74 SD-WAN Capabilities

   *  AFI/SAFI 1/77 Tunneled Traffic Flowspec 2/77 Tunneled Traffic
      Flowspec





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   *  AFI/SAFI 1/133 Dissemination of Flowspec Rules 2/133 133
      Dissemination of Flowspec Rules

   *  AFI/SAFI 1/134 L3 VPN 133 Dissemination of Flowspec Rules 2/134
      L3VPN Dissemination of Flowspec Rules

   *  AFI/SAFI 1/85 BGP MUP SAFI 2/85 BGP MUP SAFI


                                  Solution applicable to all AFI/SAFI
                                  AFI/SAFI 1/X 2/X  Where X = ALL SAFI

                        +-------+                +-------+
                        |   AS1 |  IPv6 Only     |  AS2  |
                        |   PE1 |----------------|  PE2  |
                        | (ASBR)|  IPv6 BGP Peer |(ASBR) |
                        +-------+                +-------+
                       IPv4 forwarding            IPv4 forwarding
                       IPv6 forwarding            IPv6 forwarding


    Figure 3: IPv6-Only PE Design Solution Applicability to ALL AFI/SAFI

6.  IPv4-Only PE-CE Design ALL SAFI Solution

   The IPv4-Only Edge design solution applies to ALL IPv4 Network Layer
   Reachability Information (NLRI) and IPv6 Network Layer Reachability
   Information (NLRI) over an IPv4-Only BGP Peering session.

   IPv4-Only PE Design is applicable to infrastructure networks such as
   Core networks, DC networks, Access networks as well as any PE-CE
   public or private network can now utilize this IPv4-Only Edge
   solution and reap the benefits immeditately of CAPEX and OPEX
   savings.

   Six Groupings of AFI/SAFI Use Case Scenario for the IPv6-Only PE
   Design ALL SAFI

   *  Group-1 PE-CE

   *  Group-2 PE-PE Inter-AS

   *  Group-3 L1 and L2 VPN

   *  Group-4 Multicast

   *  Group-5 Tunnel




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   *  Group-6 BGP, BGP Flowspec, BGP Misc Policy

   Group-1 Edge Customer IPv4/IPv6 NLRI PE-CE AFI / SAFI grouping (CP-
   DP) - "UNICAST"

   *  AFI/SAFI 1/1 IPv4 Unicast 2/1 IPv6 Unicast

   Group-1 Edge Customer IPv4/IPv6 NLRI PE-CE AFI / SAFI grouping (CP-
   DP) - "MULTICAST"

   *  AFI/SAFI 1/2 IPv4 Multicast 2/2 IPv6 Multicast

   *  AFI/SAFI 1/78 IPv4 MCAST-TREE SAFI 2/78 MCAST-TREE SAFI

   Group-2 ASBR-ASBR Inter-AS Customer IPv4/IPv6 NLRI AFI/SAFI grouping
   (CP-DP) - "UNICAST"

   Global Table

   *  AFI/SAFI 1/4 4PE

   L3 VPN

   *  AFI/SAFI 1/128 IPv4 VPN 2/128 IPv6 VPN

   *  AFI/SAFI 1/132 IPv4 RTC 2/132 IPv6 RTC

   *  AFI/SAFI 1/140 IPv4 VPN Auto Discovery 2/140 IPv6 VPN Auto
      Discovery

   Group-2 ASBR-ASBR Inter-AS Customer IPv4/IPv6 NLRI AFI/SAFI grouping
   (CP-DP) - "MULTICAST"

   Global Table

   *  AFI/SAFI 1/2 IPv4 Multicast 2/2 IPv6 Multicast

   L3 VPN

   *  AFI/SAFI 1/129 IPv4 MVPN 2/129 IPv6 MVPN

   *  AFI/SAFI 1/5 IPv4 MCAST-VPN 2/5 IPv6 MCAST-VPN

   *  AFI/SAFI 1/66 IPv4 BGP MDT SAFI 2/66 IPv6 BGP MDT SAFI

   *  AFI/SAFI 1/78 IPv4 MCAST-TREE SAFI 2/78 MCAST-TREE SAFI

   Group-3 - L1 and L2 VPN



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   *  L2 VPN related NLRI control plane in BGP

   *  AFI/SAFI 1/6 IPv4 Multi Segment PW 2/6 IPv6 Multi Segment PW

   *  AFI/SAFI 1/69 L1 VPN Auto Discovery 2/69 L1 VPN Auto Discovery

   Group-4 - Multicast

   *  AFI/SAFI 1/8 IPv4 MCAST-VPLS 2/8 IPv6 MCAST-VPLS

   Group-5 - Tunnel

   *  AFI/SAFI 1/64 Tunnel-SAFI 2/64 Tunnel-SAFI

   *  AFI/SAFI 1/67 BGP 4over6 Tunnel SAFI 2/67 BGP 4over6 Tunnel SAFI

   *  AFI/SAFI 1/68 BGP 6over4 Tunnel SAFI 2/68 BGP 6over4 Tunnel SAFI

   Group-6 - BGP, BGP Flowspec, BGP Misc Policy

   *  AFI/SAFI 1/73 SR-TE Policy SAFI 2/73 SR-TE Policy SAFI

   *  AFI/SAFI 1/74 SD-WAN Capabilities 2/74 SD-WAN Capabilities

   *  AFI/SAFI 1/77 Tunneled Traffic Flowspec 2/77 Tunneled Traffic
      Flowspec

   *  AFI/SAFI 1/133 Dissemination of Flowspec Rules 2/133 133
      Dissemination of Flowspec Rules

   *  AFI/SAFI 1/134 L3 VPN 133 Dissemination of Flowspec Rules 2/134
      L3VPN Dissemination of Flowspec Rules

   *  AFI/SAFI 1/79 BGP-DPS Arista 2/79 BGP-DPS Arista

   *  AFI/SAFI 1/83 BGP CAR 2/83 BGP CAR

   *  AFI/SAFI 1/84 BGP VPN CAR 2/84 BGP VPN CAR

   *  AFI/SAFI 1/85 BGP MUP SAFI 2/85 BGP MUP SAFI











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                                  Solution applicable to all AFI/SAFI
                                  AFI/SAFI 1/X 2/X  Where X = ALL SAFI

                        +-------+                +-------+
                        |   AS1 |  IPv6 Only     |  AS2  |
                        |   PE1 |----------------|  PE2  |
                        | (ASBR)|  IPv6 BGP Peer |(ASBR) |
                        +-------+                +-------+
                       IPv4 forwarding            IPv4 forwarding
                       IPv6 forwarding            IPv6 forwarding


    Figure 4: IPv4-Only PE Design Solution Applicability to ALL AFI/SAFI


                                ________
      IPv4-Only       _____    /        \                 IPv4-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  |0====VPN Overlay Tunnel ==0|      |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay ===== ==0    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv6 BGP peer        \IP / MPLS / SR domain /        IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




                      Figure 5: E2E VPN Solutionv4

7.  IPv6-Only Edge Peering Design ALL SAFI

7.1.  IPv6-Only Edge Peering Packet Walk ALL SAFI

   The IPv6-Only Edge Peering design utilizes two key E2E Softwire Mesh
   Framework scenario's, 4to6 softwire and 6to4 softwire.  The Softwire
   mesh framework concept is based on the overlay and underlay MPLS or
   SR based technology framework, where the underlay is the transport
   layer and the overlay is a Virtual Private Network (VPN) layer, and
   is the the tunneled virtualization layer containing the customer
   payload.  The concept of a 6to4 Softwire is based on transmission of
   IPv6 packets at the edge of the network by tunneling the IPv6 packets
   over an IPv4-Only Core.  The concept of a 4to6 Softwire is also based
   on transmission of IPv4 packets at the edge of the network by
   tunneling the IPv4 packets over an IPv6-Only Core.



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   This document describes End to End (E2E) test scenarios that follow a
   packet flow from IPv6-Only attachment circuit from ingress PE-CE to
   egress PE-CE tracing the routing protocol control plane and data
   plane forwarding of IPv4 packets in a 4to6 softwire or 6to4 softwire
   within the IPv4-Only or IPv6-Only Core network.  In both secneario we
   are focusing on IPv4 packets and the control plane and data plane
   forwarding aspects of IPv4 packets from the PE-CE Edge network over
   an IPv6-Only P (Provider) core network or IPv4-Only P (Provider) core
   network.  With this IPv6-Only Edge peering design, the Softwire Mesh
   Framework is not extended beyond the Provider Edge (PE) and continues
   to terminate on the PE router.

7.2.  IPv6-Only PE Design ALL SAFI over IPv4-Only Core Packet Walk

   6to4 softwire where IPv6-Edge eBGP IPv6 peering where IPv4 packets at
   network Edge traverse a IPv4-Only Core

   In the scenario where IPv4 packets originating from a PE-CE edge are
   tunneled over an MPLS or Segment Routing IPv4 underlay core network,
   the PE and CE only have an IPv6 address configured on the interface.
   In this scenario the IPv4 packets that ingress the CE from within the
   CE AS are over an IPv6-Only interface and are forwarded to an IPv4
   NLRI destination prefix learned from the Pure Transport Single IPv6
   BGP Peer.  In the IPv6-Only Edge peering architecture the PE is
   IPv6-Only as all PE-CE interfaces are IPv6-Only.  However, on the CE,
   the PE-CE interface is the only interface that is IPv6-Only and all
   other interfaces may or may not be IPv6-Only.  Following the data
   plane packet flow, IPv4 packets are forwarded from the ingress CE to
   the IPv6-Only ingress PE where the VPN label imposition push per
   prefix, per-vrf, per-CE occurs and the labeled packet is forwarded
   over a 6to4 softwire IPv4-Only core, to the egress PE where the VPN
   label disposition pop occurs and the native IPv4 packet is forwarded
   to the egress CE.  In the reverse direction IPv4 packets are
   forwarded from the egress CE to egress PE where the VPN label
   imposition per prefix, per-vrf, per-CE push occurs and the labeled
   packet is forwarded back over the 6to4 softwire IPv4-Only core, to
   the ingress PE where the VPN label disposition pop occurs and the
   native IPv4 packet is forwarded to the ingress CE. . The
   functionality of the IPv4 forwarding plane in this scenario is
   identical from a data plane forwarding perspective to Dual Stack IPv4
   forwarding scenario.










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                             +--------+   +--------+
                             |  IPv4  |   |  IPv4  |
                             | Client |   | Client |
                             | Network|   | Network|
                             +--------+   +--------+
                                 |   \     /   |
                                 |    \   /    |
                                 |     \ /     |
                                 |      X      |
                                 |     / \     |
                                 |    /   \    |
                                 |   /     \   |
                             +--------+   +--------+
                             |  AFBR  |   |  AFBR  |
                          +--| IPv4/6 |---| IPv4/6 |--+
                          |  +--------+   +--------+  |
          +--------+      |                           |       +--------+
          |  IPv4  |      |                           |       |  IPv4  |
          | Client |      |                           |       | Client |
          | Network|------|            IPv4           |-------| Network|
          +--------+      |            only           |       +--------+
                          |                           |
                          |  +--------+   +--------+  |
                          +--|  AFBR  |---|  AFBR  |--+
                             | IPv4/6 |   | IPv4/6 |
                             +--------+   +--------+
                               |   \     /   |
                               |    \   /    |
                               |     \ /     |
                               |      X      |
                               |     / \     |
                               |    /   \    |
                               |   /     \   |
                            +--------+   +--------+
                            |  IPv6  |   |  IPv4  |
                            | Client |   | Client |
                            | Network|   | Network|
                            +--------+   +--------+



      Figure 6: IPv6-Only PE Design ALL SAFI 6to4 Softwire - IPv6 Edge
                           over an IPv4-Only Core

7.3.  IPv6-Only PE Design ALL SAFI over IPv6-Only Core Packet Walk

   4to6 softwire where IPv6-Edge eBGP IPv6 peering where IPv4 packets at
   network Edge traverse a IPv6-Only Core



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   In the scenario where IPv4 packets originating from a PE-CE edge are
   tunneled over an MPLS or Segment Routing IPv4 underlay core network,
   the PE and CE only have an IPv6 address configured on the interface.
   In this scenario the IPv4 packets that ingress the CE from within the
   CE AS are over an IPv6-Only interface and are forwarded to an IPv4
   NLRI destination prefix learned from the Pure Transport Single IPv6
   BGP Peer.  In the IPv6-Only Edge peering architecture the PE is
   IPv6-Only as all PE-CE interfaces are IPv6-Only.  However, on the CE,
   the PE-CE interface is the only interface that is IPv6-Only and all
   other interfaces may or may not be IPv6-Only.  Following the data
   plane packet flow, IPv4 packets are forwarded from the ingress CE to
   the IPv6-Only ingress PE where the VPN label imposition push per
   prefix, per-vrf, per-CE occurs and the labeled packet is forwarded
   over a 4to6 softwire IPv6-Only core, to the egress PE where the VPN
   label disposition pop occurs and the native IPv4 packet is forwarded
   to the egress CE.  In the reverse direction IPv4 packets are
   forwarded from the egress CE to egress PE where the VPN label
   imposition per prefix, per-vrf, per-CE push occurs and the labeled
   packet is forwarded back over the 4to6 softwire IPv6-Only core, to
   the ingress PE where the VPN label disposition pop occurs and the
   native IPv4 packet is forwarded to the ingress CE. . The
   functionality of the IPv4 forwarding plane in this scenario is
   identical from a data plane forwarding perspective to Dual Stack IPv4
   forwarding scenario.



























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                             +--------+   +--------+
                             |  IPv4  |   |  IPv4  |
                             | Client |   | Client |
                             | Network|   | Network|
                             +--------+   +--------+
                                 |   \     /   |
                                 |    \   /    |
                                 |     \ /     |
                                 |      X      |
                                 |     / \     |
                                 |    /   \    |
                                 |   /     \   |
                             +--------+   +--------+
                             |  AFBR  |   |  AFBR  |
                          +--| IPv4/6 |---| IPv4/6 |--+
                          |  +--------+   +--------+  |
          +--------+      |                           |       +--------+
          |  IPv6  |      |                           |       |  IPv6  |
          | Client |      |                           |       | Client |
          | Network|------|            IPv6           |-------| Network|
          +--------+      |            only           |       +--------+
                          |                           |
                          |  +--------+   +--------+  |
                          +--|  AFBR  |---|  AFBR  |--+
                             | IPv4/6 |   | IPv4/6 |
                             +--------+   +--------+
                               |   \     /   |
                               |    \   /    |
                               |     \ /     |
                               |      X      |
                               |     / \     |
                               |    /   \    |
                               |   /     \   |
                            +--------+   +--------+
                            |  IPv4  |   |  IPv4  |
                            | Client |   | Client |
                            | Network|   | Network|
                            +--------+   +--------+




      Figure 7: IPv6-Only PE Design ALL SAFI 4to6 Softwire - IPv4 Edge
                           over an IPv6-Only Core







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8.  IPv4-Only Edge Peering Design

8.1.  IPv4-Only Edge Peering Packet Walk ALL SAFI

   The IPv4-Only Edge Peering design utilizes two key E2E Softwire Mesh
   Framework scenario's, 4to6 softwire and 6to4 softwire.  The Softwire
   mesh framework concept is based on the overlay and underlay MPLS or
   SR based technology framework, where the underlay is the transport
   layer and the overlay is a Virtual Private Network (VPN) layer, and
   is the the tunneled virtualization layer containing the customer
   payload.  The concept of a 6to4 Softwire is based on transmission of
   IPv6 packets at the edge of the network by tunneling the IPv6 packets
   over an IPv4-Only Core.  The concept of a 4to6 Softwire is also based
   on transmission of IPv4 packets at the edge of the network by
   tunneling the IPv4 packets over an IPv6-Only Core.

   This document describes End to End (E2E) test scenarios that follow a
   packet flow from IPv4-Only attachment circuit from ingress PE-CE to
   egress PE-CE tracing the routing protocol control plane and data
   plane forwarding of IPv4 packets in a 4to6 softwire or 6to4 softwire
   within the IPv4-Only or IPv6-Only Core network.  In both secneario we
   are focusing on IPv4 packets and the control plane and data plane
   forwarding aspects of IPv4 packets from the PE-CE Edge network over
   an IPv4-Only P (Provider) core network or IPv6-Only P (Provider) core
   network.  With this IPv4-Only Edge peering design, the Softwire Mesh
   Framework is not extended beyond the Provider Edge (PE) and continues
   to terminate on the PE router.

8.2.  IPv4-Only PE Design ALL SAFI over IPv4-Only Core Packet Walk

   6to4 softwire where IPv4-Edge eBGP IPv4 peering where IPv6 packets at
   network Edge traverse a IPv4-Only Core

   In the scenario where IPv6 packets originating from a PE-CE edge are
   tunneled over an MPLS or Segment Routing IPv4 underlay core network,
   the PE and CE only have an IPv6 address configured on the interface.
   In this scenario the IPv6 packets that ingress the CE from within the
   CE AS are over an IPv4-Only interface and are forwarded to an IPv6
   NLRI destination prefix learned from the Pure Transport Single IPv4
   BGP Peer.  In the IPv4-Only Edge peering architecture the PE is
   IPv4-Only as all PE-CE interfaces are IPv4-Only.  However, on the CE,
   the PE-CE interface is the only interface that is IPv4-Only and all
   other interfaces may or may not be IPv4-Only.  Following the data
   plane packet flow, IPv4 packets are forwarded from the ingress CE to
   the IPv4-Only ingress PE where the VPN label imposition push per
   prefix, per-vrf, per-CE occurs and the labeled packet is forwarded
   over a 6to4 softwire IPv4-Only core, to the egress PE where the VPN
   label disposition pop occurs and the native IPv4 packet is forwarded



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   to the egress CE.  In the reverse direction IPv4 packets are
   forwarded from the egress CE to egress PE where the VPN label
   imposition per prefix, per-vrf, per-CE push occurs and the labeled
   packet is forwarded back over the 6to4 softwire IPv4-Only core, to
   the ingress PE where the VPN label disposition pop occurs and the
   native IPv4 packet is forwarded to the ingress CE. . The
   functionality of the IPv4 forwarding plane in this scenario is
   identical from a data plane forwarding perspective to Dual Stack IPv4
   forwarding scenario.










































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                             +--------+   +--------+
                             |  IPv4  |   |  IPv4  |
                             | Client |   | Client |
                             | Network|   | Network|
                             +--------+   +--------+
                                 |   \     /   |
                                 |    \   /    |
                                 |     \ /     |
                                 |      X      |
                                 |     / \     |
                                 |    /   \    |
                                 |   /     \   |
                             +--------+   +--------+
                             |  AFBR  |   |  AFBR  |
                          +--| IPv4/6 |---| IPv4/6 |--+
                          |  +--------+   +--------+  |
          +--------+      |                           |       +--------+
          |  IPv4  |      |                           |       |  IPv4  |
          | Client |      |                           |       | Client |
          | Network|------|            IPv4           |-------| Network|
          +--------+      |            only           |       +--------+
                          |                           |
                          |  +--------+   +--------+  |
                          +--|  AFBR  |---|  AFBR  |--+
                             | IPv4/6 |   | IPv4/6 |
                             +--------+   +--------+
                               |   \     /   |
                               |    \   /    |
                               |     \ /     |
                               |      X      |
                               |     / \     |
                               |    /   \    |
                               |   /     \   |
                            +--------+   +--------+
                            |  IPv6  |   |  IPv4  |
                            | Client |   | Client |
                            | Network|   | Network|
                            +--------+   +--------+



     Figure 8: 6to4 Softwire - IPv6 Edge over an IPv4-Only Core Packet
                                    Walk

8.3.  IPv4-Only PE Design ALL SAFI over IPv6-Only Core Packet Walk

   4to6 softwire where IPv4-Edge eBGP IPv4 peering where IPv6 packets at
   network Edge traverse a IPv6-Only Core



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   In the scenario where IPv6 packets originating from a PE-CE edge are
   tunneled over an MPLS or Segment Routing IPv4 underlay core network,
   the PE and CE only have an IPv4 address configured on the interface.
   In this scenario the IPv6 packets that ingress the CE from within the
   CE AS are over an IPv4-Only interface and are forwarded to an IPv6
   NLRI destination prefix learned from the Pure Transport Single IPv4
   BGP Peer.  In the IPv4-Only Edge peering architecture the PE is
   IPv4-Only as all PE-CE interfaces are IPv4-Only.  However, on the CE,
   the PE-CE interface is the only interface that is IPv4-Only and all
   other interfaces may or may not be IPv4-Only.  Following the data
   plane packet flow, IPv6 packets are forwarded from the ingress CE to
   the IPv4-Only ingress PE where the VPN label imposition push per
   prefix, per-vrf, per-CE occurs and the labeled packet is forwarded
   over a 4to6 softwire IPv6-Only core, to the egress PE where the VPN
   label disposition pop occurs and the native IPv6 packet is forwarded
   to the egress CE.  In the reverse direction IPv6 packets are
   forwarded from the egress CE to egress PE where the VPN label
   imposition per prefix, per-vrf, per-CE push occurs and the labeled
   packet is forwarded back over the 4to6 softwire IPv6-Only core, to
   the ingress PE where the VPN label disposition pop occurs and the
   native IPv6 packet is forwarded to the ingress CE. . The
   functionality of the IPv4 forwarding plane in this scenario is
   identical from a data plane forwarding perspective to Dual Stack IPv4
   / IPv6 forwarding scenario.



























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                             +--------+   +--------+
                             |  IPv4  |   |  IPv4  |
                             | Client |   | Client |
                             | Network|   | Network|
                             +--------+   +--------+
                                 |   \     /   |
                                 |    \   /    |
                                 |     \ /     |
                                 |      X      |
                                 |     / \     |
                                 |    /   \    |
                                 |   /     \   |
                             +--------+   +--------+
                             |  AFBR  |   |  AFBR  |
                          +--| IPv4/6 |---| IPv4/6 |--+
                          |  +--------+   +--------+  |
          +--------+      |                           |       +--------+
          |  IPv6  |      |                           |       |  IPv6  |
          | Client |      |                           |       | Client |
          | Network|------|            IPv6           |-------| Network|
          +--------+      |            only           |       +--------+
                          |                           |
                          |  +--------+   +--------+  |
                          +--|  AFBR  |---|  AFBR  |--+
                             | IPv4/6 |   | IPv4/6 |
                             +--------+   +--------+
                               |   \     /   |
                               |    \   /    |
                               |     \ /     |
                               |      X      |
                               |     / \     |
                               |    /   \    |
                               |   /     \   |
                            +--------+   +--------+
                            |  IPv4  |   |  IPv4  |
                            | Client |   | Client |
                            | Network|   | Network|
                            +--------+   +--------+




     Figure 9: 4to6 Softwire - IPv4 Edge over an IPv6-Only Core Packet
                                    Walk







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9.  IPv4 Next Hop Encoding

   *  RFC 4798 (6PE) section 2 defines how the next hop should be
      encoded for IPv6 NLRI over an IPv4 next hop using IPv4 mapped IPv6
      address ::FFFF:192.168.1.1.

   *  RFC 4659 BGP MPLS VPNs section 3.2.1.2 defines VPN SAFI next hop
      encoding of IPv4 mapped IPv6 address ::FFFF:192.168.1.1.

   *  RFC 5549 and now updated by RFC 8950 defines the IPv6 next hop
      encoding to carry IPv4 NLRI over an IPv6 next hop.  The IPv6 next
      hop encoding defined is not an IPv6 mapped IPv4 address.  The IPv6
      next hop encoding is 16/32 byte for Unicast SAFI 1, Multicast SAFI
      2 and BGP-LU SAFI 4, and 24/48 byte for VPN SAFI 128, MVPN SAFI
      129.  The IANA BGP Capability codepoint defined with RFC 5549 is
      value 5 for Extended Next hop encoding.

   *  The industry implementation uses a mix of IPv4 mapped IPv6 address
      for IPv6 NLRI carried over an IPv4 address next hop and uses 4
      byte field for IPv4 next hop address for Unicast SAFI 1, Multicast
      SAFI2 and BGP-LU SAFI 4, and 12 byte next hop field, 4 byte IPv4
      address plus 8 byte RD (Route Distinguisher) set to 0 for VPN SAFI
      128, MVPN SAFI 129.

   *  This draft standardizes the encoding to use an IPv4 address next
      hop and uses 4 byte field for IPv4 next hop address for Unicast
      SAFI 1, Multicast SAFI2 and BGP-LU SAFI 4, and 12 byte next hop
      field, 4 byte IPv4 address plus 8 byte RD (Route Distinguisher)
      set to 0 for VPN SAFI 128, MVPN SAFI 129.

   *  This draft standardizes that encoding to ensure interoperability
      with IANA BGP Capability codepoint allocation thus providing
      parity between the RFC 5549/RFC 8950 IPv6 next hop encoding where
      the next hop address follows the underlay core protocol which is
      an IPv6 core and how the next hop here being an IPv6 address and
      not following the NLRI protocol with IPv6 mapped IPv4 address.
      Now with this draft the next hop encoding follows the underlay
      core which is an IPv4 core and so now the next hop being an IPv4
      address and not following the NLRI with an IPv4 mapped IPv6
      address.  So this parity between IPv4 next encoding and IPv6 next
      hop encoding savings in OPEX and operations troubleshooting as
      well as interoperability that all vendor implementations now use
      the same IPv4 next hop encoding is the reason the encoding must be
      standardized.

   *  This IPv4 next hop encoding is applicable for IPv6 NLRI for both
      iBGP control plane (CP) peering as well as eBGP PE-CE, PE-PE in-
      line control / data plane (CP-DP) peering which is used for



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      IPv4-Only PE design as well as any IPv4 peering.  The IPv4 Next
      hop encoding updates both RFC 4271 next hop path attribute and RFC
      MP-BGP RFC 4760 NLRI path attribute.

   *  Some of the major vendors across platforms even support a variety
      of different encodings as well in some cases on the same platform
      the control plane BGP encoding and hardware programming is even
      differnet and does not match up.

   *  For interoperability if a vendor does not support the new next hop
      encoding, it would continue to use the IPv4 mapped IPv6 address
      format until the P2P send / receive neighbors MP-BGP MP_REACH BGP
      capability exchange is for the new IPv4 Next hop encoding
      codepoint.

10.  IPv6-Only PE Design / IPv6-Only PE Design Test Results

   Listed below are the following IPv6-Only PE Design, design scenario's
   that have been tested with test results related to the two of the
   Most Common SAFIs used today listed below:

   *  <AFI/SAFI>,

   *  IPv4 Unicast <1/1>, IPv6 Unicast <2/1>,

   *  VPN-IPV4 <1/128>, VPN-IPV6 <2/128>,

   IPv6-Only PE Design Proof of conept interoperability testing of the 2
   most common SAFI with 12 of the most common design use cases between
   the 4 vendors Cisco, Juniper, Nokia and Huawei.

   Cisco, Juniper, Nokia, Huawei, platform, code revision and test
   results for all use cases

   Cisco: Edge Router- XR ASR 9910 IOS XR 7.4.1, Core Router- NCS 6000
   7.2.2, CRS-X 6.7.4, XRd (XR Docker)

   Cisco: All testing completed tests 1-12 on XRd 7.10.11 Global table
   and VRF and IPv4 MPLS core and IPv6 SRv6 core

   Juniper: Edge Router- MX platform MX480, MX960, Core Router- PTX
   Platform PTX5000, PTC10K8 (JUNOS and EVO) Release 20.4R2

   All Testing 1-4 completed for Unicast SAFI 1/1 IPv4-Unicast, 2/1
   IPv6-Unicast

   All Testing 5-12 completed for IP VPN SAFI 1/128 IPv4-VPN, 2/128
   IPv6-VPN



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   Tested v4 edge over v6 core in a virtual setup using vMX platforrm
   and 20.4R2 and LDPv6 as underlay, but there were some data plane
   forwarding issues.  Tested same setup on latest release 21.4 and it
   worked.  Investigating what the minimum version is for this setup to
   work.

   Tested on above Juniper platforms.  Completed IPv6-Only PE design
   functionality test with PE-CE IPv6 peer carrying IPv4 and IPv6
   prefixes control plane validation and data plane forwarding plane
   validation and verified end to end reachability CE to CE forwarding
   plane with Default Per-CE label allocation mode.  Tested with
   IPv4-Only Core and IPv6-Only Core and proved that the IPv6-Only PE
   design solution works.  Both IPv4 and IPv6 packets were forwarded
   identical functionality of Dual Stack without having IPv4 address
   configured.

   Nokia: Edge and Core-7750 Service Router, Release R21

   All Testing 1-4 completed for Unicast SAFI 1/1 IPv4-Unicast, 2/1
   IPv6-Unicast

   All Testing 5-12 completed for IP VPN SAFI 1/128 IPv4-VPN, 2/128
   IPv6-VPN

   Huawei: Edge and Core-VRPv8, Release VRP-V800R020C10

   Not Completed

   Juniper Mx960 24.2R1-S1.10 and Nokia IXR-X3 25.7.R1 interoperability
   testing completed over IPv4 MPLS core and IPv6 SRv6 Core, tests 1-12
   completed successfully.  No issues.

   IPv4 Only PE Design, IPv6-Only PE Design Test Cases 1-12

   Intra-AS tests PE-CE Edge Peering IPv4-Only Core, IPv6-Only Core,
   Global Table (GRT) and IP VPN

   Test Cases 1-4

   *  IPv4 Core:
         -  AFI/SAFI IPv4-Unicast SAFI 1/1 IPv6-Unicast SAFI 2/1

         -  Test-1 Global table (6PE)

         -  Test-2 IP VPN

   *  IPv6 Core:
         -  AFI/SAFI IPv4-Unicast 1/1 SAFI IPv6-Unicast SAFI 2/1



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         -  Test-3 Global table (4PE)

         -  Test-4 IP VPN

   Inter-AS Options tests IPv4-Only Core, IPv6-Only Core, Global
   Table (GRT) and IP VPN

   Test Cases 5-12

   *  IPv4 Core:
         -  AFI/SAFI IPv4-VPN SAFI 1/128 IPv6-VPN SAFI 2/128

         -  Test-5 Global table 6PE Option-B

         -  Test-6 Global table 6PE Option-C

         -  Test-7 IP VPN Inter AS Option-B

         -  Test-8 IP VPN Inter AS Option-C

   *  IPv6 Core:
         -  AFI/SAFI IPv4-Unicast SAFI IPv6-Unicast SAFI

         -  Test-9 Global table Option-B

         -  Test-10 Global table Option-C

         -  Test-11 IP VPN Inter AS Option-B

         -  Test-12 IP VPN Inter AS Option-C

11.  IPv6-Only PE Design Testing Details

   Listed below are the following IPv6-Only PE Design, design scenario's
   that have been tested with test results related to the 3 of the Most
   Common SAFIs used today listed below:

   <AFI/SAFI> IPv4 Unicast <1/1>, IPv6 Unicast <2/1>, VPN-IPV4 <1/128>,
   VPN-IPV6 <2/128>, Multicasat VPN <1/129>, Multicasat VPN <2/129>,BGP-
   LU IPV4 (GRT) <1/4>

11.1.  Test-1 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
       Table over IPv4-Only Core(6PE)








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                                ________
      IPv6-Only       _____    /        \                 IPv6-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  |                          |_      |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv6 BGP peer       \     MPLS / SR domain /         IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




        Figure 10: Test-1 E2E IPv6-Only PE-CE, Global Table over
                          IPv4-Only Core (6PE)

11.2.  Test-2 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN over
       IPv4-Only Core


                                ________
      IPv6-Only       _____    /        \                 IPv6-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  | 0====VPN Overlay Tunnel ==0|     |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv6 BGP peer       \   MPLS / SR domain   /         IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




     Figure 11: Test-2 E2E IPv6-Only PE-CE, VPN over IPv4-Only Core

11.3.  Test-3 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
       Table over IPv6-Only Core (4PE)








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                                ________
      IPv6-Only       _____    /        \                 IPv6-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  |                          |_      |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv6-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv6 BGP peer       \     MPLS / SR domain /         IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




        Figure 12: Test-3 E2E IPv6-Only PE-CE, Global Table over
                          IPv6-Only Core (4PE)

11.4.  Test-4 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN over
       IPv6-Only Core


                                ________
      IPv6-Only       _____    /        \                 IPv6-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  | 0====VPN Overlay Tunnel ==0|     |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv6-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv6 BGP peer       \    MPLS / SR domain  /         IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




     Figure 13: Test-4 E2E IPv6-Only PE-CE, VPN over IPv6-Only Core

11.5.  Test-5 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
       Table over IPv4-Only Core(6PE) - Inter-AS Option-B








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                    Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




          Figure 14: Test-5 E2E IPv6-Only PE-CE, Global Table over
                  IPv4-Only Core (6PE) - Inter-AS Option-B

11.6.  Test-6 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
       Table over IPv4-Only Core(6PE) - Inter-AS Option-C


                   Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




          Figure 15: Test-6 E2E IPv6-Only PE-CE, Global Table over
                  IPv4-Only Core (6PE) - Inter-AS Option-C

11.7.  Test-7 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN over
       IPv4-Only - Inter-AS Option-B







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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




      Figure 16: Test-7 E2E IPv6-Only PE-CE, VPN over IPv4-Only Core -
                             Inter-AS Option-B

11.8.  Test-8 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN over
       IPv4-Only Core - Inter-AS Option-C


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




      Figure 17: Test-8 E2E IPv6-Only PE-CE, VPN over IPv4-Only Core -
                             Inter-AS Option-C

11.9.  Test-9 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
       Table over IPv6-Only Core - Inter-AS Option-B







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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|----|IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




          Figure 18: Test-9 E2E IPv6-Only PE-CE, Global Table over
                    IPv6-Only Core - Inter- AS Option-B

11.10.  Test-10 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, Global
        Table over IPv6-Only Core - Inter-AS Option-C


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding





         Figure 19: Test-10 E2E IPv6-Only PE-CE, Global Table over
                     IPv6-Only Core - Inter-AS Option-C

11.11.  Test-11 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN
        over IPv6-Only Core - Inter-AS Option-B






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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding



     Figure 20: Test-11 E2E IPv6-Only PE-CE, VPN over IPv6-Only Core -
                             Inter-AS Option-B

11.12.  Test-12 IPv6-Only PE Design All SAFI E2E IPv6-Only PE-CE, VPN
        over IPv6-Only Core - Inter-AS Option-C


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




     Figure 21: Test-12 E2E IPv6-Only PE-CE, VPN over IPv6-Only Core -
                             Inter-AS Option-C

11.13.  IPv6-Only PE-CE Operational Considerations Testing









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                       Ping CE to PE when destination prefix is withdrawn
                       Traceroute CE to PE and test all ICMPv4 and ICMPv6 type codes

                   +-------+                +-------+
                   |       |  IPv6 Only     |       |
                   |   CE  |----------------|  PE   |
                   |       |  IPv6 BGP Peer |       |
                   +-------+                +-------+
                  IPv4 forwarding            IPv4 forwarding
                  IPv6 forwarding            IPv6 forwarding


       Figure 22: Ping and Trace Test Case IPv6-Only PE Design

12.  IPv4-Only PE Design Testing Details

   Listed below are the following IPv4-Only PE Design, design scenario's
   that have been tested with test results related to the 3 of the Most
   Common SAFIs used today listed below:

   <AFI/SAFI> IPv4 Unicast <1/1>, IPv6 Unicast <2/1>, VPN-IPV4 <1/128>,
   VPN-IPV6 <2/128>, Multicasat VPN <1/129>, Multicasat VPN <2/129>,BGP-
   LU IPV4 (GRT) <1/4>

12.1.  Test-1 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
       Table over IPv4-Only Core(6PE)


                                ________
      IPv4-Only       _____    /        \                 IPv4-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  |                          |_      |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv4 BGP peer       \     MPLS / SR domain /         IPv4 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




        Figure 23: Test-1 E2E IPv4-Only PE-CE, Global Table over
                          IPv4-Only Core (6PE)





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12.2.  Test-2 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN over
       IPv4-Only Core


                                ________
      IPv4-Only       _____    /        \                 IPv4-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  | 0====VPN Overlay Tunnel ==0|     |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv4 BGP peer       \   MPLS / SR domain   /         IPv4 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




     Figure 24: Test-2 E2E IPv4-Only PE-CE, VPN over IPv4-Only Core

   Huawei: Edge and Core-VRPv8, Release VRP-V800R020C10

12.3.  Test-3 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
       Table over IPv6-Only Core (4PE)


                                ________
      IPv4-Only       _____    /        \                 IPv4-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  |                          |_      |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv4 BGP peer       \     MPLS / SR domain /         IPv4 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




        Figure 25: Test-3 E2E IPv4-Only PE-CE, Global Table over
                          IPv6-Only Core (4PE)





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12.4.  Test-4 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN over
       IPv6-Only Core


                                ________
      IPv4-Only       _____    /        \                 IPv4-Only
       PE / CE       /     \__/          \___              PE / CE
   +----+  +----+   /                        \        +------+   +-----+
   |    |  |    |  | 0====VPN Overlay Tunnel ==0|     |      |   |     |
   |    |  |    |  |                             \    |      |   |     |
   | CE |--| PE |--\         IPv4-Only Core      |----|  PE  |---|  CE |
   |    |  |    |    \0=========Underlay =======0|    |      |   |     |
   +----+  +----+     \                        __/    +------+   +-----+
   IPv4 BGP peer       \    MPLS / SR domain  /         IPv4 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




     Figure 26: Test-4 E2E IPv4-Only PE-CE, VPN over IPv6-Only Core

12.5.  Test-5 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
       Table over IPv4-Only Core(6PE) - Inter-AS Option-B



                    Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding



          Figure 27: Test-5 E2E IPv4-Only PE-CE, Global Table over
                  IPv4-Only Core (6PE) - Inter-AS Option-B

12.6.  Test-6 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
       Table over IPv4-Only Core(6PE) - Inter-AS Option-C




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                   Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




          Figure 28: Test-6 E2E IPv4-Only PE-CE, Global Table over
                  IPv4-Only Core (6PE) - Inter-AS Option-C

12.7.  Test-7 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN over
       IPv4-Only - Inter-AS Option-B


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




      Figure 29: Test-7 E2E IPv4-Only PE-CE, VPN over IPv4-Only Core -
                             Inter-AS Option-B

12.8.  Test-8 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN over
       IPv4-Only Core - Inter-AS Option-C







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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv4-Only Core|----|IPv4-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




      Figure 30: Test-8 E2E IPv4-Only PE-CE, VPN over IPv4-Only Core -
                             Inter-AS Option-C

12.9.  Test-9 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
       Table over IPv6-Only Core - Inter-AS Option-B


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|----|IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




          Figure 31: Test-9 E2E IPv4-Only PE-CE, Global Table over
                    IPv6-Only Core - Inter- AS Option-B

12.10.  Test-10 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, Global
        Table over IPv6-Only Core - Inter-AS Option-C







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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Underlay==0  |    |0==Underlay==0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




         Figure 32: Test-10 E2E IPv4-Only PE-CE, Global Table over
                     IPv6-Only Core - Inter-AS Option-C

12.11.  Test-11 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN
        over IPv6-Only Core - Inter-AS Option-B


                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




     Figure 33: Test-11 E2E IPv4-Only PE-CE, VPN over IPv6-Only Core -
                             Inter-AS Option-B

12.12.  Test-12 IPv4-Only PE Design All SAFI E2E IPv4-Only PE-CE, VPN
        over IPv6-Only Core - Inter-AS Option-C







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                  Inter-AS ASBR-ASBR link is IPv6-Only PE
     IPv6-Only       __________          __________      IPv6-Only
      PE / CE       /          \        /          \      PE / CE
     +--+ +----+   /            \      /            \    +--+ +--+
     |  | |    |  |    AS 1      \     |    AS 2     \   |  | |  |
     |  | |    |  |               \IPv6|              \  |  | |  |
     |CE|-| PE |--| IPv6-Only Core|--- |IPv6-Only Core|--|PE|-|CE|
     |  | |    |  |0=Overlay===0  |    |0==Overlay===0|  |  | |  |
     +--+ +----+   \             /     \             /   +--+ +--+
     IPv6 BGP peer  \ MPLS/SR   /       \ MPLS/SR   /   IPv6 BGP peer
     IPv4 forwarding \_________/         \_________/    IPv4 forwarding
     IPv6 forwarding                                    IPv6 forwarding




     Figure 34: Test-12 E2E IPv4-Only PE-CE, VPN over IPv6-Only Core -
                             Inter-AS Option-C

12.13.  IPv4-Only PE-CE Operational Considerations Testing


                       Ping CE to PE when destination prefix is withdrawn
                       Traceroute CE to PE and test all ICMPv4 and ICMPv6 type codes

                   +-------+                +-------+
                   |       |  IPv4 Only     |       |
                   |   CE  |----------------|  PE   |
                   |       |  IPv4 BGP Peer |       |
                   +-------+                +-------+
                  IPv4 forwarding            IPv4 forwarding
                  IPv6 forwarding            IPv6 forwarding


                 Figure 35: Ping and Trace Test Case

13.  SRv6 Applicability to IPv6 Only PE Design

   SRv6 [RFC8986] applicability to IPv6-Only PE design

   SRv6 [RFC8986] Full 128 bit SID and SRv6 Compression
   [I-D.ietf-spring-srv6-srh-compression] C-SID Next C-SID (uSID)
   endpoint flavor and Replace SID C-SID (G-SID) endpoint flavor is
   fully supported for all 12 IPv6-Only PE Design use cases.







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   SRv6 Next SID utilizes a Next C-SID uSID carrier for the micro sid
   for up to 5 hops of steering without requiring an SRH.  SRv6 Next SID
   uN Node sid endpoint function for uSID F3216 format shift 16 bits and
   forward to the next node allows the vanilla IPv6 data plane to be
   used to seamlessly stitch.  across inter-as inter domain hops.

   The following SRv6 Compression C-SID Next C-SID (uSID) endpoint
   flavor 4 use cases will be fully tested by Cisco, Juniper, Nokia.

   1.  Global Table 4PE Test Scenario

   Global Table IPv6 Only PE Design where Inter-AS PE-PE core boundary
   AFI/SAFI 1/1 IPv4 Unicast 2/1 IPv6 Unicast (4PE) and are carried over
   a single IPv6 peering.  In this use case the Inter-AS PE-PE nodes are
   SRv6 Next SID endpoint behavior capable and perform the steering
   function Un endpoint behavior shift 16 bits and forward function.
   This SRv6 compression use case is applicable to IPv6 Only PE Design
   Test-9 - IPv6 Core 4PE Global table BGP overlay stitching in SRv6
   terms is Next Hop Unchanged Global BGP overlay stitching.  Use case
   where Inter-AS PE-PE Edge boundary AFI/SAFI 1/1 IPv4 Unicast 2/1 IPv6
   Unicast are carried over a single IPv6 peer the peering.

   *  Global Table (4PE) Test Scenario
         -  SRv6 Test Scenarios (Global)

         -  1.  SRv6 enabled on inter-as PE-PE nodes (SRv6 aware inter
            domain SRv6 fabric stitching and active traffic steering)

         -  2.  SRv6 disabled on inter-as PE-PE nodes (SRv6 unaware
            inter domain IPv6 Data plane stitching without traffic
            steering)

   2.  VPN Overlay Test Scenario

   VPN Overlay IPv6 Only PE Design where Inter-AS PE-PE core boundary
   AFI/SAFI 1/128 IPv4 VPN 2/128 IPv6 VPN and are carried over a single
   IPv6 peering.  In this use case the Inter-AS PE-PE nodes are SRv6
   Next SID endpoint behavior capable and perform the steering function
   Un endpoint behavior shift 16 bits and forward function.  This SRv6
   compression use case is applicable to IPv6 Only PE Design Test-11 -
   IPv6 Core L3 VPN Inter-AS Option B which in SRv6 terms is Next Hop
   Unchanged VPN overlay stitching.  Use case where Inter-AS PE-PE Edge
   boundary AFI/SAFI 1/128 IPv4 VPN 2/128 IPv6 VPN are carried over a
   single IPv6 peering.

   *  IP VPN Scenario
         -  SRv6 Test Scenarios (IP VPN)




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         -  1.  SRv6 enabled on inter-as PE-PE nodes (SRv6 aware inter
            domain SRv6 fabric stitching and active traffic steering)

         -  2.  SRv6 disabled on inter-as PE-PE nodes (SRv6 unaware
            inter domain IPv6 Data plane stitching without traffic
            steering)

14.  Typed and Untyped SAFI

   Typed SAFI are Not Applicable to this specification

   Typed SAFI are SAFI where the SAFI uses the Route Types in which case
   their is a NLRI "Route Type" field followd by NLRI Data field
   containing the IPv4 and IPv6 NLRI With Non Typed SAFI the IPv4 and
   IPv6 NLRI is encoded directly within the NLRI making it directly data
   plane dependent with CP-DP control plane RIB programming followed by
   data plane FIB programming.  This Typed SAFI case exists where the
   control plane procedures exist in which case the data plane is
   instantiated making the IPv4 and IPv6 NLRI for the Typed SAFI data
   plane agnostic.  IPv4 Only PE deisgn has a single IPv4 Peer that
   carries the IPv4 and IPv6 NLRI and the interface only has an IPv4
   address and requires a vendor specific knob for ipv6 forwarding.
   IPv6 Only PE deisgn has a single IPv6 Peer that carries the IPv4 and
   IPv6 NLRI and the interface only has an IPv6 address and requires a
   vendor specific knob for ipv4 forwarding.  Since typed routes are
   data plane agnostic and so are not directly correlated to the IPv4
   and IPv6 protocol forwarding makes the Typed SAFI listed below not
   applicable to this specification.

   *  Typed SAFI
         -  The following AFI/SAFI are not applicable (N/A) to this
            specification

         -  1.  MCAST-VPN [RFC6514]

         -  2.  MCAST-VPLS [RFC7117]

         -  3.  EVPN [RFC7432]

         -  4.  BGP-LS [RFC7752]

15.  IPv4-Only PE Design and IPv6-Only PE Design ALL AFI/SFI Operational
     Considerations

   With a single IPv4 Peer or IPv6 Peer carrying both IPv4 and IPv6 NLRI
   there are some operational considerations in terms of what changes
   and what does not change.




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   What does not change with a single IPv6 transport peer carrying IPv4
   NLRI and IPv6 NLRI below:

   Routing Policy configuration is still separate for IPv4 and IPv6
   configured by capability as previously.

   Layer 1, Layer 2 issues such as one-way fiber or fiber cut will
   impact both IPv4 and IPv6 as previously.

   If the interface is in the Admin Down state, the IPv6 peer would go
   down, and IPv4 NLRI and IPv6 NLRI would be withdrawn as previously.

   Changes resulting from a single IPv6 transport peer carrying IPv4
   NLRI and IPv6 NLRI below:

   Physical interface is no longer dual stacked.

   Any change in IPv6 address or DAD state will impact both IPv4 and
   IPv6 NLRI exchange.

   Single BFD session for both IPv4 and IPv6 NLRI fate sharing as the
   session is now tied to the transport, which now is only IPv6 address
   family.

   Both IPv4 and IPv6 peer now exists under the IPv6 address family
   configuration.

   Fate sharing of IPv4 and IPv6 address family from a logical
   perspective now carried over a single physical IPv6 peer.

   From an operations perspective, prior to elimination of IPv4 peers,
   an audit is recommended to identify and IPv4 and IPv6 peering
   incongruencies that may exist and to rectify them.  No operational
   impacts or issues are expected with this change.

   With MPLS VPN overlay, per-CE next-hop label allcoation mode where
   both IPv4 and IPv6 prefixes have the same label in no table lookup
   pop-n-forward mode should be taken into consideration.

16.  IANA Considerations

   New IANA capability codepoint is requested for next hop encoding for
   IPv4 next hop applicable to all SAFI for IPv4-Only PE design Inter-AS
   scenarios PE-PE, PE-CE as well as existing Intra-AS PE-RR peering
   Scenarios.






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17.  Security Considerations

   The extensions defined in this document allow BGP to propagate
   reachability information about IPv4 prefixes over an MPLS or SR
   IPv6-Only core network.  As such, no new security issues are raised
   beyond those that already exist in BGP-4 and the use of MP-BGP for
   IPv6.  Both IPv4 and IPv6 peers exist under the IPv6 address family
   configuration.  The security features of BGP and corresponding
   security policy defined in the ISP domain are applicable.  For the
   inter-AS distribution of IPv6 routes according to case (a) of
   Section 4 of this document, no new security issues are raised beyond
   those that already exist in the use of eBGP for IPv6 [RFC2545].

18.  Acknowledgments

   Thanks to Kaliraj Vairavakkalai, Linda Dunbar, Aijun Wang, Eduardfor
   Vasilenko, Joel Harlpern, Michael McBride, Ketan Talaulikar for
   review comments.

19.  Contributors

   The following people contributed substantive text to this document:

       Mohana Sundari
       EMail: mohanas@juniper.net


20.  References

20.1.  Normative References

   [I-D.ietf-bess-bgp-multicast]
              Zhang, Z. J., Giuliano, L., Patel, K., Wijnands, I.,
              Mishra, M. P., and A. Gulko, "BGP Based Multicast", Work
              in Progress, Internet-Draft, draft-ietf-bess-bgp-
              multicast-09, 24 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-bess-
              bgp-multicast-09>.

   [I-D.ietf-bess-ipv6-only-pe-design]
              Mishra, G. S., Mishra, M. P., Tantsura, J., Madhavi, S.,
              Yang, Q., Simpson, A., and S. Chen, "IPv6-Only PE Design
              for IPv4-NLRI with IPv6-NH", Work in Progress, Internet-
              Draft, draft-ietf-bess-ipv6-only-pe-design-04, 20 May
              2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
              bess-ipv6-only-pe-design-04>.





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   [I-D.ietf-idr-bgp-car]
              Rao, D. and S. Agrawal, "BGP Color-Aware Routing (CAR)",
              Work in Progress, Internet-Draft, draft-ietf-idr-bgp-car-
              16, 20 February 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
              car-16>.

   [I-D.ietf-idr-flowspec-nvo3]
              Eastlake, D. E., Weiguo, H., Zhuang, S., Li, Z., and R.
              Gu, "BGP Dissemination of Flow Specification Rules for
              Tunneled Traffic", Work in Progress, Internet-Draft,
              draft-ietf-idr-flowspec-nvo3-22, 6 June 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              flowspec-nvo3-22>.

   [I-D.ietf-idr-rpd]
              Li, Z., Ou, L., Luo, Y., Mishra, G. S., Chen, H., and H.
              Wang, "BGP Extensions for Routing Policy Distribution
              (RPD)", Work in Progress, Internet-Draft, draft-ietf-idr-
              rpd-19, 28 March 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-rpd-
              19>.

   [I-D.ietf-idr-sdwan-edge-discovery]
              Dunbar, L., Hares, S., Majumdar, K., Raszuk, R., and V.
              Kasiviswanathan, "BGP UPDATE for SD-WAN Edge Discovery",
              Work in Progress, Internet-Draft, draft-ietf-idr-sdwan-
              edge-discovery-25, 22 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              sdwan-edge-discovery-25>.

   [I-D.ietf-idr-segment-routing-te-policy]
              Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., and
              D. Jain, "Advertising Segment Routing Policies in BGP",
              Work in Progress, Internet-Draft, draft-ietf-idr-segment-
              routing-te-policy-26, 23 October 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              segment-routing-te-policy-26>.

   [I-D.ietf-l3vpn-bgpvpn-auto]
              Ould-Brahim, H. H., "Using BGP as an Auto-Discovery
              Mechanism for VR-based Layer-3 VPNs", Work in Progress,
              Internet-Draft, draft-ietf-l3vpn-bgpvpn-auto-09, 25 April
              2007, <https://datatracker.ietf.org/doc/html/draft-ietf-
              l3vpn-bgpvpn-auto-09>.






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   [I-D.ietf-lsvr-bgp-spf]
              Patel, K., Lindem, A., Zandi, S., and W. Henderickx, "BGP
              Link-State Shortest Path First (SPF) Routing", Work in
              Progress, Internet-Draft, draft-ietf-lsvr-bgp-spf-51, 23
              January 2025, <https://datatracker.ietf.org/doc/html/
              draft-ietf-lsvr-bgp-spf-51>.

   [I-D.ietf-spring-srv6-srh-compression]
              Cheng, W., Filsfils, C., Li, Z., Decraene, B., and F.
              Clad, "Compressed SRv6 Segment List Encoding (CSID)", Work
              in Progress, Internet-Draft, draft-ietf-spring-srv6-srh-
              compression-23, 6 February 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-spring-
              srv6-srh-compression-23>.

   [I-D.mpmz-bess-mup-safi]
              Murakami, T., Patel, K., Matsushima, S., Zhang, Z. J.,
              Agrawal, S., and D. Voyer, "BGP Extensions for the Mobile
              User Plane (MUP) SAFI", Work in Progress, Internet-Draft,
              draft-mpmz-bess-mup-safi-05, 13 February 2025,
              <https://datatracker.ietf.org/doc/html/draft-mpmz-bess-
              mup-safi-05>.

   [I-D.nalawade-kapoor-tunnel-safi]
              Nalawade, G., "BGP Tunnel SAFI", Work in Progress,
              Internet-Draft, draft-nalawade-kapoor-tunnel-safi-05, 29
              June 2006, <https://datatracker.ietf.org/doc/html/draft-
              nalawade-kapoor-tunnel-safi-05>.

   [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>.

   [RFC2545]  Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
              Extensions for IPv6 Inter-Domain Routing", RFC 2545,
              DOI 10.17487/RFC2545, March 1999,
              <https://www.rfc-editor.org/info/rfc2545>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <https://www.rfc-editor.org/info/rfc4291>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.





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   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC5195]  Ould-Brahim, H., Fedyk, D., and Y. Rekhter, "BGP-Based
              Auto-Discovery for Layer-1 VPNs", RFC 5195,
              DOI 10.17487/RFC5195, June 2008,
              <https://www.rfc-editor.org/info/rfc5195>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <https://www.rfc-editor.org/info/rfc5492>.

   [RFC5747]  Wu, J., Cui, Y., Li, X., Xu, M., and C. Metz, "4over6
              Transit Solution Using IP Encapsulation and MP-BGP
              Extensions", RFC 5747, DOI 10.17487/RFC5747, March 2010,
              <https://www.rfc-editor.org/info/rfc5747>.

   [RFC6037]  Rosen, E., Ed., Cai, Y., Ed., and IJ. Wijnands, "Cisco
              Systems' Solution for Multicast in BGP/MPLS IP VPNs",
              RFC 6037, DOI 10.17487/RFC6037, October 2010,
              <https://www.rfc-editor.org/info/rfc6037>.

   [RFC7117]  Aggarwal, R., Ed., Kamite, Y., Fang, L., Rekhter, Y., and
              C. Kodeboniya, "Multicast in Virtual Private LAN Service
              (VPLS)", RFC 7117, DOI 10.17487/RFC7117, February 2014,
              <https://www.rfc-editor.org/info/rfc7117>.

   [RFC7267]  Martini, L., Ed., Bocci, M., Ed., and F. Balus, Ed.,
              "Dynamic Placement of Multi-Segment Pseudowires",
              RFC 7267, DOI 10.17487/RFC7267, June 2014,
              <https://www.rfc-editor.org/info/rfc7267>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.








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   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [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>.

   [RFC8277]  Rosen, E., "Using BGP to Bind MPLS Labels to Address
              Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
              <https://www.rfc-editor.org/info/rfc8277>.

   [RFC8955]  Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
              Bacher, "Dissemination of Flow Specification Rules",
              RFC 8955, DOI 10.17487/RFC8955, December 2020,
              <https://www.rfc-editor.org/info/rfc8955>.

   [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>.

   [RFC9012]  Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
              "The BGP Tunnel Encapsulation Attribute", RFC 9012,
              DOI 10.17487/RFC9012, April 2021,
              <https://www.rfc-editor.org/info/rfc9012>.

   [RFC9015]  Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L.
              Jalil, "BGP Control Plane for the Network Service Header
              in Service Function Chaining", RFC 9015,
              DOI 10.17487/RFC9015, June 2021,
              <https://www.rfc-editor.org/info/rfc9015>.

20.2.  Informative References

   [I-D.ietf-idr-dynamic-cap]
              Chen, E. and S. R. Sangli, "Dynamic Capability for BGP-4",
              Work in Progress, Internet-Draft, draft-ietf-idr-dynamic-
              cap-17, 6 July 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-idr-
              dynamic-cap-17>.







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   [RFC4659]  De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,
              "BGP-MPLS IP Virtual Private Network (VPN) Extension for
              IPv6 VPN", RFC 4659, DOI 10.17487/RFC4659, September 2006,
              <https://www.rfc-editor.org/info/rfc4659>.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
              November 2006, <https://www.rfc-editor.org/info/rfc4684>.

   [RFC4798]  De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
              "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
              Provider Edge Routers (6PE)", RFC 4798,
              DOI 10.17487/RFC4798, February 2007,
              <https://www.rfc-editor.org/info/rfc4798>.

   [RFC4925]  Li, X., Ed., Dawkins, S., Ed., Ward, D., Ed., and A.
              Durand, Ed., "Softwire Problem Statement", RFC 4925,
              DOI 10.17487/RFC4925, July 2007,
              <https://www.rfc-editor.org/info/rfc4925>.

   [RFC5549]  Le Faucheur, F. and E. Rosen, "Advertising IPv4 Network
              Layer Reachability Information with an IPv6 Next Hop",
              RFC 5549, DOI 10.17487/RFC5549, May 2009,
              <https://www.rfc-editor.org/info/rfc5549>.

   [RFC5565]  Wu, J., Cui, Y., Metz, C., and E. Rosen, "Softwire Mesh
              Framework", RFC 5565, DOI 10.17487/RFC5565, June 2009,
              <https://www.rfc-editor.org/info/rfc5565>.

   [RFC6074]  Rosen, E., Davie, B., Radoaca, V., and W. Luo,
              "Provisioning, Auto-Discovery, and Signaling in Layer 2
              Virtual Private Networks (L2VPNs)", RFC 6074,
              DOI 10.17487/RFC6074, January 2011,
              <https://www.rfc-editor.org/info/rfc6074>.

   [RFC6513]  Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
              BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
              2012, <https://www.rfc-editor.org/info/rfc6513>.

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
              <https://www.rfc-editor.org/info/rfc6514>.





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   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8950]  Litkowski, S., Agrawal, S., Ananthamurthy, K., and K.
              Patel, "Advertising IPv4 Network Layer Reachability
              Information (NLRI) with an IPv6 Next Hop", RFC 8950,
              DOI 10.17487/RFC8950, November 2020,
              <https://www.rfc-editor.org/info/rfc8950>.

Appendix A.  SAFI LIST FOR PE-CE Edge Scenario

   IPv4-Only PE Design and IPv6-Only PE Design listing of PE-CE Edge ALL
   applicable SAFI.  Here we showing the catagorization grouping by
   columns of the SAFI into 2 use case categories.

   *  Unicst

   *  Multicast

    +============+=================+=========+===========+===========+
    | SAFI Value | Description     | Unicast | Multicast | Reference |
    +============+=================+=========+===========+===========+
    | 1          | Unicast         | Yes     | No        | [RFC4760] |
    +------------+-----------------+---------+-----------+-----------+
    | 2          | Multicast       | No      | Yes       | [RFC2545] |
    +------------+-----------------+---------+-----------+-----------+
    | 78         | MCAST-TREE SAFI | No      | Yes       | [RFC2545] |
    +------------+-----------------+---------+-----------+-----------+

         Table 1: IPv4-Only PE DESIGN and IPv6-Only PE DESIGN ALL
                        SAFI's PE-CE Edge Scenario

   IPv4-Only PE design supports 25 / 32 IANA SAFI's of which the 7 not
   supported do not use AFI=1 IPv4 or AFI=2 IPv6.

Appendix B.  SAFI LIST FOR Inter-AS PE-PE Scenario

   IPv4-Only PE Design and IPv6-Only PE Design listing of Inter-AS PE-PE
   ALL applicable SAFI.  All Typed SAFI are listed as Not Applicable (N/
   A) Here we show the catagorization grouping by columns of the SAFI
   into 5 use case categories.

   *  Unicst

   *  Multicast




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   *  L1-L2 VPN

   *  Tunnel

   *  BGP Policy

   +=====+=============+=======+=========+=====+======+======+========================================+
   |SAFI |Description  |Unicast|Multicast|L1-L2|Tunnel| BGP  |               Reference                |
   |Value|             |       |         | VPN |      |Policy|                                        |
   +=====+=============+=======+=========+=====+======+======+========================================+
   |1    |NLRI Unicast |Yes    |No       |No   |No    |No    |[RFC4760]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |2    |NLRI         |No     |Yes      |No   |No    |No    |[RFC4760]                               |
   |     |Multicast    |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |4    |NLRI MPLS    |Yes    |No       |No   |No    |No    |[RFC8277]                               |
   |     |Laels        |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |5    |MCAST-VPN    |No     |Yes      |No   |No    |No    |[RFC6514]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |6    |Dynamic Multi|No     |No       |Yes  |No    |No    |[RFC7267]                               |
   |     |Segment PW   |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |8    |MCAST-VPLS   |N/A    |N/A      |N/A  |N/A   |N/A   |[RFC7117]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |9    |BGP-SFC      |No     |No       |No   |No    |No    |[RFC9015]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |64   |Tunnel SAFI  |No     |No       |No   |Yes   |No    |[I-D.nalawade-kapoor-tunnel-safi]       |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |65   |VPLS         |No     |No       |No   |No    |No    |[RFC4761]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |66   |BGP MDT SAFI |NO     |Yes      |No   |No    |No    |[RFC6037]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |67   |BGP 4to6 SAFI|No     |No       |No   |Yes   |No    |[RFC5747]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |68   |BGP 6to4 SAFI|No     |No       |No   |Yes   |No    |[RFC5747]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |69   |L1 VPN Auto  |No     |No       |Yes  |No    |No    |[RFC5195]                               |
   |     |Discovery    |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |70   |BGP EVPN     |N/A    |N/A      |N/A  |N/A   |N/A   |[RFC7432]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |71   |BGP-LS       |N/A    |N/A      |N/A  |N/A   |N/A   |[RFC7752]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |72   |BGP-LS-VPN   |N/A    |N/A      |N/A  |N/A   |N/A   |[RFC7752]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |73   |SR-TE Policy |No     |No       |No   |No    |Yes   |[I-D.ietf-idr-segment-routing-te-policy]|
   |     |SAFI         |       |         |     |      |      |                                        |



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   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |74   |SD-WAN       |No     |No       |No   |No    |Yes   |[I-D.ietf-idr-sdwan-edge-discovery]     |
   |     |Capabilities |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |75   |Routing      |No     |No       |No   |No    |No    |[I-D.ietf-idr-rpd]                      |
   |     |Policy SAFI  |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |77   |Tunneled     |No     |No       |No   |Yes   |No    |[I-D.ietf-idr-flowspec-nvo3]            |
   |     |Traffic      |       |         |     |      |      |                                        |
   |     |Flowspec     |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |78   |MCAST-TREE   |No     |Yes      |No   |No    |No    |[I-D.ietf-bess-bgp-multicast]           |
   |     |SAFI         |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |80   |BGP-LS-SPF   |No     |No       |No   |No    |No    |[I-D.ietf-lsvr-bgp-spf]                 |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |83   |BGP CAR      |N/A    |N/A      |N/A  |N/A   |N/A   |[I-D.ietf-idr-bgp-car]                  |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |84   |BGP CAR VPN  |N/A    |N/A      |N/A  |N/A   |N/A   |[I-D.ietf-idr-bgp-car]                  |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |85   |BGP MUP SAFI |No     |No       |No   |No    |Yes   |[I-D.mpmz-bess-mup-safi]                |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |128  |MPLS VPN     |Yes    |No       |No   |No    |No    |[RFC4364]                               |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |129  |MPLS         |N/A    |N/A      |N/A  |N/A   |N/A   |[RFC6513]                               |
   |     |Multicast VPN|       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |132  |Route Target |Yes    |No       |No   |No    |No    |[RFC4684]                               |
   |     |Constrains   |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |133  |Dissemination|No     |No       |No   |No    |Yes   |[RFC8955]                               |
   |     |of Flowspec  |       |         |     |      |      |                                        |
   |     |Rules        |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |134  |L3VPN        |No     |No       |No   |No    |Yes   |[RFC8955]                               |
   |     |Dissemination|       |         |     |      |      |                                        |
   |     |of Flowspec  |       |         |     |      |      |                                        |
   |     |Rules        |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+
   |140  |VPN Auto     |No     |No       |No   |No    |Yes   |[I-D.ietf-l3vpn-bgpvpn-auto]            |
   |     |Discovery    |       |         |     |      |      |                                        |
   +-----+-------------+-------+---------+-----+------+------+----------------------------------------+

      Table 2: IPv4-Only PE DESIGN and IPv6-Only PE Design ALL SAFI's
                          Inter-AS PE-PE Scenario






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   IPv4-Only PE Design and IPv6-Only PE design supports 20 / 32 IANA
   SAFI's of which the 7 not supported do not use AFI=1 IPv4 or AFI=2
   IPv6 and 5 are N/A.

Authors' Addresses

   Gyan Mishra
   Verizon Inc.
   Email: gyan.s.mishra@verizon.com


   Sudha Madhavi
   Juniper Networks, Inc.
   Email: smadhavi@juniper.net


   Adam Simpson
   Nokia
   Email: adam.1.simpson@nokia.com


   Mankamana Mishra
   Cisco Systems
   821 Alder Drive,
   MILPITAS
   Email: mankamis@cisco.com


   Jeff Tantsura
   Microsoft, Inc.
   Email: jefftant.ietf@gmail.com


   Shuanglong Chen
   Huawei Technologies
   Email: chenshuanglong@huawei.com















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