BESS Working Group                                             G. Mishra
Internet-Draft                                              Verizon Inc.
Intended status: Standards Track                               M. Mishra
Expires: 8 September 2022                                  Cisco Systems
                                                             J. Tantsura
                                                         Microsoft, Inc.
                                                              S. Madhavi
                                                  Juniper Networks, Inc.
                                                                 Q. Yang
                                                         Arista Networks
                                                              A. Simpson
                                                                   Nokia
                                                                 S. Chen
                                                     Huawei Technologies
                                                            7 March 2022


                      IPv6-Only PE Design All SAFI
            draft-mishra-bess-ipv6-all-pe-design-any-safi-00

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 be able to continue to
   support IPv4 customers when both the Core and Edge networks are
   IPv6-Only.

   This document details an important External BGP (eBGP) PE-PE Inter-AS
   IPv6-Only peering design that leverages the MP-BGP capability
   exchange by using IPv6 peering as pure transport, allowing both 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 Address Family Identifiers
   (AFI) and Subsequent Address Family Identifiers(SAFI).  The design
   change provides the same Dual Stacking functionality that exists
   today with separate IPv4 and IPv6 BGP sessions as we have today.
   With this IPv6-Only PE Design, IPv4 address MUST not be configured on
   the the Provider Edge (PE) - Customer Edge (CE), or Inter-AS ASBR
   (Autonomous System Boundary Router) to ASBR (Autonomous System
   Boundary Router) PE-PE Provider Edge (PE) - Provider Edge (PE).  From
   a control plane perspective 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 to PE
   Inter-AS peering interface for both IPv4 and IPv6 packet forwarding.
   This document defines the IPv6-Only PE Design as a new PE-CE and PE-



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   PE BGP peering Standard which is described in the POC testing
   document [I-D.ietf-bess-ipv6-only-pe-design] to all AFI/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-AB and Option-C are still
   applicable and thus this extension of IPv6-Only peering architecure
   extension to Inter-AS peering is very relevant to Segment Routing as
   well.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 8 September 2022.

Copyright Notice

   Copyright (c) 2022 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
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   7
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  IPv6-Only Edge Peering Architecture . . . . . . . . . . . . .   7
     4.1.  Problem Statement . . . . . . . . . . . . . . . . . . . .   7
     4.2.  IPv6-Only PE-CE Design Solution . . . . . . . . . . . . .   9



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     4.3.  IPv6-Only Edge Peering Design . . . . . . . . . . . . . .  10
       4.3.1.  IPv6-Only Edge Peering Packet Walk  . . . . . . . . .  10
       4.3.2.  6to4 Softwire IPv4-Only Core packet walk  . . . . . .  10
       4.3.3.  4to6 Softwire IPv6-Only Core packet walk  . . . . . .  12
     4.4.  RFC5549 and RFC8950 Applicability . . . . . . . . . . . .  14
       4.4.1.  IPv6-Only Edge Peering design next-hop encoding . . .  15
       4.4.2.  RFC8950 updates to RFC5549 applicability  . . . . . .  15
   5.  IPv6-Only PE Design Edge E2E Design for all AFI/SAFI  . . . .  16
     5.1.  IPv6-Only PE Design All SAFI Case-1 E2E IPv6-Only PE-CE,
            Global Table over IPv4-Only Core(6PE), 6to4 softwire . .  16
     5.2.  IPv6-Only PE Design All SAFI Case-2 E2E IPv6-Only PE-CE,
            VPN over IPv4-Only Core, 6to4 Softwire . . . . . . . . .  17
     5.3.  IPv6-Only PE Design All SAFI Case-3 E2E IPv6-Only PE-CE,
            Global Table over IPv6-Only Core (4PE), 4to6 Softwire  .  17
     5.4.  IPv6-Only PE Design All SAFI Case-4 E2E IPv6-Only PE-CE,
            VPN over IPv6-Only Core, 4to6 Softwire . . . . . . . . .  18
     5.5.  IPv6-Only PE Design All SAFI Case-5 E2E IPv6-Only PE-CE,
            Global Table over IPv4-Only Core(6PE), 6to4 softwire
            -Inter-AS Option-B . . . . . . . . . . . . . . . . . . .  18
     5.6.  IPv6-Only PE Design All SAFI Case-6 E2E IPv6-Only PE-CE,
            Global Table over IPv4-Only Core(6PE), 6to4 softwire
            -Inter-AS Option-C . . . . . . . . . . . . . . . . . . .  19
     5.7.  IPv6-Only PE Design All SAFI Case-7 E2E IPv6-Only PE-CE,
            VPN over IPv4-Only, 6to4 softwire -Inter-AS Option-B . .  19
     5.8.  IPv6-Only PE Design All SAFI Case-8 E2E IPv6-Only PE-CE,
            VPN over IPv4-Only Core, 6to4 softwire -Inter-AS
            Option-C . . . . . . . . . . . . . . . . . . . . . . . .  20
     5.9.  IPv6-Only PE Design All SAFI Case-9 E2E IPv6-Only PE-CE,
            Global Table over IPv6-Only Core, 4to6 softwire -Inter-AS
            Option-B . . . . . . . . . . . . . . . . . . . . . . . .  20
     5.10. IPv6-Only PE Design All SAFI Case-10 E2E IPv6-Only PE-CE,
            Global Table over IPv6-Only Core, 4to6 softwire -Inter-AS
            Option-C . . . . . . . . . . . . . . . . . . . . . . . .  21
     5.11. IPv6-Only PE Design All SAFI Case-4 E2E IPv6-Only PE-CE,
            VPN over IPv6-Only Core, 4to6 softwire -Inter-AS
            Option-B . . . . . . . . . . . . . . . . . . . . . . . .  21
     5.12. IPv6-Only PE Design All SAFI Case-12 E2E IPv6-Only PE-CE,
            VPN over IPv6-Only Core, 4to6 softwire -Inter-AS
            Option-C . . . . . . . . . . . . . . . . . . . . . . . .  22
     5.13. IPv6-Only PE-CE Operational Considerations Testing  . . .  22
   6.  IPv6-Only PE ALL AFI/SFI Operational Considerations . . . . .  22
   7.  Vendor Implementations and Operator Deployments . . . . . . .  23
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  23
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  24
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  24
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  24
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  24
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  24



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     12.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  28

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.  Operators have a
   requirement to support IPv4 customers and must be able to support
   IPv4 address family and Sub-Address-Family Virtual Private Network
   (VPN)-IPv4, and Multicast VPN IPv4 customers.

   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
   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.

   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.

   The current specification for carrying IPv4 NLRI of a given address
   family via a Next Hop of a different address family is now defined in
   [RFC8950], and specifies the extended next hop encoding MP-REACH



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   capability extension necessary to do so.  This comprises an extension
   of the AFI/SAFI definitions to allow the address of the Next Hop for
   IPv4 NLRI or VPN-IPv4 NLRI to belong to either the IPv4 or the IPv6
   protocol, the encoding of the Next Hop information to determine which
   of the protocols the address belongs to, and a new BGP Capability
   allowing MP-BGP peers to dynamically discover 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
   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.

   While the savings exists at the Edge eBGP PE-PE Inter-AS peering, on
   the core side 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 and 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 IPv6 next hop.

   This document defines the IPv6-Only PE Design Architecture details
   for External BGP (eBGP) PE-PE Inter-AS IPv6-Only peering design that
   leverages the MP-BGP capability exchange by using IPv6 peering as
   pure transport, allowing both 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 Address Family Identifiers (AFI) and Subsequent
   Address Family Identifiers(SAFI).  The design change provides the
   same Dual Stacking functionality that exists today with separate IPv4
   and IPv6 BGP sessions as we have today.  With this design change from
   a control plane perspective a single IPv6-Only peer is required for
   both IPv4 and IPv6 routing updates and from a data plane forwarindg
   perspective an IPv6 address MUST ONLY be configured on the PE-CE Edge
   or PE to PE Inter-AS peering interface for both IPv4 and IPv6 packet
   forwarding.  This document extends the IPv6-Only PE-CE peering
   architecture defined in [I-D.ietf-bess-ipv6-only-pe-design] to PE-PE
   inter-as peering architecture to now apply to all AFI/SAFI
   ubiquitously.  As service providers migrate to Segment Routing



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   architecture SR-MPLS and SRv6, VPN overlay exsits as well, and thus
   Inter-AS options Option-A, Option-AB and Option-C are still
   applicable and thus this extension of IPv6-Only peering architecure
   extension to Inter-AS peering is relevant to Segment Routing as well
   as any other AFI/SAFi that is relevant.

   With this IPv6-Only PE Design, IPv4 address MUST not be configured on
   the the Provider Edge (PE) - Customer Edge (CE), or Inter-AS ASBR
   (Autonomous System Boundary Router) to ASBR (Autonomous System
   Boundary Router) PE-PE Provider Edge (PE) - Provider Edge (PE).  From
   a control plane perspective a single IPv6-Only peer MUST be
   configured for both IPv4 and IPv6 routing updates and from a data
   plane forwarindg perspective only an IPv6 address MUST be configured
   on the PE-CE Edge or ASBR-ASBR, PE to PE Inter-AS peering interface
   for both IPv4 and IPv6 packet forwarding.  This document defines the
   IPv6-Only PE Design as a new Intra-AS PE-CE Edge and Inter-AS PE-PE
   BGP peering Standard which is described in the POC testing document
   in detail, [I-D.ietf-bess-ipv6-only-pe-design].  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-AB and
   Option-C are still applicable and thus this extension of IPv6-Only
   peering architecure extension to Inter-AS peering is very relevant to
   Segment Routing as well.

   This document details an important External BGP (eBGP) PE-PE Inter-AS
   IPv6-Only peering design that leverages the MP-BGP capability
   exchange by using IPv6 peering as pure transport, allowing both 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 the following Address Family
   Identifiers (AFI) and Subsequent Address Family Identifiers(SAFI) to
   be carried over IPv6-Only Inter-AS peerings described in detail in
   this document: <AFI/SAFI> IPv4 Unicast <1/1>, IPv4 Multicast
   <1/2>,VPN-IPV4 <1/128>, Multicasat VPN <1/129>, BGP-LU IPV4 (4PE)
   <1/4>, BGP-LU IPV4 <1/4>

   This IPv6-Only PE ALL SAFI Design details an important External BGP
   (eBGP) PE-PE Inter-AS IPv6-Only peering design that leverages the MP-
   BGP capability exchange by using IPv6 peering as pure transport,
   allowing both 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 remaining
   Address Family Identifiers (AFI) and Subsequent Address Family
   Identifiers(SAFI) below as well that can be carried over IPv6-Only
   Inter-AS peerings: <AFI/SAFI> MCAST-VPN [RFC6514] <1/5>, NLRI Multi-
   Segment Pseudowires [RFC7267] <1/6>, BGP Tunnel Encapsulation SAFI
   [RFC9012] <1/7>, MCAST-VPLS [RFC7117] <1/8>, BGP SFC [RFC9015] <1/9>,
   Tunnel SAFI [I-D.nalawade-kapoor-tunnel-safi] <1/6>, Virtual Private



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   LAN Service (VPLS) [RFC4761] and [RFC6074] <1/5>, 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>, BGP EVPNs
   [RFC7432] <1/70>, BGP-LS (VPLS) [RFC7752] <1/71>, BGP-LS-EVPN
   [RFC7752] <72/>, SR-TE Policy SAFI draftxx <1/73>, BGP 6to4 SAFI
   draft xx <1/8>, SDN WAN Capabilities draftxx <1/74>, Routing Policy
   SAFI draftxx <1/75>, 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>

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

4.  IPv6-Only Edge Peering Architecture

4.1.  Problem Statement

   This specification addresses a real issue that has been discussed at
   many operator groups around the world related to IXP major peering
   points where hundreds of AS's have both IPv4 and IPv6 dual stacked
   peering.  IPv4 address depletion have been a major issue issue for
   many years now.  Operators around the world are clamoring for a
   solution that can help solve issues related to IPv4 address depletion
   at these large IXP peering points.  With this solution IXPs as well



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   as all 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 IPv4 address space saving.


                               IXP 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 - IXP 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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4.2.  IPv6-Only PE-CE Design Solution

   The IPv6-Only Edge design solution provides a means of E2E single
   protocol design solution extension of [RFC5565] Softwire Mesh
   framework from the PE-CE Edge to the Core from ingres so egress
   through the entire operators domain.  This solution eliminates all
   IPv4 addressing from end to end while still providing the same Dual
   Stack functionality of IPv4 and IPv6 packet forwarding from a data
   plane perspective by leveraging the [RFC8950] extended next hop
   encoding so that IPv4 NLRI can be advertised over a single IPv6 pure
   transport TCP session.  This IPv6-Only E2E architecture eliminates
   all IPv4 peering and IPv4 addressing E2E from the ingress CE to
   ingress PE to egress PE to egress CE and all hops along the operator
   E2E path.


                             Solution applicable to
                  any Edge peering scenario - IXP, Core, DC, Access, etc

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


              Figure 3: IPv6-Only Solution Applicability


                                ________
      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        \IP / MPLS / SR domain /        IPv6 BGP peer
   IPv4 forwarding      \__         __       /          IPv4 forwarding
   IPv6 forwarding         \_______/  \_____/           IPv6 forwarding




                       Figure 4: E2E VPN Solution



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4.3.  IPv6-Only Edge Peering Design

4.3.1.  IPv6-Only Edge Peering Packet Walk

   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.

   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.

4.3.2.  6to4 Softwire 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



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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 5: 6to4 Softwire - IPv6 Edge over an IPv4-Only Core

4.3.3.  4to6 Softwire 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 6: 4to6 Softwire - IPv4 Edge over an IPv6-Only Core

4.4.  RFC5549 and RFC8950 Applicability






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4.4.1.  IPv6-Only Edge Peering design next-hop encoding

   This section describes [RFC8950] next hop encoding updates to
   [RFC5549] applicability to this specification.  IPv6-only eBGP Edge
   PE-CE peering to carry IPv4 Unicast NLRI <AFI/SAFI> IPv4 <1/1> over
   an IPv6 next hop BGP capability extended hop encoding IANA capability
   codepoint value 5 defined is applicable to both [RFC5549] and
   [RFC8950] as IPv4 Unicast NLRI <AFI/SAFI> IPv4 <1/1> does not change
   in the RFC updates.

   IPv4 packets over an IPv6-Only core 4to6 Softwire E2E packet flow is
   part of the IPv6-Only design vendor interoperaiblity test cases and
   in that respect is applicable as [RFC8950] updates [RFC5549] for
   <AFI/SAFI> VPN-IPV4 <1/128>, and Multicasat VPN <1/129>

4.4.2.  RFC8950 updates to RFC5549 applicability

   This section describes the [RFC8950] next hop encoding updates to
   [RFC5549]

   In [RFC5549] when AFI/SAFI 1/128 is used, the next-hop address is
   encoded as an IPv6 address with a length of 16 or 32 bytes.  This
   document modifies how the next-hop address is encoded to accommodate
   all existing implementations and bring consistency with VPNv4oIPv4
   and VPNv6oIPv6.  The next-hop address is now encoded as a VPN-IPv6
   address with a length of 24 or 48 bytes [RFC8950] (see Sections 3 and
   6.2 of this document).  This change addresses Erratum ID 5253
   (Err5253).  As all known and deployed implementations are
   interoperable today and use the new proposed encoding, the change
   does not break existing interoperability.  Updates to [RFC8950] is
   applicable to the IPv6-Only PE-CE edge design for the IPv6 next hop
   encoding E2E test case of IPv4 packets over and IPv6-Only core 4to6
   Softwire.  In this test case IPv4 Unicast NLRI <AFI/SAFI> IPv4 <1/1>
   is advertised over the PE to RR core peering 4to6 softwire in <AFI/
   SAFI> VPN-IPV4 <1/128>.  In this test case label allocation mode
   comes into play which is discussed in section 8.9.

   [RFC5549] next hop encoding of MP_REACH_NLRI with:

   *  NLRI= NLRI as per current AFI/SAFI definition

   Advertising with [RFC4760] MP_REACH_NLRI with:

   *  AFI = 1

   *  SAFI = 128 or 129

   *  Length of Next Hop Address = 16 or 32



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   *  NLRI= NLRI as per current AFI/SAFI definition

   [RFC8950] next hop encoding of MP_REACH_NLRI with:

   *  NLRI= NLRI as per current AFI/SAFI definition

   Advertising with [RFC4760] MP_REACH_NLRI with:

   *  AFI = 1

   *  SAFI = 128 or 129

   *  Length of Next Hop Address = 24 or 48

   *  Next Hop Address = VPN-IPv6 address of next hop with an 8-octet RD
      set to zero (potentially followed by the link-local VPN-IPv6
      address of the next hop with an 8-octet RD is set to zero).

   *  NLRI= NLRI as per current AFI/SAFI definition

5.  IPv6-Only PE Design Edge E2E Design for all AFI/SAFI

   Proof of conept interoperability testing of the 4 test cases bet

5.1.  IPv6-Only PE Design All SAFI Case-1 E2E IPv6-Only PE-CE, Global
      Table over IPv4-Only Core(6PE), 6to4 softwire


                                ________
      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 7: Design Solution-1 E2E IPv6-Only PE-CE, Global
                    Table over IPv4-Only Core (6PE)





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5.2.  IPv6-Only PE Design All SAFI Case-2 E2E IPv6-Only PE-CE, VPN over
      IPv4-Only Core, 6to4 Softwire


                                ________
      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 8: Design Solution-2 E2E IPv6-Only PE-CE, VPN over
                             IPv4-Only Core

5.3.  IPv6-Only PE Design All SAFI Case-3 E2E IPv6-Only PE-CE, Global
      Table over IPv6-Only Core (4PE), 4to6 Softwire


                                ________
      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 9: Design Solution-3 E2E IPv6-Only PE-CE, Global
                    Table over IPv6-Only Core (4PE)






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5.4.  IPv6-Only PE Design All SAFI Case-4 E2E IPv6-Only PE-CE, VPN over
      IPv6-Only Core, 4to6 Softwire


                                ________
      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 10: Design Solution-4 E2E IPv6-Only PE-CE, VPN over
                             IPv6-Only Core

5.5.  IPv6-Only PE Design All SAFI Case-5 E2E IPv6-Only PE-CE, Global
      Table over IPv4-Only Core(6PE), 6to4 softwire -Inter-AS Option-B



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 11: Design Solution-5 E2E IPv6-Only PE-CE, Global
            Table over IPv4-Only Core (6PE) - Inter-AS Option-B






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5.6.  IPv6-Only PE Design All SAFI Case-6 E2E IPv6-Only PE-CE, Global
      Table over IPv4-Only Core(6PE), 6to4 softwire -Inter-AS Option-C



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 12: Design Solution-6 E2E IPv6-Only PE-CE, Global
            Table over IPv4-Only Core (6PE) - Inter-AS Option-C

5.7.  IPv6-Only PE Design All SAFI Case-7 E2E IPv6-Only PE-CE, VPN over
      IPv4-Only, 6to4 softwire -Inter-AS Option-B



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 13: Design Solution-7 E2E IPv6-Only PE-CE, VPN over
                     IPv4-Only Core - Inter-AS Option-B






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5.8.  IPv6-Only PE Design All SAFI Case-8 E2E IPv6-Only PE-CE, VPN over
      IPv4-Only Core, 6to4 softwire -Inter-AS Option-C



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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: Design Solution-8 E2E IPv6-Only PE-CE, VPN over
                     IPv4-Only Core - Inter-AS Option-C

5.9.  IPv6-Only PE Design All SAFI Case-9 E2E IPv6-Only PE-CE, Global
      Table over IPv6-Only Core, 4to6 softwire -Inter-AS Option-B



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 15: Design Solution-9 E2E IPv6-Only PE-CE, Global
               Table over IPv6-Only Core - Inter-AS Option-B






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5.10.  IPv6-Only PE Design All SAFI Case-10 E2E IPv6-Only PE-CE, Global
       Table over IPv6-Only Core, 4to6 softwire -Inter-AS Option-C



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 16: Design Solution-10 E2E IPv6-Only PE-CE, Global
               Table over IPv6-Only Core - Inter-AS Option-C

5.11.  IPv6-Only PE Design All SAFI Case-4 E2E IPv6-Only PE-CE, VPN over
       IPv6-Only Core, 4to6 softwire -Inter-AS Option-B



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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 17: Design Solution-11 E2E IPv6-Only PE-CE, VPN over
                     IPv6-Only Core - Inter-AS Option-B






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5.12.  IPv6-Only PE Design All SAFI Case-12 E2E IPv6-Only PE-CE, VPN
       over IPv6-Only Core, 4to6 softwire -Inter-AS Option-C



     IPv6-Only       __________         __________      IPv6-Only
      PE / CE       /          \       /          \      PE / CE
     +--+ +----+   /            \     /            \    +--+ +--+
     |  | |    |  |    AS 1      \    |    AS 2     \   |  | |  |
     |  | |    |  |               \   |              \  |  | |  |
     |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: Design Solution-12 E2E IPv6-Only PE-CE, VPN over
                     IPv6-Only Core - Inter-AS Option-C

5.13.  IPv6-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

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


                 Figure 19: Ping and Trace Test Case

6.  IPv6-Only PE ALL AFI/SFI Operational Considerations

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

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



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   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.

7.  Vendor Implementations and Operator Deployments

   Vendor implementations are with Cisco, Juniper, Nokia, Arista and
   Huawei

8.  IANA Considerations

   There are not any IANA considerations.







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9.  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].

10.  Acknowledgments

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

11.  Contributors

   The following people contributed substantive text to this document:

       Mohana Sundari
       EMail: mohanas@juniper.net


12.  References

12.1.  Normative References

   [I-D.ietf-bess-ipv6-only-pe-design]
              Mishra, G., Mishra, M., 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-00, 20 September 2021,
              <https://www.ietf.org/archive/id/draft-ietf-bess-ipv6-
              only-pe-design-00.txt>.

   [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://www.ietf.org/archive/id/draft-
              nalawade-kapoor-tunnel-safi-05.txt>.







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   [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>.

   [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>.





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   [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>.

   [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>.

   [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>.

12.2.  Informative References





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   [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-16, 21 October 2021, <https://www.ietf.org/archive/id/
              draft-ietf-idr-dynamic-cap-16.txt>.

   [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>.




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   [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>.

   [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>.

Authors' Addresses

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


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


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


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


   Qing Yang
   Arista Networks
   Email: qyang@arista.com


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



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   Shuanglong Chen
   Huawei Technologies
   Email: chenshuanglong@huawei.com
















































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