[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Nits]



BESS Working Group                                             G. Mishra
Internet-Draft                                              Verizon Inc.
Intended status: Standards Track                          April 27, 2020
Expires: October 29, 2020


IPv4 Network Layer Reachability Information with IPv6 Next Hop Use Cases
             draft-mishra-bess-ipv4nlri-ipv6nh-use-cases-00

Abstract

   As Enterprises and Service Providers upgrade their brown field or
   green field core to an IPv6 transport such as an MPLS LDPv6 core or
   SRv6 core, Multiprotocol BGP (MP-BGP)now plays an important role in
   the transition of the core from IPv4 to IPv6 being able to continue
   to support legacy IPv4, VPN-IPv4, and Multicast VPN customers.  IXPs
   (Internet Exchange points) 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.  One proposal to solve this issue is to use
   [RFC5549] to carry IPv4 (Network Layer Reachability Information) NLRI
   in an IPv6 next hop and eliminate the IPv4 peering completely using
   the concept of [RFC5565] softwire mesh framework.  So now with the
   MP-BGP reach capability exchanged over IPv4 AFI over IPv6 next hop
   peer we can now advertise IPv4(Network Layer Reachability
   Information) NLRI over IPv6 peering using the [RFC5565] softwire mesh
   framework.  Multiprotocol BGP (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 Network Layer
   Reachability Information (NLRI).  [RFC5549] specifies the extensions
   necessary to allow advertising IPv4 NLRI or VPN-IPv4 NLRI with a Next
   Hop address that belongs to the IPv6 protocol.  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 also belong to the IPv6
   Protocol.  [RFC5549] 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 dynamically discover
   whether they can exchange IPv4 NLRI and VPN-IPv4 NLRI with an IPv6
   Next Hop.  With this new MP-BGP capability exchange allows the BGP
   peering session to act as a pure transport to allow the session to
   carry Address Family Identifier (AFI) and the Subsequent Address
   Family Identifier (SAFI) for both IPv4 and IPv6.  This document
   describes the critical use case and OPEX savings of being able to
   leverage the MP-BGP capability exchange usage as a pure transport



Mishra                  Expires October 29, 2020                [Page 1]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   allowing both IPv4 and IPv6 to be carried over the same BGP TCP
   session.  By doing so allows for the elimination of Dual Stacking on
   the PE-CE connections making the peering IPv6 only carrying both IPv4
   and IPv6 Network Layer Reachability Information (NLRI).  This
   document also provides a possible solution for IXPs (Internet
   Exchange points) that are facing IPv4 address depletion at these
   peering points to use BGP-MP capability exchange defined in [RFC5549]
   to carry IPv4 (Network Layer Reachability Information) NLRI in an
   IPv6 next hop using the [RFC5565] softwire mesh framework.

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 October 29, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.










Mishra                  Expires October 29, 2020                [Page 2]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   5
   3.  Extension of AFI/SAFI Definitions for the IPv4 Address Family   6
   4.  Use of BGP Capability Advertisement . . . . . . . . . . . . .   7
   5.  Operations  . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Softwire Framework Use Cases of IPv4 NLRI with IPv6 Next Hop   10
     6.1.  VPN-IPv4 over MPLS LDPv6 or SRv6 Core . . . . . . . . . .  10
     6.2.  IPv4 VPN multicast over MPLS LDPv6 or SRv6 Core . . . . .  11
     6.3.  IPv4 Islands over MPLS LDPv6 or SRv6 Core . . . . . . . .  12
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     10.2.  Informative References . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  15

1.  Introduction

   As Enterprises and Service Providers upgrade their brown field or
   green field core to an IPv6 transport such as an MPLS LDPv6 core or
   SRv6 core, Multiprotocol BGP (MP-BGP)now plays an important role in
   the transition of the core from IPv4 to IPv6, and being able to
   continue to support legacy IPv4, VPN-IPv4, and Multicast VPN
   customers.  IXPs (Internet Exchange points) 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.  One proposal to solve this
   issue is to use [RFC5549] to carry IPv4 (Network Layer Reachability
   Information) NLRI in an IPv6 next hop and eliminate the IPv4 peering
   completely using the concept of [RFC5565] softwire mesh framework.
   Multiprotocol BGP (MP-BGP) [RFC4760] specifies that the set of
   network-layer protocols to which the address carried in the Next Hop
   field may belong is determined by the Address Family Identifier (AFI)
   and the Subsequent Address Family Identifier (SAFI).  A number of
   existing AFI/SAFIs allow the Next Hop address to belong to a
   different address family than the Network Layer Reachability
   Information (NLRI).  For example, the AFI/SAFI <25/65> used (as per
   [RFC6074]) to perform L2VPN auto-discovery, allows advertising NLRI
   that contains the identifier of a Virtual Private LAN Service (VPLS)
   instance or that identifies a particular pool of attachment circuits
   at a given Provider Edge (PE), while the Next Hop field contains the
   loopback address of a PE.  Similarly, the AFI/SAFI <1/132> (defined
   in [RFC4684]) to advertise Route Target (RT) membership information,
   allows advertising NLRI that contains such RT membership information,



Mishra                  Expires October 29, 2020                [Page 3]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   while the Next Hop field contains the address of the advertising
   router.

   Furthermore, a number of these existing AFI/SAFIs allow the Next Hop
   to belong to either the IPv4 Network Layer Protocol or the IPv6
   Network Layer Protocol, and specify the encoding of the Next Hop
   information to determine which of the protocols the address actually
   belongs to.  For example, [RFC4684] allows the Next Hop address to be
   either IPv4 or IPv6 and states that the Next Hop field address shall
   be interpreted as an IPv4 address whenever the length of Next Hop
   address is 4 octets, and as an IPv6 address whenever the length of
   the Next Hop address is 16 octets.

   There are situations such as those described in [RFC4925] and in
   [RFC5565] where carriers (or large enterprise networks acting as
   carrier for their internal resources) may be required to establish
   connectivity between 'islands' of networks of one address family type
   across a transit core of a differing address family type.  This
   includes both the case of IPv6 islands across an IPv4 core and the
   case of IPv4 islands across an IPv6 core.  Where Multiprotocol BGP
   (MP-BGP) is used to advertise the corresponding reachability
   information, this translates into the requirement for a BGP speaker
   to advertise Network Layer Reachability Information (NLRI) of a given
   address family via a Next Hop of a different address family (i.e.,
   IPv6 NLRI with IPv4 Next Hop and IPv4 NLRI with IPv6 Next Hop).

   The current AFI/SAFI definitions for the IPv6 address family assume
   that the Next Hop address belongs to the IPv6 address family type.
   Specifically, as per [RFC2545] and [RFC8277], when the <AFI/SAFI> is
   <2/1>, <2/2>, or <2/4>, the Next Hop address is assumed to be of IPv6
   type.  As per [RFC4659], when the <AFI/SAFI> is <2/128>, the Next Hop
   address is assumed to be of IPv6-VPN type.

   However, [RFC4798] and [RFC4659] specify how an IPv4 address can be
   encoded inside the Next Hop IPv6 address field when IPv6 NLRI needs
   to be advertised with an IPv4 Next Hop.  [RFC4798] defines how the
   IPv4-mapped IPv6 address format specified in the IPv6 addressing
   architecture ([RFC4291]) can be used for that purpose when the <AFI/
   SAFI> is <2/1>, <2/2>, or <2/4>.  [RFC4659] defines how the IPv4-
   mapped IPv6 address format as well as a null Route Distinguisher can
   be used for that purpose when the <AFI/SAFI> is <2/128>.  Thus, there
   are existing solutions for the advertisement of IPv6 NLRI with an
   IPv4 Next Hop.

   Similarly, the current AFI/SAFI definitions for advertisement of IPv4
   NLRI or VPN-IPv4 NLRI assume that the Next Hop address belongs to the
   IPv4 address family type.  Specifically, as per [RFC4760] and
   [RFC8277], when the <AFI/SAFI> is <1/1>, <1/2>, or <1/4>, the Next



Mishra                  Expires October 29, 2020                [Page 4]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   Hop address is assumed to be of IPv4 type.  As per [RFC4364], when
   the <AFI/SAFI> is <1/128>, the Next Hop address is assumed to be of
   VPN-IPv4 type.  As per [RFC6513] and [RFC6514], when the <AFI/SAFI>
   is <1/129>, the Next Hop address is assumed to be of VPN-IPv4 type.
   There is clearly no generally applicable method for encoding an IPv6
   address inside the IPv4 address field of the Next Hop.  Hence, there
   is currently no specified solution for advertising IPv4 or VPN-IPv4
   NLRI with an IPv6 Next Hop.

   A new specification for carrying IPv4 Network Layer Reachability
   Information (NLRI) of a given address family via a Next Hop of a
   different address family is now defined in [RFC5549], and specifies
   the extensions 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 actually 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 [RFC5549] supporting Network Layer
   Reachability Information (NLRI) and next hop address family mismatch,
   the BGP peer session can now be treated as a pure transport and carry
   both IPv4 and IPv6 NLRI at the PE-CE edge.  This allows for the
   elimination of dual stack from the PE-CE peering point, and now allow
   the peering to be IPv6 only.  The elimination of IPv4 on the PE-CE
   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-CE BGP peers by
   fifty percent, which is a tremendous cost savings for both
   Enterprises and Service Providers.  While the savings exists at the
   PE-CE edge, on the core side PE to Route Reflector peering carrying
   <AFI/SAFI> IPv4 <1/1>, VPN-IPV4 <1/128>, and Multicasat VPN <1/129>,
   the cost savings nets to a break even to be the same as with an IPV4
   Core carrying IPv6 NLRI IPV6 <2/1>, VPN-IPV6 <2/128>, and Multicasat
   VPN <2/129>.  This document also provides a possible solution for
   IXPs (Internet Exchange points) that are facing IPv4 address
   depletion at these peering points to use BGP-MP capability exchange
   defined in [RFC5549] to carry IPv4 (Network Layer Reachability
   Information) NLRI in an IPv6 next hop using the [RFC5565] softwire
   mesh framework.

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




Mishra                  Expires October 29, 2020                [Page 5]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Extension of AFI/SAFI Definitions for the IPv4 Address Family

   As mentioned earlier, 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).  The
   following current AFI/SAFI definitions for the IPv4 NLRI or VPN-IPv4
   NLRI (<1/1>, <1/2>, <1/4>, <1/128> and <1/129>) only have provisions
   for advertising a Next Hop address that belongs to the IPv4 protocol.
   This document extends the definition of the AFI/SAFI for
   advertisement of IPv4 NLRI and VPN-IPv4 NLRI to extend the set of
   usable next-hop address families to include IPv6 in addition to IPv4.

   Specifically, this document allows advertising with [RFC4760] of an
   MP_REACH_NLRI with:

   o  AFI = 1

   o  SAFI = 1, 2, or 4

   o  Length of Next Hop Address = 16 or 32

   o  Next Hop Address = IPv6 address of next hop (potentially followed
      by the link-local IPv6 address of the next hop).  This field is to
      be constructed as per Section 3 of [RFC2545].

   o  NLRI= NLRI as per current AFI/SAFI definition

   It also allows advertising with [RFC4760] of an MP_REACH_NLRI with:

   o  AFI = 1

   o  SAFI = 128 or 129

   o  Length of Next Hop Address = 24 or 48

   o  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).

   o  NLRI= NLRI as per current AFI/SAFI definition

   This is in addition to the current mode of operation allowing
   advertisement of NLRI for <AFI/SAFI> of <1/1>, <1/2> and <1/4> with a
   next hop address of IPv4 type and advertisement of NLRI for <AFI/




Mishra                  Expires October 29, 2020                [Page 6]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   SAFI> of <1/128> and <1/129> with a next hop address of VPN-IPv4
   type.

   The BGP speaker receiving the advertisement MUST use the Length of
   Next Hop Address field to determine which network-layer protocol the
   next hop address belongs to.

   o  When the AFI/SAFI is <1/1>, <1/2> or <1/4> and when the Length of
      Next Hop Address field is equal to 16 or 32, the next hop address
      is of type IPv6.

   o  When the AFI/SAFI is <1/128>, or <1/129> and when the Length of
      Next Hop Address field is equal to 24 or 48, the next hop address
      is of type VPN-IPv6.

   Note that this method of using the Length of the Next Hop Address
   field to determine which network-layer protocol the next hop address
   belongs to (out of the set of protocols allowed by the AFI/SAFI
   definition) is the same as used in [RFC4684] and [RFC6074].

4.  Use of BGP Capability Advertisement

   [RFC5492] defines a mechanism to allow two BGP speakers to discover
   if a particular capability is supported by their BGP peer and thus
   whether it can be used with that peer.  This document defines a new
   capability that can be advertised using [RFC5492] and that is
   referred to as the Extended Next Hop Encoding capability.  This
   capability allows BGP speakers to discover whether, for a given NLRI
   <AFI/SAFI>, a peer supports advertisement with a next hop whose
   network protocol is determined by the value of the Length of Next Hop
   Address field, as specified in Section 3.

   A BGP speaker that wishes to advertise to a BGP peer an IPv6 Next Hop
   for IPv4 NLRI or for VPN-IPv4 NLRI as per this specification MUST use
   the Capability Advertisement procedures defined in [RFC5492] with the
   Extended Next Hop Encoding Capability to determine whether its peer
   supports this for the NLRI AFI/SAFI pair(s) of interest.  The fields
   in the Capabilities Optional Parameter MUST be set as follows:

   o  The Capability Code field MUST be set to 5 (which indicates the
      Extended Next Hop Encoding capability).

   o  The Capability Length field is set to a variable value that is the
      length of the Capability Value field (which follows).

   o  The Capability Value field has the following format:





Mishra                  Expires October 29, 2020                [Page 7]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


            +-----------------------------------------------------+
            | NLRI AFI - 1 (2 octets)                             |
            +-----------------------------------------------------+
            | NLRI SAFI - 1 (2 octets)                            |
            +-----------------------------------------------------+
            | Nexthop AFI - 1 (2 octets)                          |
            +-----------------------------------------------------+
            | .....                                               |
            +-----------------------------------------------------+
            | NLRI AFI - N (2 octets)                             |
            +-----------------------------------------------------+
            | NLRI SAFI - N (2 octets)                            |
            +-----------------------------------------------------+
            | Nexthop AFI - N (2 octets)                          |
            +-----------------------------------------------------+


      where:

      *  each triple <NLRI AFI, NLRI SAFI, Nexthop AFI> indicates that
         NLRI of <NLRI AFI / NLRI SAFI> may be advertised with a Next
         Hop address belonging to the network-layer protocol of Nexthop
         AFI.

      *  the AFI and SAFI values are defined in the Address Family
         Identifier and Subsequent Address Family Identifier registries
         maintained by IANA.

   Since this document only concerns itself with the advertisement of
   IPv4 NLRI and VPN-IPv4 NLRI with an IPv6 Next Hop, this specification
   only allows the following values in the Capability Value field of the
   Extended Next Hop Encoding capability:

   o  NLRI AFI = 1 (IPv4)

   o  NLRI SAFI = 1, 2, 4, 128 or 129

   o  Nexthop AFI = 2 (IPv6)

   This document does not specify the use of the Extended Next Hop
   Encoding capability with any other combinations of <NLRI AFI, NLRI
   SAFI, Nexthop AFI>.  For example, the Next Hop Encoding capability
   specified in this document is not intended to be used for NLRI AFI/
   SAFIs whose definition already allows use of both IPv4 and IPv6 next
   hops (e.g., AFI/SAFI = <1/132> as defined in [RFC4684]).  Similarly,
   it is not intended that the Extended Next Hop Encoding capability be
   used for NLRI AFI/SAFIs for which there is already solution for
   advertising a next hop of a different address family (e.g., AFI/SAFI



Mishra                  Expires October 29, 2020                [Page 8]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   = <2/1>, <2/2>, or <2/4> with IPv4 Next Hop as per [RFC4798] and AFI/
   SAFI = <2/128> with IPv4 Next Hop as per [RFC4659]).

   It is expected that if new AFI/SAFIs are defined in the future, their
   definition will have provisions (where appropriate) for both IPv4 and
   IPv6 Next Hops from the onset, with determination based on Length of
   Next Hop Address field.  Thus, new AFI/SAFIs are not expected to make
   use of the Extended Next Hop Encoding capability.

   A BGP speaker MUST only advertise to a BGP peer the IPv4 or VPN-IPv4
   NLRI with an IPv6 Next Hop if the BGP speaker has first ascertained
   via BGP Capability Advertisement that the BGP peer supports the
   Extended Next Hop Encoding capability for the relevant AFI/SAFI pair.

   The Extended Next Hop Encoding capability provides information about
   next hop encoding for a given AFI/SAFI, assuming that AFI/SAFI is
   allowed.  It does not influence whether that AFI/SAFI is indeed
   allowed.  Whether a AFI/SAFI can be used between the BGP peers is
   purely determined through the Multiprotocol Extensions capability
   defined in [RFC4760].

   The Extended Next Hop Encoding capability MAY be dynamically updated
   through the use of the Dynamic Capability capability and associated
   mechanisms defined in [I-D.ietf-idr-dynamic-cap].

5.  Operations

   As Enterprises and Service Providers migrate their IPv4 core to an
   MPLS LDPv6 or SRv6 transport, they must continue to be able to
   support legacy IPv4 customers.  With the new extensions defined in
   [RFC4760], supporting Network Layer Reachability Information (NLRI)
   and next hop address family mismatch, the BGP peer session can now be
   treated as a pure transport and carry both IPv4 and IPv6 NLRI at the
   PE-CE edge.  This paves the way to now eliminate dual stacking on all
   PE-CE peering points to customers making the peering IPv6 only.  With
   this change all IPv4 and IPv6 Network Layer Reachability Information
   (NLRI) will now be carried over a single BGP session.  This also
   solves the dual stack issue with IXP (Internet Exchange Points)
   having to maintain separate peering for both IPv4 and IPv6.  From an
   operations perspective the PE-CE edge peering will be drastically
   simplified with the elimination of IPv4 peers yielding a reduction of
   peers by 50 percent.  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
   prior to elimination of the IPv4 peers.  No operational impacts or
   issues are expected with this change.





Mishra                  Expires October 29, 2020                [Page 9]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   When a next hop address needs to be passed along unchanged (e.g., as
   a Route Reflector (RR) would do), its encoding MUST NOT be changed.
   If a particular RR client cannot handle that encoding (as determined
   by the BGP Capability Advertisement), then the NLRI in question
   cannot be distributed to that client.  For sound routing in certain
   scenarios, this will require that all the RR clients be able to
   handle whatever encodings any of them may generate.

6.  Softwire Framework Use Cases of IPv4 NLRI with IPv6 Next Hop

6.1.  VPN-IPv4 over MPLS LDPv6 or SRv6 Core

   The new MP-BGP extensions defined in [RFC5549] is used to support
   IPV4 VPNs over an IPv6 MPLS LDPv6 or SRv6 backbone.  In this scenario
   the PE routers would advertise and receive VPN-IPv4 NLRI in the
   MP_REACH_NLRI along with an IPv6 Next Hop from the Route Reflector
   (RR).

   MP-BGP Reach Pseudo code:

   If ((Update AFI == VPN-IPv4)

   and (Length of next hop == 24 Bytes || 48 Bytes))

   {

   This is an VPN-IPv4 route, but

   with an IPv6 next hop;

   }

   The MP_REACH_NLRI is encoded with:

   o  AFI = 1

   o  SAFI = 128

   o  Length of Next Hop Network Address = 24 (or 48)

   o  Network Address of Next Hop = VPN-IPv6 address of Next Hop whose
      RD is set to zero

   o  NLRI = IPv4-VPN routes

   During BGP Capability Advertisement, the PE routers would include the
   following fields in the Capabilities Optional Parameter:




Mishra                  Expires October 29, 2020               [Page 10]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   o  Capability Code set to "Extended Next Hop Encoding"

   o  Capability Value containing <NLRI AFI=1, NLRI SAFI=128, Nexthop
      AFI=2>

6.2.  IPv4 VPN multicast over MPLS LDPv6 or SRv6 Core

   The new MP-BGP extensions defined in [RFC8126] is used to support
   IPV4 Multicast VPNs over an MPLS LDPv6 or SRv6 backbone.  In this
   scenario, the PE routers would advertise and receive VPN-IPv4 NLRI in
   the MP_REACH_NLRI along with an IPv6 Next Hop from the Route
   Reflector (RR).

   MP-BGP Reach Pseudo code:

   If ((Update AFI == MVPN-IPv4)

   and (Length of next hop == 24 Bytes || 48 Bytes))

   {

   This is an MVPN-IPv4 route, but

   with an IPv6 next hop;

   }

   The MP_REACH_NLRI is encoded with:

   o  AFI = 1

   o  SAFI = 129

   o  Length of Next Hop Network Address = 24 (or 48)

   o  Network Address of Next Hop = VPN-IPv6 address of Next Hop whose
      RD is set to zero

   o  NLRI = IPv4-VPN routes

   During BGP Capability Advertisement, the PE routers would include the
   following fields in the Capabilities Optional Parameter:

   o  Capability Code set to "Extended Next Hop Encoding"

   o  Capability Value containing <NLRI AFI=1, NLRI SAFI=129, Nexthop
      AFI=2>




Mishra                  Expires October 29, 2020               [Page 11]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


6.3.  IPv4 Islands over MPLS LDPv6 or SRv6 Core

   The new MP-BGP extensions defined in [RFC5549] is used to support
   IPV4 islands over an IPv6 MPLS LDPv6 or SRv6 backbone.  In this
   scenario the PE routers would use BGP labeled unicast address family
   (BGP-LU) to advertise BGP with label binding and receive labeled IPv4
   NLRI in the MP_REACH_NLRI along with an IPv6 Next Hop from the Route
   Reflector (RR).

   MP-BGP Reach Pseudo code:

   If ((Update AFI == IPv4)

   and (Length of next hop == 16 Bytes || 32 Bytes))

   {

   This is an IPv4 route, but

   with an IPv6 next hop;

   }

   The MP_REACH_NLRI is encoded with:

   o  AFI = 1

   o  SAFI = 1

   o  Length of Next Hop Network Address = 16 (or 32)

   o  Network Address of Next Hop = IPv6 address of Next Hop whose RD is
      set to zero

   o  NLRI = IPv4-VPN routes

   During BGP Capability Advertisement, the PE routers would include the
   following fields in the Capabilities Optional Parameter:

   o  Capability Code set to "Extended Next Hop Encoding"

   o  Capability Value containing <NLRI AFI=1, NLRI SAFI=1, Nexthop
      AFI=2>








Mishra                  Expires October 29, 2020               [Page 12]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


7.  IANA Considerations

   There are not any IANA considerations.

8.  Security Considerations

   The extensions defined in this document allow BGP to propagate
   reachability information about IPv6 routes over an MPLS IPv4 core
   network.  As such, no new security issues are raised beyond those
   that already exist in BGP-4 and use of MP-BGP for IPv6.  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].

9.  Acknowledgments

10.  References

10.1.  Normative References

   [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>.

   [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>.



Mishra                  Expires October 29, 2020               [Page 13]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   [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>.

10.2.  Informative References

   [I-D.ietf-idr-dynamic-cap]
              Ramachandra, S. and E. Chen, "Dynamic Capability for BGP-
              4", draft-ietf-idr-dynamic-cap-14 (work in progress),
              December 2011.

   [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>.





Mishra                  Expires October 29, 2020               [Page 14]


Internet-Draft      IPv4-NLRI with IPv6-NH Use Cases          April 2020


   [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>.

   [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>.

Author's Address

   Gyan S. Mishra
   Verizon Inc.

               13101 Columbia Pike


               Silver Spring
             ,

               MD 20904


               United States of America


   Phone:
             301 502-1347

   Email:
             gyan.s.mishra@verizon.com









Mishra                  Expires October 29, 2020               [Page 15]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/