IPv4 NLRI with IPv6 Next Hop Use Cases
BESS Working Group G. Mishra
Internet-Draft Verizon Inc.
Intended status: Standards Track M. Mishra
Expires: February 22, 2021 Cisco Systems
August 21, 2020
IPv4 NLRI with IPv6 Next Hop Use Cases
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 core from IPv4 to IPv6 being able to
continue to support legacy IPv4, VPN-IPv4, and Multicast VPN IPv4
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
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 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 to now
Mishra, et al. Expires February 22, 2021 [Page 1]
Internet-Draft IPv4-NLRI with IPv6-NH Use Cases August 2020
carry 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
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This Internet-Draft will expire on February 22, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 6
3. Extension of AFI/SAFI Definitions for the IPv4 Address Family 6
4. Use of BGP Capability Advertisement . . . . . . . . . . . . . 7
5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 9
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