IPv4 routes with an IPv6 next-hop in the Babel routing protocol
draft-ietf-babel-v4viav6-00
Network Working Group T. Bastian
Internet-Draft Ecole Normale Superieure, Paris
Updates: 6126bis (if approved) J. Chroboczek
Intended status: Experimental IRIF, University of Paris-Diderot
Expires: April 23, 2021 October 20, 2020
IPv4 routes with an IPv6 next-hop in the Babel routing protocol
draft-ietf-babel-v4viav6-00
Abstract
This document defines an extension to the Babel routing protocol that
allows annoncing routes to an IPv4 prefix with an IPv6 next-hop,
which makes it possible for IPv4 traffic to flow through interfaces
that have not been assigned an IPv4 address.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 3
2. Protocol operation . . . . . . . . . . . . . . . . . . . . . 3
2.1. Announcing v4-over-v6 routes . . . . . . . . . . . . . . 3
2.2. Receiving v4-over-v6 routes . . . . . . . . . . . . . . . 3
2.3. Prefix and seqno requests . . . . . . . . . . . . . . . . 4
2.4. Other TLVs . . . . . . . . . . . . . . . . . . . . . . . 4
3. Backwards compatibility . . . . . . . . . . . . . . . . . . . 4
4. Protocol encoding . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Prefix encoding . . . . . . . . . . . . . . . . . . . . . 5
4.2. Changes for existing TLVs . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Traditionally, a routing table maps a network prefix of a given
address family to a next-hop address in the same address family. The
sole purpose of this next-hop address is to serve as an input to a
protocol that will map it to a link-layer address, Neighbour
Discovery (ND) [RFC4861] in the case of IPv6, Address Resolution
(ARP) [RFC0826] in the case of IPv4. Therefore, there is no reason
why the address family of the next hop address should match that of
the prefix being announced: an IPv6 next-hop yields a link-layer
address that is suitable for forwarding both IPv6 or IPv4 traffic.
We call a route towards an IPv4 prefix that uses an IPv6 next hop a
"v4-over-v6" route. Since an IPv6 next-hop can use a link-local
address that is autonomously configured, the use of v4-over-v6 routes
enables a mode of operation where the network core has no statically
assigned IP addresses of either family, thus significantly reducing
the amount of manual configuration.
This document describes an extension that allows the Babel routing
protocol [RFC6126bis] to announce routes towards IPv6 prefixes with
IPv4 next hops. The extension is inspired by a previously defined
extension to the BGP protocol [RFC5549].
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