Unified IPv4-in-IPv6 Softwire Customer Premises Equipment (CPE): A DHCPv6-Based Prioritization Mechanism
RFC 8026
Internet Engineering Task Force (IETF) M. Boucadair
Request for Comments: 8026 Orange
Category: Standards Track I. Farrer
ISSN: 2070-1721 Deutsche Telekom AG
November 2016
Unified IPv4-in-IPv6 Softwire Customer Premises Equipment (CPE):
A DHCPv6-Based Prioritization Mechanism
Abstract
In IPv6-only provider networks, transporting IPv4 packets
encapsulated in IPv6 is a common solution to the problem of IPv4
service continuity. A number of differing functional approaches have
been developed for this, each having their own specific
characteristics. As these approaches share a similar functional
architecture and use the same data plane mechanisms, this memo
specifies a DHCPv6 option, whereby a single instance of Customer
Premises Equipment (CPE) can interwork with all of the standardized
and proposed approaches to providing encapsulated IPv4-in-IPv6
services by providing a prioritization mechanism.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8026.
Boucadair & Farrer Standards Track [Page 1]
RFC 8026 OPTION_S46_PRIORITY DHCPv6 Option November 2016
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1. Requirements Language . . . . . . . . . . . . . . . . 4
1.2. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. DHCPv6 S46 Priority Option . . . . . . . . . . . . . . . 5
1.4. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 6
1.5. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . 7
2. Operator Deployment Considerations for Deploying Multiple
Softwire Mechanisms . . . . . . . . . . . . . . . . . . . . . 7
2.1. Client Address Planning . . . . . . . . . . . . . . . . . 7
2.2. Backwards Compatability with Existing Softwire Clients . 7
3. Security Considerations . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
4.1. S46 Mechanisms and Their Identifying Option Codes . . . . 8
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Normative References . . . . . . . . . . . . . . . . . . 9
5.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
Boucadair & Farrer Standards Track [Page 2]
RFC 8026 OPTION_S46_PRIORITY DHCPv6 Option November 2016
1. Introduction
IPv4 service continuity is one of the major technical challenges that
must be considered during IPv6 migration. Over the past few years, a
number of different approaches have been developed to assist with
this problem (e.g., as described in [RFC6333], [RFC7596], and
[RFC7597]). These approaches, referred to as "S46 mechanisms" in
this document, exist in order to meet the particular deployment,
scaling, addressing, and other requirements of different service
providers' networks.
A common feature shared among all of the differing modes is the
integration of softwire tunnel endpoint functionality into the
Customer Premises Equipment (CPE) router. Due to this inherent data
plane similarity, a single CPE may be capable of supporting several
different approaches. Users may also wish to configure a specific
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