Lightweight 4over6: An Extension to the Dual-Stack Lite Architecture

Approval announcement
Draft of message to be sent after approval:

From: The IESG <>
To: IETF-Announce <>
Cc: RFC Editor <>,
    softwire mailing list <>,
    softwire chair <>
Subject: Protocol Action: 'Lightweight 4over6: An Extension to the DS-Lite Architecture' to Proposed Standard (draft-ietf-softwire-lw4over6-13.txt)

The IESG has approved the following document:
- 'Lightweight 4over6: An Extension to the DS-Lite Architecture'
  (draft-ietf-softwire-lw4over6-13.txt) as Proposed Standard

This document is the product of the Softwires Working Group.

The IESG contact persons are Brian Haberman and Ted Lemon.

A URL of this Internet Draft is:

Technical Summary:

DS-Lite [RFC 6333] describes an architecture for transporting IPv4
packets over an IPv6 network.  This document specifies an extension to
DS-Lite called Lightweight 4over6 which moves the Network Address and
Port Translation (NAPT) function from the centralized DS-Lite tunnel
concentrator to the tunnel client located in the Customer Premises
Equipment (CPE).  This removes the requirement for a Carrier Grade NAT
function in the tunnel concentrator and reduces the amount of
centralized state that must be held to a per-subscriber level.  A
companion document describes the DHCPv6 options necessary for
provisioning of Lightweight 4over6. 

Working Group Summary:

The working group had active discussion on the draft and the current
text of the draft is representative of the consensus of the working
group. This document and the MAP-E document are closely related and it
led to a lot of friction in the working group.

Lightweight 4over6 is a solution designed specifically for complete
independence between IPv6 subnet prefix and IPv4 address with or
without IPv4 address sharing.  This is accomplished by maintaining
state for each softwire (per-subscriber state) in the central lwAFTR
and a hub-and-spoke forwarding architecture.  

MAP-E can also offer these capabilities or, alternatively, can provide
a reduction of the amount of centralized state using rules to express
IPv4/IPv6 address mappings.  This introduces an algorithmic
relationship between the IPv6 subnet and IPv4 address. This
relationship also allows the option of direct, meshed connectivity
between users.

Document Quality:

The document has received adequate review. The Document Shepherd has
no concerns about the depth or breadth of these reviews. There are
several interoperable implementations of the scheme and they have been
demonstrated and tested during the IETF meetings.


Suresh Krishnan is the document shepherd. Ted Lemon is the responsible

RFC Editor Note:

This document is one of a set of five softwire documents that should be published with sequential RFC numbers.  The numbering should be in the following order: