Subject: [BEHAVE] Concerns with IPv4 Applications Accessing IPv6 Servers (NAT46) - draft-wing-behave-v4app-v6server-00

From: "Dan Wing" <[email-masked]>
Date: Mon, 19 Oct 2009 17:03:49 -0700

Hi.  Today we submitted "Concerns with IPv4 Applications Accessing IPv6
Servers (NAT46)", which discusses concerns with IPv4 applications accessing
IPv6 servers.  PNAT is analyzed in detail, but Virtual IPv6 Connectivity seems
to have similar drawbacks.  

The largest concern is the potential harm for V6 deployment.  The concern is
that the introduction of an AAAA record on a server will change the operation
mode of a client from NAT464 to NAT46, causing different code paths to be
taken.  This is quite different from today's behavior:  adding a new resource
record to a server, such an an AAAA record (or any other type of record), has
no effect on applications that don't query that resource record.  

The draft also demonstrates that an ALG is necessary once the operation mode
is NAT46 for the protocol examined in detail, which is FTP.  Others might be
interested in examining other protocols (SIP, H.323, RTSP, HTTP with IPv4
address literals, and so on), and how those might need an ALG to fully
function with NAT464 or with NAT46.

Abstract:
   Bump-in-the-Stack and Bump-in-the-API allow IPv4 applications to
   access IPv6 servers.  This is done by using in-host NAT46 translator.
   When used in conjunction with an in-network NAT64, it is also
   possible for the IPv4 application to access an IPv4 server via an
   IPv6-only network.  This document describes how these functions work
   in detail, and discusses some concerns especially around IPv4
   applications accessing IPv6 servers.  These concerns can be reduced
   by not having IPv4 applications access IPv6 servers.

http://tools.ietf.org/html/draft-wing-behave-v4app-v6server-00

-d