Re: [v4tov6transition] [Softwires] ISP support of Native IPv6 across NAT44 CPEs -Proposed 6a44 Specification

Rémi Després <> Fri, 08 October 2010 07:43 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 344973A6828; Fri, 8 Oct 2010 00:43:00 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.453
X-Spam-Status: No, score=-1.453 tagged_above=-999 required=5 tests=[AWL=0.496, BAYES_00=-2.599, HELO_EQ_FR=0.35, MIME_8BIT_HEADER=0.3]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id rByCXPtKOhD7; Fri, 8 Oct 2010 00:42:58 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 227443A67A3; Fri, 8 Oct 2010 00:42:58 -0700 (PDT)
Received: from (localhost []) by (SMTP Server) with ESMTP id BE5D77000089; Fri, 8 Oct 2010 09:44:01 +0200 (CEST)
Received: from [] ( []) by (SMTP Server) with ESMTP id 249917000097; Fri, 8 Oct 2010 09:43:55 +0200 (CEST)
Mime-Version: 1.0 (Apple Message framework v1081)
Content-Type: text/plain; charset=iso-8859-1
From: =?iso-8859-1?Q?R=E9mi_Despr=E9s?= <>
In-Reply-To: <>
Date: Fri, 8 Oct 2010 09:43:54 +0200
Content-Transfer-Encoding: quoted-printable
Message-Id: <>
References: <> <> <> <> <>
To: Ole Troan <>
X-Mailer: Apple Mail (2.1081)
Cc: Softwires <>,
Subject: Re: [v4tov6transition] [Softwires] ISP support of Native IPv6 across NAT44 CPEs -Proposed 6a44 Specification
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Fri, 08 Oct 2010 07:43:00 -0000

Le 7 oct. 2010 à 21:28, Ole Troan a écrit :
> ...
> issues I have with host tunneling:
> - how to communicate with native IPv6 nodes on the same network?

The 6a44-S decapsulates IPv6 packets coming from a 6a44 host and, if not destined to another 6a44 host of its network, forwards them in IPv6, in this case on the same network.

> - how to communicate to another 6a44 host on a different link in the same home?

6a44 is only for hosts on a LAN behind a NAT44 attached to a 6a44-capable ISP network.
If the LAN has several bridged links, it does apply.
Links that are behind extra NATs in the site are out of scope.

As I said to Olivier Vautrin in a previous mail on this thread, these extra NATs should be configured so that hosts behind them never receive 6a44 IPv6-Address-Indication messages. (e;g. with the 6a44 well-known port bound to an unassigned internal address.
This point isn't in the draft yet but, if co-authors agree, should be in the next version.

> - do you need non-congruent topology multi-homing policy?
>   how do you distribute that policy when you don't have a on-link router?

Not sure to understand the question.
The answer should be NO: 6a44 only needs classical topologies.

> - a general unease that now every host is supposed to have a "VPN" connection?
>   how do I configure my own firewall and other network border policy?

If the NAT binds the 6a44 well-known port to an unassigned internal address, no host will be able to receive a 6a44 IPv6 address. 
Besides, a firewall could filter all packets having this port, source or destination.

> how much would a new CPE cost the customer? 80USD? that's only 5 pints of beer (if bought in Norway.)
> I really liked the dongle idea by the way. perhaps with a L2TP LAC.

The dongle idea of 6rd-UDP, if without a stateful NAT66 in the dongle, needs an assigned /16 to the function. (The /64 subnet prefix has to contain the site IPv4 address plus the port of the tunnel).
This is in general not realistic.

Now, if there is a NAT66 in the dongle, it can work with a 6a44 external address.

I hope it helps to understand that 6a44 isn't just one more design for the pleasure to make one, but a pragmatic solution to a real problem, specified after an in depth study. 


> cheers,
> Ole