Subject: [v6ops] BIH vs 464XLAT

From: Simon Perreault <[email-masked]>
Date: Tue, 27 Mar 2012 12:32:50 +0200

I was thinking that bump-in-the-host (BIH) could be used for something like
464XLAT, and after some questioning I was pointed to the following extract from
RFC6535:

   The IETF recommends using solutions based on dual stack or tunneling
   for IPv6 transition and specifically recommends against deployments
   utilizing double protocol translation.  Use of BIH together with a
   NAT64 is NOT RECOMMENDED [RFC6180].

Wouldn't this anti-recommendation also apply to 464XLAT?

Did the consensus on double translation change?

Simon
-- 
DTN made easy, lean, and smart --> http://postellation.viagenie.ca
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---

From: Cameron Byrne <[email-masked]>
Date: Tue, 27 Mar 2012 03:59:53 -0700

>   NAT64 is NOT RECOMMENDED [RFC6180].

FYI -- i fought this restriction in BEHAVE.  Lost.

> Did the consensus on double translation change?

I have to assume so since Softwires has mountain of work that is
double translation, and in fact MAP-T is triple translation, NAT4464

It is perhaps the situation that BIH came a few months too soon for
the IESG to be responsive to the realistic need of double translation.

That said, 464XLAT seldom uses double translation in practice when
used together with DNS64

http://tools.ietf.org/html/draft-ietf-v6ops-464xlat-01#section-6.3

Double translation is only invoked in the case when NAT64/DNS64 alone
would result in failure of communication due to IPv4-only sockets or
IPv4 literals.

So, the tradeoff is double translation or communication failure.
Subscribers who don't know what IP is like the double translation
solution that loads Skype.

There is also the fact the IESG passed this
http://tools.ietf.org/html/draft-weil-shared-transition-space-request-15
... which is clearly a tip of the hat to NAT444.  It would be
unconscionable for the IESG to support NAT444 and not support
something that required IPv6 and enabled IPv6 like 464XLAT

CB

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