-----Original Message-----
From: ietf-bounces(_at_)ietf(_dot_)org
[mailto:ietf-bounces(_at_)ietf(_dot_)org] On
Behalf Of Scott Brim
Sent: Sunday, March 22, 2009 7:11 AM
To: Brian E Carpenter
Cc: Iljitsch van Beijnum; IAB; IETF Discussion Mailing List;
Lixia Zhang
Subject: Re: Comment on draft-iab-ipv6-nat-00
Brian E Carpenter allegedly wrote on 03 21 2009 4:07 PM:
So instead, you run NAT at every ISP connection. Your
internal users get
NATted to an ISP prefix at whichever exit point their
traffic happens
to reach, which automatically causes their return traffic
to come through
the same ISP. That exit point is locally chosen by the
local routing setup.
You don't need any worldwide coordination of the BGP4
advertisements,
because there aren't any expect the ISP's normal ones. Also, traffic
flows inside your network are localised, since traffic goes out and
returns through a (reasonably) local gateway.
When one of these NATs goes down, active connections will be lost,
but IGP routing will switch users automatically to a different NAT
when they retry.
If you allow your hosts to use multiple connection points into the
Internet, and external routing changes so that the packets
they send go
out different connection points, their apparent source address can
change. One of the requirements for effective use of NAT and
multihoming is that your hosts' peers need to handle this (via
Multipath, HIP, MIP, SCTP or whatever). That is, you can't allow your
hosts to use multiple connection points until everyone _else_
they talk
to has been upgraded. How will you know when that is?
A host knows if it is using HIP, MIP, or SCTP to communicate with
another host. FYI, there is also a new idea for Mobile DTLS which
provides similar address mobility, draft-barrett-mobile-dtls-00.txt.
-d
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