Subject: [BEHAVE] FW: Question Regarding Draft Stateful NAT64

From: "Philippe Champagne (pchamp)" <[email-masked]>
Date: Tue, 20 Apr 2010 07:03:34 -0700

Hi Everyone

In the draft
http://datatracker.ietf.org/doc/draft-ietf-behave-v6v4-xlate-stateful/

At the very end of section 3.5.2.2, (page 29, just before V4 SYN RCV)
"If there is no corresponding entry in the TCP BIB the packet is
silently discarded."

However, according to this RFC on NAT best practice:

http://datatracker.ietf.org/doc/rfc5382/
Bottom of page 10 section 5:
---------------
The handling of non-SYN packets for connections for which there is no
   active mapping is left unspecified.  Such packets may be received if
   the NAT silently abandons a live connection, or abandons a connection
   in TIME_WAIT state before the 4 minute TIME_WAIT period expires.  The
   decision to either silently drop such packets or to respond with a
   TCP RST packet is left up to the implementation.
---------------

>From there, I believe you should remove the silently drop and replace it
with "left up to the implementation"
Personally, since the NAT (in overload when it allocates a new source
port) gets implicated in the well being of the TCP connection, it has
the responsibility to reply on the behalf of the server that no longer
can be reached with the original tuple that has been lost. That's
perhaps a philosophical debate, but it is beyond the point. I believe
this draft should be in line with rfc5382.

Regards
Phil Champagne
Cisco Systems, Inc.