RE: [NSIS] Jari Arkko: DISCUSS: draft-ietf-nsis-ntlp

Hello,

In response to the message below I would like to point out that the ID
http://tools.ietf.org/wg/nsis/draft-pashalidis-nsis-gist-legacynats-00.t
xt 
addresses (at least some of) the issues that are raised in that message.
That is, the ID contains a description of how GIST nodes can discover
the
existence of legacy NAT(s) and how to cope with them. 

Best Regards,
Andreas

-----Original Message-----
From: john.loughney@nokia.com [mailto:john.loughney@nokia.com] 
Sent: Freitag, 15. September 2006 15:19
To: jari.arkko@piuha.net; nsis@ietf.org
Subject: [NSIS] Jari Arkko: DISCUSS: draft-ietf-nsis-ntlp 

Here's a DISCUSS from Jari about GIST.  Robert is traveling, but it
would be good to discuss this in the WG to find out ways to address his
DISCUSS.

John 

>-----Original Message-----
>From: ext Jari Arkko [mailto:jari.arkko@piuha.net]
>Sent: 14 September, 2006 16:01
>To: iesg@ietf.org
>Cc: nsis-chairs@tools.ietf.org; robert.hancock@roke.co.uk;
>hgs+nsis@cs.columbia.edu
>Subject: DISCUSS: draft-ietf-nsis-ntlp
>
>Discuss:
>>   Legacy NATs:  GIST messages will generally pass through NATs, but
>>   unless the NAT is GIST-aware, any addressing data carried in the
>>   payload will not be handled correctly.  There is a dual problem of
>>   whether the GIST peers either side of the boundary can work out
>>   how to address each other, and whether they can work out what
>>   translation to apply to the signaling packet payloads.  The
>>   fundamental problem is that GIST messages contain three or four
>>   interdependent addresses which all have to be consistently
>>   translated, and existing generic NAT traversal techniques such as
>>   STUN [23] or TURN [24] can process only two.  Appropriate
>>   behaviour for a GIST-aware NAT is discussed in Section 7.2.
>...
>>   GIST messages must carry packet addressing and higher layer
>>   information as payload data in order to define the flow signalled
>>   for.  (This applies to all GIST messages, regardless of
>how they are
>>   encapsulated or which direction they are travelling in.)  At an
>>   addressing boundary the data flow packets will have their headers
>>   translated; if the signaling payloads are not translated
>>   consistently, the signaling messages will refer to incorrect (and
>>   probably meaningless) flows after passing through the boundary.  In
>>   addition, GIST handshake messages carry additional addressing
>>   information about the GIST nodes themselves, and this must also be
>>   processed appropriately when traversing a NAT.
>
>I do not understand all the implications of running GIST over a 
>non-modified NAT. If the implications are benign, please explain why 
>that is the case. If they are serious, the protocol should fail 
>gracefully upon detecting a NAT. Without additional information I worry

>that the design is brittle enough that it may cause harm to the 
>senders, receivers, GIST nodes, or worse, outsiders when a GIST unaware

>NAT causes the address information to become invalid.
>
>
>

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