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RE: NAT-PT Applicabilty for 3GPP

At 07:05 PM 11/17/2003 +0100, Karim El-Malki (HF/EAB) wrote: 
 > >That is not the only issue IMO.
 > >According to RFC 2766 an implementation will take incoming
 > packets destined
 > >to PREFIX::a.b.c.d and translate them to IPv4 destination
 > a.b.c.d. It will
 > >also
 > >locally assign and use an ipv4 source addr/port. We don't
 > want this behaviour
 >
 > Can you please point out where in the NAT-PT RFC it says it
 > should be
 > locally assigned
 > or where it explicitly prohibits mappings installed from an
 > external entity?

I assume your question wants to highlight the fact that RFC 2766
doesn't rule that out. OK. Still I don't see your point? I


My point was, RFC2766 does not mandate you installing the mappings
locally, nor does it prevent you to install mappings from an external entity,
unlike what you have stated in your earlier email.

f it allows
local pools, which are in fact the most likely thing people
implement, and does not specify communication with an external box
then it is not the spec we want to recommend.

My point is that if we say NAT-PT is applicable for SIP then people
will expect to read RFC 2766 and implement it. If they do that
they are likely to implement a local pool of v4 addresses and a
SIP ALG (that does SIP editing). Since SIP folks are not in favour
of SIP editing I don't think we should say that NAT-PT is applicable
to the SIP case. It is much cleaner to create a SIP specific solution
for this case that is not related to generic NAT-PT and its problems.

NAT-PT RFC does not specify anything about how SIP ALG/Proxy should be implemented.
That could be a seperate document, if one needs it. If you want a SIP ALG/Proxy, you
could implement as per the SIP protocol specification and make use of the NAT-PT
header translator functionality to let the media pass through the translator. So NAT-PT
is applicable there and that is what is noted in the applicability statement. Re-inventing
something that has already been done seems to be a waste of time.

Senthil

/Karim