[Serusers] Rewriting URI in the Contact field

[Jiri Kuthan]

There is actually a plenty of options how to traverse NATs.
Sadly, none of them works in all possible scenarios.

a) STUN -- some phones (kphone for linux, snom hardphones)
   have the ability to "fool" NATs to accomplish traversal
   using the STUN protocols; particularly good if you cannot
   manipulate the NAT
b) geek tweaks -- you have a configurable NAT and configurable
   phones (there are some of both of them).  you configure static 
   port forwarding in the NAT and phones to advertise the
   public address in contacts and elsewhere
c) ALG -- use a SIP-aware NAT such as PIX or Intertex
d) UPnP -- takes UPnP enables phones (snom is) and NATs
e) SIP/media relay -- that's a too ugly story

What to choose best depends on your network setting -- can you
tweak the NAT, can you afford replacing it with a SIP-enabled
one, are the phones you are using configurable or do they use
STUN, do you have a server on the public or private NAT side
or on each of them, etc.

I remember someone shared with us he was using ser in his
network to do the translation of SIP addresses on behalf
ot the phones. The ser script was configured to statically
rewrite private IP addresses to the public address using
replace/textops.

-Jiri

At 01:32 PM 1/10/2003, Maxim Sobolev wrote:
>Folks,
>
>I need an advise on how to better implement one feature, which isn't
>currently present in SER. We need to allow UAs behind NAT properly
>register with the registrar - by "properly" I mean that host:port portion
>of URI in Contact field should not be used, but host:port the request
>came from should be used instead. By definition we know that those UAs
>will support symmetric SIP signalling, so that this scheme will work just
>fine.
>
>In my opinion there are two ways to do it: either add new rewritecontact*
>family of functions similar to rewritehost ones. or add a new flag for
>the save() function. This is where I need your help - which implementation
>looks better for you (or maybe you have even some better idea), since
>we are really interested in inclusion of our changes into the mainline to
>reduce our local hacks.
>
>Regards,
>
>Maxim
>
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--
Jiri Kuthan            http://iptel.org/~jiri/