[SR-Users] Proxying INVITE message without port information in R-URI

Klaus Darilion klaus.mailinglists at pernau.at
Wed Jan 19 07:49:04 CET 2011

Am 18.01.2011 20:27, schrieb Vikram Ragukumar:
> Hello,
> Alex, Klaus thank you for your replies.
>> Usually the softphones register to the proxy or SIP server. Thus, the
>> proxy or SIP server knows under which IP:port (The IP:port from which
>> the REGISTER was received) it can contact the sofpthone.
> Yes, the softphones are registered to the SIP server, and hence the SIP
> server has the IP:port information required to contact the softphone.
> However, the SIP server does not include the port number in the R-URI of
> the INVITE that it generates.

Does the SIP server perform NAT traversal?

Does the SIP proxy perform NAT traversal?

How does the SIP server route the INVITE requests? Does it route based 
on registered Contact or does it route them statically to the SIP proxy? 
Depending on the routing behavior on the SIP server you can build a 
workaround on the proxy.


> This port number is dynamically assigned by the firewall and is not
> fixed, so manipulating the pseudo variable $rp by assigning it a fixed
> number will not work.
> If it is not mandatory to include the port number in the R-URI, how does
> the proxy determine the port to which the SIP message must be forwarded ?
> Thanks and Regards,
> Vikram.

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