[Serusers] Routing subsequent SIP traffic through the proxy

Jan Janak jan at iptel.org
Mon Mar 24 19:57:56 CET 2003


On 24-03 13:20, jaime.gill at orange.co.uk wrote:
> Hello Jiri,
> Of course, I meant the non-paranoic meaning, that is forcing the subsequent
> requests to go through the proxy.
> The question is related to the FCP module I'm trying to complete. In order to
> close the previously opened ports, the module needs to see BYE and CANCEL
> messages. When adding record-routing header from a natted proxy, this address
> must be changed to a public one whenever the message is for the public Internet.
> Is my understanding correct?

 Yes, your understanding is correct, but we will solve the problem in a
 different way. Instead of modifying record-route headers, it is
 possible to insert two of them, one with internal IP address and the
 other with public IP address.

 Suppose that callee is in the public internet and caller in private
 network. The caller sends an INVITE, the INVITE will reach your proxy
 and it will insert rr with private IP address and after that another rr with
 public IP address of your NAT.

 When the caller wants to send a BYE, it will use the rr with public IP
 of your NAT box. Your proxy will detect that there are 2 route headers and 
 remove both of them.

 Callee sending BYE will reverse the order of all record-route header
 fields and therefore it will use record-route with private IP address -
 the message will hit your proxy directly. Again, the proxy detects
 presence of 2 route fields and will remove both of them.

> My other concern with Record Routing is whether this translation for the request
> involves translating the RR field back to the one of the natted proxy, when the
> response hits the proxy.

  Don't worry about Record-Routes, I am currently working on the trick
  described above so you will get this feature for free with the new


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