[Serusers] NAT & RTPPRoxy

Jan Janak jan at iptel.org
Wed Sep 3 12:32:02 CEST 2003


On 03-09 11:14, Gary Brewer wrote:
> Thanks Jan,
> 
> I should have made myself a little bit clearer; I am using the RTC 1.2 API
> (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/rtcclnt/rt
> c/real_time_communications_rtc_client_start_page.asp)

  I have no experience with that API, so you will have to experiment.
  But if the webpages are correct and they really implemented everything
  as they describe then it should work.

> What I find the most interesting is -
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/rtcclnt/rtc
> /traversal_of_upnp_enabled_nats.asp specifically the last sentence of the
> third paragraph. Why I can't provide it my external IP address and port on
> the NAT is annoying! I wonder if it would be possible to modify the REGISTER
> message on the way to the SIP server and change the IP:Port to my external
> NAT address mapping - or get NATHelper to do this for me.

  Yes, the sentence is right, it says that the communication is not
  possible without an Application Level Gateway.

  Application Level Gateway is something that can configure your NAT box
  so the media traffic gets through. In the simplest form it could be a
  couple of rules in your NAT that allow traffic from a specified port
  range (as described in my previous email), it can be also an
  application that monitors all the SIP traffic and opens the pinholes
  accordingly, or it can be a separate application that is told to open
  a pinhole using some other protocol -- like FCP, see
  http://iptel.org/fcp.

  Ad REGISTER, yes, nathelper can do this for you on the server.  

   Jan.




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