New subject: [Serusers] SER + RTPProxy and Client behind NAT

23 Nov 2004


      UA is Sipura2000/Snom190/UnidenUIP200/etc.
I am running rtpproxy in verbose mode  (to be precise, as "rtpproxy -f 
-l  <internal ip>/<external ip>  )
The core problem is,
    - SER sends rtpproxy the port from the SDP (which in what the UA 
generated *behind* the NAT)
    - The UA is sending/receiving media on a *different* port  to rtpproxy.
    - How does one get rtpproxy to "point" at the NAT port, and not at 
the SDP port?
cheers
Matt Schulte wrote:
...
Yes it can do this, RTPproxy is just that, a proxy. It has the ability
to use whatever port it pleases, try running rtpproxy command line mode
(rtpproxy -f ) to see if it's passing any errors. What kind of device is
the UA? Be sure that the device has "NAT mode" on, this sounds like a
problem I was having early on.
-----Original Message-----
From: Kanakatti Mahesh Subramanya [mailto:mahesh@aptela.com] 
Sent: Sunday, November 21, 2004 5:00 PM
To: serusers@lists.iptel.org
Subject: [Serusers] SER + RTPProxy and Client behind NAT
I'm having a strange problem with getting  SER+RTPProxy to work when the
UA is behind NAT
Setup is as follows
UA --> NAT1 --> SER+RTPProxy --> NAT2 --> Asterisk
I've got RTPProxy running in "bridge" mode, gatewaying 'tween Asterisk 
and the Public Internet
SIP traffic all routes perfectly.  STUN enabled clients work perfectly.
The problem is that if the outbound port on NAT1 for the RTP stream is 
*different* from the outbound port from the UA, then RTPProxy persists 
in sending the packets to the UA port, *not* the NAT1 port.
e.g.
if the SDP payload from the UA contains
       c=IN IP4 192.168.5.100
       m=audio 16396 RTP/AVP....


but NAT1 sends the RTP stream out on port 64003, then rtpproxy sends the
media from Asterisk back to port 16393 at NAT1, instead of to port 64003
at NAT1!
Is it supposed to do this?  Am I missing something really obvious?
The relevant section from ser.cfg is as follows
if (nat_uac_test("3")) {
   if (method == "REGISTER" || ! search("^Record-Route:")) {
     fix_nated_contact(); # Rewrite contact with source IP of
signalling
     if (method == "INVITE") {
       fix_nated_sdp("1"); # Add direction=active to SDP
     };
     setflag(6);    # Mark as NATed
   };
 };
rewritehostport("........");
 if (force_rtp_proxy("FEI")) {
   t_on_reply("4");
 };
.
.
.
onreply_route[4] {
 if (!(status=~"183" || status=~"200")) {
  break;
 };
 fix_nated_contact();
 force_rtp_proxy("F");
  break;
}

Re: [Serusers] SER + RTPProxy and Client behind NAT