16 Mar
2004
16 Mar
'04
4:01 p.m.
My confusion over symmetric / cone NAT. But does look possible to
communicate between symmetric NATs in many cases - but first starting
with RTP proxy or TURN. Using the RTP proxy to learn which class of
symmetric NAT you have, and predicting the port allocation - then
switching to direct communication if the port prediction test gives good
results.
Simon
Jiri Kuthan wrote:
At 07:16 PM 3/15/2004, Simon Barber wrote:
possible way to get through symmetric NAT without
permanent rtpproxy.
Initiate the connection using rtpproxy, as normal. Now, learn the udp port the NAT is
sending RTP from. Now send a re-invite to both parties, and switch the stream to the udp
port the NAT is using, instead of the rtpproxy. This will only work if the NAT uses the
same external ip/port pair when the same internal ip/port pair is used
Which is non-symmetric NAT. Symmetric NATs are only traversable the way
Klaus described.
-jiri
(and I'm expecting that most sip phone will
reuse the same internal ip/port pair when you re-invite). Apparently some NATs do this.
(although I'm not a NAT expert - I have only read a few papers on the subject).
Simon
Klaus Darilion wrote:
--
Jiri Kuthan http://iptel.org/~jiri/
You can't overcome symmetric NAT with STUN. To
traverse a symmetric NAT you need:
- A SIP proxy with NAT traversal (nathelper module)
- An RTP proxy (or an generic TURN server and a SIP UA which supports TURN)
- A symmetric SIP UA (symmetric SIP & symmetric RTP)
regards,
Klaus
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Hi,
Can someone please help me if my dialer does not support symmetric
signalling, is there anyway to go through symmetric nat through the server
or configure from the server that asking the dialer to point to a STUN
server before reaching the UA. Please help........
regards, shirley
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