8 Apr
2005
8 Apr
'05
1:32 p.m.
Lucas Aimaretto schrieb:
The only circumstances that I know where STUN does not help is when the
UA is located behind a symmetric nat. In the othre 3 cases of nat, it
should help you just fine. Or if the clients do not implement a good
stun-client or the stun server does not implement the protocol
correctly. But, let say that every body follows the standars ( JA!, ask
cisco ) ... you should not have problems at all.
Regards,
Lucas
Hi everyone!
There's another problem with STUN:
If you have two UAs behind the *same* (not symmetric) NAT and the NAT
doesn't support hairpinning (i.e. sending data back in the direction of
the source in order to reach the target) RTP traffic won't work. Each
client tries to send its RTP stream to the external port of the firewall
which in this case wouldn't send the packets back into the net. So those
2 UAs wouldn't be able to communicate when traffic isn't handled by an
external RTP Relay (e.g. MediaProxy, RTPProxy, etc.)
The WinStun-Client from Vovida can detect if your NAT supports hairpinning.
Talking about priorities: STUN beats Mediaproxy, because SER can't
distinguish between a NAT'ed STUN client and a client with a real public
IP. That's no problem as long as you don't have two UAs behind the same
hairpinning-disabled NAT.
Alex Mack
>>>>>>Make sure you are not behind a
Symmetric NAT. If
>>>>>>
>>>>>>
so, you're
>>>>>>dead. STUN does not work
with Symmetric NAT.
>>>>>>
>>>>>>
>>>>>If a UA is behind Symmetric NAT, and
>>>>>UA use STUN, and
>>>>>SER have [RTP/Media]Proxy to handle Symmetric NAT, this UA
>>>>>should be fine, right?
>>>>>
>>>>>
>>>>Yes, but, if UA is behind symmetric NAT, I would not
>>>>
>>>>
configure
>>>>STUN to it. I'd just led
mediaproxy solve the problem.
>>>>
>>>>
>>>But if you have 100 clients,
>>>it would be hard to put all clients in one group.
>>>
>>>
>>LA> Good point !
>>
>>LA> Yes, it is true. If stun can not solve the nat problem,
>>media proxy
>>LA> should fix it with no trouble at all.
>>
>>
>>
>If there is no symmetric NAT and I have installed STUN and
>Mediaproxy on my server. Which one will have higher priority
>to handle this call session? Is it always STUN? Of course if
>I don't need to pass the call to PSTN gateway. Just IP-phone
>to IP-phone. Can you set the priority in ser.cfg? and how?
>
>
LA> It is not a matter of priorities. It depends on how you get your
LA> mediaproxy configured. You need to be aware that nated clients
LA> should use the media proxy, because of the nat problem.
But, if your
LA> client can find ( using stun for example ) his public
ip/port, then,
LA> from mediaproxy point of view, this client is not nated,
and so, it
LA> needs not treatment ( no fixing from part of media proxy ).
LA> You can always do this: Get every traffic proxied along
mediaproxy.
LA> But, if clients can talk to each other being able to bypass
LA> mediaproxy, why should you proxy your communications ???
LA> Hope to be clear
LA> Regards,
LA> Lucas
Thank you, it makes sence.
It would be the best solution I'd say, but it reminds me
JavaRocks statement that STUN makes problems in some
circumstances.. Just wondering what problems? Maybe some UA's
not supporting STUN?