[Serusers] Symmetric NATs and RTP Proxy - Question

Jiri Kuthan jiri at iptel.org
Thu Feb 10 23:49:49 CET 2005


There is a recent discussion about SBCs on the sip forum mailing list.
shortly, sbcs are a technique to harm QoS through bandwidth consumption
and packet latency, and to affect reliability through introduction
of a single point of failure. There are also extensibility concerns.

One can still achieve NAT traversal and failover capability without
SBCs. Which is not a blank statement -- my company, iptelorg, has developed 
such product recently. 

-jiri

At 11:41 PM 2/10/2005, Marian Dumitru wrote:
>Hi Darren,
>
>Disregarding any implementation aspects, the only complication a SBC can introduce is an additional hop in the signaling path.
>On the other hand, the SBC comes into focus when is about:
>        -decoupling the NAT traversal from the routing logic - in case of a very complex service and routing logic or when is about considerations like yours;
>        - distributed NAT traversal - keeping the media as local as possible in platforms with a wide-geographical coverage.
>
>Best regards,
>Marian
>
>Darren Sessions wrote:
>>I sent the email to the mailing list and realized the answer about 15
>>minutes afterwards. Your email Jan, confirms it.
>>I had discussed session border controllers with Jiri many months ago and was
>>told a session border controller was not a good approach as they severely
>>complicate signaling matters.
>>Other than using a session border controller, are there any viable solutions
>>to this problem without resorting to a IP failover cluster or something of
>>that nature?
>>Thanks,
>>- Darren
>>
>>On 2/8/05 5:49 PM, "Jan Janak" <jan at iptel.org> wrote:
>>
>>>No, because RTP proxy would relay media only. SIP signalling would still
>>>go through one of the proxy servers and SIP messages would only make it
>>>to the user agent behind symmetric NAT if they were sent by the proxy
>>>server originally contacted by the user agent (with the same IP address).
>>>
>>> Jan.
>>>
>>>On 08-02 13:19, Darren Sessions wrote:
>>>
>>>>We currently do not use an RTP proxy in our service (so the audio does not
>>>>ride our internet bandwidth).
>>>>
>>>>Our biggest issue at the moment is the redundancy between two SER servers in
>>>>dealing with symmetric NATs (specifically dealing with the individual SER
>>>>server unique IP addresses and the far end customer's symmetric NAT).
>>>>
>>>>If we were to use an RTP proxy, as a backup mechanism for dealing with NATs,
>>>>would this alleviate the issue of multiple SER servers and symmetric NATs?
>>>>
>>>>
>>>>_______________________________________________
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>>>>serusers at lists.iptel.org
>>>>http://lists.iptel.org/mailman/listinfo/serusers
>>
>>_______________________________________________
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>>serusers at lists.iptel.org
>>http://lists.iptel.org/mailman/listinfo/serusers
>
>-- 
>Voice System
>http://www.voice-system.ro
>
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--
Jiri Kuthan            http://iptel.org/~jiri/ 




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