[Serdev] Concept for a SIP cluster implementation

[Klaus Darilion]

Andreas Granig wrote:
> Klaus Darilion wrote:
> 
>> Jan Janak wrote:
>>
>>>   - A user agent does not have to send INVITE messages through the same
>>>     proxy instance as REGISTER messages. The proxy server that received
>>>     the INVITE request can make sure that the uac is reachable
>>>     for the duration of the transaction by retransmitting the
>>>     provisional response periodically (simulates NAT ping). All other
>>>     transactions finish immediately and do not need this.
>>
>>
>>
>> What happens in the callee hangs up (send the BYE)? This will be 
>> loose-routed via the same proxy, which may not have a pinhole to 
>> traverse the NAT :-(
> 
> 
> Not if the proxy which receives the first INVITE from the caller sets a 
> record-route and NAT-pings the caller until the BYE is received. But 
> this would require some sort of dialog-stateful mechanism.

So, we just have to make ser call-stateful first :-)

> I'd say it's much easier to handle if the outbound proxy equals the 
> registrar from the UACs point of view. So the UAC always sends all 
> requests to the same edge proxy, which then splits up REGISTERs from 
> other requests and forwards them to the appropriate server.

Of course it would be much easier. How will you handle load blalancing 
between the edge proxies? SRV? If you use SRV, the clients are free send 
the request to whatever edge proxy. RFC 3263 says to use SRV lookup for 
each transaction.

regards
klaus