On Tue, May 11, 2010 at 8:08 PM, Scott Lawrence <[email protected]> wrote:
> On Tue, 2010-05-11 at 14:17 -0400, WORLEY, Dale R (Dale) wrote:
>
>> The sipXecs Registrar executes a call pickup by sending a SUBSCRIBE
>> message to the targeted extension.  It then waits a configured period
>> of time (default 2 seconds), then examines all of the NOTIFY responses
>> it got to the SUBSCRIBE to determine what calls are ringing on the UAs
>> for the targeted extension.  Among those calls, the Registrar chooses
>> the call that has been ringing the longest to be picked up.
>>
>> As issue XX-8372 shows, this strategy does not work well in an HA
>> environment:  if the SUBSCRIBE goes to a proxy which is down, the
>> Registrar's SIP stack takes 2.5 seconds to fail over to the other
>> proxy.  By that time, the Registrar has given up waiting for NOTIFYs
>> from the SUBSCRIBE, and reports the pickup as failing.  Conversely, if
>> we raise the wait time to 4.5 seconds, all pickup operations are
>> unduly delayed.
>
> If the pickup redirector sends the SUBSCRIBE to the proxy using tcp,
> shouldn't you be able to detect the failure much faster than 2.5
> seconds?


Proxy liveness can be rapidly tested by sending a ping to port 5060
(i.e. a CRLFCRLF packet). I use this in sipxbridge to cut down the
failover time. I do not think it is necessary to wait for the SIP
transaction state machine to time out. Just send a UDP ping to the
proxy server.


Ranga


>
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-- 
M. Ranganathan
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