[Serusers] invite timer & calls to PSTN

[Jiri Kuthan]

At 01:08 PM 8/22/2004, Steve Blair wrote:
>>Is there a way to avoid that bogus fr_inv_timer failure?  I don't know
>>enough about call routing to say, but from this perspective it seems to
>>me that if there's no failure_route defined, the fr_inv_timer should
>>never go off.

That is not doable -- the timer must be there and it must hit, otherwise
the server would become storage of transaction memory, subject to very
quick memory exhaustion and increased DoS vulnerability. The only think
we can do is not to initial CANCEL on the timer, which is not always
doable (see my previous email).


>> 
> We have several instances of SER running for just this purpose. One instance with a
>specific value for fr_inv_timer for inbound calls that need to goto SEMS after 4 rings.
>A different instance for outbound calls where fr_inv_timer is set to 45 seconds to handle
>the range of called devices and their resective "answer" times. This works pretty well.

That may be a reasonable remedy. Having multiple proxy servers may also 
provide some additional bonus points. In particular, if you deploy a simple
PSTN gateway-guarding proxy, which does not do a lot (for example resolve
DNS), the simpler logic will be harder to circumvent.

-jiri