[SR-Users] Using DNS in Dispatcher for SRV Clarification

[JR Richardson]

Hey All,

I'm in the lab testing kamailio 5.2 with DNS SRV records. The scenario
is simple, using dispatcher with hard coded IP URIs
[sip:10.10.10.10:5060] and also a DNS name URI [sip:sip.domain.com].
There are 2 SRV servers.

The DNS SRV records are setup and resolving OK, during startup,
kamailio list the DNS name in the dispatcher list.

During a call scenario, when the dispatcher selects the DNS name URI
for the next destination, the TM module takes over, resolves the
_sip._udp.sip.domain.com for both SRV records OK and sends the call to
the first SRV server in the list. But if I take the first SRV server
offline, make another call, the TM module does not route to the second
SRV server until the DNS record timeout is reached, in my lab was set
for 300 seconds. I decreased the DNS SRV record TTL down to 5 seconds
with same results above, but 5 seconds lapse when TM routes call to
next SRV server.

I think this is working as expected but not sure if this is by design
so my question is, should the TM module route to another SRV server in
the list in the event of a no response timeout or send the transaction
back to the dispatcher to select another target?

Should I play around with the TM Module parameter
"max_noninv_lifetime" to get quicker results or it is better to have
DNS SRV record TTL set really low?

Thanks.

JR
-- 
JR Richardson
Engineering for the Masses
Chasing the Azeotrope