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

[Federico Cabiddu]

Hi,
if you want failover support, you need to have a couple of core dns
parameters enabled:
https://www.kamailio.org/wiki/cookbooks/5.2.x/core#use_dns_cache

and

https://www.kamailio.org/wiki/cookbooks/5.2.x/core#use_dns_failover

The latter defaults to off.

Cheers,

Federico

On Thu, Jun 6, 2019 at 10:10 PM JR Richardson <jmr.richardson at gmail.com>
wrote:

> 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
>
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