[Serusers] Failover PSTN Gateways

[Klaus Darilion]

Gerhard Zweimueller wrote:
> Hi list,
> 
> We have a setup with 2 redundant stateful SER SIP-Servers with
> accounting.
> 
> For calls to the PSTN we have 2 ISDN-PRI gateways connected to
> different ISDN-PRI lines.
> 
> We need to implement a dynamic failover mechanism and load balancing.
> 
> a) Incoming calls: No problem, the PSTN switch takes care of that
> b) Outgoing calls:
>   Both GWs are registered at both SERs; calls are usually relayed with
> "t_relay_to_udp(x.x.x.x, "5060");"
>   But how can I implement a quick failover including load-distribution
> between those gatways?
>   I.e. if I receive "busy here" or no response after a short period
> after the "invite", the call should be redirected to the other GW.

Just make a failure_route for the outgoing calls. If the GW answers "486 
busy", the script enters the failure route where you will send the call 
to the second GW.

Handling the "no response" scenario is much more complex - you can't to 
this with timers as they don't differentiate between "no response" or 
"180 Ringing" response.

regards,
klaus