[Serusers] Failover PSTN Gateways

There is some work in progress: http://download.dns-hosting.info/SERLCR/README Adrian 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. Thanks in advance for your help! Best regards, Gerhard