Hi I'm trying to get something to work that I thought should work out of the box, but when implemented didn't work the way I thought it would... Please comment.
I'm using OpenSER as a core SIP proxy, among other things to connect to a POTS network via two independent Cisco PGW2200 SS7 GW. These gateways have fully DNS resolvable SIP domains (rfc 3263, NAPTR, SRV and A records). NAPTR (udp only) => SRV (udp only) => 2x A records (one for each redundant GW). Calls directed to POTS nicely load shares between the two A records. So far so good.
Now, if I disable one of the Gateways, I hang every second call. OpenSER does not try the second A record address if the first doesn't answer. How can I solve this? Shouldn't OpenSER fail over to the second A record listed in the NAPTR => SRV resolving? Or will OpenSER continue to resend all SIP INVITES until timers fire? Would it help if the proxy recieved an ICMP port/destination unreachable from the network? Is there anyway to get around this? In the other direction, from POTS to sip, the PGW2200 nicely switches over to the second of my two OpenSER servers if I shut one of them down. These servers have the same DNS entries (but for another SIP domain, NAPTR => SRV => 2x A record).
I would love some best practice implementation clues regarding OpenSER and multiple GW fail over, if anyone of you have such knowledge or experience.
Best regards, /Staffan
--- Staffan Kerker, Saab Communication Ljungadalsgatan 2, 35180 Växjö, Sweden
p. +46 470 42185 c. +46 705 391365 m. staffan.kerker@saabgroup.com w. http://www.saabgroup.com