[Users] NEW FEATURE: DNS-based failover

Hi everybody, OpenSER 1.2.0 has now the capability to do DNS based failover, according to RFC3263 (http://www.ietf.org/rfc/rfc3263.txt). The SIP resolver was enhanced to to be able to save and resume later the DNS queries in order to get all possible IP destinations. The resolving process is step-by-step done (get next IP only on demand) to minimize the total number of DNS queries. So having this support does not imply, in normal processing, more load on the DNS server. Additional queries are done only when needed (after failure detected). The scanning for new IP destinations is done by the SIP resolver on all DNS levels: NAPTR, SRV, A. Both core and TM are using this new feature. In core, the stateless forwarding can do only DNS-based failover at transport level (if no egress interface found or send operation failed due whatever reason). In TM, the DNS-based failover is extended to transaction level. If the transaction completes with 503 or 408 with no reply, automatically, a new branch will be fork if any destination IP can be found by the DNS resolver. Read more here http://www.openser.org/docs/modules/1.2.x/tm.html#AEN103 For controlling this feature use: - newly added core parameter "disable_dns_failover" - use to generally disable the DNS-based failover. By default is false. - in TM, t_relay() take a new flag for turning off the DNS-based failover. This setting is per transaction. By default, the failover is done. Any feedback is appreciated. regards, Bogdan