The SIP routing system uses the Routing Profile field from the matched subscriber/server flow to take routing decisions. The SIP routing system uses the Next Hop servers specified on the Routing Profile page to determine the communication addresses and transport of the SIP entity for which the incoming SIP call is retargeted.

The Next Hop Address fields on the Routing Profile page can be configured with an IP Address / IP Address: Port / Domain / Domain: Port. The SIP routing system routes the call to the appropriate server based on the selected load balancing algorithm.

• Heartbeat failure: If the server fails to respond to a heartbeat message, subsequent routing takes places towards the next Next Hop server.

• SIP Timer expiration: SIP RFC 3261 Timer. By default, this functionality is available for all the request messages. If you want to overwrite RFC 3261 timer, use the server interworking profile timer configuration.

• Server Error Message: If the server sends a 5xx message, Avaya SBC considers the server as currently unavailable.

The Next Hop Address fields must resolve to a valid Server Configuration for the SIP routing system to correctly route the SIP calls.

Routing profile can be provisioned with support for DNS NAPTR/SRV procedures as per RFC 3263. DNS support for A-queries is enabled by default and not configurable. The system internally employs an LRU-based DNS cache for facilitating faster lookups.

After the route entry is resolved, the system proceeds with locating SIP servers.