A- Load balancing of calls outbound from Unified CVP
Four options are possible
1- Local Static SIP Routes
Only recommended for LAB use
If you have multiple routes, CVP is only going to try the first one even if it is down or failed
If there is a need to change one route then all the CVP Call Servers must be touched
2- Local CVP SRV Records
This is the most scalable and efficient method when coupled with SIP Proxy Servers as mentioned in the following example.
If there are multiple SIP Proxy servers (or any SIP entity for that matter like VXML-GW) in the network the call can be distributed in the round-robin method by defining equal weight and the equal priority.
Within CUP SIP Proxy itself you can configure static routes with Priority and Weight.
Below is an example local SRV configuration file. It must be named in a text file named srv.xml and manually placed in the c:\cisco\cvp\conf directory of the Call Server where the SIP Service is running.
With local SRV how does CVP behave if the SIP end point sends
Or other standard SIP error message
Question: Is CVP going to retry the next destination with priority=2 route automatically, if it receives one of the above SIP error messages? And would it happen after some timeout or immediately?
Answer: If the other SIP end-point responds with a 4XX responses like 480 or 486, this indicates to CVP that the final endpoint was reached and that this is the final disposition. Therefore, the failover does not occur. The CVP Local SRV implementation is such that it only rolls over to the next element in the SRV table if it gets a 503 service unavailable rejection or an timeout occurs. The CVP will not roll over with a 500 rejection either. Unlike the proxy servers (Unified SIP Server SIP Proxy and Unified Proxy Server), CVP local SRV does not have the SRV configurability to specify more rollover codes beside 503
SRV rollover is only applicable to initial INVITE requests. It does not apply to mid call requests such as reinivtes.