Hi We are discussing how to deal with this scenario:
A SIP UA is communicating with two redundant SIP servers - a primary and a secondary. The addresses and priorities of these servers are obtained through DNS SRV. The primary server is failing and the UA needs to communicate with the secondary server. As I understand RFC3263 the UA must try to communicate with the primary server for every new transaction and then fail over to the secondary. However, this will introduce very long call setup delays as RFC3261 specifies a timeout of 32 seconds (timer B = 64 x T1). A solution for this could be to reduce the timeout but is that a good idea? On the other hand RFC3263 page 4 states: -------------- The identity of the available server would ideally be cached for some amount of time in order to reduce call setup delays of subsequent calls. The client cannot query a failed server continuously to determine when it becomes available again, since this does not scale. Furthermore, the availability state must eventually be flushed in order to redistribute load to recovered elements when they come back online. -------------- This indicates that it would be a good idea to remember that the primary server is unavailable for some time. This could reduce the call setup delays while using the secondary server. However, the UA would not switch back to the primary server as soon as possible. To make the situation even more complicated our UA contains up to 1000 wireless endpoints. This could enable us to use the information gathered by one endpoint for the rest of the endpoints. What is the preferred way to handle this problem? Thank you /Kenneth _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
