> From: Guo-Wei Chiuan > > However, I tried several SIP phones, only one SIP phone does it > perfectly. It does send INVITE to another SIP proxy specified in > Contact field of "305 SIP Proxy". Other SIP phones do something wierd. > For instance, it does change To: field to be uri specified in Contact: > field but it still keeps sending INVITE to original SIP proxy. (Only > To: field is changed but destination IP is not changed)
Many SIP phones, if they are configured to have an outbound proxy, send *all* requests to the outbound proxy. (Even though this behavior is not recommended -- see RFC 3261 section 8.1.2.) So it may be that the phone will do what you want if the outbound proxy setting is turned off. > I am wondering if "305 Use Proxy" supported by most SIP phone vendors > currently? I would like to redirect INVITE request from one SIP proxy > to another SIP proxy by this manner. But, it requires that most SIP > phone vendors support "305 Use Proxy". Have you considered providing a set of DNS SRV records for the SIP domain? A lot of SIP agents process SRV records correctly, and SRV records include a load-balancing mechanism. But in your case, I don't see the 305 saving much effort by the proxy, compared to alternative policies. If the proxy won't Record-Route itself, it will only have to handle the INVITE and 200 messages, which is not much more work than handling the INVITE to generate the 305. If the proxy would Record-Route itself if it handled the call, one alternative is for it to forward the call to another proxy without Record-Routing itself, and leave that proxy to do the Record-Route. Dale _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
