I am evalulating VoIP solutions to sit on an existing MPLS network and need some help to determine the pros and cons of SIP vs PRI. The MPLS is a Metro-E fiber at a corporate site, then T1 at 10 branch sites all within a 100 mile radius. There would be approximately 20 phones at the corporate location and 7 to 10 at each branch site.
Our telco has pictched a SIP solution, which has a monthly fee associated with it depending upon the number of sessions we need. I have read some reports that SIP is cheaper that PRI but not as stable? Some of the phone systems we have looked at would have a box that resides at the corporate site - in the event of an corporate outage we would like calls to still like calls to go to and from the branch offices - I have also read that the SIP trunking configuration can handle this.
Any feed back and information would be helpful.