Just to elaborate on the response as to why a single gatekeeper would be the correct way to go.The gatekeeper just provides a consolidation of VoIP call routing configuration on one box that would otherwise have to reside on every one of your gateway...
There are some new features specifically related to early cut through of voice paths on ISDN calls.I had some problems of not hearing call progress tones on a system without any ISDN.Try:http://www.cisco.com/univercd/cc/td/doc/product/software/ios121...
I can recommend the Radiator server from OSC ( www.open.com.au ). It is actually written in Perl which might seem a little weird but it is a top notch product at a very reasonable price.They have excellent documentation and I have been billing from A...