Media in SIP and H.323 is transferred over RTP. It's a protocol that is quite asymmetric with respect to the sender’s and receiver’s responsibilities. Everything that sender does is splits the audio stream into packets, puts a header on top and sends...

At some point I was planning to explain how to bring “dead” Cisco gateway (or router, at that stage there is no difference in functionality) back to life and one of our AS5400 conveniently just “died” in the lab. How do I know that it’s “dead”? Well,...

First, the only call xfer type available for us (at least at this moment) is tromboning ("hair-pin"). It has quite obvious pros and cons: it works no matter what kind of telephony protocol you're using (interoperable as long as your gateway can perform...

Telephony... Where to start? Well, it you already got your gateway, you already have to know what kind of telephony link you’ll be working with because the hardware modules are different for analog and digital lines. If you have T1 (or E1) lines coming...

I admit I have some kind of a soft spot for Cisco. Though at some point my picture was probably on the dart board in their TAC (Technical Assistance Center) considering the number of issues we discovered in early versions of H.323 implementation and configuration...