Cisco Call Manager

And what would be a product that supposedly requires Cisco CallManger? Is it Cisco phones? Cisco Voice Gateways? Cisco routers? Do you have existing environment?

Cisco supports many protocols for different purposes. For example, it uses SCCP to communicate to phones. It uses MGCP to talk to gateways. It supports H.323 for other devices. It has QSIG support for trunks. As well as many other protocols and options.

If you need a product, which can support same features, as Cisco CallManager, you can check Asterisk PBX. It's freeware OpenSource software, which runs on Linux/ It has a lot of features, but it has very weak interface. A lot of things should be configured as a text files. So, you are not paying for a software, but you have to learn a lot.

Good luck,

Mike