said by nokiatech :

VOIP is Voice over IP. The method of transmission and the protocal being transmitted really have nothing to do with one another. They are doing pretty much the same thing that a company like Vonage does. The difference is the vast majority of call routing is done on their private cable network vs using the internet like Vonage does.

said by Cabal :

VoIP is Voice over IP. Comcast is running Voice over IP. Not sure what the confusion is, they just do a better job of insuring quality over other competitors.

Q: If the cable goes out, will my phone go out too?

A: No. Comcast uses the power of broadband to deliver Comcast Digital Voice, cable television, and High-Speed Internet services to our customers over a single coaxial cable. To ensure reliability, these services function independently of each other, so if one Comcast service is affected, it does not necessarily mean your other Comcast services will be affected. But is a storm or accident knocks out our network, then muliple services may be affected.

Q: Are Comcast Digital Voice calls routed across the Internet?

A: No! Comcast keeps the calls on their private broadband network until our switch delivers the call on the PSTN (public switched telephone network).