VoIP Modes of Operation

PC to PC
PC-to-Telephone calls
Telephone-to-PC calls
Telephone-to-Telephone calls via the Internet
Premises to Premises
- use IP to tunnel from one PBX/Exchange to another
- see Time Warner’s “Telecom One Solution”
Premises to Network
- use IP to tunnel from one PBX/Exchange to a gateway of an operator
Network to Network
- from one operator to another or from one operator’s regional/national network to the same operator in another region or nation

Transcript

[slide34] So how do we use VoIP today? Well, one of the major methods is, of course, PC to PC. But another approach is, of course, PC to physical telephones. By people putting in gateways between the Internet or private networks and the public switched telephoning network, you can then reach anyone who had a traditional telephone. There are also telephone to PC calls, and one of the really fascinating things is telephone to telephone calls. You put a gateway at each end, you move the traffic the long distance over your IP network, and off you go. Another was premises to premises. You're a business. You have several locations. What do you do? Well, in the past, you'd rent a circuit switch channel scaled to handle the number of simultaneous calls you expected to handle, and you calculated that using Erlang's law, and you paid a lot for it. Now what do you do? You set up a gateway in each of your premises, you mix it with your data traffic, you send it, off it goes. Premises to network. One of the interesting things here in Kista was, many years ago, when we moved into the Forum building down the street, it had been owned by IBM, and IBM owned a digital telephone company, so they had their own wiring for their own system. But when KTH moved in, interestingly enough, we had three salespeople from one particular telecom operator, who each came to try to sell a business telephoning system for the building. And the first one said, ah, we'll put in a DECT cordless telephoning system, and we'll connect that PBX to our local switch, and you have cordless telephones, which we had in this building at the time. They're really cheap, they act just like wired telephones, but you can walk all around between the buildings. Next salesman said, ah, I can sell you something even better, I can sell you this IP telephoning system. Third salesperson comes, we sell you a traditional wired PBX. In the end, they came back and said, actually, you have to buy the voice over IP system. And the university, [said] why? You have these three different offers, why can't we choose from the other two? Is it because we've run out of ports on our local public switch? We can't attach another PBX to it. So here in Europe, the traditional way of connecting to public switches were E1 circuits, 2.048 kilobits per second, but you have to have physical ports on the switch, and when you run out of those ports, you can't connect anything more to the switch. And since they'd run out of ports on their local switch, they said, actually, buy the IP solution. So suddenly, we had premises to network being done by IP. And at the other end, they could take the IP back and inject it into their infrastructure so you could call anyone else with a telephone. And a very popular technique today is network-to-network. So if you're going across the Atlantic, the Pacific, et cetera, what do you do? You turn all your traffic into IP traffic, you send it across, and you get that factor of two savings.