While telephone networks and computer networks have some things in common, they have a lot of differences between them.
Before we compare and contrast them, a brief overview of the principle of operation of a telephone network is given below:
- Telephone networks use circuit switching, wherein a dedicated circuit or a path is reserved for a call, end to end from the caller to the called party. This circuit is reserved for the entire duration of the call and is used to carry the signals of the actual telephonic conversation. No other call can share this end to end dedicated circuit, till the call is completed.
- A separate signalling protocol is used for setting up and tearing down the dedicated circuit during call establishment and call disconnection respectively. Also the signalling protocol uses a separate path (out-of-band signalling), that is different from the data circuit path.
The diagram given below illustrates a typical telephone call initiated from Chennai (India) to Connecticut (USA).
- As seen in the diagram, an end to end dedicated path is first established and reserved between Chennai and Connecticut (via. Mumbai and New York intermediate exchanges) for the entire duration of the call. The dedicated path is shown in red colour.
As we already know, Computer networks use packet switching and next hop routing as its basic principle of operation.
The common things between telephone and computer networks are given below:
- End Nodes & Intermediate Nodes are Electronic Devices
- Actual node to node Communication is using electrical voltages & Currents
- Use Telecommunication Links
- Intermediate Networks with routing intelligence needed
- End-End Telecommunication (physical) Path Needed
- Each end node requires Unique number/address
The differences between telephone and computer networks are given in the table below:
- As seen in the table above, while telephone networks use circuit switching, with dedicated signalling and data channels, computer networks use packet switching with no end to end path reservation.
- So computer networks utilize the underlying telecommunication links in a better manner, as it permits packets from multiple senders to simultaneoulsy share the same link.