Talk:Circuit switching

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Question[edit]

From the entry: "Time-division multiplexing could be seen as a compromise between circuit and packet switched by giving exclusive control to different nodes for a specific time slot." Is this correct? -- Tompsci 14:14, 4 April 2006 (UTC)[reply]

Not really, since TDM is a multiplexing technology and thus not have the same "scope" as circuit or packet switched technology. Circuit switched technologies very often use TDM. The largest exception is ATM that is a circuit switched technology using small, fixed size packets (cells) for transport. ATM is then rather the "compromise" between circuit and packet switching.

See also DTM for a discussion on TDM, packet and circuit switching.

The whole sentence on Time-division multiplexing should be dropped. It is a poor perspective to introduce at this point. TDM is a transport technology not a switching technology.

ATM should not be discussed either. ATM is both a transport technology and a switching technology. From the switching perspective, the circuits being switch are virtual. The basic scope of the current article should not try to deal with this advanced topic, at least not yet.

Regarding "For traffic connection control (and other administrative purposes), it is possible to use a separate dedicated signalling channel. ISDN is one such protocol that uses a separate signalling channel while the Public Switched Telephone Network is not." It is much more accurate to say "For traffic connection control (and other administrative purposes), it is possible to use a separate dedicated signalling channel. ISDN is one such service that uses a separate signalling channel while Plain Old Telephone Service (POTS) does not.

There are several points here: 1. ISDN is a service and/or technology built on several protocols none of which is the ISDN protocol. (There is no ISDN Protocol.) 2. The comparison to be made here is that the access connection to the service provider uses either in band or out of band signalling. ISDN uses out of band signalling. POTS uses in band, touch tone or DTMF signalling. 3. The Public Switched Telephone Network (PSTN) does, in fact, use out of band signalling, namely CCS7. 4. ISDN service, between exchanges, uses CCS7 signalling also. 5. ISDN service and POTS service also both use the same inter exchange transport system. 6. To put all of this in perspective, keep in mind that although these statements are true about the network at large today, it wasn't always this way.