ISDN Protocols

The Right Protocol

There are several different protocols in common use that are used to recognise data over the B channels. The two oldest are X.75 and V.110. These are both slower protocols, typically up to 56K, and are probably best avoided in favour of the two other main choices.

These are V.120, which is a protocol suitable for BBSes, etc, which can happily manage 64K, and PPP. PPP comes in two main forms, sync and async. Synchronous PPP is the faster of the two, and can typically manage 80K over a single channel (don't ask). An extension of PPP, called PPP/MP ( RFC 1717), supports channel bonding. PPP is most likely to be encountered with ISPs, as PPP is one of the native formats used to propogate ethernet packets over serial lines.

PPP/MP has an extension that permits the addition and subtraction of an extra channel on demand. This is known as BAP/BACP, and is currently an Internet Draft, which means it will be released as an RFC in due course. See Dan Kegel's page for full details.

Any of these protocols can be combined with a compression method, such as V.42bis or STAC, to give greater throughput for suitable material.

Words and design by:
Paul Lynch
Last updated: 11 November 1996.

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