MODEM-COMMUNICATION STANDARDS

5/31/97

Modem/Communication Standards: For the most part computer communications standards have been established by modem vendors building a number of different (marginally at best) compatible modem designs and making a standard out of the design that survives the resulting shakeout. Different standards/conventions are used for various communications speeds:

Standard Description
Bell 103T 0-300 bps in North America
V.21 300 bps -- not Bell 103-T compatible
Bell 212A 1200 bps in North America
V.22 1200 bps outside of North America
V.23 1200bps/75bps Asymmetric
V.22bis 2400 bps worldwide
V.32 9600 bps worldwide
V.32bis 14400 bps worldwide
V.32terbo 19600 bps worldwide
V.34 28800 worldwide
*HST US Robotics 9600-16800
*V.FC 28800 pre V.34. Similar to V.34 but not fully compatible
*V.FAST/V.34 28800 worldwide
*X2 One of two competing "56K" standards
*K56Flex One of two competing "56K" standards
*V.90 Universal 56K modem standard. Will connect to an X2 ot K56Flex modem at 28.8.
*v.pcm the final 56K standard to be compatible with both X2 and K56Flex. Probable hardware availability -- early 1998

Over and above transmission speed, standards are used for error correction and compression.
Standard Description
*MNP [Microcom Networking Protocol] Levels Error Correction/ compression. Comes in various levels.
MNP1 Asynchronous half duplex
MNP2 Asynch Simple Error Correction (Included in V.42)
MNP3 Synch Simple Error Correction (Included in V.42)
MNP4 Improved Simple Error Correction (Included in V.42)
MNP5 Simple Data Compression (2:1)
MNP6 Statistical duplexing, Universal Link Negotiation.
MNP7 Improved Data Compression (3:1)
MNP8 MNP7 for pseudo duplexed modems
MNP9 V.32 Data Compression
MNP10 Cellular enhancements

*These are "informal" standards. Translation -- They possibly will not work properly with many other modems today, and probably will work with even fewer in the future.

It was pointed out in the discussion of this article in the forum, that devices that actually comply to a real standard (if such are available) will be more likely to operate reliably and at the claimed speed in normal usage than non/pre-standard modems.

Return To Index Copyright 1994-2002 by Donald Kenney.