tnixon@hsfmsh.UUCP (Toby Nixon) (07/05/90)
In article <1990Jul04.130105.3502@nstar.uucp>, Larry Snyder asks:
- Is LAMP a DUPLEX protocol - or a compression form?
Well, George has the acronym wrong: the error control protocol
defined in CCITT Recommendation V.42 is "LAPM", which stands for
"Link Access Procedure for Modems". It is NOT a data compression
scheme, but an error-control protocol. The CCITT data compression
standard is "V.42 bis"; the compression technique itself is a form
of Lempel-Ziv-Welch compression, extended for real-time modem
operation with enhancements designed at British Telecom and Hayes.
To answer your question, LAPM is a duplex protocol, and V.42bis is
designed to compress in both directions simultaneous when run on top
of LAPM.
-- Toby
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-----------------------------------------------------------------------------tnixon@hsfmsh.UUCP (Toby Nixon) (07/08/90)
In article <3853@galena2.UUCP>, Justin A. Smith asks:
- does V.42 use the zipp-lemfel (sorry about spelling :-) )
- compression. When i was working at BT they were doing somthing like
- this. Is this the resulting standard????
CCITT V.42bis is based on Lempel-Ziv-Welch compression, with
extensions created at British Telecom and Hayes Microcomputer
Products.
Did you work with Alan Clark at BT? Did you know that he is no
longer with them, but is now technical director at Dowty?
-- Toby
-----------------------------------------------------------------------------
Toby Nixon, Principal Engineer Fax: +1-404-441-1213 Telex: 6502670805
Hayes Microcomputer Products Inc. Voice: +1-404-449-8791 CIS: 70271,404
Norcross, Georgia, USA BBS: +1-404-446-6336 MCI: TNIXON
Telemail: T.NIXON/HAYES AT&T: !tnixon
UUCP: ...!uunet!hayes!tnixon Internet: hayes!tnixon@uunet.uu.net
MHS: C=US / AD=ATTMAIL / PN=TOBY_L_NIXON / DD=TNIXON
-----------------------------------------------------------------------------leech@threonine.cs.unc.edu (Jonathan Leech) (10/04/90)
In article <sR1Fq1w163w@mudos.ann-arbor.mi.us>, mju@mudos.ann-arbor.mi.us (Marc Unangst) writes: |>protocol for 2400 and 1200 bps modems. V.42bis is a compression |>protocol that can increase speed up to four times over a V.42 link. How well does V.42bis work for interactive sessions (editing, reading news, etc.)? I saw a 2400 baud modem with V.42bis advertised in MacWeek for $200, which would be attractive if it could deliver near-9600 baud throughput.