Path: utzoo!utgpu!watserv1!watmath!att!pacbell!pacbell.com!ucsd!sdd.hp.com!zaphod.mps.ohio-state.edu!wuarchive!uunet!hayes!tnixon From: tnixon@hayes.uucp (Toby Nixon) Newsgroups: comp.dcom.modems Subject: Re: Modem Speed Message-ID: <1493@hayes.uucp> Date: 7 Sep 90 04:16:31 GMT References: <1664@gvgpvd.GVG.TEK.COM> <1990Aug30.023220.8554@ncsuvx.ncsu.edu> <659@texas.dk> <1990Sep4.150259.12379@savant.uucp> <887@stsim.ocs.com> <2495@crdos1.crd.ge.COM> Followup-To: news.newusers.questions Organization: Hayes Microcomputer Products, Norcross, GA Lines: 77 In article <2495@crdos1.crd.ge.COM>, davidsen@crdos1.crd.ge.COM (Wm E Davidsen Jr) writes: > There are currently three major players in the 9600 and up modem > protocol game. The standard is V.32, but it's not as widely used as the > others. If you are buying modeems for both ends you don't care. V.32 is much more widely used that either Trailblazer or HST, if you consider the entire marketplace and not certain limited applications. V.32 modems are available from virtually all major modem manufacturers, and have the distinct advantage of running all unix-related protocols with no need for strange settings or protocol "spoofing". > PEP protocol (Trailblazer) offers higher throughput than the line > speed for some protocols, notably uucp and (I believe) xmodem and > kermit. The packet envelope is stripped at the sending end and > reconstructed at the other end. Only the data flows, and throughput can > be 20-40% faster. All error-control modems strip the start and stop bits from async characters, so they'll all experience a 25% speed increase. The other "increase" you mention is due to protocol "spoofing" in the Trailblazer. But V.32 modems don't need to do this, because they're full duplex to start with; the Trailblazer (and other multicarrier and assymetrical modems) need to do it to make up for the negative impact on protocol performance caused by the basically half-duplex nature of their modulation schemes. > The standard used by many ham radio and CP/M systems is (the HST US > Robotics). I'm not sure what this buys you other than compatibility. > That's not saying something bad, I just don't have a lot of time on > these modems. The HST is "popular" primarily because USRobotics practically gave them away ("sold" them for less than manufacturing costs) to BBS sysops all over the country. Telebit did basically the same thing with Trailblazer modems a few years ago, which accounts for their "acceptance" in the unix community. The HST, like the Trailblazer, is OK for some applications like file transfer, but due to the extremely slow turnaround time is unacceptable for other applications. > V.42 is a data compression scheme, and it may be effected by the > recent UNISYS patent on data compression. The last word I heard was that > software compression would be ignored, hardware compression (like a > modem) would be licensed. V.42 is the international standard for error control in modems, defining two protocols: the primary protocol, LAPM, and an "alternative protocol" for backward compatibility with MNP2-4 modems. You may be thinking of V.42bis, which is the international standard for data compression in modems. It is based on Lempel-Ziv compression, and two companies, Unisys and IBM, claim that patents issued to them apply to the LZ compression used in modem applications; British Telecom also claims that patents for which they have filed for but that have not yet been issued will also apply to V.42bis modems. > If I were buying modems I'd go Telebit T2500, with PEP and V.32. One should select a modem based on, among other things, what the people use that one intends to call. But you're quite right in preferring a modem with V.32 over one with only proprietary high-speed protocols, since V.32 is the international standard and very quickly gaining in worldwide acceptance. -- 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 -----------------------------------------------------------------------------