chau@caen.engin.umich.edu (Hin Fai Chau) (01/22/91)
I have seen an ad in the January issue of Computer Shopper about the V.42bis
external modem by Zoom for a price of $189. It claims that it can achieve
9600 bd compressed through-put with a 2400 bd data-pump; fully V.42 COMPLIANT,
100% Hayes and MNP-5 compatible.
My questions are:
(1) How does it compare to the real 9600 baud modems in terms of performance
and usage?
(2) Does it require a special kind of software to operate?
(2) What do V.42, V.42bis, Hayes and MNP-5 mean?
(3) I have seen that some modems can be addressable with COM1, COM2, COM3 and
COM4. What are they?
(4) What is the limit of ordinary phone lines? Can it handle 9600 baud data
transmission?
(5) I assume some of you know X. I have a 386/33 IBM PC-compatible system at
home. What do you think the minimum baud rate necessary of a modem if I
want to run jobs "remotely" on DECs say, and display graphics "locally"
and efficiently on my PC screen via X window?
Please use my email address in your response if possible. Your help will be
greatly appreciated. Thanks.
-- H. Chauv082mv5d@ubvmsd.cc.buffalo.edu (William M Utter) (01/31/91)
In article <1991Jan21.204216.27162@engin.umich.edu>, chau@caen.engin.umich.edu (Hin Fai Chau) writes... >I have seen an ad in the January issue of Computer Shopper about the V.42bis >external modem by Zoom for a price of $189. It claims that it can achieve >9600 bd compressed through-put with a 2400 bd data-pump; fully V.42 COMPLIANT, >100% Hayes and MNP-5 compatible. > >(2) What do V.42, V.42bis, Hayes and MNP-5 mean? V.42 and MNP are methods of error correction and DATA compression. MNP5 can make you modem go "twice" as fast. throughput up to 4800bps on a 2400 modem. v.42 is a much better compression and might get you 9600. I have both a USR 2400 MNP5 modem and I would say that average throughput is about 3600bps. I also have a USR HST modem with v42. I can notice the difference in a mnp5 and v.42 connection. Even when connected at 14400. >(4) What is the limit of ordinary phone lines? Can it handle 9600 baud data > transmission? I use the USR HST on regular phone lines. I have heard that there might be some problems in Europe but I haven't seen any here in the states. No problems with long distance calls either. One ince thing about MNP/v.42 is that you will never have LINE NOISE.
bob@MorningStar.Com (Bob Sutterfield) (02/01/91)
(Listen in on comp.dcom.modems sometime, where these issues are often discussed. I've included c.d.m in the Newsgroups: line, and directed followups there.) In article <56917@eerie.acsu.Buffalo.EDU> v082mv5d@ubvmsd.cc.buffalo.edu (William M Utter) writes: In article <1991Jan21.204216.27162@engin.umich.edu>, chau@caen.engin.umich.edu (Hin Fai Chau) writes... (2) What do V.42, V.42bis, Hayes and MNP-5 mean? V.42 and MNP are methods of error correction and DATA compression. MNP5 can make you modem go "twice" as fast... v.42 is a much better compression and might get you 9600. Just to be picky... V.42 and MNP4 are error correction protocols. They are very similar if not identical, and I know of no technical advantage of one over the other. V.42bis and MNP5 are data compression protocols. MNP5 will yield a best-case throughput improvement of 2:1, and V.42bis will manage a 4:1 speedup. Of course, not many people send megabytes of "A"s every day, so you won't see those theoretical values. All the above are independent of the underlying carrier technology, whether V.22 (1200), V.22bis (2400), V.32 (9600), V.32bis (14400) or whatever. Hayes is a company that makes modems and other stuff. They invented and popularized the modem control command set that starts every instruction with "AT". To be "Hayes-compatible" means that your modem's instructions must begin with "AT" too. (4) What is the limit of ordinary phone lines? Can it handle 9600 baud data transmission? We use Telebit T1600s to carry TCP/IP over PPP between SPARCstations over regular voice-grade telephone lines. The DTEs are set at 38400, and we use V.32/V.42/V.42bis (9600 carrier with error correction and data compression). We see FTP throughput figures of 1.7 to 2.8 Kbytes/sec in a one-way transfer, or 1.5 to 2.2 Kbytes/sec if files are being shipped both directions at the same time. The variance reflects the degree of compressibility of the data being transferred. I'm looking forward to trying out a V.32bis modem someday!