jching@watnow.waterloo.edu (John Y. Ching) (01/19/91)
I am looking for a 2400 baud modem for my pc and a salesman insisted that I need a modem with MNP5. I have a relatively low budget and would like to know if I really have to pay extra for MNP5. Most of my communication would be long-distance. Thanks. -- ________________________________________________________________________________ John Y. Ching (jching@watnow.waterloo.edu) | "Thought without Learning is Pattern Analysis and Machine Intelligence Group | Useless; Learning without Department of Systems Design Engineering | Thought is Dangerous."
steven@ozonebbs.UUCP (Steven Rubin) (01/23/91)
jching@watnow.waterloo.edu (John Y. Ching) writes: > I am looking for a 2400 baud modem for my pc and a salesman insisted that I > need a modem with MNP5. I have a relatively low budget and would like to > know if I really have to pay extra for MNP5. Most of my communication would > be long-distance. > Thanks. > I think MNP would be a BIG mistake. If you transfer alot of GIFS and other compressed data, the MNP compression would just make everything take alot longer. --- Steven Rubin E-Mail: steven%ozonebbs@netcom.uucp Snail: 3670 Rollingside Dr, San Jose, CA 95148-2822 Phone: +1 408 238 2818, +1 408 223 1738 (bbs) Disclaimer: My mommy told me not to talk to strangers (Note: The FROM: line is incorrect, use steven%ozonebbs@netcom.uucp)
tad@ssc.UUCP (Tad Cook) (01/23/91)
In article <1991Jan18.194613.13435@watserv1.waterloo.edu>, jching@watnow.waterloo.edu (John Y. Ching) writes: > I am looking for a 2400 baud modem for my pc and a salesman insisted that I > need a modem with MNP5. I have a relatively low budget and would like to > know if I really have to pay extra for MNP5. Most of my communication would > be long-distance. > Thanks. It will only help if you are communicating with another MNP5 modem on the other end. I use an MNP5 modem, and I like it for downloading long ASCII files from a local Fidonet board, because it has a compatible modem, and I can get 30-40% higher throughput. I also like it for my MCI Mail activity when I have to upload or download long files. For many things that I do, it is not appropriate, either because the modem at the other end is not compatible, or because I am downloading compressed program files that do not benefit from compression like plain text files do. It also has the advantage of having better noise immunity, but again, only when talking to another MNP compatible modem. Tad Cook Seattle, WA Packet: KT7H @ N7HFZ.WA.USA.NA Phone: 206/527-4089 MCI Mail: 3288544 Telex: 6503288544 MCI UW USENET:...uw-beaver!sumax!amc-gw!ssc!tad or, tad@ssc.UUCP
billd@fps.com (Bill Davidson) (01/28/91)
In article <1991Jan27.160653.7104@nstar.rn.com> larry@nstar.rn.com (Larry Snyder) writes: >Sorry - but incorrect with MNP5. MNP5 over a 2400 baud connection >if properly installed will produce transfer rates of 280 cps even >sending GIFs and ZIPs I find this *VERY* difficult to believe. GIF's are already LZW compressed and so in general cannot be further compressed by *ANY* one dimmensional digital compression method I am aware of without data loss. If the MNP modems are really running a 2400 baud link, 280cps seems impossible. The theoretical max for 2400 baud is something like 266cps (8 data + 1 stop) and anything higher would require compression and as I said, I don't believe you can compress a GIF => 280cps impossible. My theory tends to agree with my experience with MNP modems as well; in fact they tend to do only slightly better for me than normal old Hayes 2400's on ascii transfers. The protocol does seem to adversly affect turnaround time during interactive work for some strange reason (my guess is it's due to sampling for compression). Also, when one MNP modem connects to another MNP modem and one has MNP turned on and the other has it off, it's been my experience that you get only garbage. Both can talk to non-MNP modems fine. They can only talk to each other if they both have MNP off or both on (this experience has been with Microcom's; the inventors of MNP). The only thing good I have to say about MNP is that it does tend to allow less line noise through. --Bill Davidson
rfarris@rfengr.com (Rick Farris) (01/28/91)
In article <15126@celit.fps.com> billd@fps.com (Bill Davidson) writes: In article <1991Jan27.160653.7104@nstar.rn.com> larry@nstar.rn.com (Larry Snyder) writes: Larry> MNP5 over a 2400 baud connection if properly Larry> installed will produce transfer rates of 280 cps even Larry> sending GIFs and ZIPs Bill> I find this *VERY* difficult to believe...280cps seems Bill> impossible. The theoretical max for 2400 baud is Bill> something like 266cps (8 data + 1 stop) and anything Bill> higher would require compression... Get a clue, Bill. Larry said he got 280 cps using MNP5 from experience. So have I. None of your "beliefs" will affect that. In particular, "perfect" 2400 bps, 8,n,1 transimission achieves 240 cps; 1 start bit, 8 data bits and 1 stop bit. By stripping start and stop bits, the data rate can reach a theoretical 300 cps (240 * 10/8). Add protocol overhead, and a little bit of file expansion due to trying to compress pre-compressed data and you're in the neighborhood of 280 cps. Note that we're talking about MNP *5* here. -- Rick Farris RF Engineering POB M Del Mar, CA 92014 voice (619) 259-6793 rfarris@rfengr.com ...!ucsd!serene!rfarris serenity bbs 259-7757
swansonc@acc.stolaf.edu (Chris Swanson, St. Olaf College) (01/29/91)
In article <0cD8V3w163w@ozonebbs.UUCP> steven@ozonebbs.UUCP (Steven Rubin) writes: jching@watnow.waterloo.edu (John Y. Ching) writes: > I am looking for a 2400 baud modem for my pc and a salesman insisted that I > need a modem with MNP5. I have a relatively low budget and would like to > know if I really have to pay extra for MNP5. Most of my communication would > be long-distance. > Thanks. > I think MNP would be a BIG mistake. If you transfer alot of GIFS and other compressed data, the MNP compression would just make everything take alot longer. I think that MNP5 would be a GOOD idea. Since you are going to be mainly going long distance, anything that could save some transmission time will save you money. MNP5 can give aprox %80 faster throughput on text-based transfers. On other transfers the throughput could be less, but would still provide some increase in throughput in most circumstances. The extra cost is usually only $50 or so more - well worth the investment. If the compression technique actually increases the transfer time, as it might in cases where the material being transfered is already compressed. If this is the case, you can turn off the MNP5 compression for the transfer, reversing (to the throughput of a normal 2400 bps modem) the throughput decrease. -Chris -- Chris Swanson, Chem/CS/Pre-med Undergrad, St. Olaf College, Northfield,MN 55057 DDN: [CDS6] INTERNET: swansonc@acc.stolaf.edu UUCP: swansonc@stolaf AT&T: Work: (507)-645-6845 Home: (507)-663-6424 I would deny this reality, but that wouldn't pay the bills...
ch@dce.ie (Charles Bryant) (01/29/91)
In article <15126@celit.fps.com> billd@fps.com (Bill Davidson) writes: >In article <1991Jan27.160653.7104@nstar.rn.com> larry@nstar.rn.com (Larry Snyder) writes: >>Sorry - but incorrect with MNP5. MNP5 over a 2400 baud connection >>if properly installed will produce transfer rates of 280 cps even >>sending GIFs and ZIPs > >I find this *VERY* difficult to believe. GIF's are already LZW >compressed and so in general cannot be further compressed by *ANY* one >dimmensional digital compression method I am aware of without data >loss. If the MNP modems are really running a 2400 baud link, 280cps >seems impossible. The theoretical max for 2400 baud is something like >266cps (8 data + 1 stop) and anything higher would require compression >and as I said, I don't believe you can compress a GIF => 280cps >impossible. When MNP level 3 is used, the data is sent synchronously so no start or stop bits are required. The raw throughput is therefore 2400/8 = 300. Normally an MNP modem will allow the compression to be disabled which may result in an increase in throughput for data that cannot be compressed by MNP5. If another protocol is run on top of MNP (e.g. XMODEM) the throughput may be reduced by MNP2/3/4 because a small extra delay must be added (the whole packet must arrive before the CRC can be examined). -- Charles Bryant (ch@dce.ie) -- /usr/ch/.signature: Block device required
pj@pnet51.orb.mn.org (Paul Jacoby) (01/29/91)
Bill, I routinely got 285 cps file transfers using Ymodem-g between two PP2400/MNP5 modems. Both ends of the connection had port speeds locked at 9600 baud. I was on a Mac running ZTerm, the other end was a PC with TBBS. Didn't matter what kind of file; 285 cps was the fastest we could go. This was with compression on or off. .-----------------------------------------------------------------------------. | UUCP: {crash tcnet}!orbit!pnet51!pj | RTFD = Read The Silly Doc! | | INET: pj@pnet51.orb.mn.org | | `-----------------------------------------------------------------------------'
woan@nowhere (Ronald S Woan) (01/30/91)
In article <1991Jan27.160653.7104@nstar.rn.com> larry@nstar.rn.com (Larry Snyder) writes: >Sorry - but incorrect with MNP5. MNP5 over a 2400 baud connection >if properly installed will produce transfer rates of 280 cps even >sending GIFs and ZIPs According to the periodic FAQ, MNP 5 slows things down compared to just running MNP 4 for precompressed files... V.42bis automatically detects precompression and lets it go through without the compression overhead. -- +-----All Views Expressed Are My Own And Are Not Necessarily Shared By------+ +------------------------------My Employer----------------------------------+ + Ronald S. Woan woan@peyote.cactus.org or woan%austin@iinus1.ibm.com + + other email addresses Prodigy: XTCR74A Compuserve: 73530,2537 +
swansonc@acc.stolaf.edu (Chris Swanson, St. Olaf College) (01/31/91)
Whomever set up one of the MNP5 modems up that you had problems with really screwed up. MNP5 defines a method for negotiating between two MNP5 modems what kind of connection is to be used. If one of the modems had compression strictly disabled, then the other modem should have stepped down to the disabled modems capability level. If that did not happen, then the second modem had compression forced on (most MNP5 modems have 3 settings, 1-No compression ever, 2-compression if the other modem can handle it, and 3-compression no matter what). It seems as that whomever set-up the modem that was using compression set it up in "mode 3", a very stupid move; either that or the hardware was broken or the firmware did not impliment the MNP5 protocol correctly. Either way that is not cause to blame the protocol it self. -Chris -- Chris Swanson, Chem/CS/Pre-med Undergrad, St. Olaf College, Northfield,MN 55057 DDN: [CDS6] INTERNET: swansonc@acc.stolaf.edu UUCP: swansonc@stolaf AT&T: Work: (507)-645-6845 Home: (507)-663-6424 I would deny this reality, but that wouldn't pay the bills...
tnixon@hayes.uucp (02/03/91)
In article <3455@d75.UUCP>, woan@nowhere (Ronald S Woan) writes: >>Sorry - but incorrect with MNP5. MNP5 over a 2400 baud connection >>if properly installed will produce transfer rates of 280 cps even >>sending GIFs and ZIPs > > According to the periodic FAQ, MNP 5 slows things down compared to > just running MNP 4 for precompressed files... V.42bis automatically > detects precompression and lets it go through without the compression > overhead. MNP4 is capable of throughput of about 292cps (2400/8 bits per character = 300cps, then you subtract for protocol overhead [7 bytes of overhead for every 256 bytes of user data]). MNP5's _average_ token length is 9 bits, which means that on _completely_ random data, MNP5 sends an average of 9 bits per character instead of 8 -- but this is still less than the 10 bits per character of "pure" async. MNP5 would therefore, worst case, send only 260cps on random files. It is rare to find a precompressed file that is "totally" random, so slightly better throughput might be possible, but I doubt you'd see 280 -- but maybe so. -- Toby Nixon, Principal Engineer | Voice +1-404-449-8791 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net
pj@pnet51.orb.mn.org (Paul Jacoby) (02/06/91)
TB> MNP5 would therefore, worst case, send only 260cps on random files. TB> It is rare to find a precompressed file that is "totally" random, TB> so slightly better throughput might be possible, but I doubt you'd TB> see 280 -- but maybe so. Actually, when talking between two 2400 baud Practical Peripherals modems running MNP5 with Macintosh 'StuffIt' compressed files, Ymodem-g regularly gave me 285 cps. Hardware handshaking in effect, TBBS system on a PC on the far end. I like that alot. Of course the PP9600 is a heck of a lot MORE fun...if I could just get it to talk LAPM reliably with a Telebit T2500...:-( .-----------------------------------------------------------------------------. | UUCP: {crash tcnet}!orbit!pnet51!pj | RTFD = Read The Silly Doc! | | INET: pj@pnet51.orb.mn.org | | `-----------------------------------------------------------------------------'