peter@sugar.uu.net (Peter da Silva) (01/28/89)
I'm considering one of the following 2400 baud external modems: Zuckerboard/ATD EXT-24. Anchor Automation Patriot. Supra Modem 2400. GVC/HISLAND. Packard Bell PB2400 Plus. Smart One 2400 External. Tailyn 2400. TidBit24. I'm particularly looking for 10-number phone directory and auto-redial. The modem will spend most of its time on a dial-out terminal. -- Peter "Have you hugged your wolf today" da Silva `-_-' Hackercorp. ...texbell!sugar!peter, or peter@sugar.uu.net 'U`
Vince.Cleniuk@f70.n140.z1.FIDONET.ORG (Vince Cleniuk) (09/12/90)
Pardon, but what exactly is an MNP modem... are there advantages from using them over the 'regular' type of modem? Vince -- Vince Cleniuk - via FidoNet node 1:140/22 UUCP: ...!alberta!herald!weyr!70!Vince.Cleniuk Domain: Vince.Cleniuk@f70.n140.z1.FIDONET.ORG Standard Disclaimers Apply...
UH2@psuvm.psu.edu (Lee Sailer) (09/13/90)
In article <826.26EF2259@weyr.FIDONET.ORG>, Vince.Cleniuk@f70.n140.z1.FIDONET.ORG (Vince Cleniuk) says: > >Pardon, but what exactly is an MNP modem... are there advantages from >using them over the 'regular' type of modem? > >Vince > When your computer gives the modem a packet of bytes to send, there are two choices, 1) send the bytes as is, or 2) compress the bytes and add error checking and error correcting bits. In case 1, if some problem occurs on route it is up to the sending and receiving computers to realize that an error has occurred, and arrange to retransmit the packet of bytes. In case 2, the modems themselves can recognize that an error occurred and often times repair it without bothering the computers at all. Of course, there are many many compression and error correction methods. MNP is one of them. The main practical advantage of MNP is that, because of the compression, transmission rates can be higher. If you can pack 100 bytes of text into 50 bytes of binary gibberish, and then unpack them at the other end, then your 1200 bps modem will seem to run at 2400 bps. It occurs to me. Does this mean that little will be gained for the transmission of ZOO and LZ files, since they are already compressed? (assuming error free lines, of course)
huebner@aerospace.aero.org (Robert E. Huebner) (09/14/90)
In article <90256.111652UH2@psuvm.psu.edu> UH2@psuvm.psu.edu (Lee Sailer) writes: > >It occurs to me. Does this mean that little will be gained for the >transmission of ZOO and LZ files, since they are already compressed? >(assuming error free lines, of course) Yes. The throughput of a compressed data stream is hardly constant. Many download protocols give you an indication of the current BPS for this very reason. Using something like an HST-DS (Dual Standard) V.32 you get more compression transmitting a text file than something that's been .lzh'ed. There is a significant speed increase on both, however. I wouldn't say "little is gained." I think the speed achievable is still on the order of 2:1 for even the most densely packed files using HST-DS. Robert Huebner huebner@aerospace.aero.org
c150-ec@danube.Berkeley.EDU (Johnson Sieu) (09/14/90)
Just one question -- Do you need special modems on both sides of the line for the data to be packed and unpacked properly? Johnson email address: sieu@sim.berkeley.edu
huebner@aerospace.aero.org (Robert E. Huebner) (09/14/90)
In article <27777@pasteur.Berkeley.EDU> c150-ec@danube.Berkeley.EDU.UUCP (Johnson Sieu) writes: > > Just one question -- Do you need special modems on both sides of the line > for the data to be packed and unpacked properly? > Yes. If an MNP modem or V.32 modem connects to a no-compression modem, it simply drops gears into normal mode, much like a 2400 baud modem can downshift into 1200 in need be. Most modems I've worked with are quite good at finding the best compression mode to work with. They will usually agree on the most efficient method they both possess. huebner@aerospace.aero.org
thad@cup.portal.com (Thad P Floryan) (09/14/90)
c150-ec@danube.Berkeley.EDU (Johnson Sieu) in <27777@pasteur.Berkeley.EDU> asks: Just one question -- Do you need special modems on both sides of the line for the data to be packed and unpacked properly? Yes, you would need, for example, MNP modems at both ends of the line to realize the error correction and compression. Note, too, there are "classes" of MNP; I'm presently 'playing' with a set of Microcom QX/V.32c modems with MNP class 9 (whew!) since I test several hundred modems each year for correct operation with my own products. As a quick ref from the Microcom manual (the "inventors" of MNP): MNP Description 2 asynchronous framing for data transmission and error correction. Because of the protocol overhead, actual throughput is less than the bps rate of the modem 3 synchronous framing, giving 20% thoughput increase over class 2, with thoughput higher than the bps rate of the modem. For example, a 2400 baud modem operating at Class 3 transmits data at 2600 bps. 4 synchronous framing with adaptive packet assembly and "Optimized Data Phase" developed by Microcom. A 2400 baud modem operating at Class 4 transmits data at 2900 bps. 5 includes data compression which, with class 4, provides throughput of almost twice the connection speed. 6 half-duplex, fast train reliable connections at 4800 to 9600 bps, giving from 11000 to 19200 bps. 7 "Enhanced Data Compression" which, with Class 4 service, provides more than twice the connection speed 8 (not described) 9 the features of Class 7 plus V.32 operation. Believe me, the MNP stuff DOES work, and it's mind-boggling how a dial-up line can give performance surpassing direct hard-wired connections to a local computer (at least at my company! :-) I call Chile, England, Holland and elsewhere, and the connections are literally perfect (from California). Plus, my phone bill has dropped from $200+/month to around $40/month; these modems pay for themselves very quickly. Thad Floryan [ thad@cup.portal.com (OR) ..!sun!portal!cup.portal.com!thad ]
nfs1675@dsacg3.dsac.dla.mil ( Michael S Figg) (09/14/90)
In article <90256.111652UH2@psuvm.psu.edu>, UH2@psuvm.psu.edu (Lee Sailer) writes: > > It occurs to me. Does this mean that little will be gained for the > transmission of ZOO and LZ files, since they are already compressed? > (assuming error free lines, of course) I don't know from personal experience but it seems like it has been said more than a couple times that this is true. I think there is actually a slight loss of speed because the modem takes the time to try to compress something that is already compressed. When I can afford to replace the 2 dead modems I have maybe I can test this! ---Mike, -- A man said to the Universe "Sir, I exist!" | Michael Figg DSAC-FSD "However," replied the Universe, | DLA Systems Automation Center "The fact has not created in me a | Columbus, Ohio sense of obligation."- Stephen Crane | mfigg@dsac.dla.mil CIS: 73777,360
h112706@assari.tut.fi (Herranen Henrik) (09/17/90)
In article <90256.111652UH2@psuvm.psu.edu> UH2@psuvm.psu.edu (Lee Sailer) writes: >The main practical advantage of MNP is that, because of the compression, >transmission rates can be higher. If you can pack 100 bytes of text >into 50 bytes of binary gibberish, and then unpack them at the other >end, then your 1200 bps modem will seem to run at 2400 bps. > >It occurs to me. Does this mean that little will be gained for the >transmission of ZOO and LZ files, since they are already compressed? >(assuming error free lines, of course) Yes. The MNP packing method is quite simple, much simplier then the one used with ZOO and LZH-files, so I don't there will be any gain (except error free transmission) while moving packed files. -- Name: Henrik 'Leopold' Herranen h112706@lehtori.tut.fi Address: TTKK/P{{rakennuksen neuvonta/PL527/33101 Tampere/Suomi Finlandia "On d{htinen daevas ja kuutamoy|, on morsiamelta katkaistu p{{" E.L.1989
h112706@assari.tut.fi (Herranen Henrik) (09/17/90)
In article <27777@pasteur.Berkeley.EDU> c150-ec@danube.Berkeley.EDU.UUCP (Johnson Sieu) writes: > Just one question -- Do you need special modems on both sides of the line > for the data to be packed and unpacked properly? Yes. If you have an MNP modem only at the other end, you'll gain nothing. -- Name: Henrik 'Leopold' Herranen h112706@lehtori.tut.fi Address: TTKK/P{{rakennuksen neuvonta/PL527/33101 Tampere/Suomi Finlandia "On d{htinen daevas ja kuutamoy|, on morsiamelta katkaistu p{{" E.L.1989
Bruce.Wesson@p3.f22.n140.z1.FIDONET.ORG (Bruce Wesson) (09/20/90)
You will find that MNP modems do not compress compressed files properly in fact it slows down transmission speed by a large margin. The compression mode is actually for text type files. When using an HST type modem and you send .WRP, .LZH, etc type files you turn off the commpression mode to transfer data, this way you will realize the maximum transfer rates these modems were ment to funtion at. -- Bruce Wesson - via FidoNet node 1:140/22 UUCP: ...!alberta!herald!weyr!22.3!Bruce.Wesson Domain: Bruce.Wesson@p3.f22.n140.z1.FIDONET.ORG Standard Disclaimers Apply...