gandrews@netcom.COM (Greg Andrews) (05/06/91)
In article <NF6g22w164w@graphics.rent.com> bobl@graphics.rent.com (Bob Lindabury - SysAdm) writes: > >The standard in the entire industry and the world for 9600 bps modems >is V.32. V.32bis will probably supercede V.32 in the next year. >V.32 gives you a 9600 baud carrier with compression giving you up to >4 times that speed in theory. V.32bis will give you a 14,400 baud >carrier with the same 4 times increase (theoretically) with >compression. > > InterNet: bobl@graphics.rent.com | Raven Enterprises Hi Bob, V.32 doesn't have compression. That's handled by an entirely different set of standards. V.32 (and V.32bis) are simply the modulations that allow the modems to fling bits back and forth through the telephone line. V.32 runs at 9600 bps, and V.32bis at 14400 bps. There are 'fallback' speeds if the line is impaired, but they are all slower than the bit rate which the standards are known for. Whether you can get 4:1 compression depends on what compression method the modems achieve, and what kind of data is sent through them. If the modems only get MNP5 compression, they will not be able to compress much higher than 2:1. 4:1 compression is possible with the V.42bis method. Mentioning compression in the same breath as a modulation probably isn't that good an idea. Compression is achieved through extensions to error correction protocols, and is not directly related to the modulation. Linking compression and a modulation without mentioning the error correction step in between them can lead to confusion. -- .------------------------------------------------------------------------. | Greg Andrews | UUCP: {apple,amdahl,claris}!netcom!gandrews | | | Internet: gandrews@netcom.COM | `------------------------------------------------------------------------'
bobl@graphics.rent.com (Bob Lindabury - SysAdm) (05/07/91)
gandrews@netcom.COM (Greg Andrews) writes: > In article <NF6g22w164w@graphics.rent.com> bobl@graphics.rent.com (Bob Lindab > > > >The standard in the entire industry and the world for 9600 bps modems > >is V.32. V.32bis will probably supercede V.32 in the next year. > >V.32 gives you a 9600 baud carrier with compression giving you up to > >4 times that speed in theory. V.32bis will give you a 14,400 baud > >carrier with the same 4 times increase (theoretically) with > >compression. > > > > InterNet: bobl@graphics.rent.com | Raven Enterprises > > Hi Bob, > > V.32 doesn't have compression. That's handled by an entirely different > set of standards. V.32 (and V.32bis) are simply the modulations that > allow the modems to fling bits back and forth through the telephone line. > V.32 runs at 9600 bps, and V.32bis at 14400 bps. There are 'fallback' > speeds if the line is impaired, but they are all slower than the bit rate > which the standards are known for. Sorry, I guess I wasn't clear. I meant with *additional* compression routines you would get those rates. I know that V.32 and V.32bis are modulation schemes and that V.42bis is a compression scheme as is MNP5. Sorry for the murkyness of my posting. > Whether you can get 4:1 compression depends on what compression method > the modems achieve, and what kind of data is sent through them. If the > modems only get MNP5 compression, they will not be able to compress much > higher than 2:1. 4:1 compression is possible with the V.42bis method. > > Mentioning compression in the same breath as a modulation probably isn't > that good an idea. Compression is achieved through extensions to error > correction protocols, and is not directly related to the modulation. > Linking compression and a modulation without mentioning the error correction > step in between them can lead to confusion. Totally correct and I'm sorry if anyone got off on the wrong foot with my posting. So I guess you should mention that MNP4 and V.42 are the "standard" error correction schemes. So we have: Modulation (connection) Standards: V.32 - 9600 bps V.32bis - 14400 bps Error correction Standards: MNP4 V.42 Compression Standards: MNP5 - 2:1 V.42bis - 4:1 These look to me to be the current standards of the industry. Although there are other methods for the above, these are the most popular and most widly used (or predictably will be). -- Bob The Graphics BBS 908/469-0049 "It's better than a sharp stick in the eye!" ============================================================================ InterNet: bobl@graphics.rent.com | Raven Enterprises UUCP: ...rutgers!bobsbox!graphics!bobl | 25 Raven Avenue BitNet: bobl%graphics.rent.com@pucc | Piscataway, NJ 08854 Home #: 908/560-7353 | 908/271-8878