Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!cornell!batcomputer!itsgw!steinmetz!davidsen From: davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr) Newsgroups: comp.dcom.modems Subject: Re: MNP make for a faster modem? Keywords: MNP Message-ID: <9308@steinmetz.steinmetz.UUCP> Date: 25 Jan 88 17:22:01 GMT References: <3027@killer.UUCP> <6678@agate.BERKELEY.EDU> Reply-To: davidsen@crdos1.UUCP (bill davidsen) Organization: General Electric CRD, Schenectady, NY Lines: 53 In article <6678@agate.BERKELEY.EDU> chapman@eris.UUCP (Brent Chapman) writes: | In article <3027@killer.UUCP> tony@killer.UUCP (Tony Holden) writes: | | >I've seen ads claiming that with the various MNP levels that the throughput | >on a 2400 baud modem is that of 9600 baud. | > | >Is it hype or is it real? | | It's hype. MNP is an error detection and correction protocol. A modem running | at 2400 baud with MNP will probably actually have slightly (_very_ slightly) | lower throughput than without MNP, because of the extra bits needed for the | protocol. I happen to think it's worth it, though, because of the error | correction. This statement is, at best, partially correct. MNP levels 4 and 5 include data compression, and on text data the effective thruput will be just about doubled. MNP 1-3 levels are error correcting only. You will get 4000-4400 baud effective at 2400, up in the 17k range with 9600 baud. Obviously you won't get this if you restrict the flow of data to 2400 baud. The secret is to let the modem do speed conversion. {you}---9600baud---{your modem}======== || || || || 2400 baud dialup (MNP class 4 or more) || || || || {them}---9600 baud---{their modem}===== The thing which makes this work is the 9600 baud between you and your modem. The modem will do flow control to adjust the speed of the data you send, and uses the higher speed to deliver the data as fast as it's decompressed. If you fail to understand that the modem must have a higher speed path to deliver the compressed data to yourterminal or system, you will not see an improvement. I knew someone who connected his new 2400 baud modems using 1200 baud and felt that he didn't see much difference. Others using the same hardware felt that it was "much faster." This works on MultiTech 224E (with new ROM) and several other modems which support MNP class 5. Your milage may vary. Already compressed data will not run much faster. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs | seismo}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me