Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!snorkelwacker!think!bbn!news From: news@bbn.COM (News system owner ID) Newsgroups: comp.dcom.modems Subject: Re: should i expect MNP4 to be faster than non-MNP? Message-ID: <50944@bbn.COM> Date: 15 Jan 90 23:29:42 GMT References: Reply-To: pplacewa@antares.bbn.com (Paul W Placeway) Distribution: comp Organization: Bolt Beranek and Newman Inc., Cambridge MA Lines: 41 chet@arc.UUCP (Chet Wood) writes: < The new modem he sent has the same problem-- here are the effective < baud rate numbers I get when connected to the everex running the < latest version of Mac Kermit, 900 byte packets, a 10KB compressed file < in binary mode: This is a good setup in general for MacKermit. Get a copy of 0.98 from watsun.cc.columbia.edu if you havn't yet (in the kermit/test directory, but it's more stable than 0.9 and _much_ more stable than 0.97). < non-MNP 1653 < reliable 1550 As I recall, MNP-4 is sync over the phone-wire, with longer MNP packets and a slightly smarter when-to-transmit heuristic. All other things being equal, this _should_ give you faster data transmision... However, trying to layer a non-windowing packet based protocol on top of this is probably causing havoc with MNP -- the underlying packet protocol (MNP) may be delaying the transmition of the final parts of the upper protocol (Kermit) packets. In other words, you are seeing latency between packets. The best thing to avoid this for the moment is to use big packets, which you are allready doing... Latency wouldn't be much of a problem if you were running something real (TCP on IP on PPP) or quazi-real (TCP on IP on SLIP or Zmodem), but you need not to be running through anything wierd to make the quazi-real things work right. It's a trade-off: Kermit works right almost all the time without twiddling it, and is very resistant to bad conditions. Zmodem works faster, but only on computer -> modem -> modem -> computer connections, and you may have to dink with flow control to make it work right. Your choice... Making Kermit better behaved for this (read: adding the sliding windows protocol extention) is currently at the top of my To Do list, but that won't happen real soon (looks like about 3 months until the first beta-test versions, but no promises). -- Paul Placeway MacKermit Coordinator/Programmer