Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!uunet!hayes!tnixon From: tnixon@hayes.uucp Newsgroups: comp.dcom.modems Subject: Re: Why HST's and UUCP don't mix (was Re: uucico and HST) Message-ID: <3962.284251f5@hayes.uucp> Date: 28 May 91 12:49:57 GMT References: <93HX21w164w@ijpc.UUCP> <1991May22.145955.20039@bluemoon.uucp> <1991May25.022520.4101@spock.UUCP> Followup-To: comp.dcom.modems Organization: Hayes Microcomputer Products, Norcross, GA Lines: 47 In article <1991May25.022520.4101@spock.UUCP>, lancelot@UUCP (Thor Lancelot Simon) writes: > In article <1991May22.145955.20039@bluemoon.uucp> grant@bluemoon.uucp (Grant DeLorean) writes: >>bobl@graphics.rent.com (Bob Lindabury - SysAdm) writes: >> >> [various contentions about MNP classes above 5] > > This is *absolutely* false. I type this while logged in using a pair of MNP 6 > modems. In fact, MNP 6 is a modulation scheme, not an error-control protocol. > I am fairly sure it's one of the many variants on v.29ft (or is that 27ft?) a > 9600 bps main channel with a 300 bps backchannel. File transfer performance > is about like the old HST protocol, which figures. I am pretty sure MNP 8 > exists. I've also heard of MNP 10 being used in Microcom's specialized > cellmodems, but I don't have any confirmation for this. Followup to > comp.dcom.modems. Mr. Simon is basically right. Microcom has defined up through Class 10. Here is a brief summary of the MNP Classes above 5: MNP6: V.29-based fast-turnaround ping-pong modulation scheme. MNP7: Adaptive Huffman compression scheme based on character pairs rather than single characters for which throughput is claimed up to 3-to-1. MNP8: Announced, but never shipped. MNP9: Several minor protocol enhancements, including piggybacked acknowledgements and multiple selective reject. MNP10: "Adverse Link" enhancements, including repacketizing of data into smaller frames during retransmission, higher number of retries before giving up, automatic retraining including changes in modulation scheme, and automatic adjustable carrier level. I'm only aware of one other company that ever made an MNP6 modem (Multitech), and don't know of ANY others that have done MNP7 or MNP9. Microcom has licensed MNP10 for cellular telephone modems to Rockwell to make chipsets and to a couple of other companies, and intends to license it widely. The CCITT is studying data transmission on cellular networks, and may adopt similar techniques for enhancement of LAPM (but won't adopt MNP10 because the V.42 "alternative protocol" is officially "frozen"). -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 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