Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site oliveb.UUCP Path: utzoo!linus!decvax!ittvax!dcdwest!sdcsvax!sdcrdcf!hplabs!oliveb!jerry From: jerry@oliveb.UUCP (Jerry Aguirre) Newsgroups: net.news,net.dcom Subject: 2400 baud modems and uucp inefficiencies Message-ID: <184@oliveb.UUCP> Date: Mon, 1-Oct-84 19:47:32 EDT Article-I.D.: oliveb.184 Posted: Mon Oct 1 19:47:32 1984 Date-Received: Wed, 3-Oct-84 06:42:43 EDT Organization: Olivetti ATC, Cupertino, Ca Lines: 40 There have been some articles posted lately about the advantages of using 2400 baud modems for the distribution of news. Before someone spends money to upgrade their modems consider that the same effect could be had by improving the software involved. I will ignore for the moment the news software and the relative efficiencies of batching, compression, and "I have/send me" distribution. Instead I want to examine the efficiencies of uucp itself. Uucp uses a fairly efficient protocol. It places the line in RAW mode so that data can be sent without escapes. It buffers multiple packets so that turn-around delays are eliminated. If I examine the uucp log entries I see entries like 109 bytes per second of transmission. If a 1200 baud modem gives 120 bytes per second then the efficiency should be 109/120=90%. This sounds pretty good. But, it is still only using half the bandwidth available! Remember that this is a full duplex modem. It really allows 1200 baud in EACH direction so the real bandwidth is 1200 baud x 2 directions = 2400 baud! Bet you didn't know you already had 2400 baud modems. However uucp does not make use of the full duplex capability. It insists on sending files in one direction at a time. The only data coming back are the packet acknowledgements which consume about 12% of the available bandwidth. Just watch the send/receive lights on your modem. The send light comes on solid but the receive light flickers on and off (mostly off). Presumably two backbone sites would have roughly equal amounts of news to send to each other. If the sending and receiving could be overlapped then the time consumed could be cut by almost half. As uucp does protocol negotiation perhaps a new "full duplex" protocol could be added as a preferred option. The advantage is that the improvement could be made available to all sites instead of just those that can afford expensive modems. Jerry Aguirre {hplabs|fortune|idi|ihnp4|ios|tolerant|allegra|tymix}!oliveb!jerry