Aduke.1642 net.news utcsrgv!utzoo!decvax!duke!trt Tue Jan 19 18:40:20 1982 Re: utah-cs.164: Truncated Articles People here (mainly duke!swd and duke!trt) have been considering ways to reliably transmit articles across the net. The following handshaking method might be reasonable: 1) Determine when an article has been correctly received. This can be approximated by appending to the article its checksum. If an article is received intact and then inserted locally the receiver sends a confirmation to the sender. This confirmation would also be done if the article were a duplicate. 2) Determine when an article has not been correctly sent. The sender could run a daemon occasionally which rebroadcasts locally stored articles to those sites which should have gotten it but have not yet confirmed receipt. Comments: A. This method doubles the number of Usenet messages (a confirmation for every article transmission); however, the confirmations are short messages. It also requires that the sender maintain a ".confirmed" file (or a new field in .nindex) with entries like "ucbvax.12743:mcnc,phs" indicating that mcnc and phs have received ucbvax.12743. When an article is cancelled, its entry in ".confirmed" can be removed. B. It is necessary to avoid unbounded rebroadcast to systems that happen to be slow or off the net-waves. Suppose the sender maintained a file of the dates of recent complete conversations with the receiver since the last rebroadcast. Then rebroadcasting should occur if there was a complete conversation at least XQTTIME (say, two hours) before the current time, and another complete conversation at least XQTTIME before that one. On a news rebroadcast, the file must be truncated. In fact, it must be truncated on an original broadcast as well, so a broadcast should invoke the rebroadcast daemon. C. A similar scheme could be used by mail(I), for which reliable delivery is important. Tom Truscott (duke!trt) ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.