Path: utzoo!utgpu!watserv1!watmath!att!bu.edu!rpi!julius.cs.uiuc.edu!wuarchive!uunet!van-bc!robinson Newsgroups: comp.protocols.tcp-ip Subject: Re: LAT Message-ID: <1991Jan14.015852.26228@mdivax1.uucp> Date: 14 Jan 91 01:58:52 GMT References: <12578@hubcap.clemson.edu> Reply-To: mdivax1!robinson (Jim Robinson) Organization: Mobile Data International, Richmond, B.C., Canada Lines: 36 Return-Path: Apparently-To: van-bc!rnews In article <12578@hubcap.clemson.edu> hubcap@hubcap.clemson.edu (System Janitor) writes: >Would anyone in this forum care to comment on these claims? > >*********** LAT/ TELNET comparison *********** > > >- LAT causes less of a burden on the CPU and the network > "In preliminary test using KI Research's KiNet, DR Labs found > the DEC's LAT protocol imposed lower overhead on both the host > CPU and the network than TELNET. For example, with 45 active > TELNET session on a Mips M/120-5 system, the CPU had zero > percent idle time, meaning that it was overload, and only 4.4 > percent of the network bandwidth was utilized. With 64 active > LAT sessions to the same machine, the CPU was still 50 percent > idle, and only 2 percent of the network bandwidth was > utilized. This difference is due in large part to the fact > that LAT does not use the full DECnet stack, whereas TELNET > uses the full TCP/IP stack." (Lee Schlesinger, Digitial > Review, August 27, 1990) A good question to ask is whether LAT performs checksumming. Given that LAT is a LAN protocol, it seems that it is quite possible that it (perhaps optionally) does no checksumming and instead relies on the LAN to detect and discard corrupted packets (as does ethernet). If this is the case then it would have a natural, and arguably unfair, advantage over TCP due to the rather CPU intensive nature of checksumming. I believe that checksumming is *not* a TCP option (although in practice it is usually possible to turn it off in BSD derived implementations), but even if it is the above comparison is less meaningful without knowing whether both protocols were running with checksumming on or off. -- Jim Robinson {uunet,ubc-cs}!van-bc!mdivax1!robinson robinson@mdivax1.uucp