jv@mhres.mh.nl (Johan Vromans) (08/10/89)
Last week I wrote the following question to the net: > > I've been working with a VAXstation3100 for a few weeks. It was > connected to our Ethernet using a dropcable to one of the DELNIs. > Recently I switched to a local thin-wire Ethernet, which is connected > to our main network via a DESPR. > > When I'm connected to a system on the network, e.g. via DECterm, the > connection frequently stucks for about three seconds, and then > continues. Sometimes it is even worse: about six seconds. This did not > happen when I was connected directly to the DELNI. > > Does this problem sound familiar to anyone? Any hints? Thanks everyone who responded with useful suggestions. A quick summary of responses: * Your thin-net wire is probably cut to the wrong length, or perhaps the tap off of the thick ethernet is broken. Or possibly your hardware is broken. You can figure out what's going on by renting a LANalyzer and watching to see what's happening to the packets. * Ethernet is a radio transmission system, and is very sensitive to misconfiguration of cabling and to kinks in the cables. It's also sensitive to stacked analog repeaters, which often strip bits off the beginning of packets, eventually resulting in an unreadable packet. All of these things explain why network experts are expensive, sigh. * Do you have a terminator on the thin-wire cable? The behavior you describe sounds like DESPR is periodically shutting down the thinwire segment due to collisions or jams. * Note that the DESPR should be connected directly to the main ethernet thru an H4005 or equivalent transceiver with a heartbeat disable option. Well, in my case, it appeared that the H4005 COMPATIBLE transceiver which was used did not meet the full specs of the H4005. With a drop-cable length up to about 30 meters everything was ok. With a drop-cable of 40 meters -the one we use- the DESPR started shutting of the line. The H4005 did not have problems with this length. [Don't flame me, this is what I understood after the technician explained me what happened.] Thanks again, everyone. Johan -- Johan Vromans jv@mh.nl via internet backbones Multihouse Automatisering bv uucp: ..!{mcvax,hp4nl}!mh.nl!jv Doesburgweg 7, 2803 PL Gouda, The Netherlands phone/fax: +31 1820 62944/62500 ------------------------ "Arms are made for hugging" -------------------------