jmg@cernvax.UUCP (jmg) (02/14/85)
We have a real mixed bag of Ethernet hardware hung on one cable: DEC, 3-Com, Interlan transceivers, DEC and Sension repeaters (local and remote), Vaxes (VMS and 4.2BSD), workstations, PCs etc. etc. etc. We have experimented with Cheapernet cable: seems to work OK when connected via repeater, and even when connected end-on to normal Ethernet cable! Have also a mixture of version 1.0, version 2.0 and (what is called) 8802.3 standard. It all seems to work (apart from one minor glitch when the same value for a protocol ID field was used by two different systems). Note, however, that we try not to mix transceiver and controller. BUT: We make a lot of use of DELNIs as fan-out boxes. This, of course, means that often a non-DEC controller goes onto a DELNI as transceiver. I have the impression that this can cause problems: sometimes we have a phenomenon whereby packets can be sent but not received. Changing the DELNI, or using shorter transceiver cables, often cures the problems. Question, therefore. Does anyone have any recipe for what one can or cannot do when putting equipment onto DELNIs? Also, the DELNI manual says that one can hang DELNIs off a DELNI or off a real cable, but a DELNI off a DELNI off a real cable is supposed not to be allowed (even though we have tried it and it seems to work). Of course, the DEC DELNI manual is sometimes rather vague in its specifications. Over to you, World. While you ponder it I shall go off for a week of skiing. Mike (Back off, man, I'm an Ethernetbuster) Gerard.
david@daisy.UUCP (David Schachter) (02/21/85)
We have a very large Ethernet installation: over 300 nodes in two buildings. Most of the nodes are multiplexed through DELNIs. However we have about sixty nodes going through a three-level DELNI tree. We have had few problems. The only time our network is funny is when we grossly violate specs. So we don't do that. (Like when we had 150 nodes on a 700 meter cable, violating both the max nodes limit, the max cable length limit, and, in most cases, the minimum transceiver spacing limit. Even then, the network worked but at a reduced rate.) By the way, our installation also includes a fiber-optic link connecting two buildings and it includes several Xerox repeaters. We have had very good results with Interlan equipment: the stuff is usually flawless and the few problems we have had have been fixed quickly. We find Interlan to be a responsive vendor. If you get good results mixing Ether cable and Cheaper cable, fine. But we won't do that: surely it must be pretty violent on impedance mismatching! Of course, if you do not have a long cable and if the number of nodes is low, you can get away with almost anything, it seems.