Brian_S._Cashman@UM.CC.UMICH.EDU (10/19/87)
I'd like to thank all of you that have responded for the information.
I should have mentioned previously that we do have a Netwatch program
running. Our problem is that periodically our Ethernet jams so that
Netwatch-type programs won't run. We haven't been able to figure out
yet exactly what the problem is. Our Ethernet consists of several
segments connected by inline barrel connectors with a total length of
less than 500m. We've found that we can fix the problem by
disconnecting the "backbone" at one of these connectors and
reconnecting it. If a more hardware oriented Ethernet analyzer can
diagnose this sort of problem that's the sort of thing I'd like to
get. I asked about DELNIs because we have several and I wondered what
effect they have when mixed with real transceivers on an Ethernet.
DELNIs aren't mentioned in the 802.3 standard and I haven't been able
to find any definitive DEC documentation.
Brian S. Cashmanmead@tut.cc.rochester.EDU (10/20/87)
Brian, In addition to the TDR's and the Network Monitors, there is a third device that is useful for troubleshooting networks, they are called Ethernet component testers. These devices allow for a functional verification of transceivers (single, multiport, fiber), transceiver cables, single/multiport transceivers, bridges and routers (the last three require two devices. There are two companies that make this product, Cabletron and TITN. We have the TITN. As mentioned above, to test out repeaters, bridges, and routers, two component testers are required. If you have or plan to buy the LAN- alyzer, the next software release will provide the ability to transmit a packet based on the reception of a packet. This will allow you to setup the component tester and LANalyzer in a master/slave configuration, thereby allowing you to check out the repeaters, bridges, and routers. This is also very useful in measuring propagation delay over you network as it expands. Do you have a TDR? Ron Natalie mentioned that he has a Cabletron TDR and I would recommend that also. The Cabletron product has two options that allow you to TDR an operational network without damaging transceivers or causing havoc on the network. These capabilities are provided by DC coupling on the output of the TDR and a negative pulse feature, which sends out an inverted pulse on the network rather than positive. The positive pulse can damage some of the old version 1 transceivers without overvoltage protection. The Cabletron product also provides a collision forcing mechanism. This allows for an unobstructed CRT image of the network under test. This will also show which transceiver collision detectors are not properly recognizing colisions. This is indicated on the CRT by movememnt in the TDR signature. If you need any other information, please drop me a note. Thanks, Ted (mead@tut.cc.rochester.edu)