Newsgroups: comp.dcom.sys.cisco Path: utzoo!utgpu!cunews!bnrgate!bcars223!fortinp From: fortinp@bcars223.bnr.ca (Pierre Fortin) Subject: Re: help needed debugging DDS 56kb prob Message-ID: <1990Sep11.065249.26325@bnrgate.bnr.ca> Summary: V35 problems? BOY!! Did we have V35 problems... Sender: news@bnrgate.bnr.ca (USENET News System) Organization: Bell-Northern Research, Ltd. Ottawa Ontario CANADA References: <25924@boulder.Colorado.EDU> <3970@ursa-major.SPDCC.COM> Date: Tue, 11 Sep 90 06:52:49 GMT In article <3970@ursa-major.SPDCC.COM>, dyer@spdcc.COM (Steve Dyer) writes: > > In any event, the "fix" appears to have been a coincidence. Having moved the > equipment to its permanent resting place, the carrier transitions and > interface resets (after a stable, peaceful weekend) have returned with a > vengeance, even with the parameter set to 56kb. I think I'm in the > nether world of flaky cables/modems, and will pursue it on that level. Here's a short list of the V.35 problems I've encountered over the last 17 months: - V.35 applique Rev 3: inverted clocks; mods applied to some boards - V.35 applique Rev 4: inverted clocks; mods for Rev 3 boards applied inadvertently to these boards (I have personally seen at least three different attempts at clearing up this problem) We even had one unit in which the RxD line was leaking back out over one of the clock leads, giving the appearance of a bad DCE. - DL551V T1 CSU/DSU: most units bad (power supply drifting, incorrect factory options, bad repairs, poor QC, etc.) All units were to be returned to Digital Link for checkout; don't know current status of this. - Screws (Yes, SCREWS!): WHY is it that something as simple as a screw (actually screw threads) can cause problems; I guess we need patience testers... V.35 connectors are available with EITHER single- or double-helix retaining screws! Go figure... - V.35 cables: Nearly all cables we tested were of poor quality. We designed our own cable (verified to 70 feet) where each pair is individually shielded (with the source end only grounded); then an overall shield grounded at both ends via a six-inch pig-tail to a spade-lug. Major improvements!!! - MCI HDLC controller: The Rockwell HDLC controller chips with a date-code prior to a certain date (contact cisco for date) had bugs when the applied voltage was less than EXACTLY 5.00V. In some literature I received from cisco, there was a small piece of pink paper which said that this should only affect short X.25 packets with odd packet lengths; but, where there's smoke... - V.35 applique Rev 6: This applique is correct. We are continuing to replace all pre-Rev-6 appliques with these newer ones. - Operations: Our operations personnel used to make statements like: "The CSU/DSUs never work in loopback"; this has since been corrected. Any comm gear which does not work in loopback when the manufacturer claims it does should be highly suspect. In another instance, two links from different remotes (should have been [A]---[B0&B1]---[C]) were connected incorrectly ([A]---[B1&B0]--[C]). With our fully redundant mesh topology, the ciscos never complained, but you should have seen the highly inefficient routing, BUT IT WORKED from the users' perspective (a tip of the hat to cisco!!). - "Nah!" ;^) Someone I talked to in another company which shall forever remain nameless managed to find a cable and screw it in. Upon closer inspection, the cable was found to have a female connector. If you fail to spot the humor in this, check the sex of the V.35 appliques on your cisco... These are the major points I can think of off the top of my head at this time (it's 02:45). The general thrust of my message here is that, for what should be a mature interface, expect problems ANYWHERE. Likely you will find MORE than one problem. Perhaps this has to do with the fact (someone please prove me wrong) that there is no V.35 standard beyond the original which only covers the approx. 40KB speed. Other things to note about V.35: - the DCE supplies both clocks SCR and SCT - the DTE *returns* the Tx clock (SCTE) to the DCE to account for varying cable lengths at higher speeds - double-check cable polarities on ALL pairs Otherwise, V.35 was a piece of cake.... in the face! ...and now we're getting ready (hah!!) for the onslaught of T3 equipment... Huh? Why am I standing on this chair with a V.35 cable around my neck? > > -- > Steve Dyer > dyer@ursa-major.spdcc.com aka {ima,harvard,rayssd,linus,m2c}!spdcc!dyer > dyer@arktouros.mit.edu, dyer@hstbme.mit.edu Pierre Fortin fortinp@bnr.ca P.S.: If enough people send in their $35 (easy to remember ;^) ), we will seriously consider publishing "Living with V.35" complete with over 400 pages of tests, results, multi-channel scope traces, levels, power supply voltages, pictures of modifications, plus much more... :^) :^) P^) ;^)