Sun-Spots-Request@RICE.EDU (William LeFebvre) (06/24/88)
SUN-SPOTS DIGEST Thursday, 23 June 1988 Volume 6 : Issue 121 Today's Topics: Looking for feedback on 15-pin Ethernet connectors (9) DELNI's on Suns Re: Pointers to performance studies on TCP/IP Send contributions to: sun-spots@rice.edu Send subscription add/delete requests to: sun-spots-request@rice.edu Bitnet readers can subscribe directly with the CMS command: TELL LISTSERV AT RICE SUBSCRIBE SUNSPOTS My Full Name Recent backissues are available via anonymous FTP from "titan.rice.edu". For volume X, issue Y, "get sun-spots/vXnY". They are also accessible through the archive server: mail the request "send sun-spots vXnY" to "archive-server@rice.edu" or mail the word "help" to the same address for more information. ---------------------------------------------------------------------- Date: Mon, 13 Jun 88 11:57:24 PDT From: dmc@tv.tv.tek.com Subject: Looking for feedback on 15-pin Ethernet connectors (1) [[ This note was also posted to the tcp-ip list, and it produced a flood of responses. I am including that discussion in this issue. --wnl ]] I am looking for feedback on the quality and reliability of the slide latch mechanism used on the DB-15 ethernet connectors. I have used these myself for the past five years, and have discovered a number of problems with them. Additionally, various nasty remarks about these connectors have surfaced on the net from time to time. The Society of Motion Picture and Television Engineers has a standard known as RP-125 which specifies a parallel digital television interface. The connector for that interface is a 25 pin D-type (DB-25) with a slide latch like the ethernet connector. The RP-125 standard is up for revision, and the Tektronix representative submitted a note from me outlining my experience and problems with the ethernet slide latch connector. Sun Microsystems also has a representative on the RP-125 committee. He has asked the component engineer for connectors at Sun if there was any data concerning the mechanical integrity of the slide latch locking mechanism used in the ethernet connector. Here is the response: "I am the Component Engineer for connectors at Sun. In regards to your question concerning the Ethernet DB-15, these are used through out industry by the millions, in many applications. I am not aware of any significant problems with mechanical integrity of the lock, or for that matter with the connector in any aspect. If the connector is properly installed and handled in a semi-reasonable manner you should not have any problems. As far as Sun is concerned, usage of D-Sub connectors in general, that is various sizes and configurations, will probably increase. When all things are considered it often turns out to be the best way to go! Hope this helps!!!" In the face of this informal statement by Sun's component engineer, I now need data about other people's experience with the DB-15 slide latch ethernet connector. Help save another standard from the same fate! Please send your comments email to: dmc@tv.tv.tek.com or tektronix!videovax!dmc Thank you, Don Craig Tektronix Television Systems ------------------------------ Date: 14 Jun 88 15:28:03 GMT From: phri!roy@nyu.edu (Roy Smith) Subject: Re: Looking for comments on the 15-pin ethernet connector (2) dmc@videovax.Tek.COM (Donald M. Craig) writes: > I am looking for feedback on the quality and reliability of > the slide latch mechanism used on the DB-15 ethernet connectors. In a nutshell, they suck! There is no doubt that the single most common cause of problems in our entire network (19 Suns, a Vax, and maybe a dozen Macintoshes and PCs) is loose ethernet tranciever cables, particularly on the backs of Sun-3/50's which provide no mechanical support for the cable at all. On our rack-mount systems, we support the cables with cable ties to various convenient supports. On our deskside suns, we've constructed assorted mechanical strain reliefs. Some of our 3/50's seem to be OK with just wedging the cable behind a desk but some are a constant cause of trouble. For the worse ones, we install a support bracked we've designed which helps a little (it's just a plexiglass bar notched to fit on the card extractor ears and with cutouts for the various cables and attachment points for cable ties in the appropriate places). > "I am the Component Engineer for connectors at Sun. In regards to your > question concerning the Ethernet DB-15 [...] I am not aware of any > significant problems with mechanical integrity of the lock, or for that > matter with the connector in any aspect. I'm not given to public flamage, but this guy must have his head firmly wedged in a dark place. If he's not aware of any problems, it because he hasn't been listening. I've complained loudly about this on the net before. I've complained to Sun field service. I've complained to Sun tech support. Clearly those complaints havn't gotten back to the right people. The stupid little stamped sheet metal clips are simply not strong enough to secure a connector with a big fat, heavy, and fairly stiff tranciever cable on it. As long as the cable is secured so it can't move if accidentally moved, it's OK. For example, on the tranciever ends, we lash the cable to the main ethernet trunk cable with 2 (or sometimes 3) wire ties a few inches away. But on systems which might move a little (like a deskside Sun on wheels), or in situations where the cable might be disturbed (like hanging off the back of a desk) forget it. What was wrong with good-old RS-232-style screws? Or, if they really wanted a tool-less installation, why not Macintosh-style knurled screws, or maybe even centronics-style wire bails? We recently got a 3-Com 3C503 ethernet card for an IBM-PC. The connector is a bit different, with screw holes instead of binding posts. Unfortunately, to use the screw holes you need a special adaptor bracket which I havn't been able to locate yet (OK, we just got the thing; I havn't had a chance to look very hard). It looks like it might be a bit more secure. Our Interlan ethernet board for the vax has a slight variation on the slide connector which looks like it might be marginally stronger (it has small extra ridges along the sides), but I doubt it would still be strong enough if we weren't able to lash the cable to various places in the vax's rack frame. I really don't know what the DIX guys had in mind when they designed this connector. Administering a network is hard enough without having to worry about which $5 connector is falling out. Roy Smith, System Administrator Public Health Research Institute 455 First Avenue, New York, NY 10016 {allegra,philabs,cmcl2,rutgers}!phri!roy -or- phri!roy@uunet.uu.net ------------------------------ Date: 14 Jun 88 17:58:28 GMT From: ron@TOPAZ.RUTGERS.EDU (Ron Natalie) Subject: Re: Looking for comments on the 15-pin ethernet connector (3) Yep, by the way, we've gone and replaced the slide clips with the good old RS-232 screws and threaded inserts on all the Ethernet cables of importance. -Ron ------------------------------ Date: 14 Jun 88 19:54:09 GMT From: bzs@bu-cs.bu.edu (Barry Shein) Subject: Re: Looking for comments on the 15-pin ethernet connector (4) I'll second Roy Smith's gripes about those slide-latch ethernet connectors to quote Roy: "In a nutshell, they suck!" Actually, if there were some negative pressure they might work... We have around 100 Suns here and other assorted items (this lousy slide-latch is not unique to Suns by any means, it's ubiquitous) and they're always falling out, the worst catastrophes occur when they fall out of centralized server machines, we've been out for hours and hours while some poor operator tries to figure out what the problem is (they're learning, we're all learning.) Worse, much worse, it falls out of MY SUN all the time, like when I swing my chair around to gulp coffee or some other critical maneuver and brush the deskside tower, to get it to stay back in I have to re-arch the cable at a precarious angle so it provides pressure towards the plug. Now *that's* unacceptable, the public be damned. I'll also add a vote to the Mac-like knurled screws, that would be the ticket. -Barry Shein, Boston University ------------------------------ Date: 14 Jun 88 17:41:50 GMT From: hp-sdd!ncr-sd!se-sd!cliff@hplabs.hp.com (Cliff Bamford) Subject: Re: Looking for comments on the 15-pin ethernet connector (5) The problem is that it's impossibly impractical to give that connector "reasonable care" in the field. Regardless of type, connectors always seem to be just-barely-visible and just-barely-out-of-reach. The D-sub requires good visibility (to tell which way the slider is slid) and good tactile access to [un]couple. Since these conditions rarely obtain, THE !#@$%&* CONNECTER DRIVES PEOPLE CRAZY. Which is one of the reasons you see so many of them torn asunder, at which point they become worse than useless. Except as mute testimony to the limits of human patience. cliff.bamford@sandiego.ncr.com (619)693-5724 {ucsd,cbosgd}!ncr-sd!se-sd!cliff ------------------------------ Date: 14 Jun 88 21:02:30 GMT From: ati.tis.llnl.gov!bae@tis.llnl.gov (Hwa Jin Bae) Subject: Re: Looking for comments on the 15-pin ethernet connector (6) In general, I don't like DIX 15 pin adapter without any secure screws. My Symmetric 375 comes with 9 pin output which can be interface to regular transceiver with a 9 pin to 15 pin drop cable. You can use RS-232 like screw attachment with it, and it's so much nicer than SUN's way of doing attachment. But then again you can always use "Crazy Glue" or something... 8-) Hwa Jin Bae | Control Data Corp. | (415) 463 - 6865 4234 Hacienda Drive | bae@tis.llnl.gov (Internet) Pleasanton, CA 94566 | {ames,ihnp4,lll-crg}!lll-tis!bae (UUCP) ------------------------------ Date: 14 Jun 88 20:41:12 GMT From: kwe@bu-cs.bu.edu (kwe@bu-it.bu.edu (Kent W. England)) Subject: Re: Looking for comments on the 15-pin ethernet connector (7) In article <23340@bu-cs.BU.EDU> bzs@bu-cs.BU.EDU (Barry Shein) writes: > >I'll also add a vote to the Mac-like knurled screws, that would be the >ticket. That would just about do it, but there are some little touches that the hardware guys could do if they just thought about how the equipment gets used. Hardware engineers--you listening?? Redesign the host side of the connection for better strain relief. We can handle the xcvr side with ty wraps alright. First, use a 90 degree angle on the cable into the connector. Then provide a ty wrap mount an inch or so away from the connector mounting point so we can tie the cable down and provide strain relief. Barry will also be able to shove his deskside closer to the wall and that will help. If you can't angle the cable put a standoff bar somewhere on the back of the box so that when the unit IS shoved into the wall it won't crush the cable/connector and pop it off. Ideally, put a strain relief point on the standoff bar so we can tie the cable down. (Smart guys will do both.) This would help a great deal even without a major session of 802.3 devoted to rehashing this. Kent England, also BU ------------------------------ Date: Tue, 14 Jun 88 23:02:31 pdt From: Robert Michaels <robert@atom.hpl.hp.com> Subject: Re: Looking for comments on the 15-pin ethernet connector (8) Telephone: +1(415)857-3403 (PST/PDT UT+8) > The stupid little stamped sheet metal clips are simply not strong >enough to secure a connector with a big fat, heavy, and fairly stiff >tranciever cable on it... >What was wrong with good-old RS-232-style screws? To me the problem is that the little clips are "standard". I would be very surprised if a vendor will have enough courage to promote something more effective. To alleviate your problem you could try using a lighter weight transceiver cable. For us most transceivers are within 5 meters of the host. For short runs you don't need these really big fat cables. I think several vendors build these short lightweight transceiver cables ( yes even HP does). - Robert Michaels HP Labs ------------------------------ Date: 14 Jun 88 23:13:34 GMT From: cs.utexas.edu!execu!dewey@husc6.harvard.edu (dewey henize) Subject: Re: Looking for comments on the 15-pin ethernet connector (9) Here at Execucom we have a slightly different term for this 'device'. I won't put it out on the net, however, since this probably isn't the place to put adjectives regarding personal ancestory or public sexual habits. Suffice it to say that if the person who designed the slide latch connector were to come here and visit, his/her employer should only buy a one-way ticket - we'd be able to ship what remains there were back in a shoebox! Seriously, those things are a joke. When each and every part is made to exact and perfect spec, they seem to work ok (at least until you touch them in some fashion). The ones we got with at least 3 of our Suns and the cables that we also got from Sun seem to be made to different specs entirely. We had to do a good bit of reverse engineering to get them to handle the normal vibration of someone merely walking in the office (concrete floors). Junk em. Use screws. Please, since you are protecting this 'Component Engineer', help him/her/it :-) become aware of 'significant problems'. execu!dewey Dewey Henize @ Execucom Systems Corp 512/346-3008 ------------------------------ Date: Tue, 14 Jun 88 16:21:20 edt From: sdrc!crken@uunet.uu.net (Ken Shackelford) Subject: DELNI's on Suns >From: lrj@helios.tn.cornell.edu >What problems are there with DELNI's? I believe that some of the new systems that have both thin and thickwire ethernet ports have som kind of circuitry for detecting which is attached. I think it works by trying to detect a power draw from the the transceiver. If it detects this draw (a certain amperage range), it attempts to use the thick port. Otherwise, it uses the thinwire. The problem occurs when you attach one of these systems to a DELNI. The DELNI is self-powered, and as such, draws no power from your machine. The detect circuitry finds no draw so you have no ethernet. On the machine we have, I was able to find a jumper in the hardware documentation that turned off the thinwire, and hence, the detect circuitry. Once I did that everything worked fine. Ken Shackelford (The Wizard of Odd) UUCP: uunet!sdrc!crken ------------------------------ Date: 14 Jun 1988 23:41-EDT From: KSEO@G.BBN.COM Subject: Re: Pointers to performance studies on TCP/IP The SATNET (Atlantic Packet Satellite Network) Measurement Taskforce just completed some work analyzing TCP/IP performance over the SATNET. As part of this effort, we developed an instrumented TCP/IP implementation and a separate IP measurement tool. For additional information: a) Our experimental methodology, tools and results are described in a paper to be presented at SIGCOMM 88 in August. Send me your paper address if you'd like a copy. b) There will be 3 additional writeups describing the taskforce's work in more detail. These will probably be done by the end of the summer. Let me know if you'd like copies when they're complete. c) For specific details about the TCP and IP tools, please contact: TCP tool: Jon Crowcroft (jon@cs.ucl.ac.uk) IP tool: Paal Spilling (paal@tor.nta.no) Let me know if you have further questions, Karen ------------------------------ End of SUN-Spots Digest ***********************