Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!mips!pacbell.com!lll-winken!ptavv.llnl.gov!oberman From: oberman@ptavv.llnl.gov Newsgroups: comp.dcom.lans Subject: Re: Ethernet "heartbeat" Message-ID: <1991May19.133507.1@ptavv.llnl.gov> Date: 19 May 91 20:35:07 GMT References: <12164@uwm.edu> <1991May16.004523.21301@berlioz.nsc.com> <105002@sgi.sgi.com> Sender: usenet@lll-winken.LLNL.GOV Lines: 45 Nntp-Posting-Host: ptavv.llnl.gov In article <105002@sgi.sgi.com>, vjs@rhyolite.wpd.sgi.com (Vernon Schryver) writes: > Ok, it seems an unnamed workstations (which brand and models?), some older > Cisco routers (what about newer ones?), and VMS-VAXen pay attention to > heartbeat. Are there any others? Can and are any or all three of these > commonly configured to ignore the absense of heartbeat? > > Consider that Cisco routers tend to be far less common than workstations, > and are less likely to have loose or disconnected cables (tho with > unhappier consequences). VAXen are not the most popular machine this > decade. If these are the only machines that care, it seems to me that > heartbeat (or SQE which is not identical, but close enough) is almost > useless in real life. > > I care, because I'm wondering if a bunch of BSD-style ethernet drivers I > know about should be changed to notice missing hearbeats. They did notice > about 3 years ago, but only by mistake. If they should care, where should > they report the problem? Would a printf be appreciated or cursed? Say one > printf on the first missing heartbeat? My guess is it would be cursed, > because almost all transceivers have heartbeat turned off. The bottom line is that SQE is badly understood. This thread just goes to prove it. It was not designed to detect loose cables, although it's quite good at it. It is there to detect the failure of MAUs and especially collision detect circuitry. And, since MAUs tend to be very reliable, people don't see the importance of this, so they don't bother with SQE. That's a lazy action. It violates the standard (8802-3), and that alone is, IMHO, a reason to use it. Trouble-shooting a LAN is non-trivial. I have spent hours of time tracking down components which were sending out garbled packets which were breaking other things. Any tool I can use is valuable. SQE MIGHT have saved me several hours, IF IT WAS PROPERLY IMPLEMENTED by those who write the software. On the other hand, I would probably curse a printf. The failure should be counted and logged. I don't want to fill 10 KB of disk space every time there is a failure. That's what SNMP is for. The failure information needs to be there so I can use it to track down a problem. But since errors tend to occur in large numbers (1 per packet), I feel a printf is over-kill. R. Kevin Oberman Lawrence Livermore National Laboratory Internet: oberman@icdc.llnl.gov (415) 422-6955 Disclaimer: Don't take this too seriously. I just like to improve my typing and probably don't really know anything useful about anything. Especially anything gnu.