Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!lll-winken!sun-barr!newstop!sun!amdcad!jetsun!pyramid!lstowell
From: lstowell@pyrnova.pyramid.com (Lon Stowell)
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet "heartbeat"
Message-ID: <156130@pyramid.pyramid.com>
Date: 20 May 91 19:37:09 GMT
Sender: daemon@pyramid.pyramid.com
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Organization: Pyramid Technology Corp., Mountain View, CA
Lines: 41

In article <1991May20.185642.6704@berlioz.nsc.com> mikel@berlioz.nsc.com (Michael G. Lohmeyer) writes:

>Sorry to have caused any confusion.  In any case, in my opinion, you
>should not disable the SQE.  Also, it would be nice if driver software,
>in general, reported heartbeat errors, but, as has been stated, this is
>not the case.
>
  It would be nice if drivers reported physical errors period.

  Many drivers ignore SQE errors simply because it is so poorly
  understood...and mis-jumpered by installers.  

  V1 did not support it....if it is enabled, the station thinks
  it is getting a collision signal....which most drivers had
  trouble ignoring if associated with Xmit Done status....unless
  the hardware and software could note that it happened AFTER
  data was xmitted.

  V2 did support it, but not all "V2" compliance claiming
  hardware did....and few installers are/were aware of the
  subtle difference....since as noted they will interoperate as
  long as the transceiver and the station don't annoy each
  other.

  SQE is there to protect OTHER stations on the LAN from a
  station/MAU combination which is unable to detect a collision.
  Depending on your philosophy about designing products for
  cost-effective service, you would try to be a good LAN citizen
  or not.

  Absence of SQE is intended to have the offending station/MAU
  shut down after the first xmission attempt....to protect other
  stations from collisions.  It infers that your MAU is unable
  to detect a collision...or that your DTE is unable to see the
  collision signal--as the only difference between the two is
  WHEN the signal occurs.  

  There are other techniques for noticing that you have physical
  level problems (with software).   SQE status would just help
  out the poor techie,,,,and we all know how most programmers
  feel about service technicians.... >:-)