From: mwr@tridom.uucp (Mark Reardon)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: SQE On or Off?
Date: 29 Jul 92 13:23:50 GMT
Reply-To: mwr@tridom.uucp (Mark Reardon)
Organization: AT&T Tridom; Marietta, Georgia

In article <9207290025.AA06177@tsiang-ss2.cisco.com>, tsiang@cisco.com writes:
|> 
|> I think that cisco has had some customers who had problems with their
|> network that were fixed by turning SQE off on their transceivers.
|> This may have been due to the fact that they were using repeaters or
|> had equipment that was generating dribble bits, in which case SQE
|> could cause serious problems.
|> 
|> Cisco routers ignore SQE so there is nothing to be gained by turning
|> SQE on (and nothing to be lost either).
I'm glad the people at the IEEE wasted everybodies time specifing
something (SQE) that is of no benefit to users :-).  Does this
statment mean that cisco doesn't support the 802.3 specification?
Aren't SQE at least counted so that people that want to use it can?
I've also solved network problems by shortening AUI cables.  SHould
i recommend for now on that no one use AUI cables longer than two
meters or should I instead suggest that they wire their network
properly?
|> 
|> Given the above, it makes sense to turn SQE off as a rule on all
|> transceivers connected to cisco routers.  
Only for those that don't care to use the standard methods for locating
faulty AUI cables and tranceivers.
|> 
|> By the way, the keepalive mechanism is a more thorough test of an
|> interface's integrity than SQE.`
I agree that the keepalive will test the tranceiver and AUI cable to
a degree but not completly.  If no collisions occur is it because
there wasn't one or was it because it wasn't detected?
How does the keepalive test the AUI collision wire?  
|> 
|> 
|> David Tsiang
|> High End Systems Development
|> cisco Systems - HW engineering
|> Menlo Park, California
|> email:  tsiang@cisco.com
|> 
This topic has been widely discussed by the comp.dcom.lans.ethernet
group and the people on the committee that developed the SQE 
functionality have contributed to it.  They wanted something that
would test the ability to detect collisions and they didn't want it 
to be in some test mode that was never used.  SQE was the solution.

FLAME ON>>>

I don't have a problem with people that don't use the blade guard
on their table saws if they made a knowledgable decision to do so.
I DO HAVE A PROBLEM with people that tell them to do it and don't
explain the pros and cons.  I watched a man get publicly fired when
his trading investment company's LAN failed because of a bad AUI
cable.  His network was down for two days until the cable was found.
IF HE HAD ENABLED SQE and IF HE HAD LOOKED AT THE ERROR COUNTERS,
the problem would have been spotted quickly and the company would
have not even noticed a problem.  Instead, he was out of a job and
his company lost the use of the LAN because he listened to some 
advice without thinking things through.

FLAME OFF>>>

-- 
Mark

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| Mark Reardon           |  AT&T Tridom                             |
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