Ethernet LAN Newbie: cheap cable tester?

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Subject Author Date
Newbie: cheap cable tester? Chris 06-03-07
Posted by Chris on June 3, 2007, 6:30 pm
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How do I test to see if a particular cat 6 connection will run at full
speed?

I'm not sure that every punchdown we've done is a good one. Is there an
easy way to test the quality of a connection?

Posted by Walter Roberson on June 3, 2007, 8:11 pm
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>How do I test to see if a particular cat 6 connection will run at full
>speed?

>I'm not sure that every punchdown we've done is a good one. Is there an
>easy way to test the quality of a connection?

There are several different types of measurements that have to be done,
most over a range of frequencies. It's the sort of thing that is easy
if you have the right tool, and cumbersome to impossible otherwise.

Looking around a bit and sampling some prices, there appear to
be a number of tools available, including:

Ideal Lantek 6, about $6000 to $9000
Fluke DTX-1200, about $7000 to $13000 (possibly for the exact same thing)
Fluke DSP-4000, about $6000 to $7000, DTX is the newer line
Fluke Etherscope, about $20000-ish, possibly superceeded
Agilent FrameScope 350 plus DualRemote 350
Agilent Wirescope 350, about $5000
Test-um NT950 Validator, about $1100


These are only a brief survey, not recommendations. I haven't
used any of these; I've never heard of Test-um before.
I have used the much older Fluke LanMeter (Cat 5); it was fairly simple
for the ethernet tests (more complex for fibre tests.)

I see the Fluke DTX-1200 quoted at 9 seconds for a full Cat6 test
in one place, and quoted at 12 seconds in another. I didn't look
to see whether that's a general improvement over the lifetime of the
product, or if special licenses or extras are needed for the faster
testing.

Posted by Walter Roberson on June 4, 2007, 10:11 pm
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>>How do I test to see if a particular cat 6 connection will run at full
>>speed?

>Looking around a bit and sampling some prices, there appear to
>be a number of tools available, including:

There also appears to be the Fluke CableIQ Qualification Tester, about
$1000. According to the flukenetworks.com information,

Qualifies - Sees if your existing cabling has the bandwidth to support
voice, 10/100, VoIP or Gigabit Ethernet

Troubleshoots -- shows why existing cabling cannot support the network's
bandwidth requirement (e.g., crosstalk at 11 meters)

Hmmm, you might need the CIQ-GSV "CableIQ Gigabit Service Kit", which
probably costs more.

Posted by Robert Redelmeier on June 4, 2007, 11:09 am
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> How do I test to see if a particular cat 6 connection will
> run at full speed?

Try it and see. You can always take two hot laptops with built-in
GBE and run `ttcp` or `netperf`. Try across a known good patchcord
to see what the machines are cabable of. Don't expect them to be
able to saturate the link (120 MByte/s) but record what they can
do (30-50) and see if the test links are close (1-5%). If the
links are 12 or below, it's likely they've fallen back to 100,
most likely due to a bad pair.

> I'm not sure that every punchdown we've done is a good one.
> Is there an easy way to test the quality of a connection?

Walter has given you the pricing rundown on certification
equipment. Simple continuity/wiremaps are much cheaper.
You could also call a local dcom cabling contractor. If not
busy, she should be able to certify the links for $20-50 each.

I expect less than 10% of all wiring has been certification
tested, mostly due to the cost of test equipment. The wire
that has been tested was mostly installed by govt/megacorps
who always want a spec. They will occasionally save themselves
some very nasty, hard to find network problems (split pair).

-- Robert



Posted by glen herrmannsfeldt on June 4, 2007, 6:02 pm
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Robert Redelmeier wrote:

(snip)

> Walter has given you the pricing rundown on certification
> equipment. Simple continuity/wiremaps are much cheaper.
> You could also call a local dcom cabling contractor. If not
> busy, she should be able to certify the links for $20-50 each.

It shouldn't be so hard to build a simple detector for
split pairs, though I don't know that anyone has done it.

If they are terminated, and maybe even if they aren't,
send a balanced signal down each pair, one at a time,
and measure the signal on the other pairs. Though if one
is actually trying to do it right, the probability of
continuity on each wire (that is, pin 1 to pin 1, pin 2
to pin 2, etc.) being right and the pairs being wrong
is fairly small. I used to know someone with a little
box with eight LEDs that would plug into one end, and
a transmitter for the other end. The LEDs should light
in sequence if the pins were connected right. Simple,
but will catch a large fraction of errors.

-- glen


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