[c-nsp] PA-T3 vs. PA-T3+

[Lukas Krattiger]

Hi,
We had several issues with T3-Lines and the PA-T3 on both sides, problem was
packet loss, crc, overruns etc.

Our workaround sounds maybe a little special, but works perfect:
 - Increase the resistance between your T3-Card and the Carrier Port (50m
cable is enough)
 - Set you clock source on both side to LINE (T3 specification says you have
to provide the timing, we just don't do it)

After this changes our T3-Lines with the PA-T3 are working without errors
since more then half a year.
We dont't have the issues if we use a PA-T3+ or ADC Kentrox IDSU on one
side.

-Lukas


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Sonntag, 19. September 2004 11:04
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] PA-T3 vs. PA-T3+

Hi,

this is one of the questions that comes up every now and then, but I haven't
seen the answer yet...

Are the exact differences between the PA-T3 and the PA-T3+ documented
anywhere?

I know that they are different regarding subrating/scrambling and
compatibility with non-Cisco DSUs (Kentrox etc.) on the other end.

But what I found yesterday seems to suggest that the electrical
specifications of the receiver and/or transmitter are different as well.

Reasoning: I have a customer T3 that will work perfectly on a PA-T3+ (no
errors over many weeks).  Moving the T3 to a PA-2T3, it will become very
unstable (about 10% packet loss, CRC errors, framing errors, etc).

So I assumed "the PA-2T3 is broken" and swapped it with a spare PA-2T3 -
imagine my surprise when the customer T3 didn't work on that port either.

So I took the "broken" PA-2T3, connected a different T3, and ran some "sweep
range of sizes" tests on it - everything worked perfectly.

Summary:

  - a given T3 line works only on a PA-T3+, but not on PA-2T3s
  - given PA-2T3s work flawlessly with a different T3

-> the only way I can explain this is "the customer T3 line is somehow
different from the other T3 lines" (stronger or weaker signal, or maybe
something else?) and the tolerance range of the PA-T3+ is higher.

Anyone?

gert


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Gert Doering - Munich, Germany
gert at greenie.muc.de
fax: +49-89-35655025
gert at net.informatik.tu-muenchen.de
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