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

[Lukas Krattiger]

Hi,
Yes we did talk to our carrier. The engineer sent me a part from his
reference handbook where the "T3" is explaind. Afterall the piece from this
book was useless, because as soon as we run it like that, we are getting
lots of errors on the line.
We decided to implement the T3's by our best practice.
I suggest everyone who has problem with a PA-T3 and "Line-Internal-Clocking"
should try it with "Line-Line-Clocking". If you still get crc-errors try it
with a Long-Cable or/and "Resistance-Pieces" (this was also suggested by our
carrier to solve the entire problem).

With two carriers (Swisscom and Colt) our "best practice" implementation
works perfect.

Cheers
-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 12:17
To: Lukas Krattiger
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] PA-T3 vs. PA-T3+

Hi,

On Sun, Sep 19, 2004 at 11:43:50AM +0200, Lukas Krattiger wrote:
> 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)

In my case, the cable is very short indeed (some 3m or so).  So it might be
a case of "signal too hot", instead of "signal too weak" (which was my first
assumption).

>  - Set you clock source on both side to LINE (T3 specification says 
> you have to provide the timing, we just don't do it)

Funny you mention this.  The *other* T3 on the mentioned PA-2T3 is now
running in exactly this configuration (both sides clocking from LINE), and
is much more stable than the "correct" configuration.

> After this changes our T3-Lines with the PA-T3 are working without 
> errors since more then half a year.

Thanks for your data.  Have you talked to your Carrier about this?  Maybe
they can reduce the output signal of their T3 port?  (I certainly plan to do
this, instead of putting addition 50m of cabling into this already-crowded
edge router rack...)

> We dont't have the issues if we use a PA-T3+ or ADC Kentrox IDSU on 
> one side.

Ditto :-)

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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