[c-nsp] Adtran MX-2800 to PA-MC-T3

[Bill Wichers]

>> Sounds like a clocking issue. All the T1s need to be in sync, and you
>> have
>> to have one common master clock source coming from somewhere. If you
>> don't
>> have a master clock, or if the T1s aren't all really synchronous (a real
>> possibility with multiple carriers), then you might get time slips which
>> can cause all kinds of wierd framing errors. I have seen similar
>> problems
>> on circuits that have both ends set to 'slave' for timing.
>
> Yes, but wouldn't those errors manifest themselves at the DS1 level and
> not at the DS3 level? We have 1 way LCV errors INBOUND to the Cisco from
> the MUX (I.E. the Mux side is clean).

Normally I would say "yes", but I'm not sure how the MUX would deal with
the problem of T1 frames that don't arrive at the right times to map into
the DS3. There is supposed to be a limited amount of bit-stuffing going on
in the MUX to allow for some difference between the incoming DS1 circuits,
but if you're going beyond what the MUX can handle I'm not sure how it
would behave.

Might be worth trying the M23 coding instead of C-bit to see if that
helps. I did a quick check on one of our own CT3 circuits and M23 is what
we're using and everything works. Your framing errors could be caused by
an incorrect linecode too, and the problems with mapping DS1s into a DS3
can look similar between timing problems and line code problems in some
cases.

> I can certainly go down that route. However, working with SBC, X/O and ICG
> to try and get that accomplished may be like pulling teeth. I might just
> be better off selling the PA-MC-T3 and the MUX and getting PA-MC-8T1
> cards.

Never said it would be easy :-) I know XO can do it, but with SBC I've
usually had to take timing from them. I've never worked with ICG. At least
it will probably be an easy yes/no answer from your carriers whether or
not they can let you source clocking to your circuits.

Using a PA-MC-8T1 would remove a possible source of failure (the MUX) from
your network too. If you have enough available PA slots in your router
it's probably a better way to go than taking a CT3 and breaking it out
into seperate DS1 circuits.

     -Bill


*****************************
Waveform Technology
Systems Engineer