[cisco-nas] Clocking on AS5400 virtually guarantees slips?

[Joseph Mays]

Okay, so here's where we stand after working on this for a few days.

We have several circuits that are coming into an AS5400 that are getting 
slips, whereas most of them don't.

Most of the circuits come in as T1 channels on a T3. Most of those don't get 
slips, some do. We also have two t1 circuits for which we have bypassed our 
mux, so they are T1's that plug into dedicated T1 ports on the AS5400. One 
gets slips, one doesn't.

We can change which lines are getting slips and which ones aren't by 
changing the tdm clock priority to match one of the lines. Basically, we can 
bring the backplane clock into sync with one line, it won't get slips, 
several of the others will.

The problem is that I have not found a way to tell all the circuits except 
the one setting the backplane clock how to set their timing via the clock. 
T1's on the AS5400 only set clocking to line. You can't tell the T1's to 
sync to the internal clock. If you could, we could set the clock that way, 
set the remote end to line, and everything would then be synced to the 
clocking of the line that was setting the primary TDM clock.

If this is true, there is no way to accept t1's from multiple sources in 
which the clocking may not agree with each other, nor is there any way to 
provide clocking for an outgoing T1. The AS5400 simply won't work for this, 
because while it sets the internal clock according to the primary tdm clock 
circuit, there is no way to tell the other T1's to synchronize according to 
the internal clock. They are virtually guaranteed to slip.

What we want is to be the clock source for all the T1's except for specific 
trunks we having coming from the phone company. Most specifically it matters 
for PRI's we are providing to customers. We need to be the clock source 
because in those cases the phone company simply passes the T1's through 
without providing any clocking themselves.

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