[c-nsp] Clocking for T1's on AS5400 virtually guarantees slips?

[Scott Granados]

I could be smoking crack here so I apologize if I'm wrong but doesn't the local Telco provide clock on all T1s that you can recover?  Even in the case where you're providing PRI service doesn't the local loop the carrier provides contain line clocking that you can recover?

What am I missing?

On Oct 10, 2012, at 3:15 PM, Joseph Mays <mays at win.net> wrote:

> 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.
> 
> <ATT00001.c>