[Fwd: Re: (ASCEND) tnt clocking]

[mdobra@mtco.com]

Thanks for all the great responses! Been involved in updating IP's on a
completely seperate TNT and installing a new max20. Hopefully this
afternoon I'll get around to playing with the clocking issue again. I'll
post my findings as soon as I'm done.

maxed_out_user@hotmail.com wrote:
> 
> The TNT will take clock from one line and pass that recovered timing out
> all other T1 WAN ports.  It doesn't matter if you have more than one 8
> port T1 card plugged into the TNT since the timing is sync'd to the
> TNT's TDM backplane.  When you configure a T1 port for Clock-Source =
> eligible, it means that this WAN port is eligible to accept timing
> should the TNT need to find a clock source.  If more than one line is
> configured for eligible, then the one that is configured with a higher
> priority will end up taking clock from the line if needed.
> 
> If you have a PRI plugged into the TNT, then I would definitely set that
> port to clock-source=eligible and set the clock-priority=high-priority
> since PRIs will always have timing referenced to a highly accurate
> master clock out in telcoland somewhere.  If it's plain T1s, then that's
> not always the case (unless the T1 is going through a DACS, in which
> it's always timed by the DACS).  Probably when you configured the
> currently clocked line on TNT A to not-eligible, the other nailed line
> that ended up being eligible might not have had any timing on it so all
> other lines didn't have any accurate timing either since the TNT will
> take timing from one line and pass that timing out all ports (in this
> case, though, either bad clock or no clock was being supplied).
> 
> Does anyone have a clear understanding of clocking sources on the TNT's?
> 
> Here is my senario:
> 
>  tntA --> nailed t1 --> tntB
>       --> multiple nailed and switched lines -->
> 
> I am seeing a lot of frame slips on the nailed t1 and am guessing it is
> due to clocking issues. My understanding of tnt clock sources is this:
> any lines can be eligible as a clock source and the tnt selects the one
> with the highest priority, or selects one at random, or if none are
> available it uses an internal clock source.
> 
> While playing around with tntA I set the line that it was currently
> using for clocking to not-eligible. the tnt picked up another eligible
> source (as indicated by the clock command) but all nailed lines dropped.
> 
> Set the initial line back to eligible and the other it had picked up as
> not-eligible, the tnt grabbed the initial line as a clock source and all
> 
> the nailed lines came back up.
> 
> Any insites?
> 
> --
> Mick Dobra
> MTCO Communications
> 
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-- 
Mick Dobra
MTCO Communications
1-800-859-6826
http://www.mtco.com
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