Re: (ASCEND) tnt clocking

[maxed_out_user@hotmail.com]

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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