[VoiceOps] Adtran TA900 timing problems

[Mick Burns]

Just a tip from the best practices of TDM world...
Never use DS1 clocking recovered from a mux'ed DS3.  I'm not sure if
that's what what the original poster is doing, but I thought this
warning may not hurt.

The stuffing bits involved in the muxing process may render the clock
unreliable.
Plesiochronous synchronization accounts for some differences in the
clocks from the original signal that was muxed and then demuxed.

For your VXR, use a valid BITS source if possible, otherwise use
another clean DS1 line as the source, or use the DS3 line (clock
source line) if your provider's MUX is using a reliable clock source.
If all of that is not possible, you'll need to fall back to use the
internal oscillator while crossing fingers on its precision and
stability and prepare yourself for weird sudden problems as season
changes and/or room temperature fluctuates.

Cheers,
Mick

On Mon, Nov 4, 2013 at 4:14 PM, Jay Hennigan <jay at west.net> wrote:
> On 11/4/13 9:41 AM, Matt Yaklin wrote:
>>
>> I forgot to mention that the cisco T1s on the DS3 use line
>> timing in my setup. So line and line on both sides. The T1
>> and the Adtran.
>
> Don't do that then.  :-)
>
> Every T1 span must have exactly one source of clocking.
>
> My recommendation is to configure the T3 controller on the 7206VXR to
> internal clocking on all of its T1s, and clock the Adtrans from T1 0/1
> (line).
>
> If both sides are set to internal, you'll get clock slips as the
> oscillators drift slightly with respect to each other.
>
> If both sides are set to line, then there's no reference clock.  The
> line will probably sync up initially as the free-running T1 will be
> close enough to sync.  Over time the frequency will drift up or down
> until one side can no longer sync.  In some cases they'll recover on
> their own, and in others you need to shut/no shut or otherwise force a
> resync.
>
> So, don't do that.
>
> --
> Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
> Impulse Internet Service  -  http://www.impulse.net/
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