[cisco-voip] Question about T1 clocking

Ed Leatherman ealeatherman at gmail.com
Wed Feb 4 14:59:49 EST 2009

That makes sense.. so DSP's sitting off on a NM can synch up with a
different clock than from the main board. I vaguely remember something like
that at a networker's session but apparently it didn't sink in deep enough
to stick.

The second T1 is eventually going to be a secondary local provider
connection (they think they need two for busy period later in the year).. so
I will likely end up ordering another PVDM chip for them anyway, maybe I
should just plan for a NM-HDV also and avoid the problem. I'll have to find
out what their tolerance for problems are if we don't go that route.

Thanks for the help Justin and Timothy!

On Wed, Feb 4, 2009 at 2:51 PM, Justin Steinberg <jsteinberg at gmail.com>wrote:

> not necessarily.  like you mention if both vwics use the onboard PVDMs,
> then they will both participate in the same clocking domain which means
> there is potential for slip.  To get two clocking domains, you would have to
> add something like a NM-HDV with its own DSPs to create a second clocking
> domain.
> Of course you could just order the T1 and try the open slot in the existing
> VWIC, you might get lucky and find that both are on the same clock.
>  However, if you see slips, you'll probably need to order a NM.
> Unless something has changed with the new VWIC3s ...?.?.?
> On Wed, Feb 4, 2009 at 2:18 PM, Ed Leatherman <ealeatherman at gmail.com>wrote:
>> My main concern is since both these are voice connections and they will be
>> faxing over both links.. clock slips seem to cause trouble in that regard.
>> Would adding the second VWIC eliminate the slip problem?

Ed Leatherman
Assistant Director, Voice Services
West Virginia University
Telecommunications and Network Operations
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