[cisco-voip] T1 Clock source question

[Rob Dawson]

Whichever interface you select in the ‘network-clock-select’ command provides signal to the PLL, which controls the on-board clocking domain. The other interface will get clock from the line on the RX buffer, but since the TX buffer is using the on-board domain for clock you will get slips on that interface. You can only have one clock source for the on-board PLL.

It may not cause issues, but I have certainly seen instances of dropped calls and other anomalies where the only abnormal diagnostic was clock slips, and correcting the slips resolved the issues.

I think that you can use network modules to split the clock domains since they have their own onboard PLLs.

Rob


From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Ryan Huff
Sent: Wednesday, April 22, 2015 3:38 PM
To: Matthew Loraditch; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] T1 Clock source question

That's correct, and that is where I am at. I have different carriers and I am wondering if I should/need to use multiple clock sources? I'm in way-back mode myself here.

I have a T1 PRI and a T1 CAS (separate providers). Can't I just clock source one and it provides that clock on the backplane to everything?

Thanks,

-r
________________________________
From: MLoraditch at heliontechnologies.com<mailto:MLoraditch at heliontechnologies.com>
To: ryanhuff at outlook.com<mailto:ryanhuff at outlook.com>; cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: RE: [cisco-voip] T1 Clock source question
Date: Wed, 22 Apr 2015 19:33:26 +0000
This is one of my foggier areas, but wouldn’t you use multiple when you have T1s from multiple carriers? I could be wrong.. very wrong..  I love Ethernet circuits! :P
Matthew G. Loraditch – CCNP-Voice, CCNA-R&S, CCDA
Network Engineer
Direct Voice: 443.541.1518
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From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Ryan Huff
Sent: Wednesday, April 22, 2015 3:27 PM
To: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: [cisco-voip] T1 Clock source question

I have always subscribed to the idea that you should use one clocking source in situations where you have multiple T1's. In fact, I've read (not experienced) that when you use multiple clocking domains, that in-fact can sometimes cause slips.

Can anyone explain the advantages of using multiple clocking sources?

Thanks,

Ryan
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