[cisco-voip] Avoid Clocking issues with PRI

Wed Oct 17 12:37:36 EDT 2012

Many times you can have a different carrier by name but it is still going into either the same CO switch, or a switch that is using the same stratum clock. It is one of those things you only find out the hard way which is when you are trying to bring up a circuit late at night.

Dennis Heim | Sr. UC Engineer
World Wide Technology | 314.212.1814 | dennis.heim at wwt.com<mailto:dennis.heim at wwt.com>
"Creating Impact, Ignition & Scalability"

From: Nate VanMaren [mailto:VanMarenNP at ldschurch.org]
Sent: Wednesday, October 17, 2012 12:03 PM
To: Ted Nugent; Heim, Dennis
Cc: cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] Avoid Clocking issues with PRI

I have a lot (5-9 or so) of carriers coming into our main site.  I haven't had any clocking issues, except when we were first integrating with our PBX.

My plan was to move offending carriers to a different gateway, but I just haven't had the need.  Most of the circuits come in on a DS3 that we break out to T1s, but I don't think that has a major impact.

So knowing the limitations of the clocking domains is important, but I would only deal with it once you have confirmed there really is a difference between the clocks on the different carriers.

-Nate

From: cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net> [mailto:cisco-voip-bounces at puck.nether.net]<mailto:[mailto:cisco-voip-bounces at puck.nether.net]> On Behalf Of Ted Nugent
Sent: Tuesday, October 16, 2012 6:41 PM
To: Heim, Dennis
Cc: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: Re: [cisco-voip] Avoid Clocking issues with PRI

Oh I absolutely agree and that's how it's always been however I thought I had heard that was one of the "great things" announced about the ISR2 and the newer VWIC3s but it's very possible I was not paying attention closely enough. I'll find the slides tomorrow and confirm but it's probably just what was listed in that doc posted above about having data and voice clocked independently off the same card, that would make a lot more sense since I don't see any new commands to "partition" the DSP or anything of that nature.
On Tue, Oct 16, 2012 at 7:30 PM, Heim, Dennis <Dennis.Heim at wwt.com<mailto:Dennis.Heim at wwt.com>> wrote:
The problem like Jason said with voice is those DSPs. The NM module works because it has its own dedicated PVDMs.

Dennis Heim
Sr. UC Engineer
World Wide Technology
Office: 314.212.1814<tel:314.212.1814>
Email: dennis.heim at wwt.com<mailto:dennis.heim at wwt.com>
www.wwt.com<http://www.wwt.com/>

From: cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net> [mailto:cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net>] On Behalf Of Jason Aarons (AM)
Sent: Tuesday, October 16, 2012 7:26 PM
To: Steven Sarte; Ted Nugent

Cc: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: Re: [cisco-voip] Avoid Clocking issues with PRI

I suspect you still can't have 2 voice PRIs with different clocks.  How would your carve up the mother board/backplane DSP resources to clock to each port?    I'd still go with a separate router for voice PRIs to separate carriers.

From: Steven Sarte [mailto:steven.sarte at gmail.com]<mailto:[mailto:steven.sarte at gmail.com]>
Sent: Tuesday, October 16, 2012 7:23 PM
To: Ted Nugent
Cc: Jason Aarons (AM); cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
Subject: Re: [cisco-voip] Avoid Clocking issues with PRI

With the new VWIC3 you can have independent clocking when you have a voice PRI and data T1 on a 2 port card.

As for NM I'm reading that it's a separate clocking domain from the VWIC cards.

Sent from my iPhone

On Oct 16, 2012, at 7:08 PM, Ted Nugent <tednugent73 at gmail.com<mailto:tednugent73 at gmail.com>> wrote:
Hmm, does this imply that you can have 2 seperate VWIC3s in the same ISR2 chassis supporting thier own voice clocking domains or are we still under the same restrictions where the ISR2 only supports a single clocking domain for voice? Thought that was what I heard but it's possible this is what I'm remembering.

http://www.cisco.com/en/US/prod/collateral/routers/ps5855/prod_qas0900aecd8028d2e5_ps10537_Products_Q_and_A_Item.html

Q. How do the Cisco VWIC3 cards differ from the VWIC2 cards?
A. The Cisco VWIC3 cards are supported only on the Cisco Integrated Services Router (ISR) 1900, 2900, 3900 and 3900E series platforms. The VWIC3 cards add enhancements to the previous generation VWIC2 cards, including:
Enhanced clocking capabilities: The Cisco VWIC3 cards can enable each port to be clocked from an independent clock source for data applications. Data ports can also be clocked independent of voice ports. All voice ports on the card much use the same clock source.
Q. Can the 2- and 4-port VWIC3 cards support different clocking domains?
A. When the 2- or 4-port VWIC3 is used in data only, non-ATM applications, each port can connect to a different clocking domain, for example, when two different T1/E1 carriers are used. When the VWIC3 is used for voice applications, all voice T1/E1s have to be synchronized to a single clock source and any difference in clocks risk clock slips or interface flaps. When the VWIC3 is used for mixed data and voice applications, each data port can use an independent clock, and the voice ports can use a clock source independent from the data ports.

On Tue, Oct 16, 2012 at 5:48 PM, Ted Nugent <tednugent73 at gmail.com<mailto:tednugent73 at gmail.com>> wrote:
I thought for sure I heard at a partners summit or networkers that ISR2/VWIC3 no longer fall under those restrictions. Time to start scouring my slides...

On Tue, Oct 16, 2012 at 5:44 PM, Steven Sarte <steven.sarte at gmail.com<mailto:steven.sarte at gmail.com>> wrote:
Take a look at this white paper:
http://www.cisco.com/en/US/prod/collateral/routers/ps5854/prod_white_paper0900aecd805b9915.html

Under the section titled: Clocking and Timing Options

Thanks,
Steven

On Tue, Oct 16, 2012 at 5:32 PM, Jason Aarons (AM)
<jason.aarons at dimensiondata.com<mailto:jason.aarons at dimensiondata.com>> wrote:
> This doesn't work when you have PRIs from different providers.
>
>
>
> The original VWIC2 has a single PLL and backplane could not clock from
> multiple sources.
>
>
>
> From: cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net>
> [mailto:cisco-voip-bounces at puck.nether.net<mailto:cisco-voip-bounces at puck.nether.net>] On Behalf Of Roger Wiklund
> Sent: Tuesday, October 16, 2012 4:40 PM
> To: Steven Sarte
> Cc: cisco-voip at puck.nether.net<mailto:cisco-voip at puck.nether.net>
> Subject: Re: [cisco-voip] Avoid Clocking issues with PRI
>
>
>
>
>
> Dunno about the NM, I just use network-clock-select 1 e1 x/y/z and
> ensure you have clock source line. That's enough to keep it slips
> free.
>
> Regards
> Roger
>
> On Tue, Oct 16, 2012 at 10:28 PM, Steven Sarte <steven.sarte at gmail.com<mailto:steven.sarte at gmail.com>>
> wrote:
>> I have two SP's for my PRI's on a 2921 currenty using a
>> VWIC3-4MFT-T1/E1. I opened a Cisco Partner case and they told me you
>> can avoid timing slips by using a Network Module PRI, like a
>> NM-HDV2-T1/E1 and a VWIC3-4MFT-T1/E1 in the WIC slots.
>>
>> Has anyone configured this before? What would the clocking
>> configuration look like. I did open a Cisco TAC case but he was not
>> very helpful in his first reply.
>>
>> Thanks in advance,
>> Steven
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> itevomcid

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