[cisco-voip] ISR G2 PVDM3 DSPs on backplane

Tue Jun 29 12:07:52 EDT 2010

I think this is more of a carrier over from all our Route Switch days, when providers weren't clocking P2P T1s for us.

On every service provider voice circuit I've encountered, and probably that most people have encountered, the service provider clocks are soo close to each other it doesn't cause problems if you pick your best/most reliable trunk to clock off of.

Think of a PBX, the WHOLE thing has to clock off ONE source.  We had 3 DS3s worth of T1s coming into one system all clocked of one circuit.

Where the trouble came was hooking into a Cisco 6608 and the guy didn't know how to clock off the PBX AND there wasn't a good reference clock on their side.

-Nate

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Dennis Heim
Sent: Tuesday, June 29, 2010 7:54 AM
To: Nick Matthews; Bill Riley
Cc: cisco-voip
Subject: Re: [cisco-voip] ISR G2 PVDM3 DSPs on backplane

It is just bad design practice to get into to have PRIs from different provider on the same clocking domain. You might be able to get away with it, but really you are just putting the end-customer in a bad spot down the road.

Dennis Heim
Network Voice Engineer
CDW  Advanced Technology Services
11711 N. Meridian Street, Suite 225
Carmel, IN  46032

317.569.4255 Office
317.569.4201 Fax
317.694.6070 Cell
dennis.heim at cdw.com
cdw.com/content/solutions/unified-communications/

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Nick Matthews
Sent: Monday, June 28, 2010 11:27 PM
To: Bill Riley
Cc: cisco-voip
Subject: Re: [cisco-voip] ISR G2 PVDM3 DSPs on backplane

I've seen this dozens of times.  Most people probably don't even realize they have a problem.  Some may even have two providers that have managed to be on the same clocking domain.  I've even seen some people with providers that were willing to be the slave because the provider is SIP on the other side of the router.

The only way to provide two different voice clocking domains is by having two separate groups of DSPs - this means HDV cards.

If you have one PRI for failover or that is not used until the first is filled, you can probably get away with slips.  The basic rule I've gone by is:  if you don't need to fax or modem over the T1, you're probably alright with slips if it's not your primary line.  There are chances for voice quality, it all depends.  It could be a cell-phone like quality issue you probably won't notice, or distinct chirps on the line that can be annoying.

-nick

On Mon, Jun 28, 2010 at 8:38 PM, Bill Riley <bill at hitechconnection.net> wrote:
> I am not concerned with what works, and more concerned with what is 
> the best solution.
>
>
>
> From: Jason Aarons (US) [mailto:jason.aarons at us.didata.com]
> Sent: Monday, June 28, 2010 5:25 PM
> To: Jim Reed; Bill; Beck, Christopher; cisco-voip
> Subject: RE: [cisco-voip] ISR G2 PVDM3 DSPs on backplane
>
>
>
> While it's working, from a solution design standpoint I'm being told 
> that if the timing varies from the providers it could result in 
> problems, so design preference should be to have separate routers in this scenario.
>
>
>
> I'm with you, I've done it before and it did work, and I'd hate to 
> explain it to customer they need another router if the clocks are far apart.
>
>
>
> From: Jim Reed [mailto:jreed at swiftnews.com]
> Sent: Monday, June 28, 2010 6:09 PM
> To: Bill; Beck, Christopher; Jason Aarons (US); cisco-voip
> Subject: Re: [cisco-voip] ISR G2 PVDM3 DSPs on backplane
>
>
>
> I am currently using PRIs from different vendors - AT&T and Integra - 
> on the same router.  Two (2) separate VWICs on the same 2851.  VWIC2-1MFT-T1/E1.
>  No problems with voice quality, errors, etc.  Configured as follows:
> network-clock-participate wic 0
> network-clock-participate wic 1
> network-clock-select 1 T1 0/0/0
> Just thought I'd pass it along.
> --
> Jim Reed
> Manager of Technical Services
> Swift Communications, Inc.
> 970-384-9141 (Direct)
> 775-772-7666 (Cell)
> Sorry, no faxes accepted.
> Please send documents by eMail.
>
>
>
> On 6/28/10 3:44 PM, "Bill" <bill at hitechconnection.net> wrote:
>
> Are you sure that is the case currently? I think you can have multiple 
> PRI's inside the same router on an ISR but they can not be on the same VWIC.
>
> Jason said you can not have multiple PRI's within the same router.
>
>
> ________________________________
>
> From: Beck, Christopher [mailto:CBeck at usg.com]
> Sent: Monday, June 28, 2010 4:40 PM
> To: Bill; 'Jason Aarons (US)'; 'cisco-voip'
> Subject: RE: [cisco-voip] ISR G2 PVDM3 DSPs on backplane
>
> This is true on the 2800/3800 today (except in the case of the NM-NDV 
> modules mentioned, but I don't think so even in that case).  It is 
> because there is a "single" PLL clocking circuit shared for all PRI's.  
> The WIC must be configured to participate in that clocking circuit 
> prior to setting up the PRI.   I can't remember  any device that could 
> handle this in 20 years of installing channel banks, muxes, routers, etc.
>
> That said, a lot of times it will work acceptably because the clocks 
> are close enough, especially if the local loop provider is the same on 
> all links.  But, you have to test it to know in any case.
>
>
>
> -Chris
>
>
> From: cisco-voip-bounces at puck.nether.net
> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Bill
> Sent: Monday, June 28, 2010 4:21 PM
> To: 'Jason Aarons (US)'; 'cisco-voip'
> Subject: Re: [cisco-voip] ISR G2 PVDM3 DSPs on backplane
>
> What? I know you could not do different Telco's on the same two port 
> card but you can't do two telco's in the same router? Is there an 
> official response to this? Is there a specific defect I can reference 
> with my Cisco AM?
>
>
> ________________________________
>
> From: cisco-voip-bounces at puck.nether.net
> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Jason Aarons 
> (US)
> Sent: Monday, June 28, 2010 4:12 PM
> To: cisco-voip (cisco-voip at puck.nether.net)
> Subject: [cisco-voip] ISR G2 PVDM3 DSPs on backplane
>
> A TAC engineer at Cisco Live confirmed you can't have multiple voice 
> PRIs from separate telcos come into a G2 with different clocks. For 
> example you have a AT&T PRI, a Verizon PRI, a Century Link PRI, a 
> Alltell PRI, a Paetec PRI all in the same router. You can't clock the 
> backplane to  more than one source!  You'll get slips, etc audio will sound bad, faxes/modems will fail.
>  Fix is separate routers.  He said he thought a 2800 with DSPs on a 
> NM-HDV module would work though.  My exact question was can you carve 
> up the backplane PVDM3 clocking for separate PRIs somehow.
>
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