[cisco-voip] SRST (in 2821 and 3825) vs. CMM vs. AWG and somesurvivability design Qs

Wed Apr 12 21:16:59 EDT 2006

You could have multiple routers for SRST-use if you have that many phones to go over the limit on one router, and in CCM divide the phones at the site into different device pools each with a different SRST reference. Then have dial-peers on those back to the main-voice/SRST router at site with PSTN connectivity. 

But this all depends on the type of failure that occurs, how it impacts network, site, etc. How about if a site loses power and only some components are on UPS/gen power and not the whole network IPT-wise? 

If you have a bigger remote site with a large number of phones, or it is important for them to have full phone services, etc in a total link failure to HQ maybe you want to look at putting a subscriber locally perhaps, etc.

Currently with the old PBX, how do the phones work if you lose total connectivity for old PBX system back to HQ? Do you have a local PBX on site for the phones that is linked to PBX in HQ?  (same concept as local subscriber).

----- Original Message ----
From: Netfortius <netfortius at gmail.com>
To: cisco-voip at puck.nether.net
Sent: Wednesday, April 12, 2006 5:54:59 PM
Subject: Re: [cisco-voip] SRST (in 2821 and 3825) vs. CMM vs. AWG and somesurvivability design Qs

Scott,

Thanks for replying - just to give you an idea of what I am worried about, 
compared to what I have:
- I have complete redundancy inside the building, all the way to the perimeter 
(as explained - dual 2821s meshed with dual 6500s of 4500s);
- I have dual connectivity to the HQ, via two different providers, through two 
different COs (in the remotes), and a Sonet at the HQ ...

... and still being worried that if all links fail - who am I to decide who 
would need connectivity in case of a life-threatening scenario (e.g. my 
understanding of Cisco IPT solutions is that the SRST only allows the 
<max-supported-nb-of-registered-phones> to connect among themselves, or with 
the outside world)? How could someone provide less than 100% survivability 
mode, in case of link failure?!?

Business? Manufacturing - nothing exciting.
Call load - I am not sure if it would be relevant to the scenario above - but 
anyway, FYI, right now I have 6-10 dedicated channels on fractional T1s, 
coming all back to HQ, under normal T1 functional conditions, and - if not 
available - going out locally via PSTN, in the remotes. The trick is that the 
old PBX I am trying to replace allows in any location any phone to still work 
inside the building, or any of them (up to the max nb of POTS lines) to go 
out, even when I loose the channelized T1s - and this is what I am trying to 
replace with IPT solutions.
How many sites [have] go[ne] down? None, since the full redundancy was put in 
place, as I explained above.

If my requirements sound ridiculous, from a statistical or probabilistic 
perspective, my commitment is to not deliver less functionality in the IPT 
than in the old PBX environment.

.... it looks like your recommendation is along the same line as my thoughts: 
other routers.

Thx again,
Stefan

On Wednesday 12 April 2006 16:47, Voll, Scott wrote:
> Stefan--
>
> What is your Business?
>
> How are the dual 2621 connected back?
>
> What kind of Call load do you have?
>
> Are you centralizing PSTN connectivity?
>
> How often do your remote sites go down?
>
> If you are looking for 100% survivability you should get a router that
> will support that many phones.
>
> If you don't need 100% then you can setup the phones that do need
> survivability via a device pool.  IE.  I have a remote site with a 3640
> that supports 24 phones.  I setup the receptionist and the admins to
> connect to SRST where as the other employees would not have a phone
> during an outage.  But since I'm running MetroE I don't have a lot of
> outages.
>
> We personally have the CMM blade in our HQ and it works very well.  Hope
> that helps some.
>
> Just my 2 Cents.
>
> Scott
>
> -----Original Message-----
> From: cisco-voip-bounces at puck.nether.net
> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Netfortius
> Sent: Wednesday, April 12, 2006 8:19 AM
> To: cisco-voip at puck.nether.net
> Subject: [cisco-voip] SRST (in 2821 and 3825) vs. CMM vs. AWG and
> somesurvivability design Qs
>
> Does anyone have a pointer to features comparison and/or - mostly -
> personal
> experience/opinions about differences between IP telephony capabilities,
> as
> far as survivability of remote sites, between the traditional SRST
> available
> for the integrated svcs routers, and CMMs (for 6500s), as well AWGs
> (4000s -
> wondering if the 4500s still accept them?!?). Here is the challenge I am
>
> faced with: planning for VoIP, with all remotes being provided with dual
>
> 2821s (for redundancy), dual-connected to either two 650x or two 450x.
> We are
> having a very heated debate, in my group (mostly out of lack of complete
>
> knowledge about VoIP/IPT Cisco products, for any of us), in regards to
> which
> way to go, knowing the followings:
> - all remotes will have anywhere between 100-240 phones;
> - our design consists in a cluster of CMs at the HQ;
> - we have identified the need for some survivability (of course) for
> when the
> links between remotes and HQ is not available (no CM for the phones to
> register with);
> - my definition of survivability is: remote phones should still be able
> to ALL
> communicate with each other, and any one of them being able to go "out"
> via
> PSTN, in case of disaster (of course within the limitation of number of
> POTS
> lines we will be providing fr each site).
>
> Considering all of the above, I would really like to avoid scrapping the
>
> 2821s, just because of their limited capability in support of phones
> (48/ea,
> compared to my requirements), but I am also very much inclined to
> believe
> that the best solution is a 3825/45 w/SRST. Some of the other guys are
> of the
> opinion that we would be better off putting CMM module(s) in the 65xx
> (where
> we have them), or AWGs in the 45xx (where we have those).
>
> I would appreciate any comments to the above, or - as stated originally
> - an
> RTFM link to some product comparison.
>
> TIA,
> Stefan
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