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

Thu Apr 13 07:52:29 EDT 2006

If you have invested as heavily as it appears with your redundant
network, I would replace the 2600s with a pair of routers that can each
support the maximum number of phones.  Seems like a small drop in the
bucket compared to what you already invested in.  You could then use
HSRP for redundancy.  However, that means you will need to have
duplicate PSTN connections on both routers. 

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Erick Bergquist
Sent: Wednesday, April 12, 2006 9:17 PM
To: netfortius at gmail.com; cisco-voip at puck.nether.net
Subject: Re: [cisco-voip] SRST (in 2821 and 3825) vs. CMM vs. AWG
andsomesurvivability design Qs

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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