[asterisk-users] Yet another processor question

Tim Panton tim at mexuar.com
Sat Sep 30 03:28:52 MST 2006

On 28 Sep 2006, at 19:18, Mark Farver wrote:

> Here's my setup, I'd like to hear what everyone suggests is the  
> best route:
> I have three sites, a main and two outlying buildign, each has a  
> Mitel SX200 system with a PRI interface.  The outlying sites  
> currently each have a PTP T1 line back to the main site.
> Right now I have a P2 700mhz Asterisk server at each site with a  
> Digium 4 port T1 card.  Each Asterisk server sites between its  
> site's external T1 line and Mitel switch.  Each Asterisk box is  
> also connected to the PtP T1 line.  I am using ZaptelPPP to send  
> data on 12 channels, and the rest are left free for voice calls.   
> The Asterisk boxes do some limited LCR, and route outbound calls  
> over the PtP T1 to whichever site has the most affordable outbound  
> calling plan for the call in question, as well as sending site to  
> site calls over the PtP.
> It works, but using ZaptelPPP is a bit of a pain, and it makes  
> upgrading a hassle, since I haven't found ppp packages for a recent  
> OS so now I have to have the compiler on each box, etc.  Making  
> changes to the asterisk servers means taking down the data  
> connections as well, which is unpopular with the users.  One site  
> has never worked, despite having identical configuration to the  
> other site.  The data bandwidth is always limited to 12 channels,  
> even when the voice channels are idle.
> So what route would everyone recommend?  I can move the PtP  
> connections to independent WAN routers with QOS, then the Asterisk  
> boxes will need to do TDM to SIP and back.  Right now everything is  
> TDM switching.  Will the slow P2s have the horsepower to handle 12  
> or 13 TDM to SIP calls?
> Or should I stick to my current system and just deal with the  
> upgrade hassle? (I wouldn't even upgrade, except that Caller ID  
> Name information doesn't work on my current 1.0 version)

Key question: do you need to do fax (or analog modem)  between the  
sites ?

If you don't then your best bet will probably be to take PtP  
connections over to pure IP, set up some sort
of bandwidth sharing or Qos to keep the split roughly the way you  
have it now. Then run IAX trunking between
the Asterisk boxes. Provided you aren't transcoding the load on those  
boxes won't be much different.
You will however lose about half a channel's worth of capacity due to  
the packet overheads of running
IAX, but that's much less than you would lose with SIP.

If you do need Faxing, then you need to stay with TDM on the T1s, but  
perhaps replace the ZaptelPPP with
a box that splits the T1 into 2 separate T1's each with fewer  
channels (can't think of the name for it ...) or
a Cisco that does the same thing.

> Mark
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Tim Panton


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