[asterisk-users] estimation on phone network capacity

[Hans Witvliet]

On Mon, 2008-03-24 at 14:29 -0400, Alex Balashov wrote:
> mark morreny wrote:
> > Hi
> > 
> > I am working on deploying voip for my company and would like to seek 
> > some advice on the number of E1 lines we need to rent.  Our telco told 
> > us that there can be at most 30 concurrent channels on an E1 line.  
> > Typically, what is the maximum number of DIDs that we can allocate to 
> > that E1 line before users get frequent "all lines are busy"?  We are 
> > running a support center with mostly incoming calls.  Is there any rule 
> > of thumb that are typically used for this kind of estimation?
> 
> That depends on the application.
> 
> In general, phone lines for voice (not fax or modem) are considered to 
> have a 30:1 oversubscription ratio, but that can vary immensely.
> 
> Also, it is instructive to inquire what portion of the DIDs will be used 
> with what frequency, and whether the distribution is truly uniform. 
> VoIP is a DID-intensive industry;  often, DIDs are assigned to every 
> employee in an organisation so that everyone has one in principle, even 
> if relatively few people actually use them.
> 

At my former employer, a telco equipment supplier, they used for the
normal office area a 10:1 oversubscription ratio.
For inbound line, like faxes no oversubscription.
But that is for any ordinary office with people doing research &
development, pre-aftersales support...

But for a support centre, you might ask whether you want any
oversubscription at all. As the main job for the people is accepting
inbound phone calls. Ask yourself (or your team) Should a customer get a
message that all staf are busy, (and put them in a waiting queueue with
a fifo) or that a customer should get "all lines are busy" and have to
dial another fifty time before he gets through...

As a customer, i would rather opt for the first one, but can you afford
that?

hw