asterisk users - Mar 2008 - estimation on phone network capacity

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?

Thanks,
Mark
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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.

-- 
Alex Balashov
Evariste Systems
Web    : http://www.evaristesys.com/
Tel    : (+1) (678) 954-0670
Direct : (+1) (678) 954-0671
Mobile : (+1) (706) 338-8599

mark morreny schrieb:
> 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.
E1 is not VoIP. :-)
> 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?
How about logging how many concurrent calls you have _today_?
And I'd say it depends on how much "lost" calls you can tolerate.

Regards,
   Philipp Kempgen

-- 
amooma GmbH - Bachstr. 126 - 56566 Neuwied - http://www.amooma.de
     Let's use IT to solve problems and not to create new ones.
           Asterisk? -> http://www.das-asterisk-buch.de

Gesch?ftsf?hrer: Stefan Wintermeyer
Handelsregister: Neuwied B 14998

On Mon, Mar 24, 2008 at 2:14 PM, mark morreny <markmorreny at gmail.com>
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?
>
> Thanks,
> Mark
>
Google Erlang Calculator.

http://www.google.com/search?q=erlang+calculator&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

Thanks,
Steve Totaro

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