[Asterisk-Users] Small office requirements - Can this be done?

[Steve Kennedy]

On Wed, Mar 10, 2004 at 08:41:00PM +0000, Michael T Farnworth wrote:

> Mark Phillips wrote:
> >What codecs are you using? You should be able to get quite a few speex
> >channels or even a load of 729 or gsm channels down your 256K.
> You always have to remember that a UK ADSL line has a contention ratio 
> of 20:1 if you have business ADSL or 50:1 if you have the consumer option.
> This means that in the worst event you could find out that your 256K on 
> a business line is actually 12Kbit/s and the consumer option is only 
> around 1Kbit/s.  These are worst case scenario, but it would mean event 
> one GSM call was too big to get down the pipe.  In reality I suspect you 
> would probably never see more than 4-5 people competing with you, but 
> even then it is only around 50-64Kbit/s.  I often find I get pretty much 
> the full pipe, but you can't really plan on that and it would be bad to 
> run too many calls over the line at a time.  Typically we find that 5 is 
> about the reasonable limit.

It't not quite that simple, DSL in the UK is PPPoATM, so you need to
take into account who IP is encoded at the ATM layer etc. If you're
using a reasonable bit rate codec, you can't really expect to get much
more than 1 voice channel out of an ADSL service (assume something like
1/4 of the upstream rate is usable - so with a 256K upstream service,
that's a 64K channel).

Steve

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