[asterisk-users] Bandwidth requirements

[hugolivude]

So much detail!  Thanks very much guys, I'm sure that all this excellent
info will be valuable to others as well.

Gratefully yours,
H

On 10/5/06, Brian Candler <B.Candler at pobox.com> wrote:
>
> On Thu, Oct 05, 2006 at 10:53:14AM +0200, raphael Jacquot wrote:
> > Brian Candler wrote:
> >
> > >However on ADSL, you have to add the 15% ATM cell tax. And you would be
> > >wise
> > >to add 20% headroom (i.e. so your line is not more than 80% full)
> >
> > ATM cell tax is actually 10% as there's 5 header bytes for each 53 bytes
> > cell,
>
> Only if all cells are filled. On average there will be half a cell empty
> at
> the end of each packet.
>
> A common case is 1500-byte packets; these will take 32 cells, or 1696
> bytes
> total, giving a tax of 13%. Mix some smaller packets in with that and you
> get a higher tax. So I tend to work on 15% as a rule of thumb.
>
> However it's worse for VoIP as has been pointed out. e.g. if you are
> sending
> 60 byte packets (20 IP, 8 UDP, 12 RTP, 20 G729) then they will take two
> 53-byte cells, so you pay 46 extra bytes to carry 60 bytes of IP; the tax
> is
> then 77%
>
> (You will also have encapsulation, e.g. PPPoA, but that probably fits in
> the
> wasted space without needing another cell)
>
> Regards,
>
> Brian.
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