[Asterisk-Users] maximum concurrent conference peers in asterisk

[trixter aka Bret McDanel]

On Wed, 2005-11-09 at 01:16 -0800, trixter aka Bret McDanel wrote:
> Bandwidth is a tricky issue.  You have your IP + UDP + RTP + whatever
> headers (iax2 combines stuff so potentially that skews this a bit) but
> something most often forgotten is link layer framing.

I should have added to this that for home users using DSL with PPPoE
(which seems increasingly popular) the framing issues can be compounded
because PPPoE has 6 bytes of headers and PPP has 2 bytes, this is added
to the total frame sent over a DSL + PPPoE link.  But if you are running
max connections on VoIP over DSL you are either doing special purpose
stuff or a very bad provider and have other issues.  DSL, especially
with PPPoE is not a 'carrier class' link :)

Addiitonally ATM has a 8 byte SAR trailer, and I forgot to subtract that
from the 16 bytes of padding so that is really only 8 bytes of padding
(not nearly as bad).  

To clarify, if you have a straight ATM link, then you have 5 bytes per
cell padding and 8 bytes at the end of all the cells that make the
packet.  So 40 bytes then add in increments of 48 bytes of usable data,
to avoid waste.  

A little isnt that big of a deal (you shouldnt be trying to run your
links at 100% anyway), but if you transmit 41 bytes of packet data for
example you have 47 bytes of padding, which puts you about 50%
efficiency, which is really bad.

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
UK +44 870 340 4605   Germany +49 801 777 555 3402
US +1 360 207 0479 or +1 516 687 5200
FreeWorldDialup: 635378
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