istop.com

[Taavi Burns]

On Wed, Mar 17, 2004 at 05:23:02PM -0500, James Knott wrote:
> I generally don't notice much slow down.  However, all the subscribers 
> don't share the same 3 Mb download.  There are several channels 
> avaiable, which (IIRC) run around 30 Mb or so, which are divided among 
> users on an as needed basis, up to the 3 Mb limit.  Rogers will also add 
> equipment, as demand grows.

The coaxial cable cablemodems have a 30Mbps bandwidth allocation for
downloading from the CO to the cable segment (users).  The limitation
of 3Mbps is purely in software on the cablemodem.  Most cablemodems
contain only a 10Mbps ethernet PHY, and so are limited in hardware
to 10Mbps (such as in Edmonton; I've had 800KBps (yes, capital B!)
at the wee hours of the morning from sunsite.ualberta.ca).  I have
heard rumour of some cablemodems having 10/100 ethernet PHYs on them,
but I cannot substantiate that claim.

I do not know what the upload bandwidth for a cable segment is,
but the uncapped cablemodems in Edmonton upload at a maximum
rate of 768kbps each.

DSL on the other hand has a maximum physical transfer rate of 8Mbps
per copper loop.  I do not know if that includes upstream
on adsl (it would definitely include it for sdsl, for obvious
reasons).  People then only share the bandwidth from the wire
centre, which is--as others have alluded--probably some huge ATM,
shared out between way more than 30 people.  Hence, the statistical
probability that the trunk line will be saturated is lower.

-- 
taa

   "The idea that Bill Gates has appeared like a knight in shining
   armour to lead all customers out of a mire of technological chaos
   neatly ignores the fact that it was he who, by peddling second-rate
   technology, led them into it in the first place." - Douglas Adams
/*eof*/
--
The Toronto Linux Users Group.      Meetings: http://tlug.ss.org
TLUG requests: Linux topics, No HTML, wrap text below 80 columns
How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml