[c-nsp] cable/dsl/ftth policing, traffic shaping or something else??

[Doug McIntyre]

On Tue, Jun 19, 2012 at 01:19:29PM -0400, Chris Evans wrote:
> Question for you service provider folks.  How do cable modems, dsl, ftth,
> etc limit bandwidth? I believe that everything is limited at the customer
> edge demarq device, performing bandwidth limits on a central network device
> would be too costly to do.
> 
> Do the CE devices use a form of traffic shaping, policing or some other
> algorithm?? I believe it's just traffic shaping as I've looked at packet
> captures and never see too many retrans taking place.


First off, DOCIS (ie. Cable Modem) and all the others are totally
different for the answer. 

DOCIS devices do mostly get the number of channels and speeds they can
use from the profile they download from the CMTS. 

OOTH, DSL, and ethernet type solutions are bandwidth limited at the
termination device in the field. It is NOT too costly to do it there,
and is done all the time. DSL routers have zero control over what they
get for bandwidth setups.