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

[Ross Halliday]

On Tuesday, June 19, 2012 1:19 PM, 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.
> 
> Thanks for any info you can provide!

This is highly dependent on the type and brand of CPE, the type of network, and service provider's network design. Generally whatever method that controls speed is done by the CPE and the access gear. For example like Doug said, DOCSIS uses channel assignment and rate limiting to determine your rate, a DSL modem in bridge modem's speed is limited by the channel bandwidth from the DSLAM, most wireless gear uses a combination of time slice allocation from the AP and rate limiting on the CPE... which could be hard policing or traffic shaping, might have buffering capability... etc etc.

Cheers
Ross