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cable/dsl/ftth policing, traffic shaping or something else??

 

 

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chrisccnpspam2 at gmail

Jun 19, 2012, 10:19 AM

Post #1 of 5 (915 views)
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cable/dsl/ftth policing, traffic shaping or something else??

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!
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merlyn at geeks

Jun 19, 2012, 2:31 PM

Post #2 of 5 (859 views)
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Re: cable/dsl/ftth policing, traffic shaping or something else?? [In reply to]

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.

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ross.halliday at wtccommunications

Jun 19, 2012, 3:42 PM

Post #3 of 5 (867 views)
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Re: cable/dsl/ftth policing, traffic shaping or something else?? [In reply to]

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

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jared at puck

Jun 19, 2012, 4:34 PM

Post #4 of 5 (873 views)
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Re: cable/dsl/ftth policing, traffic shaping or something else?? [In reply to]

On Tue, Jun 19, 2012 at 04:31:30PM -0500, Doug McIntyre wrote:
> 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.

Some CPE devices can do the rate-limit on the device. I've
seen this in the Zhone active ethernet CPE hardware.

eg: http://www.zhone.com/products/znid/ae-indoor/

- Jared

--
Jared Mauch | pgp key available via finger from jared [at] puck
clue++; | http://puck.nether.net/~jared/ My statements are only mine.
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jkrejci at usinternet

Jun 19, 2012, 7:35 PM

Post #5 of 5 (876 views)
Permalink
Re: cable/dsl/ftth policing, traffic shaping or something else?? [In reply to]

CTS and ZyXEL both make AE residential FTTH products with individual ingress/egress rate limiting on all ports. ZyXEL also has DSL products too though beyond the DSL train rate I am not sure if you can do further rate limiting on the LAN Ethernet ports or wifi where available.

Also various packet shapers exist which can do this centrally as well. Procera and Sandvine come to mind. They typically have more flexible shaping and policing capabilities with a lot of knobs to tune the traffic controls.

As for Ethernet CPE devices it probably varies from vendor to vendor and platform to platform on how they achieve their rate control. I am guessing policing is easiest and therefore most common but I don't have any empirical data on that specifically. I have also seen in several cases where enabling Ethernet flow control allows traffic flows to actually achieve the rate defined in the bandwidth limit settings in cases where the traffic would otherwise surpass the limit, compared to where otherwise throughput was dismal without flow control on the customer access ports.

In an effort to bring the thread to Cisco on this Cisco list, in the past we've used VBR-NRT on Cisco for T-1 and DSL bandwidth controls on 7200VXR platform as well where the clients train to the ILEC DSLAMs instead of our own DSLAMs. VBR-NRT worked well from what I recall though it has been a while.



-----Original Message-----
From: Jared Mauch <jared [at] puck>
Sender: cisco-nsp-bounces [at] puck
Date: Tue, 19 Jun 2012 19:34:32
To: Doug McIntyre<merlyn [at] geeks>
Cc: cisco-nsp<cisco-nsp [at] puck>
Subject: Re: [c-nsp] cable/dsl/ftth policing, traffic shaping or something else??

On Tue, Jun 19, 2012 at 04:31:30PM -0500, Doug McIntyre wrote:
> 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.

Some CPE devices can do the rate-limit on the device. I've
seen this in the Zhone active ethernet CPE hardware.

eg: http://www.zhone.com/products/znid/ae-indoor/

- Jared

--
Jared Mauch | pgp key available via finger from jared [at] puck
clue++; | http://puck.nether.net/~jared/ My statements are only mine.
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archive at http://puck.nether.net/pipermail/cisco-nsp/

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