Re: CAR

["Christopher L. Morrow" <chris () UU NET>]

On Thu, 18 Apr 2002, Ken Yeo wrote:

> Hi Christopher,
>
> If CAR is applied to the routers closest to upstream provider, the traffics
> can still consume the link to the provider. Plus the rate limit ACL will be
> huge. If we can apply CAR to the router at the upstream provider, the

Yes, car isn't a solution... which was my point... I made it obliquely
sorry. Somewhere the packets have to backup, you can't tell the sources to
stop so somewhere in the middle the traffic must backup :(

> problem is solved. But of course we do not have access to the upstream
> equipments. Anyone has comments about the TCP window theory?

I venture to guess your upstream won't CAR for you either :)

> Suan "Ken" Yeo
> Network Engineer
> Aurum Technology
> ken.yeo () aurumtechnology com
> ----- Original Message -----
> From: "Christopher L. Morrow" <chris () UU NET>
> To: "Ken Yeo" <kenyeo () on-linecorp com>
> Cc: <nanog () merit edu>
> Sent: Thursday, April 18, 2002 11:40 AM
> Subject: Re: CAR
>
>
> > On Thu, 18 Apr 2002, Ken Yeo wrote:
> >
> > > Hi Nanog,
> > >
> > > Scenario:
> > >
> > > Transits -----(router A)Backbone(router B)----- Customers
> > >
> > > We applied Cisco CAR at the edge routers (B) in the Backbone to rate
> limit
> > > inbound and outbound traffics to/from Customers. If transmission rate is
> > > higher than the rate limit threshold, IP packets are being dropped by
> router
> > > B. How do we prevent the excess IP packets to consume the transit links
> and
> > > the Backbone? Here is my understanding:
> >
> > You can't unless you CAR on all ingress interfaces on your network toward
> > the customers... so:
> >
> > Ingress-Provider->RTA->RTBB->RTB->Customers
> >
> > You need to CAR on all 'Ingress-Provider' links, this is a very sticky
> > problem (obviously)
> >
> > > -For TCP traffics (HTTP, FTP), TCP senders will stop sending packets
> when
> > > the TCP windows threshold is reached.
> > > -For UDP based audio/video trafffics, if the applications use RTSP and
> > > H.323, RTCP/H.245 will signal the sender to slowdown the transmission if
> the
> > > receiver lost packets.
> > >
> > > Did I miss anything? How about UDP traffics that are not using
> RTSP/H.323?
> > > Thanks.
> > >
> > > Suan "Ken" Yeo
> > > Network Engineer
> > > Aurum Technology
> > > ken.yeo () aurumtechnology com