From: Bob Sinclair (bsin@cox.net)
Date: Sat Dec 06 2003 - 23:51:08 GMT-3
Anas,
I would agree that Cisco could do a better job of explaining the policing
mechanism in the MQC, but I think I would disagree that it permits buffering
during congestion. There are Bc and Be parameters, but according to the
documentation this does not buffer packets to shape the traffic. The best
explanation I have found is at the link below, which says that the policer
does not buffer, but "drops packets less aggressively" during congestion.
Could you check it out and see what you think of it?
Thanks!
-Bob Sinclair
CCIE #10427, CISSP, MCSE
bsinclair@netmasterclass.net
----- Original Message -----
From: "Anas Tarsha" <ra3i@yahoo.com>
To: "Bob Sinclair" <bsin@cox.net>; "ccie2be" <ccie2be@nyc.rr.com>; "Group
Study" <ccielab@groupstudy.com>
Sent: Saturday, December 06, 2003 9:07 PM
Subject: Re: CAR vs Police
> Also theoretically there is a major difference between
> CAR and policing, a difference which Cisco hardly
> explains it well in my opinion. CAR is a rate-limit
> mechanism to limit the input or output transmission
> rate on an interface or subinterface based on a
> configured value. All the exceeding traffic is dropped
> in case the exceeding action is dropping. Policing is
> more like a shaping mechanism. As the name implies,
> shaping does not drop packets in case of congestion,
> it buffers them. You will see delay but no data loss.
> So this is the major difference, CAR does not buffer.
>
> Anas
>
> --- Bob Sinclair <bsin@cox.net> wrote:
> > dt,
> >
> > Cisco considers CAR to be legacy, is not developing
> > new features for it, and
> > discourages its use. As far as functionality goes,
> > class-based policing
> > allows more extensive match criteria, including
> > NBAR, CoS, and RTP port
> > numbers. The major difference appears to be support
> > for RFC 2697 and 2698,
> > which add the Violate action and the Peak
> > Information Rate. You can find a
> > detailed comparison of the two at the following
> > link:
> >
> >
>
http://www.cisco.com/en/US/tech/tk543/tk545/technologies_tech_note09186a00800d7276.shtml#topic5
> >
> > Hope that helps,
> >
> > -Bob Sinclair
> > CCIE #10427, CISSP, MCSE
> > bsinclair@netmasterclass.net
> >
> >
> > ----- Original Message -----
> > From: "ccie2be" <ccie2be@nyc.rr.com>
> > To: "Group Study" <ccielab@groupstudy.com>
> > Sent: Saturday, December 06, 2003 10:13 AM
> > Subject: CAR vs Police
> >
> >
> > > Hi Group,
> > >
> > > Aside from the fact that the above features are
> > configured differently
> > (CAR
> > > uses the "rate-limit" command and "Police" is used
> > within the MQC), is
> > there
> > > any difference in functionality?
> > >
> > > If there are differences, could someone explain
> > what they are and what
> > > specific requirements would require the use of one
> > rather then the other.
> > >
> > > Thanks, dt
> > >
> > >
> >
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