Re: shape average vs shape peak

From: WorkerBee (ciscobee@gmail.com)
Date: Sat Apr 14 2007 - 13:21:39 ART

Specifying Average Rate or Peak Rate Traffic Shaping Design Rule
================================================

Traffic shaping limits the rate of transmission of data.

You can specify two types of traffic shaping; average rate shaping and
peak rate shaping. Average rate shaping limits the transmission rate
to the committed information rate (CIR). Using the CIR ensures that
the average amount of traffic being sent conforms to the rate expected
by the network.

Peak rate shaping configures the router to send more traffic than the
CIR. To determine the peak rate, the router uses the following
formula:

peak rate = CIR(1+Be/Bc) >> peak = CIR + [Be/Tc] which is more than CIR.

where:

Be is the Excess Burst rate.

Bc is the Committed Burst rate.

Peak rate shaping allows the router to burst higher than average rate
shaping. However, using peak rate shaping, the traffic sent above the
CIR (the delta) has the potential of being dropped if the network
becomes congested.

If your network has additional bandwidth available (over the
provisioned CIR) and the application or class can tolerate occasional
packet loss, that extra bandwidth can be exploited through the use of
peak rate shaping. However, there may be occasional packet drops when
network congestion occurs. If the traffic being sent to the network
must strictly conform to the configured network provisioned CIR, then
you should use average traffic shaping.

R6(config-pmap-c)#shape ?

  average configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
                      send out Bc only per interval

  peak configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
                      send out Bc+Be per interval

http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guide09186a00800800fc.html#wp1019894

On 4/14/07, Mike O <mikeeo@email.msn.com> wrote:
> I'm a little confused on these. Does shape average just use Bc and peak uses
> Bc and Be? I'm trying to figure out why you would use one over the other?
>
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