RE: shape peak

From: Athaide, Dwayne (DAthaide@epco.com)
Date: Fri May 30 2008 - 10:17:25 ART

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I think the Cisco example you mentioned below is incorrect in the DOC CD. If
you want a throughput of 512K then you will need to do a shape peak of 256K
(if bc=be).

The following example uses peak rate shaping to ensure a bandwidth of 300
kbps

but allow throughput up to 512 kbps if enough bandwidth is available on the

interface:

bandwidth 300

shape peak 512000

why is shape peak 512000 on cisco article ?

if i shape peak then i will get 1024000; is this correct ? or other way round

? pls explain ? Traffic Shaping Target/Average Byte Sustain

Excess

Interval Increment Rate Limit bits/int bits/int

(ms) (bytes) 1024000/512000 3200 12800 12800

25 3200

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of raul
raul
Sent: Thursday, May 29, 2008 10:49 PM
To: ccielab@groupstudy.com
Subject: shape peak

Hi ;

need help

Usage Guidelines

Traffic shaping limits the rate of transmission of data. In addition to using

a specifically configured transmission rate, you can use Generic Traffic

Shaping (GTS) to specify a derived transmission rate based on the level of

congestion.

You can specify two types of traffic shaping; average rate shaping and peak

rate shaping. Average rate shaping limits the transmission rate to the 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)

where:

Be is the Excess Burst size.

Bc is the Committed Burst size.

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)

could be 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.

Examples

The following example sets the uses average rate shaping to ensure a
bandwidth

of 256 kbps:

shape average 256000