From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Thu Sep 01 2005 - 22:41:50 GMT-3
Gladston and Simon,
All I can say is that shape peak was created for a specific customer
that to my knowledge ended up not wanting it.
Gladston, the algorithm for shape peak is different, trying to reconcile
it with the way shape average works in terms of Be and Bc will only tie
you in knots, and it does not matter for the R&S exam.
I fully believe you know what you need to know in terms of what efects
the value of Be and Bc have on the shaping rate.
Let it rest there :)
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
gladston@br.ibm.com
Sent: Thursday, September 01, 2005 11:09 AM
To: Chris Lewis (chrlewis)
Cc: ccielab@groupstudy.com
Subject: RE: Shape Peak and Shape Average
Thanks for the reply Chris,
You are totally right.
==========================
quoted
I would bet heavily
that it is related to the test method being used
==========================
I tested it again, this time using 'timeout 3' and 'frequency 3' (tested
using SAA) and the rate was the specified for 'shape average 64000':
Rack2R4#sh int e 0/1 | i output rate
1 minute output rate 63000 bits/sec, 107 packets/sec
Rack2R4#sh pol int e 0/1 | i offered rate
1 minute offered rate 133000 bps, drop rate 69000 bps
For 'shape peak 64000 8192 8192', the rate grows up until it reach
target
rate:
Rack2R4#sh int e0/0 | i output rate
5 minute output rate 127000 bits/sec, 193 packets/sec
Rack2R4#sh policy-map int e 0/0.46 | i offered rate
5 minute offered rate 305000 bps, drop rate 194000 bps
What is not clear yet is about the algorithm for 'shape peak'. I am
considering the model where Be bucket will only receive tokens if Bc
tocken fills up. As there is high traffic on this test, I was expecting
Be does not receive tokens. But I see from the result that the behavior
is similar to two rates, where each bucket receives tokens
independently.
Cordially,
------------------------------------------------------------------
Gladston
"Chris Lewis \(chrlewis\)" <chrlewis@cisco.com>
01/09/2005 12:26
To
Alaerte Gladston Vidali/Brazil/IBM@IBMBR, <ccielab@groupstudy.com> cc
Subject
RE: Shape Peak and Shape Average
Hi Gladston,
The output from the show policy seems to be as expected. The only issue
I see here is the throughput you are seeing, and I would bet heavily
that it is related to the test method being used (pings won't do it and
a single TCP flow has other dependencies). I accept there are plenty of
bugs in IOS, but the shape accuracy has been pretty good for a long
period of time. But in any case, during the exam you are not given any
traffic generators at this time, so it should not be a concern for this
list.
I believe you accurately represent the difference in theory between
shape peak and shape average, and the target rate is as you would expect
for the burst parameters you put in for the two options.
As you point out, with shape average, Be is available for transmission
during the first time interval only, whereas for shape peak, it is
available for each time period. For shape peak settings of
shape peak 64000 8192 8192
Means that during each time interval you can send 8192 of Bc and 8192 of
Be, yielding a Target rate of 128000, shape pea 64000 8192 16384 gives
you a target rate of 192000 as expected, as you can send a total of 8192
plus 16384 per time interval.
Besides the observed throughput rate, what is not clear?
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
gladston@br.ibm.com
Sent: Thursday, September 01, 2005 9:09 AM
To: ccielab@groupstudy.com
Subject: Shape Peak and Shape Average
Trying to understand the differences between 'shape average' and 'shape
peak'. Any comments appreciated.
Byte limit and increment results are similar to FRTS when using shape
average. Byte limit was Bc + Be
When using shape peak, byte limit and increment have the same value, no
matter what value is used for Bc and Be. It is always Bc+Be.
From the teory, Bc and Be are sent each interval for shape peak.
As Be will have tokens only if there is no traffic for a while, I am
wondering how come shape peak can send Bc+Be per interval.
Or maybe it means: 'in case there was no traffic and Be fills', each
interval will send Bc+Be.
Tests:
Shape Average
Rack2R4(config-pmap-c)#shape average 64000 8192 16384
Rack2R4(config-pmap-c)#do sh pol int e0/0.46
Ethernet0/0.46
Service-policy output: CB-shaping-peak
Class-map: class-default (match-any)
403 packets, 27781 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval
Increment
Rate Limit bits/int bits/int (ms) (bytes)
64000/64000 3072 8192 16384 128 1024
Shape Peak
Rack2R4(config-pmap-c)#shape pea 64000 8192 16384
Rack2R4(config-pmap-c)#do sh pol int e0/0.46
Ethernet0/0.46
Service-policy output: CB-shaping-peak
Class-map: class-default (match-any)
318 packets, 21892 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval
Increment
Rate Limit bits/int bits/int (ms) (bytes)
192000/64000 3072 8192 16384 128 3072
Another test, I tried to see if the target rate goes further than 64000
for shape peak, as it shows "Target" equal 128000. Traffic is limited to
79000, a little more than when using shape average:
Rack2R4(config-pmap-c)#shape peak 64000 8192 8192
Rack2R4(config-pmap-c)#do sh pol int e0/0.46
Ethernet0/0.46
Service-policy output: CB-shaping-peak
Class-map: class-default (match-any)
963 packets, 67186 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval
Increment
Rate Limit bits/int bits/int (ms) (bytes)
128000/64000 2048 8192 8192 128 2048
Rack2R4#sh int e0/0 | i output rate
5 minute output rate 79000 bits/sec, 116 packets/sec
Rack2R4#sh policy-map interface e0/0.46 | i drop rate
5 minute offered rate 127000 bps, drop rate 58000 bps
Strangely, shape average applyed to ethernet 0/1 does not let the rate
reaches 64000. The maximum I got was 42000, whith shaping dropping
anything above it.
Rack2R4(config-pmap-c)#shape average 64000 Rack2R4#sh pol int e0/1 | i
drop rate
1 minute offered rate 102000 bps, drop rate 55000 bps
Rack2R4#sh int e0/1 | i output rate
1 minute output rate 42000 bits/sec, 69 packets/sec
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