From: Robert L. DuBell (bobdu11@xxxxxxx)
Date: Sat Apr 13 2002 - 08:24:18 GMT-3
This formula works and is available on the doc cd for your lab use
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_
c/qcprt2/qcdconmg.htm#xtocid840033
Step 1 For each queue, divide the percentage of bandwidth you want to
allocate to the queue by the packet size, in bytes. For example, assume the
packet size for protocol A is 1086 bytes, protocol B is 291 bytes, and
protocol C is 831 bytes. We want to allocate 20 percent for A, 60 percent
for B, and 20 percent for C. The ratios would be:
20/1086, 60/291, 20/831 or
0.01842, 0.20619, 0.02407
Step 2 Normalize the numbers by dividing by the lowest number:
1, 11.2, 1.3
The result is the ratio of the number of packets that must be sent so that
the percentage of bandwidth that each protocol uses is approximately 20, 60,
and 20 percent.
Step 3 A fraction in any of the ratio values means that an additional
packet will be sent. Round up the numbers to the next whole number to obtain
the actual packet count.
In this example, the actual ratio will be 1 packet, 12 packets, and 2
packets.
Step 4 Convert the packet number ratio into byte counts by multiplying
each packet count by the corresponding packet size.
In this example, the number of packets sent is one 1086-byte packet, twelve
291-byte packets, and two 831-byte packets or 1086, 3492, and 1662 bytes,
respectively, from each queue. These are the byte counts you would specify
in your custom queueing configuration.
Step 5 To determine the bandwidth distribution this ratio represents,
first determine the total number of bytes sent after all three queues are
serviced:
(1 x 1086) + (12 x 291) + (2 x 831) = 1086 + 3492 + 1662 = 6240
Step 6 Then determine the percentage of the total number of bytes sent
from each queue:
1086/6240, 3492/6240, 1662/6240 = 17.4, 56, and 26.6 percent
As you can see, this is close to the desired ratio of 20/60/20.
Step 7 If the actual bandwidth is not close enough to the desired
bandwidth, multiply the original ratio of 1:11.2:1.3 by the best value,
trying to get as close to three integer values as possible. Note that the
multiplier you use need not be an integer. For example, if we multiply the
ratio by two, we get 2:22.4:2.6. We would now send two 1086-byte packets,
twenty-three 291-byte packets, and three 831-byte packets, or
2172/6693/2493, for a total of 11,358 bytes. The resulting ratio is 19/59/22
percent, which is much closer to the desired ratio that we achieved.
----- Original Message -----
From: "Alex Paulino" <Alex@2s.com.br>
To: <ccielab@groupstudy.com>
Sent: Saturday, April 13, 2002 1:53 AM
Subject: custom queue question
> Hi folks, how to calculate the byte count to a Custom-queue with the
follow
> configuration:
>
> Queue1) www - byte count 500 and 25% of link
> Queue 2) ipx- byte count 1412 and 10 % of link
> queue 3) default - byte count 700 and 65 % of link
>
> Please, show me how to calculate the values for the each queues.
>
> thanks
>
>
> alex
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