From: steven.j.nelson@xxxxxx
Date: Thu Apr 04 2002 - 09:26:23 GMT-3
All
What is the simplest formula for working out bandwidth allocation when using
custom queueing.
I have been using the following but I am looking for a quicker way.
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.
Steve Nelson
Customer Engineer
BT Ignite- National Solutions
T: +44 (0)1422 338881 M: +44 (0)7811 944172
e-mail: steven.j.nelson@bt.com
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