3.
If the downstream device is unable to handle the amount of bursty traffic allowed
using the initial burst size configuration, reduce the burst-size limit until you achieve
acceptable results.
5 ms Method for Selecting Initial Burst Size for Gigabit Ethernet Interface with
200 Mbps Bandwidth
The following sequence illustrates the use of the 5 ms method for selecting an initial
burst size for test configurations for a Gigabit Ethernet interface configured with a
200 Mbps bandwidth limit. This example calculation shows how a larger burst-size limit
can affect the measured bandwidth rate.
1.
If you configure a 5 ms burst-size limit, the maximum amount of traffic allowed to
pass through the interface unrestricted is 125,000 bytes (approximately 83 1500-byte
packets), calculated as follows:
200,000,000 bps x 0.005 s
200 Mbps x 5 ms = —————————————————————————— = 125,000 bytes
8 bits per byte
On a Gigabit Ethernet interface, a configured burst-size limit of 5 ms creates a burst
duration of 1 ms at Gigabit Ethernet line rate, calculated as follows:
125,000 bytes 1,000,000 bits
——————————————— = ——————————————————— = 0.001 s = 10 ms
1 Gbps 1,000,000,000 bps
The average bandwidth rate in 1 second becomes 200 Mbps + 1 Mbps = 201 Mbps,
which is a minimal increase over the configured bandwidth limit at 200 Mbps.
2.
If you configure a 600 ms burst-size limit, the maximum amount of traffic allowed to
pass through the interface unrestricted is 15 Mbytes (approximately 10,000 1500-byte
packets), calculated as follows:
200,000,000 bps x 0.6 s
200 Mbps x 600 ms = ————————————————————————— = 15,000,000 bytes
8 bits per byte
On a Gigabit Ethernet interface, a configured burst-size limit of 600 ms creates a burst
duration of 120 ms at Gigabit Ethernet line rate, calculated as follows:
15,000 bytes 120,000 bits
—————————————— = ——————————————————— = 0.012 s = 120 ms
1 Gbps 1,000,000,000 bps
The average bandwidth rate in 1 second becomes 200 Mbps + 120 Mbps = 320 Mbps,
which is much higher than the configured bandwidth limit at 200 Mbps.
Copyright © 2016, Juniper Networks, Inc.
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Traffic Policers Feature Guide for EX9200 Switches
Summary of Contents for EX9200 Series
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