Brocade TurboIron 24X Series Configuration Guide - Manual (Page 1063)

Brocade TurboIron 24X Series Configuration Guide 1029
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Chapter
34
Configuring Rate Limiting and Rate Shaping
In this chapter
• Rate limiting overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029
• Rate limiting in hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1029
• Rate shaping overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1032
Rate limiting overview
This chapter describes how to configure rate limiting and rate shaping.
Rate limiting applies to inbound ports and rate shaping applies to outbound ports.
Port-based fixed rate limiting is supported on inbound ports. This feature allows you to specify the
maximum number of kilobits a given port on a device can receive. The port drops bytes or kilobits
that exceed the limit you specify. You can configure a Fixed Rate Limiting policy on a port inbound
direction only. Fixed rate limiting applies to all traffic on the rate limited port.
Fixed rate limiting is at line rate and occurs in hardware. Refer to “Rate limiting in hardware” on
page 1029.
When you specify the maximum number of kilobits, you specify it in bits per second (bps). The
Fixed Rate Limiting policy applies to one-second intervals and allows the port to receive the number
of kilobits you specify in the policy, but drops additional bytes or kilobits. Unused bandwidth is not
carried over from one interval to the next.
NOTE
Brocade recommends that you do not use Fixed Rate Limiting on ports that receive route control
traffic or Spanning Tree Protocol (STP) control traffic. If the port drops control packets due to the
Fixed Rate Limiting policy, routing or STP can be disrupted.
Rate limiting in hardware
Each device supports line-rate rate limiting in hardware. The device creates entries in Content
Addressable Memory (CAM) for the rate limiting policies. The CAM entries enable the device to
perform the rate limiting in hardware instead of sending the traffic to the CPU. The device sends
the first packet in a given traffic flow to the CPU, which creates a CAM entry for the traffic flow. A
CAM entry consists of the source and destination addresses of the traffic. The device uses the
CAM entry for rate limiting all the traffic within the same flow. A rate limiting CAM entry remains in
the CAM for two minutes before aging out.