IronPort Systems ES-1528 User Manual

Chapter 12 Port Rate Limit and Storm Control

ES-1528 User’s Guide

Click a port number in the Port Rate screen to bring up the screen as shown next.

Figure 43   Rate Limit Configuration 

The following table describes the related labels in this screen. 

Ingress Rate

Displays the maximum bandwidth allowed in kilobits per second (Kbps) for the 

incoming traffic flow on a port. 

Egress Rate

Displays the maximum bandwidth allowed in kilobits per second (Kbps) for the out-

going traffic flow on a port. 

Table 22   Rate Limit and Storm Control (continued)

Table 23   Rate Limit Configuration

Ingress Rate

Specify the maximum bandwidth allowed in kilobits per second (Kbps) for the incoming 

traffic flow on a port. 

Egress Traffic 

Shaping

Select Disabled to not have any bandwidth limits for outgoing traffic on the port or 

select Enabled to enable bandwidth limits for outgoing traffic on the port. 

Rate

This is a read only field indicating the rate limit of outgoing traffic on the port in Kbps. 

This value changes depending on the number of Tokens Added Per Interval. 

Tokens 

Added Per 

Interval 

The switch uses a “Token Bucket” algorithm to limit the outgoing rate on the ports and 

to limit the largest amount of packets that can leave the port in any one instance. 
In this algorithm each “token” represents an allowed amount of bandwidth to be sent 

out on the port. 
The “bucket” holds the tokens. In other words, the number of tokens in the bucket 

represents the maximum allowed bandwidth to go out on the port. The size of the 

bucket is specified by the “burst size” (see below).
Every time traffic goes out on the port, tokens (representing used up bandwidth) are 

removed from the bucket, thus limiting the amount of traffic allowed to go out on the 

port. Tokens are also added to the bucket every Token Update Interval, thus 

resetting the amount of bandwidth allowed to go out. If the bucket is empty, the data 

packets are dropped until more tokens are added to the bucket.
Select the number of tokens that should be added to the bucket per Token Update 

Interval. Each token represents .5 bit in bandwidth allowed to go out on the port.