IronPort Systems ES-1528 - Manual (Page 80)

Chapter 12 Port Rate Limit and Storm Control
ES-1528 User’s Guide
80
12.1.1 Rate Limit Screen
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)
LABEL DESCRIPTION
Table 23 Rate Limit Configuration
LABEL DESCRIPTION
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.