Chapter 12 Port Rate Limit and Storm Control

 

Table 23 Rate Limit Configuration (continued)

 

LABEL

DESCRIPTION

 

 

Tokens

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

 

 

Added Per

to limit the largest amount of packets that can leave the port in any one instance.

 

 

Interval

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.

 

 

Burst Size

The burst size specifies the maximum amount of traffic that can be allowed out the port

 

 

 

at any one instance. In the “Token Bucket” algorithm this is referred to as the size of

 

 

 

the bucket as this value limits the number of tokens that can accumulate in the bucket.

 

 

 

 

 

 

Apply

Click this to save your changes to the switch.

 

 

 

 

 

12.1.2 Broadcast Storm Control Setup

Broadcast storm control limits the number of broadcast, multicast and unknown unicast (also referred to as Destination Lookup Failure or DLF) packets the switch receives per second on the ports. When the maximum number of allowable broadcast, multicast and unknown unicast packets is reached per second, the subsequent packets are discarded. Enable this feature to reduce broadcast, multicast and unknown unicast packets in your network.

Click Rate > Storm Control in the navigation panel to display the screen as shown next.

 

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ES-1552 User’s Guide