Intel 460T User Manual download pdf (Page 20)

CHAPTER 2

Intel Express 460T Standalone Switch Users Guide

Flow Control

When network traffic is heavy, the switch’s port buffers fill up faster than

the switch can send the information. In cases like this, the switch tells the

transmitting device to wait until the information in the buffer can be sent.

This traffic control mechanism is called flow control.

The method of flow control depends on whether the port is set to full-duplex

or half-duplex. If a port operates at half-duplex, the switch sends a collision

(also called backpressure) which causes the transmitting device to wait. If

the port operates at full-duplex, the switch sends out an IEEE 802.3x PAUSE

frame. You can enable or disable flow control for each port on the 460T

switch.

Spanning Tree Protocol

Spanning Tree is a protocol that prevents loops within the network

topology. A loop can occur if there is more than one path for information to

travel between devices. The Spanning Tree Protocol works by determining

the “cost” of a connection. For example, if two devices are connected by two

links, Spanning Tree uses the connection with the lowest cost and blocks

the second connection.

Spanning Tree prevents loops by allowing only one active path between any

two network devices at a time. However, you can also use this behavior to

establish redundant links between devices that can take over if the primary

link fails.

Path: 3

Cost: 100

Path: 2

Cost: 200

Path: 1

Cost: 100

Switch A

Switch C

Server BPC Client A

Switch B

In this example, Client A can communicate with Server B over two different

paths. The primary path is Path 1 because the cost of the connection

between switches A and C is lower than the cost between switches A, B and

C. If the primary path fails, then traffic is automatically sent over the backup

path.

Primary Path from Client A to Server B: Switch A –> Switch C

Backup Path from Client A to Server B:

Switch A –> Switch B –> Switch C

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Intel 460T User Manual Page 20