Flow Control; Spanning Tree Protocol - Intel ES460MSX - Ethernet 1000Base SX Switch Module User Manual

C H A P T E
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460T Ch2.p65
R 2 Intel Express 460T Standalone Switch Users Guide

Flow Control

During times of heavy network activity, the switch's port buffers can
receive too much traffic and fill up faster than the switch can send the
information. In cases like this, the switch tells the transmitting device to
wait so 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- or
half-duplex. If a port is operating 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
Express 460T switch.

Spanning Tree Protocol

Spanning Tree is a protocol designed to help prevent any 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 from working.
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 which can take over in the event
the primary link fails.
Backup Path from Client A to Server B:
Switch A –> Switch B –> Switch C
Switch A
PC Client A
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 sent over the backup path
automatically.
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Switch B
Path: 1
Cost: 100
Primary Path from Client A to Server B: Switch A –> Switch C
4/19/00, 4:09 PM
Switch C
Server B