What Is A Switch - 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

What is a Switch?

A switch segments traffic, providing each port its own collision domain.
This is different than a hub where all ports belong to the same collision
domain.
Segments and Hubs
Hubs combine multiple wires so all attached devices behave like they are on
the same wire. Since the devices share the same segment, data sent by one
device is retransmitted to all devices on the same hub. This is equivalent to
having all devices connected in a bus topology as illustrated below.
Signal sent to all ports
Client A sends
signal to Client B
The disadvantage is all devices must share the total available bandwidth.
The more devices that are attached to the hub the less bandwidth for each
user. Also, network performance suffers since all devices receive traffic and
collisions from other users because the hub retransmits data across all ports.
Switches
Switches send traffic only to specific ports, rather than transmit data across
all ports. This means that each device attached to the switch receives fewer
collisions and the entire bandwidth is available to the device.
MAC Address
006011FB34DB
00A027D36FAA
The switch maintains a table that associates a device's MAC address to a
port on the switch. When Client A communicates with Client B, the switch
looks in the table to determine which port Client B is attached to and then
forwards the traffic to that port. If a device sends traffic to an address that is
not in the table (or sends broadcast or multicast traffic) the switch will send
the traffic out to all ports on the switch. When the switch receives a
response it will update the table with the new address.
12
Client A
Client B
receives signal
Port
2
8
The signal is not
sent to all ports
Client A sends
signal to Client B
4/19/00, 4:09 PM
Client B
Client B
receives signal