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All Rights Reserved. Copyright © 2000, Yokogawa Electric Corporation
TI 04L01A01-02E
3.4.4
Points to be noted when configuring a network
The point to note when configuring a network using Ethernet is designing the network by considering the
collision domain and broadcast domain. By dividing the collision domain with a switch and the broadcast
domain with the router, the network traffic can be reduced.
Collision domain
Because multiple terminals use one transmission line in an Ethernet communication, a collision of
packets occurs when multiple terminals transmit data simultaneously.
Therefore, the terminal that wishes to transmit data determines whether or not other communication is
taking place, and if the line is available, it starts sending data. If a collision occurs, the timing is
altered for retransmission. The network unit in which other communications must be confirmed is
called the collision domain unit.
Broadcast domain
In a TCP/IP network, broadcast is used as a method to collect address information. The range over
which the broadcast packet is able to reach is called the broadcast domain. This domain is equivalent
to one network. When packets are to be passed over the broadcast domain, they must be relayed using
a router.
The configuration which is the simplest is one with only a collision
domain.
A packet that is transmitted from PC A to DX1 also reaches PC B,
DX2, DX3, and DX4. PC B cannot transmit packets to any of the
DXs during this period.
Because MAC address filtering is carried out by the switch, PC B is
able to transmit packets to DX3 or DX4, while PC A is transmitting
packets to DX1. (Since DX1 and DX2 are in the same collision
domain, PC B cannot transmit packets to DX2.)
A router relays the packets (routing) according to the network
address.
DX3
HUB
DX4
DX
1
HUB
DX2
A
B
HUB
DX
1
HUB
DX2
Switch
A
B
HUB
DX3
HUB
DX4
DX
1
HUB
DX2
Router
DX3
HUB
DX4
A
B
HUB
Collision Domain
Broadcast Domain