Tree Topology; Rule - WAGO 750 Series Manual

130 • ETHERNET
Network Architecture – Principles and Regulations

Tree Topology

The tree topology combines characteristics of linear bus and star topologies.
It consists of groups of star-configured workstations connected to a linear bus
backbone cable. Tree topologies allow for the expansion of an existing
network, and enables schools, etc. to configure a network to meet their needs.
Fig. 5-5: Tree Topology

5-4-3 Rule

A consideration in setting up a tree topology using ETHERNET protocol is
the
5-4-3 rule. One aspect of the ETHERNET protocol requires that a signal sent
out on the network cable must reach every part of the network within a
specified length of time. Each concentrator or repeater that a signal goes
through adds a small amount of time. This leads to the rule that between any
two nodes on the network there can only be a maximum of 5 segments
connected through 4 repeators/concentrators. In addition, only 3 of the
segments may be populated (trunk) segments if they are made of coaxial
cable. A populated segment is one that has one or more nodes attached to it. In
Figure 5-5, the 5-4-3 rule is adhered to. The furthest two nodes on the network
have 4 segments and 3 repeators/concentrators between them.
This rule does not apply to other network protocols or ETHERNET networks
where all fiber optic cabling or a combination of a backbone with UTP cabling
is used. If there is a combination of fiber optic backbone and UTP cabling, the
rule is simply translated to 7-6-5 rule.
G012904e
WAGO-I/O-SYSTEM 750
ETHERNET TCP/IP