Overview
6
In this case there are two clusters. The first contains nodes 1 and 2, and
the second contains nodes 3 and 4. Within each cluster, the traffic levels
are around 13000 frames per second, while the traffic between the groups
is around 4000 per second. A bridge could be placed between nodes 2 and
3. Note that placing a bridge between nodes and 2 in this case would
make the overall performance worse, because the traffic between these
two stations (130(0 frames/sec) is higher than the throughput of most
bridges.
As the network becomes larger it becomes increasingly difficult to find the
group boundaries without the assistance of network analysis application
programs. Some network installers can provide a network analysis service
to help you decide where to place bridges.
Network Topology
A bridged network takes on one of two basic forms. The first is a cascaded
network, where a set of networks are connected together by a series of
bridges. An example of this configuration is given in Figure 6. A cascaded
network is useful when a small number of bridges is being used. If many
bridges are used, the delay associ ated with each bridge may accumulate
to unacceptable levels between networks at the extremities.
The second form used is a tree topology. The simplest form of a tree
topology is one level deep and is known as a backbone network. Figure 7
shows this type of network. ln a backbone network, each Work Group has
its own network, and there is one network used only for communicating
between the Work Groups. The advantages of a tree network far outway
the need for an additional network, and are listed below:
1.
There is never more than two bridges between any two networks. The
delays introduced by bridges are therefore minimized.
From
To
Frames/Second (Average)
1
2
9000
1
2
1000
1
4
1000
2
3
1000
2
4
1000
3
4
9000
Table 2: Traffic Between Nodes
Figure 6: A Cascaded Bridged
Network
