What is Topology?
Network topology is the arrangement of the various elements
(links, nodes, etc.) of a computer.
There are two basic categories of network topologies.
1 Physical topologies-The physical topology of a network refers
to the configuration of cables, computers, and other peripherals.
2 Logical topologies- Is the method used to pass information
Main Types of Physical Topologies
Tree (Expanded Star).
Linear Bus Topology..
A linear bus topology consists of a main run of cable with a terminator at each end .
All nodes (file server, workstations, and peripherals) are connected to the linear
Entire network shuts down if there is a break in the main
Terminators are required at both ends of the backbone
Difficult to identify the problem if the entire network shuts
Easy to connect a computer or peripheral to a linear
Requires less cable length than a star topology.
Works well for smaller networks.
A star topology is designed with each node (file server, workstations, and
peripherals) connected directly to a central network hub, switch, or
Data on a star network passes through the hub, switch, or concentrator
before continuing to its destination.
The hub, switch, or concentrator manages and controls all functions of the
Advantages of a Star Topology
Easy to install and wire.
No disruptions to the network when connecting or removing devices.
Easy to detect faults and to remove parts
Disadvantages of a Star Topology
Requires more cable length than a linear bus topology.
If the hub, switch, or concentrator fails, nodes attached are disabled.
More expensive than linear bus topologies because of the cost of the hubs,
Tree or Expanded Star
A 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.
Advantages of a Tree Topology
Point-to-point wiring for individual segments.
Supported by several hardware and software venders.
Disadvantages of a Tree Topology
Overall length of each segment is limited by the type of cabling used.
If the backbone line breaks, the entire segment goes down.
More difficult to configure and wire than other topologies.
A network topology that is set up in a circular fashion in which data travels
around the ring in one direction and each device on the right acts as a
repeater to keep the signal strong as it travels.
Each device incorporates a receiver for the incoming signal and a
transmitter to send the data on to the next device in the ring.
Data packets travel at great speed
Easier to fault find.
Requires more cable than bus.
A break in the ring will bring it down
some or all of the devices are connected to more than one other device.
A fully connected mesh topology is one in which every device is
connected to every other device. This makes it possible for one device to
send data to all other devices simultaneously. This is usually considered too
complex and costly for large networks.
Improve fault tolerance.
Can carry more data.
Difficult to manage.
Difficult to trouble shoot
Why multiple topologies?
Each has advantages and disadvantages
Ring ease synchronization; may be disabled if any cable is cut.
Star easier to manage and more robust;
requires more cables.
Bus requires fewer cables; may be disabled if cable is cut.
Industry setting on start topology as most widely used.
Factors on deciding topology
Ease of installation
Ease of fault finding and maintenance.