Network Topology

A network topology refers to the layout of the computers and devices in a communications network. The popular topologies are bus, ring and star.

1) Bus Network
All computers and devices connect to central cable or bus.

Advantages:

• Easy to connect a computer or peripheral to a linear bus
• Requires less cable length than a star topology
• Works well for small networks.

Disadvantages:

• Entire network shuts down if there is a break in the main cable
• Terminators are required at both ends of the backbone cable
• Difficult to identify the problem if the entire network shuts down
• It is slow when more devices are added into the network

2) Ring Network
Cable forms closed ring, or loop, with all computers and devices arranged along ring.
Data travels from device to device around entire ring, in one direction.

Advantages:

• Very orderly network where every device has access to the token and the opportunity to transmit
• Performs better than a bus topology under heavy network load
• Does not require a central node to manage the connectivity between the computers

Disadvantages:

• Moving, adding and changing the devices can affect the network
• Communication delay is directly proportional to number of nodes in the network
• Bandwidth is shared on all links between devices

3) Star Network
In a star network devices are connected to a central computer, called a hub.
Nodes communicate across the network by passing data through the hub.

Advantages:

• Better performance because star topology prevents the passing of data packets through an excessive number of nodes.
• No disruptions to the network when connecting or removing devices.

Disadvantages:

• Reliance on central device: star topology relies on the central device (the switch, hub or computer). This device is a single point of failure -- if this device fails, the whole network will fail in turn.
• Higher costs: the need for a central device increases costs compared to the bus and ring topologies. The star topology also requires more cable when using Ethernet cables than ring and bus topologies.
• Limited capacity for nodes: as this type of network needs all connections to go through a central device the amount of nodes in a network is limited by this factor whereas bus and ring topologies are not limited in such a way.

4) Mesh Network
In a mesh network, devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network.

There are two types of mesh topologies:

Full mesh topology
Occurs when every node has a circuit connecting it to every other node in a network. Full mesh is very expensive to implement but yields the greatest amount of redundancy, so in the event that one of those nodes fails, network traffic can be directed to any of the other nodes. Full mesh is usually reserved for backbone networks.

Partial mesh topology
Less expensive to implement and yields less redundancy than full mesh topology. With partial mesh, some nodes are organized in a full mesh scheme but others are only connected to one or two in the network. Partial mesh topology is commonly found in peripheral networks connected to a full meshed backbone.

5) Tree Topology
This is a "hybrid" topology that combines characteristics of linear bus and star topologies. In a tree network, groups of star-configured networks are connected to a linear bus backbone cable.

Advantages

• A Tree topology is a good choice for large computer networks as the tree topology "divides" the whole network into parts that are more easily manageable.

Disadvantages

• The entire network depends on a central hub and a failure of the central hub can cripple the whole network.

Eric Ling Kaiyue 1001437025