Part 5: Local Area Network Topologies

Bus

Connects each node in a line - cable runs from one PC to the next and from there to the next, etc.

Actually there are two variations of the Bus topology:

• In small networks, cable is run from one NIC to the next on each node - the "Tee" is attached to the NIC.
• In larger networks, a single bus, or backbone cable runs through an entire building and the nodes are cabled to a BNC connector on a wall plate - the "Tee" is behind the wall plate.

The Bus topology's disadvantage is that a break in the backbone takes down the entire network, although the malfunctioning of a single node does not affect the network as long as the integrity of the cable is maintained.

Star or Hub

Connects all nodes to a centralized hub. Most popular topology for Ethernet.

If all of a hub's ports are in use then it can simply be connected to another hub.

Advantages

• Inexpensive cable (UTP)
• Offers greater flexibility in wiring than Bus
• If cable to one node breaks, the rest of the network still works

Disadvantages

• Because each node gets connected to the hub it uses a lot of cable
• Requires a hub

Ring

Although the Ring looks a lot like the Star because each node is connected to a central device, the two work very differently.

Packets are (attached to a token and) sent around the ring and examined by each node.

Difficult to maintain because just one down node breaks the chain.