Types by Topology

Bus

Every end system will receive any signal that is sent on the main or backbone medium. The medium can be guided or unguided.

Limitations

• A break in the cable will disrupt the entire network.

• Only one system can transmit at a time.

Ring

In this topology, end systems communicate with each other through each other. So the message travels along the ring passing each system until the target system itself is reached. Theoretically, $n/2$ systems can be transmitting to their adjacent neighbor at the same time.

Limitations

• The basic ring topology is unidirectional so $n -1$ end systems would have to transfer messages for end system #1 to talk to end system #n

• A break in the cable will disrupt the entire network.

Star

All end systems talk to each other through one central device such as a router or switch. Routers and switches are discussed in-depth in the data link layer chapter!

Limitations

• Hosts can all be transmitting at the same time. However, if the central device fails, the network is completely down.

Tree

This topology is also known as the star-bus topology. It essentially consists of a bunch of star networks connected together with a large bus.

Mesh

In this topology, every end system is directly connected to every other end system.

Limitations

The mesh topology (if physically realized as a mesh):

• Is expensive
• Hard to scale
• Used in specialized applications only

Quick Quiz!

Starting in the next lesson, we’ll learn about how the working of the Internet is organized into conceptual layers.