Network Topology Summary

I received a comment on my last blog entry that made me realize that perhaps I needed to start on a more basic level. Rather than identifying the benefits and shortcomings of a particular wireless mesh solution, I need to identify what the issues are for community wireless networks.

The issue that sparked the comment is a question of network topology. Before you completely zone out, give me a paragraph to explain topology. It's pretty easy to explain, I think, and then we can address further issues.

Computer networks are about creating connections between various locations. Locations, whether they are computers or geographic locations, are often referred to as nodes. The way that nodes are connected to one another is the network topology. Diagrams that indicate the ways that the locations are referred to as topologies. Take a look at Diagram 1. I've diagramed three network topologies, each having its own unique characteristics.

Diagram 1

What is important in this discussion is the ramifications of each topology. Networks that use the bus topology (left) are very vulnerable to failure. A break in the line may halt all communication on the network. The star topology (center) is less vulnerable to a single break in the network, as a break in one line only cuts off one node. The drawback is that the network is completely dependent on the central node, which may fail or reach its capacity. The mesh network (right) is the most fault-tolerant, as a break in any one line doesn't mean that the connection to any node is lost. Unfortunately, it is also the most expensive, or at least it is the most expensive solution for wired networks. For more information about the various topologies, take a look at Wikipedia.

Wireless Networks

Wireless networks almost always use one of these three topologies, but the language is sometimes different. Wireless bus topologies are often called point-to-point. Star topologies in wireless networks are usually referred to as point-to-multipoint. Mesh, fortunately, is still mesh.

For wireless networks, meshing does not have the high overhead that it does for wired networks. If one combines the fault-tolerance of a mesh network and with cost-effectiveness, one can easily appreciate why community networks that are interested in wireless are excited about mesh.

In a follow-up post, I hope to outline the wireless solutions that are aimed at community networks. For now, this should suffice to explain the basics of network topology.

Comment from Kevin Bulger on March 26, 2007 - 10:38am

How do you build a wireless mesh topology? Is Meraki the only way or are there other options? What are the costs and benefits of each?

Comment from Ross Musselman on May 11, 2007 - 12:22pm

Kevin,

There are other ways. CUWiN has a solution. There is a project through Rice University that is developing what I understand to be a wireless mesh system, although I am frankly less familiar with that project than I ought to be.

Hope this helps.

Ross Musselman rgmussel@cuwireless.net