The physical features, such as shapes, surfaces and patterns, are collectively called the topography. The description of how these features relate to each other is called the topology.
This page explains the difference between the LIC topology and the topography. Basically, if you want to cut the crap, use a topology diagram. If you want to tell it like it is, use a topography diagram.
We are moving away from the theory and towards the physical features. The topography is the map of the landscape. There are many diagrams and photos of the topographical features of the LIC in these pages.
The bad news is the more real the picture the less useful it is at describing what it is for. Looking at a computer gives no clue about what it is working on. A topology diagram is much better at showing the ideas behind a system.
The three diagrams below are topology diagrams of a big, clever and complicated network. Each successive diagram shows increasing amounts of physical detail: each one is closer to the topography. The more detail I add the more the diagram looks like the view I get from standing by a rack full of computers and the less clear and helpful it is.
The rack page shows a topography diagram full of computers.
|LIC topology: towards a topography|
|1. DMZs, PCs and cables||2. DMZs, PCs, cables and ethernet switches||3. PCs, cables and VLAN switches - part topology, part topography|
|Figure 1 shows a dozen computers in a complex arrangement. You can get information from this picture. For example, you can get an idea of what each IBM PC does by looking at which DMZ it is in. It leaves out many details like the ethernet switches used to connect everything together.||Figure 2 shows ethernet switches and computers. One set of computers in a DMZ is a LAN. To make the LAN work you need an ethernet switch: three LANs means three switches. What if this setup uses only one big switch that pretends to be three little ones? This is a common setup but you can't see that kind of thing in this diagram.||Figure 3 shows something approaching reality. You can no longer tell which computer is which because the dozen PCs are now stacked up and the ethernet switches have all been replaced by one big switch.|