An example visualization of Internet topology produced by Walrus:

Source: Courtesy of Young Hyun, CAIDA

The image above is a screengrab of a Walrus visualization of a huge graph. The graph data in this particular example depicts Internet topology, as measured by CAIDA's skitter monitor [3] based in London, showing 535,000-odd Internet nodes and over 600,000 links. The nodes, represented by the yellow dots, are a large sample of computers from across the whole range of Internet addresses.

Walrus is an interactive visualization tool that allows the analyst to view massive graphs from any position. The graph is projected inside a 3D sphere using a special kind of space based hyperbolic geometry. This is a non-Euclidean space, which has useful distorting properties of making elements at the center of the display much larger than those on the periphery. You interact with the graph in Walrus by selecting a node of interest, which is smoothly moved into the center of the display, and that region of the graph becomes greatly enlarged, enabling you to focus on the fine detail. Yet the rest of the graph remains visible, providing valuable context of the overall structure. (There are some animations available on the website showing Walrus graphs being moved, which give some sense of what this is like.) Hyperbolic space projection is commonly know as “focus+context” in the field of information visualization and has been used to display all kinds of data that can be represented as large graphs in either two and three dimensions [4]. It can be thought of as a moveable fish-eye lens. The Walrus visualization tool draws much from the hyperbolic research by Tamara Munzner [5] as part of her PhD at Stanford. (Map of the Month examined some of Munzner's work from 1996 in an earlier article, Internet Arcs Around The Globe.)