## 3.4 Topology     continued...

Another common topology is a planar (2D) mesh, shown in Figure 13. This network is basically a matrix

Figure 13: Mesh Topologies.

of nodes, each with connections to its nearest neighbors. Meshes usually have ``wraparound'' connections, e.g. the node at the top of the grid has an ``up'' link that connects to the node at the bottom of the grid. If you visualize only north-south links in a rectangular mesh, you can see these links turn the 2D mesh into a 3D cylinder. Now if the east-west links are added, it connects the ends of the cylinder to form a toroidal solid. Thus a mesh topology with wraparound connections is often referred to as a torus. In many systems the wraparound connections are skewed by one or more rows (or columns, or both); in this case the topology is known as a twisted torus. Note that a path that starts in the northwest corner of a twisted torus and heads continually east will visit every node exactly once before returning to the northwest corner.