5.2 Scaling to 3D
Mesh-of-Torus network can also be extended to 3D fields for the construction of 3D Mesh-of-Torus network data center. Each plane of the 3D Mesh-of-Torus network data center is composed of 2D Mesh-of-Torus network, and 3D network will inherit the classification and network configuration mechanisms of 2D network. And each node in 2D Mesh-of-Torus network are able to communicate with nodes in the other planes. The node degree in 4*4 torus network is unequal when forming a 2D Mesh-of-Torus network, so we will utilize those nodes as the communication path during the extension to 3D to balance the node degree in the whole network. Specifically, as shown in Figure 5, the node degree for four vertices in torus network is 6 and that for other edge nodes is 5, but the node degree for nodes inside the torus network is 4.
Node in this network can be represented in a coordinate (F, S, T, H). And F, S, T represent for the node hierarchical number in the plane, while H for the plane H the node located in. When extending 2D network to 3D fields, we choose to connect only four nodes inside the network with nodes in another plane respectively instead of connecting all the nodes inside in a plane with nodes in another plane.
The routing process for packets in the 3D Mesh-of-Torus network consists of three steps:
1) For packets routing in the plane where source node is located, if they are in the plane where the source node is in, they will find out the same coordinate of node Dtemp firstly, and then route packets to their corresponding intermediate nodes that are closest to Dtemp in the smallest subnet. Figure 6. Defines four intermediate nodes and divide the whole network into several small areas according to the location of the nodes in the net. So, nodes belong to the same area have the same corresponding intermediate nodes. Packets have to be routed to their corresponding intermediate node before routing to another plane.
2) For packets routing in the third dimension, the point-to-point path will be applied and each intermediate node will store the path and calculate the corresponding output ports for arrived packets. After these processes, it will guide packets to those ports.
3) For packets routing in the plane where destination node located in, packets will go to the corresponding intermediate nodes in the destination plane after passing through the point-to-point path. And from those intermediate nodes, they will continue to route to the destination nodes. Figure 7 lists multiple routing directions from intermediate nodes to other nodes in a 4×4 torus network.