The MetaRouter Concept

  • Topology: Our topology is based on group theory. It reduces the number of rows needed to achieve complete connectivity. A Banyan or Butterfly network requires log 2 N rows to achieve complete connectivity. Our topology achieves complete connectivity in log X N rows, where x is half of the fanout of a switching module. This difference in topology reduces the hardware needed to build a multi-stage switching network by more than a factor of 2.

    We call this topology a Galois Network, named after the French mathematician, Évariste Galois. This was easier than constantly referring to the network as a "blocking compensated cyclic group networks."

  • Routing Algorithm: Our destination-based routing algorithm is similar to that used by the Internet. Each switching module uses its own table to determine how a packet is routed. Our routing algorithm requires more hardware than the routing algorithm used by a Banyan or Butterfly network. It also requires global network information to update the tables. However, our routing algorithm can handle a wider range of topologies; exploit external network redundancy; and tolerate more faults in the network.

  • Switching Module: Our switching module consists of buffers, a crossbar, and decision logic which analyzes the packet header, looks up the destination address in a table, and schedules the crossbar.

    We noticed that the functionality of our switching module was similar to that of an off-the-shelf IP router. We then realized that we could avoid having to develop custom hardware via a judicious choice of module interfaces and algorithms. This can be accomplished by:

    • using an IP bit stream format between the modules instead of a proprietary format;

    • using PPP (point-to-point protocol) for flow control instead of a proprietary hardware handshake; and

    • using IP routing between modules instead of a proprietary routing algorithm.

In perspective, any terabit router can be deconstructed into "Cisco" equivalents. This follows from the fact that they are all based on multi-stage switching networks. The only real differences are in the topology, the routing algorithm, and the packaging. In retrospect, it is difficult to construct a proprietary hardware position on top of an open standard such as TCP/IP. (IBM discovered this with their PC.)

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