Output Port Blocking

The probability of a Butterfly switching module not blocking is 1/2.  A 16 input Butterfly multi-stage network requires 4 levels.  The overall non-blocking probability is thus (1/2)⁴ = 0.0625, or 6.25%

The probability of a 12 port MetaRouter switching module requires 3 levels.  The overall non-blocking probability is thus (5/6)³ = 0.578, or 57.8%.

The non-blocking probability for a 532 port MetaRouter is 0.57 while the non-blocking probability for a 512 port Banyan or Butterfly Network is 0.0037.  The probability that a packet will traverse a 532 port MetaRouter without collision is more than 2 orders of a magnitude larger than the probability that a packet will traverse a 512 port Banyan or Butterfly.  The larger the non-blocking probability, the larger the effective isochronous bandwidth.

Output blocking also affects the topology of the Internet.  Currently the Internet is designed to maximize the connectivity rather the end-to-end bandwidth.  The effective bandwidth of the Internet goes down exponentially with the number of hops.

The current backbone architecture minimizes the number of links and not the number of hops. The push to handle voice and video traffic will forces the Internet to evolve from a backbone to a fully connected topology.

The fiber network will physically remain a backbone, however a virtual fully connected network will be constructed out of wavelength division multiplexed channels and digital access crossconnects.