The SP-2 interconnection network is composed of a set of frames,
each consisting of 8 
crossbars , with bi-directional ports,
connected in some regular way.
In our network module, each frame is modeled by a C-structure,
called a frame structure.
Embedded within this frame structure is an array of
crossbar structures, each of which corresponds to one of the
eight crossbars on a frame.
The crossbar structure contains several fields,
some of which are worth noting. There is a 3-tuple,
which identifies
each switch. Also, there are arrays of in port and
outport types, which correspond to the bi-directional ports
of the crossbar. Of importance is the outport type.
This structure contains the ports status bits and the
service time, which is used to simulate packet delays.
Lastly, there is a FIFO queue on each frame structure, one for each output port, on which blocked packets get queued when an output port is busy. Using structures to represent the major building blocks of the interconnection network lends itself to easy initialization and manipulation.
The SP-2 does not use canonical wormhole [3] routing. It buffers the worms in the network on a central queue in the incident switch. In our implementation, we decided to make it simple to get something working. Thus, we simulate canonical wormhole routing. That is, if a worm is blocked on an output port, all of the switches that it may have traversed before blocking are marked as busy, possibly leading to severe contention in the network. Performance is sacrificed for simplicity.