[755-1] Priority bit

[Konstantinos Dovrolis <dovrolis@cs.wisc.edu>]

Folks

We decided with Prof.Wood that the priority bit stuff
can be optional for the 3-people groups. For the 4-people
groups, you can either implement the priority bit 
specification, or focus on higher performance using
dynamic circuit structures.

Regarding the 2DRR (2-dimensional round-robin) scheduler
that we discussed on Friday: I think that the
extension to two priorities is relatively simple. 
We have two tables, one for each priority level.
Normally, we apply the algorithm to the table for the
high-priority packets. At each cycle that we do so,
we check if there are also any low-priority packets
that can fill-in the empty slots of the diagonal that
we chose from the high-priority table. If the high-priority
table is totally empty, we apply the 2DRR algoirthm to
the low-priority table. If you want us to discuss this
further please let me know.

Of course the bookkeeping for the two priorities will
be significantly more, which is why we decided to make the priority
bit a "dessert" rather than part of the main dish..

C.