[comm] Throughput on a lossy link

[James Robnett]

   I don't think his math is quite correct.  It assumes 1 to 1 ack
correspondence and doesn't take into account larger windows
sizes and whether selective acks are enabled (tcp_sack).

   Certainly packet loss is murder but I don't think it explains
the entire problem.  We're clearly suffering packet loss here but
once that's solved I think we'll still have other issues.  Our
loss doesn't explain the slow rate from CV to UNM for instance.

   We're doing more tests now but I think we're just tackling the first
of many problems.

james