This agent is based on the Reno TCP agent, but which modifies the
action taken when receiving new ACKS.
In order to exit fast recovery, the sender must receive an ACK for the
highest sequence number sent.
Thus, new ``partial ACKs'' (those which represent new ACKs but do not
represent an ACK for all outstanding data) do not deflate the window
(and possibly lead to a stall, characteristic of Reno).