Test ecn:
This is a simple test of two flows with ECN.

#######################################################################
# Tahoe Tests #
#######################################################################

The first set of tests explores various scenarios 
representing a single instance of congestion, with either a
single ECN, a single packet drop, or various combinations of ECN
and packet drops.  Because these events occur in one window of data,
they are interpreted by the sender as a single instance of
congestion, and result only in a single reduction on the
congestion window.  All six of the following tests show
a connection that cuts its congestion window in half, sometimes
with a preceeding slow-start.

ecn_nodrop_tahoe: A single ECN.
ecn_twoecn_tahoe: ECN followed by another ECN
ecn_drop_tahoe: ECN followed by a Fast Retransmit. 
ecn_drop1_tahoe: A Fast Retransmit where the second duplicate 
  acknowledgement carries an ECN-echo. 
ecn_drop2_tahoe: A Fast Retransmit followed by a duplicate acknowledgement
  carrying ECN-echo.
ecn_noecn_tahoe: A Fast Retransmit, no ECN.

The second set of tests all illustrate a burst of packet drops.
The first two tests (Fast Retransmit with and without ECN) show
the same performance.  

ecn_bursty_tahoe: A Fast Retransmit.
ecn_burstyEcn_tahoe: ECN followed by a Fast Retransmit.

The third test illustrates the pathologies
that can occur without "bugFix_".

ecn_noBugfix_tahoe: The Fast Retransmit without bugFix_

The following set of tests show that performance is not
worsened if a packet gets its ECN bit set rather than being
dropped at the router.  These scenarios illustrate a retransmit 
timeout.

ecn_timeout2_tahoe: A Retransmit Timeout.
ecn_timeout_tahoe: ECN followed by a Retransmit Timeout.  (The first 
  packet has the ECN bit set rather than being dropped.)
ecn_timeout3_tahoe: A Retransmit Timeout with an ECN in the middle
  of the dropped packets.  (The second packet has the ECN bit set
  rather than being dropped.)

This test shows that an ECN on a packet sent after a
Retransmit Timeout in properly interpreted as an instance
of new congestion.

ecn_timeout1_tahoe: ECN followed by a Retransmit Timeout, followed
  by an ECN representing a new instance of congestion.

#######################################################################
# Reno Tests #
#######################################################################

The following tests are similar to the Tahoe tests:
ecn_nodrop_reno, ecn_twoecn_reno, ecn_drop_reno,
ecn_drop1_reno, and ecn_noecn_reno. 

ecn_bursty_reno: A Fast Retransmit followed by a Retransmit Timeout. 
  Ssthresh is reduced twice, once for each event.
ecn_burstyEcn_reno: An ECN followed by a Fast Retransmit followed by a
  Retransmit Timeout.

ecn_noBugfix_reno: This shows the unnecessary Fast Retransmit from
  the absence of Bugfix_.

ecn_timeout_reno: An ECN followed by a Retransmit Timeout. 
ecn_timeout1_reno: ECN followed by a Retransmit Timeout, followed
  by an ECN representing a new instance of congestion.

#######################################################################
# Sack Tests #
#######################################################################

The following tests are similar to the Tahoe tests:  ecn_nodrop_sack,
ecn_twoecn_sack, ecn_drop_sack, ecn_drop1_sack, ecn_noecn_sack.

ecn_bursty_sack: A Fast Retransmit followed by a Retransmit Timeout.  
  The sender doesn't send a new packet when it receives the ACK for the
  retransmitted packet because "pipe_" indicates that it still
  has too many outstanding packets.
ecn_burstyEcn_sack: An ECN followed by a Fast Retransmit.  Because
  of the ECN, the sender has fewer packets in flight when the
  three dup acks arrive.
ecn_burstyEcn1_sack: An ECN followed by a Fast Retransmit, followed
  by a Retransmit Timeout.  This test has two more packets dropped 
  that "ecn_burstyEcn_sack".

ecn_noBugfix_sack: This shows the unnecessary Fast Retransmit from
  the absence of Bugfix_.

ecn_timeout_sack: An ECN followed by a Retransmit Timeout.
ecn_timeout1_sack: ECN followed by a Retransmit Timeout, followed
  by an ECN representing a new instance of congestion.
ecn_fourdrops_sack: ECN followed by four interspersed packet drops.

#######################################################################
# Other Tests #
#######################################################################
ecn1