This is a brief description of the tests in the filetest-suite-tcp.tcl.  These tests can be run with thecommand "./test-all-tcp".ECN:The "ecn" test shows two TCPs, where one is ECN-capable and theother is not.TIMERS:The "timers" test is the first of a series of tests that test thebehavior of TCP's retransmit timers.  This test shows the retransmittimeout value when the first packet of a connection is dropped,and the backoff of the retransmit timer as a subsequent packet isdropped.  This test also shows that once the retransmit timer isbacked off, it is later un-backed.For the connection in the top row, the first packet sent by theconnection is dropped, and the retransmitted packet is itselfdropped.  The connection has a maximum window of three packets, sothe TCP sender has to wait for a retransmit timer to recover fromany packet drop.  When another packet from the top connection isdropped at time 21, the test shows that the retransmit timer is nolonger backed off.  Further, by this time the estimated averageroundtrip time is close to its true value, and the retransmit timerexpires relatively quickly.The bottom connection has an intermittent demand, constructed togive the desired behavior for the top connection.  The bottomconnection has a maximum window of five packets, and generallyrecovers from a packet drop with a Fast Retransmit.The reported statistics show the values of theretransmit timer variables "srtt_", "rttvar_", and "backoff_" for the top connection. TIMERSA:The "timersA" test shows the retransmit timer when the third packetof the top connection is dropped.  Because the top connection hasa maximum window of three packets, the TCP sender always has towait for a retransmit timer to recover from a packet drop.The behavior of the "backoff_" variable in this test requires someexplanation.  After packet 2 of the top connection is dropped, thefirst retransmit timer expires, packet 2 is retransmitted, andthe value for "backoff_" is increased to 2.  When the ACK for theretransmitted packet 2 is received, Karn's algorithm is invoked,and that ACK is not used in updating the retransmit timer variables.When packet 5 is sent, "backoff_" is increased to 2, and a largevalue is used in setting the retransmit timer.  When the ACK forpacket 5 is received, "backoff_" is reset to 1, so the retransmittimer is no longer backed off.  When the outstanding retransmittimer expires (because packet 6 is outstanding), packet 6 istransmitted, "backoff_" is again increased to 2, and a backed-offretransmit timer is again set.TIMERS1, TIMERS2, and TIMERS3:The test "timers1" uses the default value in the simulator of 0.1seconds for "tcpTick_", the TCP clock granularity.  "Timers2" uses"tcpTick_" set to 0.5 seconds, and "timers3" uses "tcpTick_" setto 0.001 seconds.  These tests use Reno TCP, and in each test thesecond packet dropped has to wait for a retransmit timer to expirebefore it is retransmitted.TIMERS4 and TIMERS5:This test shows that the estimated round-trip time for the retransmittimers is updated once a roundtrip time, and not once for everyarriving ACK packet.There are no packets dropped in either of these two tests.  Thetwo connection differ only in their maximum window.  The reportedvalues for "srtt_" show that the value for "srtt_" converges at asimilar fashion for the two connections, even though the rate ofarriving ACK packets is very different in the two connections.STATS1:This test shows some of the available statistics.At time 10.0, for each connection the statistics show the number of packets sent by the sender (in packets and in bytes), the number of ACK packets received by the sender,the number of retransmitted packets (in packets and in bytes), and the number of retransmit timeouts.