TCP packets generated by one of the one-way TCP agents and destined for a TCP sink agent passing over a traced link (see section 21) will generate a trace file lines of the form:
+ 0.94176 2 3 tcp 1000 ------ 0 0.0 3.0 25 40 + 0.94276 2 3 tcp 1000 ------ 0 0.0 3.0 26 41 d 0.94276 2 3 tcp 1000 ------ 0 0.0 3.0 26 41 + 0.95072 2 0 ack 40 ------ 0 3.0 0.0 14 29 - 0.95072 2 0 ack 40 ------ 0 3.0 0.0 14 29 - 0.95176 2 3 tcp 1000 ------ 0 0.0 3.0 21 36 + 0.95176 2 3 tcp 1000 ------ 0 0.0 3.0 27 42The exact format of this trace file is given in section 21.4. When tracing TCP, packets of type tcp or ack are relevant. Their type, size, sequence number (ack number for ack packets), and arrival/depart/drop time are given by field positions 5, 6, 11, and 2, respectively. The + indicates a packet arrival, d a drop, and - a departure. A number of scripts process this file to produce graphical output or statistical summaries (see, for example, test-suite.tcl, the finish procedure.