# tcpdump -ni en0 port 80 -w output.trace
# tcptrace -G output.trace
# xplot *tput.xpl


From the online manpage:

• Yellow: instantaneous packets
• Red: Throughput for the last few packets
• Blue: Throughput since the start of the stream/connection

Other useful graphs:

• _owin.xpl – outstanding data/congestion
• _rtt.xpl – round trip time/time
• _ssize.xpl – segment size/time
• _tput.xpl – throughput/time
• _tsg.xpl – time sequence graph
• _tline.xpl – Timeline graph – W Richard Stevens style

Just some notes here so I don’t forget the basics – manual over at here.