$6 !~ /^ack/ && $5 !~ /[SFR]/ {
# given a tcpdump ftp trace, output one line for each send
# in the form
# <send time> <seq no>
# where <send time> is the time packet was sent (in seconds with
# zero at time of first packet) and <seq no> is the tcp sequence
# number of the packet divided by 1024 (i.e., Kbytes sent).
#
# convert time to seconds
n = split ($1,t,":")
tim = t[1]*3600 + t[2]*60 + t[3]
if (! tzero) {
tzero = tim
OFS = "\t"
}
# get packet sequence number
i = index($6,":")
printf "%7.2f\t%g\n", tim-tzero, substr($6,1,i-1)/1024
}