$6 ~ /^ack/ && $5 !~ /[SFR]/ {
# given a tcpdump ftp trace, output one line for each ack
# in the form
#
# where is the time packet was acked (in seconds with
# zero at time of first packet) and is the tcp sequence
# number of the ack divided by 1024 (i.e., Kbytes acked).
#
# 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
printf "%7.2f\t%g\n", tim-tzero, $7/1024
}