# Setting traffic in small medium and large packets
# where we know the proportion of BYTES in packets of each size

#############################

proc maketraffic {perc size rez} {

# First parameter - percentage of traffic in packets of each size (a list)
# Second parameter - size of each of the packet types (a list)
# Third parameter - the NAME of a variable to use for a returned list

# We want to output a list of packet sized from this proc, which we
# do via the regular "return". However, we may also want to pass
# back a table of percentages for each packet size which we'll do
# via the third parameter

upvar $rez tealeaves

set ecount [llength $perc]
set totrat 0

# Work out the number of packets of each size for a megabit of data

for {set i 0} {$i < $ecount} {incr i} {
        set nprop [expr 1000000 * [lindex $perc $i] / 100. / [lindex $size $i]]
        lappend prop $nprop
        set totrat [expr $totrat + $nprop]
        }

# Work out the PROPORTION of each size of packet to get the required
# proportion of traffic

set ratiosofar 0
for {set i 0} {$i < $ecount} {incr i} {
        set nprop [expr [lindex $prop $i] / $totrat]
        set ratiosofar [expr $nprop + $ratiosofar]
        lappend ratios $ratiosofar
        lappend c 0
        }

# Use the randomiser to choose which packet to send

for {set counter 0} {$counter < 10000} {incr counter} {
        set trigger [expr rand()]
        for {set i 0} {$i < $ecount} {incr i} {
        if {$trigger < [lindex $ratios $i]} {
                set c [lreplace $c $i $i [expr 1 + [lindex $c $i]]]
                lappend stream [lindex $size $i]
                break
                }
        }
}

# Go work out how much traffic in each size of packet

set tottra 0
for {set i 0} {$i < $ecount} {incr i} {
        set thistraffic [expr [lindex $c $i] * [lindex $size $i]]
        lappend traffic $thistraffic
        set tottra [expr $tottra + $thistraffic]
        }

# And reduce that to a percentage

for {set i 0} {$i < $ecount} {incr i} {
        lappend tperc [expr 100 * [lindex $traffic $i] / $tottra ]
        }

# Use the upvar variable to return the statistics

set tealeaves $tperc

# And return the relating list of packet sizes

return $stream

}

#############################

# Seed the random number generator (default is actually
# clock seconds - we have added here explicitly to show
# how to do it)

puts [clock seconds]
expr srand([clock seconds])

# Set up some sample patterns

set cellular_pc "80 5 15"
set cellular_sz "64 576 1518"

set data_pc "30 10 60"
set data_sz $cellular_sz

set sophie_pc "60 10 7 2 6 15"
set sophie_sz "64 99 150 237 576 1518"

# Generate and test those patterns

set generate [maketraffic $cellular_pc $cellular_sz tlevs]
# puts $generate
puts $tlevs

set generate [maketraffic $cellular_pc $cellular_sz tlevs]
# puts $generate
puts $tlevs

set generate [maketraffic $data_pc $data_sz tlevs]
# puts $generate

set generate [maketraffic $sophie_pc $sophie_sz twiddle]
puts $tlevs
puts $twiddle