[ns] Packet size being ignored?

[Meier, David J]

How come the below configuration still sends 1040byte packets even
though 500 is specified?

TIA!!!

#TCP Agent on tcp0
set tcp [new Agent/TCP]
$tcp set fid_ 2
set sink [new Agent/TCPSink]
$ns attach-agent $n1 $tcp
$ns attach-agent $n6 $sink
$ns connect $tcp $sink

#Move Data
set e1 [new Application/Traffic/CBR]
$e1 attach-agent $tcp
$e1 set packetSize_ 500
$e1 set interval_ 0.05
$ns at 0.5 "$e1 start"