Hi,
I've a 2-node(static) wireless link(802.11b). The tracefile is showing me
that ACK packets being sent from node1 to node0 are being dropped(which is
OK), however, the fourth column in the tracefile is IFQ which implies that
these packets are being dropped due to the ifq. How can this be? PAckets on
the return path don't enter a queue at any point surely??? My simulation is
transferring FTP data from node0 to node1. The TCP agent is on node0 and the
sink is on node1. below is a section from my trace file. What does IFQ mean
in column 4. If (as I understand it) this means that these packets are being
dropped by the ifq, then why is there an IFQ on the return path as all the
traffic is going from node0 to node1? (My simulation script is below also).
Thanks
L
D 30.32288741 _0_ IFQ --- 15598 tcp 1084 [0
D 30.34824777 _0_ IFQ --- 15611 tcp 1084 [0
D 30.62936723 _1_ IFQ --- 15759 ack 60 [0
D 30.6869282 _1_ IFQ --- 15792 ack 60 [0
D 30.70534317 _1_ IFQ --- 15801 ack 60 [0
D 30.72629153 _1_ IFQ --- 15813 ack 60 [0
set val(chan) Channel/WirelessChannel ;# channel type
set val(prop) Propagation/TwoRayGround ;# radio-propagation
model
set val(netif) Phy/WirelessPhy ;# network interface type
set val(mac) Mac/802_11 ;# MAC type
Mac/802_11 set dataRate_ 11Mb ;# Data Rate 11
Mbps
Mac/802_11 set basicRate_ 1Mb ;# Basic Rate 1
Mbps
# Mac/802_11 set RTSThreshold_ 3000 ;# Turn off RTS
/ CTS
Mac/802_11 set SlotTime_ 0.000020 ;# 20us
Mac/802_11 set sifs_ 0.000010 ;# 10us
Mac/802_11 set PreambleLenght_ 144 ;# 144 bits
Mac/802_11 set PLCPHeaderLength_ 48 ;# 48 bits
Mac/802_11 set PLCPDataRate_ 1Mb ;# 1Mbps
set val(ifq) Queue/DropTail ;# interface queue type/PriQueue
set val(ll) LL ;# link layer type
set val(ant) Antenna/OmniAntenna ;# antenna model
set val(ifqlen) 10 ;# max packet in ifq
set val(nn) 2 ;# number of mobilenodes
set val(rp) DSDV ;# routing protocol DSDV
set ns [new Simulator]
$ns color 0 blue
$ns color 1 red
# set up topography object
set topo [new Topography]
$topo load_flatgrid 400 200
#Open the trace file
set tf [open out.tr w]
$ns trace-all $tf
#Open the nam trace file
set nf [open out.nam w]
$ns namtrace-all-wireless $nf 400 200
# Create God
create-god $val(nn)
Agent/DSDV set perup_ 15000000 ;# ~ infinite periodic update
$ns node-config -adhocRouting $val(rp) \
-llType $val(ll) \
-macType $val(mac) \
-ifqType $val(ifq) \
-ifqLen $val(ifqlen) \
-antType $val(ant) \
-propType $val(prop) \
-phyType $val(netif) \
-channelType $val(chan) \
-topoInstance $topo \
-agentTrace OFF \
-routerTrace OFF \
-macTrace ON \
-movementTrace OFF
# Create and configure nodes
set nodeA [$ns node]
$nodeA random-motion 0
$nodeA set X_ 100.0
$nodeA set Y_ 100.0
$nodeA set Z_ 0.0
set nodeB [$ns node]
$nodeB random-motion 0
$nodeB set X_ 300.0
$nodeB set Y_ 100.0
$nodeB set Z_ 0.0
$ns at 0.0 "$nodeA setdest 100.0 100.0 0.0"
$ns at 0.0 "$nodeB setdest 300.0 100.0 0.0"
# Setup TCP Connection
set tcpA [new Agent/TCP]
$ns attach-agent $nodeA $tcpA
$tcpA set packetSize_ 1024
set tcpSinkB [new Agent/TCPSink]
$ns attach-agent $nodeB $tcpSinkB
$ns connect $tcpA $tcpSinkB
# Setup FTP over TCP Connection
set ftpA [new Application/FTP]
$ftpA attach-agent $tcpA
$ftpA set type_ FTP
# Schedule simulation events
$ns at 1.0 "$ftpA start"
$ns at 31.0 "$ftpA stop"
$ns at 31.0000001 "stop"
$ns at 31.0000002 "puts \"NS EXITING...\" ; $ns halt"
proc stop {} {
global ns tf nf
$ns flush-trace
close $nf
close $tf
exit 0
}
puts "Starting Simulation..."
$ns run
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