ns 2.35 柯志亨书-实验3笔记-TCP UDP模拟

上图是笔记

下面是tcl代码：

#Create a simulator object
set ns [new Simulator]

#Set different color for dif flow
$ns color 1 Blue
$ns color 2 Red

set tracefd [open example1.tr w]
$ns trace-all $tracefd
set namtracefd [open example1.nam w]
$ns namtrace-all $namtracefd

proc finish {} {
		global ns tracefd namtracefd
		$ns flush-trace
		close $tracefd
		close $namtracefd
		exec nam example1.nam &
		exit 0
}

# Set nodes, s1's id is 0, s2'id is 1
set s1 [$ns node]
set s2 [$ns node]

# Set router node, id of r is 2
set r [$ns node]
# Set dest node, id of r is 3
set d [$ns node]

# Set link parameters
$ns duplex-link $s1 $r 2Mb   10ms DropTail
$ns duplex-link $s2 $r 2Mb   10ms DropTail
$ns duplex-link $r  $d 1.7Mb 20ms DropTail

# Set Queue limit 10 for r and d
$ns queue-limit $r $d 10

# Set Node pos for NAM
$ns duplex-link-op $s1 $r orient right-down
$ns duplex-link-op $s2 $r orient right-up
$ns duplex-link-op $r  $d orient right

# Observe the change of queue between r and d for NAM
$ns duplex-link-op $r $d queuePos 0.5

# Setup TCP agent and FTP traffic
set tcp [new Agent/TCP]
$ns attach-agent $s1 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $d $sink
$ns connect $tcp $sink

# In NAM, TCP will diplay in Blue
$tcp set fid_ 1

set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ftp set type_ FTP


# Setup a UDP Agent and CBR Traffic
set udp [new Agent/UDP]
$ns attach-agent $s2 $udp
set null [new Agent/Null]
$ns attach-agent $d $null
$ns connect $udp $null

$udp set fid_ 2

set cbr [new Application/Traffic/CBR]
$cbr attach-agent $udp
$cbr set type_ CBR
$cbr set packetSize_ 1000
$cbr set rate_ 1mb
$cbr set random_ false


# Setup time line
$ns at 0.1 "$cbr start"
$ns at 1.0 "$ftp start"
$ns at 4.0 "$ftp stop"
$ns at 4.5 "$cbr stop"

$ns at 5.0 "finish"

$ns run

运行tcl后，会生成.tr文件，利用awk分析.tr文件，awk代码如下，计算cbr_delay的awk：

# Measure the end to end delay by the trace file

BEGIN{
	# program initialize
	highest_packet_id = 0;
}

{
	# awk会自动循环执行这个{}
	action = $1;
	time = $2;
	from = $3;
	to = $4;
	type = $5;
	pktsize = $6;
	flow_id = $8;
	src = $9;
	dst = $10;
	seq_no = $11;
	packet_id = $12;

	# Record the current max packet ID
	if ( packet_id > highest_packet_id )
		highest_packet_id = packet_id;

	# Record the tx time of packet
	if ( start_time[packet_id] == 0 )
		start_time[packet_id] = time;

	# Record CBR flow_id=2 rx time
	# 这里既要判断flow=2，没有drop，还要判断recv
	# drop是必须的，因为有可能1-2 recv，2-3 drop了
	# CBR 路径是1-2-3，整条路径上都有可能drop
	if ( flow_id == 2 && action != "d" )
	{
		if (action == "r")
		{
			end_time[packet_id] = time;
		}
	}
	else
		end_time[packet_id] = -1;
}

END {
# When read over, start to calculate
	for ( packet_id=0; packet_id<=highest_packet_id; packet_id++ )
	{
		start = start_time[packet_id];
		end = end_time[packet_id];
		duration = start-end;
		if (start<end)
			printf("%f %f\n", start, duration);
	}
}

执行awk的shell文件如下：

#!/bin/bash

awk -f cbr_delay.awk example1.tr > cbr_delay

执行gnuplot绘图的shell文件如下：

#!/bin/bash

gnuplot -persist<<EOF

set terminal gif
set output "cbr_delay.gif"
set title "cbr_delay"
set xlabel "simulation time"
set ylabel "throughput/kbps"
unset key

plot "cbr_delay" with linespoints

EOF

上面那个

-persist<<EOF

能够阻止gnuplot弹出一堆东西，具体原因没有找到，找到了gnuplot的手册，但没看明白persist的意思？手册解释如下：

To give gnuplot commands directly in the command line, using the "-persist" option so that the plot remains
on the screen afterwards:
gnuplot -persist -e "set title ’Sine curve’; plot sin(x)"

加persist之后，可以不用弹出一堆信息，即不会进入gnuplot的session

后面的<<EOF也不太清楚是什么意思？

cbr delay的图形