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简述#xff1a;建立有4个节点的拓扑#xff0c;其中一个节点作为路由器#xff0c;用来将两个节点发出的数据包转发到第四个节点上面。
在这里将解释将两个节点的数据流区分开来的方法#xff0c;展示如何去检测一个队列是否是满…下面来学习更加复杂一点的TCL脚本的编写
简述建立有4个节点的拓扑其中一个节点作为路由器用来将两个节点发出的数据包转发到第四个节点上面。
在这里将解释将两个节点的数据流区分开来的方法展示如何去检测一个队列是否是满的以及一个数据包是如何被丢弃的。
1、建立拓扑
Tcl脚本大多是大同的我们需要做的是在基础上进行自己需要的修改。基础代码如下 #Create a simulator object
set ns [new Simulator]#Open the nam trace file
set nf [open out.nam w]
$ns namtrace-all $nf#Define a finish procedure
proc finish {} {global ns nf$ns flush-trace
#Close the trace fileclose $nf
#Execute nam on the trace fileexec nam out.nam exit 0
}
# Insert your own code for topology creation
# and agent definitions, etc. here#Call the finish procedure after 5 seconds simulation time
$ns at 5.0 finish#Run the simulation
$ns run做出修改如下
① 添加四个节点 set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]② 添加链接 $ns duplex-link $n0 $n2 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
$ns duplex-link $n3 $n2 1Mb 10ms DropTail其实上面这样就可以了但是为了让它更加美观在跑nam的时候不要太懵逼我们需要变一下链接的位置使用的语句如下$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right 在改变的时候我们可以使用right, left, up, down以及这些单词的结合结合方式某-某 2、添加事件
① 设置代理——建立起两个CBR代理和一个NULL代理。CBR代理给n0和n1n0、n1用于发送数据n3用于接收数据。 #Create a UDP agent and attach it to node n0
set udp0 [new Agent/UDP]
$ns attach-agent $n0 $udp0# Create a CBR traffic source and attach it to udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0#Create a UDP agent and attach it to node n1
set udp1 [new Agent/UDP]
$ns attach-agent $n1 $udp1# Create a CBR traffic source and attach it to udp1
set cbr1 [new Application/Traffic/CBR]
$cbr1 set packetSize_ 500
$cbr1 set interval_ 0.005
$cbr1 attach-agent $udp1set null0 [new Agent/Null]
$ns attach-agent $n3 $null0 ② CBR代理和NULL代理进行连接 $ns connect $udp0 $null0
$ns connect $udp1 $null0③ 设置数据流开始的时间和结束的时间 $ns at 0.5 $cbr0 start
$ns at 1.0 $cbr1 start
$ns at 4.0 $cbr1 stop
$ns at 4.5 $cbr0 stop3、区别流
因为有俩发送端为了区别数据流的情况我们来给他们加点颜色 $udp0 set class_ 1
$udp1 set class_ 2
$ns color 1 Blue
$ns color 2 Red然后这样就udp0发出的数据流变蓝色另外一个变红色。 4、查看链接的队列
添加下面的语句来监视链接的情况 $ns duplex-link-op $n2 $n3 queuePos 0.5为了得到相对公平的情况我们可以更换使用队列
$ns duplex-link $n3 $n2 1Mb 10ms SFQ SQF随机公平排队这样最后得到的是相对公平的结果 本节完完整代码如下 #Create a simulator object
set ns [new Simulator]#Define different colors for data flows
$ns color 1 Blue
$ns color 2 Red#Open the nam trace file
set nf [open out.nam w]
$ns namtrace-all $nf#Define a finish procedure
proc finish {} {global ns nf$ns flush-trace
#Close the trace fileclose $nf
#Execute nam on the trace fileexec nam out.nam exit 0
}#Create four nodes
set n0 [$ns node]
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]#Create links between the nodes
$ns duplex-link $n0 $n2 1Mb 10ms DropTail
$ns duplex-link $n1 $n2 1Mb 10ms DropTail
$ns duplex-link $n3 $n2 1Mb 10ms SFQ$ns duplex-link-op $n0 $n2 orient right-down
$ns duplex-link-op $n1 $n2 orient right-up
$ns duplex-link-op $n2 $n3 orient right#Monitor the queue for the link between node 2 and node 3
$ns duplex-link-op $n2 $n3 queuePos 0.5#Create a UDP agent and attach it to node n0
set udp0 [new Agent/UDP]
$udp0 set class_ 1
$ns attach-agent $n0 $udp0# Create a CBR traffic source and attach it to udp0
set cbr0 [new Application/Traffic/CBR]
$cbr0 set packetSize_ 500
$cbr0 set interval_ 0.005
$cbr0 attach-agent $udp0#Create a UDP agent and attach it to node n1
set udp1 [new Agent/UDP]
$udp1 set class_ 2
$ns attach-agent $n1 $udp1# Create a CBR traffic source and attach it to udp1
set cbr1 [new Application/Traffic/CBR]
$cbr1 set packetSize_ 500
$cbr1 set interval_ 0.005
$cbr1 attach-agent $udp1#Create a Null agent (a traffic sink) and attach it to node n3
set null0 [new Agent/Null]
$ns attach-agent $n3 $null0#Connect the traffic sources with the traffic sink
$ns connect $udp0 $null0
$ns connect $udp1 $null0#Schedule events for the CBR agents
$ns at 0.5 $cbr0 start
$ns at 1.0 $cbr1 start
$ns at 4.0 $cbr1 stop
$ns at 4.5 $cbr0 stop
#Call the finish procedure after 5 seconds of simulation time
$ns at 5.0 finish#Run the simulation
$ns run
