incast.tcl

 # Basic Incast Simulation
 # Check Args
 if {$argc != 5} {
   puts "Usage: ns incast <srv_num> <adv_win-pkt> <SRU-KB> <link_buf-pkt> <seed>"
   exit 1
 }

 #################################################################
 # Argments
 # ServerNum: $argv(0)
 set svr_num [lindex $argv 0]
 # Advertised Window size (pkt): $argv(1)
 set adv_win [lindex $argv 1]
 # SRU Size (Byte) ... only Payload: $argv(2)
 set SRU [expr [lindex $argv 2] * 1024]
 # Link Buffer (pkt): $argv(3)
 set link_buf [lindex $argv 3]
 # Random Seed: $argv(4)
 set seed [lindex $argv 4]

 ################################################################
 # Variables
 # Create a simulator object
 set ns [new Simulator]

 # Bandwidth (Gbps)
 set bw_Gbps 1

 # Link Delay (us)
 set link_del_us 25
 # Maximum Random Link Delay: 0--maxrand (us)
 set maxrand_link_del_us 20

 # SYN Interval Delay (us) for each Request
 set SYN_del_us 0
 ## For Aggressive Optimization for Goodput (may cause incast)
 # set SYN_del_us [expr int(${SRU} * 8 / (${bw_Gbps} * pow(10, 9)) * pow(10, 6))]
 ## For Conservative Optimization for Goodput (never cause incast)
 # set SYN_del_us [expr int(${SRU} * 8 / (${bw_Gbps} * pow(10, 9)) * pow(10, 6)\
 #   + ${link_del_us} * 4 * (1 + \
 #   (log10( ${link_del_us} * 4 * pow(10, -6) * ${bw_Gbps} * pow(10, 9) \
 #   / (1500 * 8) ) / log10(2))))]

 # Maximum Random SYN Delay: 0--maxrand (us)
 set maxrand_SYN_del_us 0

 # Total Size of All Servers SRU with TCP/IP Header and Handshake
 set Block_trans [expr ((int($SRU / 1460) + 1)* 1500 + 40) * $svr_num]

 # Link Error Rate (Unit:pkt) 0.001 = 0.1% (a loss in 1000 pkt)
 # set err_rate 0.001
 set err_rate 0

 #############################################
 # Random Model
 set rng [new RNG]
 # seed 0 equal to current OS time (UTC)
 # so seed should be more than 1 for repeatability
 $rng seed [expr ${seed} * ${svr_num} + 1]

 #################################################################
 # Tracing Message
 puts -nonewline "Server: $svr_num, win: ${adv_win}pkt, "
 puts -nonewline "SRU: [lindex $argv 2]KB, link_buf: ${link_buf}pkt, "
 puts "Seed: $seed, "
 puts -nonewline "Block_trans: ${Block_trans}B, "
 puts -nonewline "RTT: [expr $link_del_us * 4]us, "
 puts -nonewline "RTT_rand: ${maxrand_link_del_us}us, "
 puts "SYN_del: ${SYN_del_us}-[expr $SYN_del_us + $maxrand_SYN_del_us]us"

 Agent/TCP set trace_all_oneline_ true
 Agent/TCP set packetSize_ 1460
 Agent/TCP set window_ $adv_win
 Agent/TCP set singledup_ 0 ;      # 0: Disabled Limited Transmit
 Agent/TCP set tcpTick_ 0.0000001 ;  # 100ns (default 0.01: 10ms)
 Agent/TCP set minrto_ 0.2

 #Open the ns trace file
 set nf [open out.ns w]
 $ns trace-all $nf
 set ef [open out.et w]
 $ns eventtrace-all $ef
 set tf [open out.tcp w]
 # For Queue Monitoring
 # set q_trans [open queue_trans.ns w]

 proc finish {} {
     global ns nf ef tf
     # For Queue Monitoring
     # global q_trans
     $ns flush-trace
     close $nf
     close $tf
     close $ef
     # close $q_trans
     puts "Done."
     exit 0
 }

 #Create two nodes
 set nx [$ns node]
 set nc [$ns node]
 $ns duplex-link $nx $nc ${bw_Gbps}Gb ${link_del_us}us DropTail
 $ns queue-limit $nx $nc ${link_buf}

 # Link Error Module between Switch and Client
 set loss_module [new ErrorModel]
 $loss_module unit pkt
 $loss_module set rate_ $err_rate
 set loss_random_variable [new RandomVariable/Uniform]
 $loss_random_variable use-rng ${rng}
 $loss_module ranvar ${loss_random_variable}
 $loss_module drop-target [new Agent/Null]
 $ns lossmodel $loss_module $nx $nc

 for {set i 0} {$i < $svr_num} {incr i} {
     set n_($i) [$ns node]
     $ns duplex-link $nx $n_($i) ${bw_Gbps}Gb ${link_del_us}us DropTail
     $ns queue-limit $n_($i) $nx 1000
     set tcp_($i) [new Agent/TCP/Newreno]
     $tcp_($i) set fid_ $i
     $tcp_($i) attach-trace $tf
     $tcp_($i) trace maxseq_
     $tcp_($i) trace ack_
     set ftp_($i) [new Application/FTP]
     $ftp_($i) attach-agent $tcp_($i)
     $ftp_($i) set type_ FTP
     $ns attach-agent $n_($i) $tcp_($i)
     set snk_($i) [new Agent/TCPSink]
     $ns attach-agent $nc $snk_($i)
     $ns connect $tcp_($i) $snk_($i)

     # Caluclate Delay (us)
     set del_us [expr $link_del_us * 2 + $SYN_del_us * $i \
                     + [$rng uniform 0 ${maxrand_SYN_del_us}]]

      $ns at [expr 1.0 + $del_us * 0.000001] "$ftp_($i) send $SRU"
 }
 $ns at 0.0 "debug"
 $ns at 0.99 "check_trans"
 $ns at 21.0 "finish"

 # For Queue Monitoring
 # set q_mon [$ns monitor-queue $nx $nc [open queue_mon.ns w] 0.0001]
 # [$ns link $nx $nc] queue-sample-timeout

 proc update_link_del {} {
     global ns nx n_ link_del_us maxrand_link_del_us svr_num rng
     for {set i 0} {$i < $svr_num} {incr i} {
         $ns delay $nx $n_($i) [expr $link_del_us \
                + [$rng uniform 0 ${maxrand_link_del_us}]]us duplex
     }
 }

 proc check_trans {} {
     global ns Block_trans svr_num snk_
     # 0.0001 = 100 us = 1 RTT
     set time 0.0001
     set now [$ns now]

     # check traffic to each TCP sink agent
     # puts "$now: Server: 0, bytes: [$snk_(0) set bytes_]"
     set total_bytes 0
     for {set i 0} {$i < $svr_num} {incr i} {
         set total_bytes [expr $total_bytes + [$snk_($i) set bytes_]]
     }

     # Is any data to be transmitted?
     if {$total_bytes >= $Block_trans} {
         # All SRU is transmitted.
         if {$total_bytes == $Block_trans} {
             # Finish in just.
         } else {
             # Unnecessary Retransmit is exist.
         }
         flush stdout
         $ns at [expr $now + 1] "finish"
     }

     # For Queue Monitoring
     # $q_mon instvar parrivals_ pdepartures_ bdrops_ bdepartures_ pdrops_
     # puts $q_trans "$now $bdepartures_"

     # For update_link
     update_link_del

     $ns at [expr $now+$time] "check_trans"
 }

 proc debug {} {
     global ns
     set next_time 1.0
     set now [$ns now]
     puts -nonewline "$now."
     flush stdout
     $ns at [expr $now+$next_time] "debug"
 }

 #Run the simulation
 $ns run

/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

<NS2网络模拟器的原理和应用>-王辉

这本书P42的例子和P47的基本语法还是很有用的。

Agent简单地说是表示节点的协议Protocol。