Post on 21-Dec-2015
Applications and transport agent API
695430050
許庭瑋
Outline
Application in NSClass ApplicationAttaching applicationsClass TrafficGeneratorSimulated Applications
Application in NS
On top of transport agents Two basic types
Traffic generators Simulated applications
Application in NS
Class Application
class Application : public TclObject {public:Application();virtual void send(int nbytes);virtual void recv(int nbytes);virtual void resume();protected:int command(int argc, const char*const* argv);virtual void start();virtual void stop();Agent *agent_;int enableRecv_; // call OTcl recv or notint enableResume_; // call OTcl resume or not};
*see trafgen.cc/.h
Attaching transport agent
set src [new Agent/TCP/FullTcp]
set sink [new Agent/TCP/FullTcp]
$ns_ attach-agent $node_(s1) $src
$ns_ attach-agent $node_(k1) $sink
$ns_ connect $src $sink
Attaching applications
Use attach-agent function
set ftp1 [new Application/FTP]
$ftp1 attach-agent $src Set agent_ Call attachApp() [agent.cc]
An alternative
Set ftp1 [$src attach-app FTP]
System calls to use transport agent
send(int nbytes) send nbytes of data to peer if nbytes==-1 , infinite send
sendmsg(int nbytes, const char* flags = 0) Identical to send(int bytes) Additional string flags
MSG_EOF
System calls to use transport agent
close() Requests the agent to close the connection (onl
y applicable for TCP) listen()
Requests the agent to listen for new connections (only applicable for Full TCP)
set_pkttype(int pkttype) This function sets the type_ variable in the agen
t to pkttype.
Agent upcalls to application
In NS, no actual data transfering between applications
Agents upcalls application to notify events Incoming number of bytes of data
Two types of upcalls recv(int nbytes) resume()
Done() All data has been transferred, and ACKed Done does nothing by default
An exampleset myagent [new Agent/TCP/FullTcp]
$myagent proc done
... code you want ...
Example for FTP
set src [new Agent/TCP/FullTcp]set sink [new Agent/TCP/FullTcp]$ns_ attach-agent $node_(s1) $src$ns_ attach-agent $node_(k1) $sink$ns_ connect $src $sink# set up TCP-level connections$sink listen;$src set window_ 100set ftp1 [new Application/FTP]$ftp1 attach-agent $src$ns_ at 0.0 "$ftp1 start"
Class TrafficGenerator
class TrafficGenerator : public Application {public:TrafficGenerator();virtual double next_interval(int &) = 0;virtual void init() {}virtual double interval() { return 0; }virtual int on() { return 0; }virtual void timeout();virtual void recv() {}virtual void resume() {}protected:virtual void start();virtual void stop();double nextPkttime_;int size_;int running_;TrafficTimer timer_;};
Class TrafficGenerator
Four classes derived from TrafficGenerator EXPOO_Traffic
Exponential on/off duration Fixed rate,packet size
POO_Traffic Pareto on/off distribution
CBR_Traffic TrafficTrace
Generates traffic according to trace file
Exponential distribution
Exponential On/Off
packetSize_ the constant size of the p
ackets generated burst_time_
the average “on” time for the generator
idle_time_ the average “off” time for t
he generator rate_
the sending rate during “on” times
Next_packet_time=tr_time+idle_time
Example:set e [new Application/Traffi
c/Exponential]$e set packetSize_ 210$e set burst_time_ 500ms$e set idle_time_ 500ms$e set rate_ 100k
Pareto Distribution
α,β>0 Shape in NS is β
Pareto On/Off
packetSize_ the constant size of the packet
s generated burst_time_
the average "on" time for the generator
idle_time_ the average "off" time for the g
enerator rate_
the sending rate during "on" times
shape_ the "shape" parameter used b
y the pareto distribution
Example:set p [new Application/Traffic/Par
eto]$p set packetSize_ 210$p set burst_time_ 500ms$p set idle_time_ 500ms$p set rate_ 200k$p set shape_ 1.5
CBR
rate_ the sending rate
interval_ (Optional) interval between packets
packetSize_ the constant size of the packet
s generated random_ flag
indicating whether or not to introduce random “noise” in the scheduled departure times (default isoff)
maxpkts_ the maximum number of pack
ets to send (default is (228)
Example: set e [new Application
/Traffic/CBR] $e set packetSize_ 48 $e set rate_ 64Kb $e set random_ 1
Traffic Trace
Enable multiple Traffic/Trace associated with one trace file
2 32-bit fields in trace file Next packet generates
time (ms) Length of next packet
(bytes)
Example:
set tfile [new Tracefile]
$tfile filename example-trace
set t1 [new Application/Traffic/Trace]
$t1 attach-tracefile $tfile
set t2 [new Application/Traffic/Trace]
$t2 attach-tracefile $tfile
Random variable in NS
Pareto Distribution Constant Distribution Uniform Distribution Exponential Distribution HyperExponential Distribution
Pareto Distribution
# Pareto 分佈,柏拉圖分佈 set r1 [new RandomVariable/Pareto] $r1 use-rng $rng $r1 set avg_ 10.0 $r1 set shape_ 1.2 for {set i 1} {$i<=3} {incr i} { puts [$r1 value] }
Constant Distribution
set r2 [new RandomVariable/Constant] $r2 use-rng $rng $r2 set avg_ 5 for {set i 1} {$i<=3} {incr i} { puts [$r2 value] }
Uniform Distribution
Set min & max set r3 [new RandomVariable/Uniform]
$r3 use-rng $rng $r3 set min_ 0.0 $r3 set max_ 10.0 for {set i 1} {$i<=3} {incr i} { puts [$r3 value] }
Exponential Distribution
set r4 [new RandomVariable/Exponential] $r4 use-rng $rng $r4 set avg_ 5.0 for {set i 1} {$i<=3} {incr i} { puts [$r4 value] }
Example-Exponential traffic
set src [new Agent/UDP]set sink [new Agent/UDP]$ns_ attach-agent $node_(s1) $src$ns_ attach-agent $node_(k1) $sink$ns_ connect $src $sinkset e [new Application/Traffic/Exponential]$e attach-agent $src$e set packetSize_ 210$e set burst_time_ 500ms$e set idle_time_ 500ms$e set rate_ 100k$ns_ at 0.0 "$e start"
Simulated applications
Two simulated applications : FTP & TelnetFTP methods:attach-agent start stop produce n producemore n send n
Simulated applications
TelnetPacket inter-packet time:
Chose from exponential distribution , with average=interval_ ; (if interval not zero)
Chose according tcplib distribution (see ns-2.28\tcp\tcplib-telnet.cc)
Example
CBR + FTP Node 1 CBR Node 2 FTP