Dear all,
I wanted to implement a Round Robin packet scheduler just following the
process in the book Introduction to Network Simulator ns2 from Ekran
Hossain:
According to the process I have created the following *.cc and *.h files:
*//classifier-flow.h*
#ifndef ns_gw_flow_classifier_h
#define ns_gw_flow_classifier_h
#include "packet.h"
#include "ip.h"
#include "classifier.h"
class FlowClassifier : public Classifier {
protected:
int classify(Packet *p);
};
#endif
*//classifier-flow.cc*
#include "gw_flow_classifier.h"
#include <stdlib.h>
static class FlowClassifierClass : public TclClass {
public:
FlowClassifierClass() : TclClass("Classifier/Flow") {}
TclObject* create(int, const char*const*) {
return (new FlowClassifier());
}
} class_flow_classifier;
int FlowClassifier::classify(Packet *p) {
return hdr_ip::access(p)->flowid();
}
*//pkt-sched.h*
#ifndef ns_gw_pkt_sch_h
#define ns_gw_pkt_sch_h
#include "packet.h"
#include "ip.h"
#include "connector.h"
#include "queue.h"
#define NS 10
class PktScheduler : public Connector {
public:
PktScheduler();
virtual void handle(Event*);
virtual void recv(Packet*, Handler*);
protected:
void send(int fid, Handler* h);
virtual void resume();
int getFlowID(Packet* p) {return hdr_ip::access(p)->flowid();};
virtual int nextID() = 0;
Handler* qh_[NS];
Packet* pkt_[NS];
int blocked_;
int active_flow_id_;
};
//RR
class RRScheduler : public PktScheduler {
public:
RRScheduler();
private:
virtual int nextID();
int current_id_;
};
#endif
*//pkt-sched.cc*
#include "gw_pkt_sch.h"
PktScheduler::PktScheduler()
{
int i;
for (i=0;i<NS ;i++) {
pkt_[i] = 0;
qh_[i]=0;
}
blocked_ = 0;active_flow_id_ = -1;
}
void PktScheduler::recv(Packet* p, Handler* h)
{
int fid = getFlowID(p);
pkt_[fid] = p;qh_[fid] = h;
if (!blocked_) {
send(fid,this);
blocked_ = 1;
active_flow_id_ = fid;
}
}
void PktScheduler::send(int fid_idx, Handler* h)
{
Connector::send(pkt_[fid_idx],h);
pkt_[fid_idx] = 0;
}
void PktScheduler::handle(Event*) { resume(); }
void PktScheduler::resume()
{
qh_[active_flow_id_]->handle(0);
int index = nextID();
blocked_ = 0;
if (index >= 0) {
send(index,this);
blocked_ = 1;
active_flow_id_ = index;
}
}
//RR
RRScheduler::RRScheduler()
{
current_id_ = -1;
}
static class RRSchedulerClass: public TclClass {
public:
RRSchedulerClass() : TclClass("PktScheduler/RR") {}
TclObject* create(int, const char*const*) {
return (new RRScheduler());
}
} class_rr_scheduler;
int RRScheduler::nextID()
{
int count = 0;
current_id_++;current_id_ %= NS;
while((pkt_[current_id_] == 0)&&(count < NS)){
current_id_++;current_id_ %= NS;
count++;
}
if (count == NS)
return -1;
else{
return current_id_;
}
}
*And the following Otcl file:*
*#ns-link.tcl*
Class LinkSch -superclass Link
LinkSch instproc init {src dst bw delay num_queues} {
$self next $src $dst
$self instvar link_ queue_ head_ toNode_ ttl_
$self instvar drophead_
$self instvar num_queues_ sch_ flow_clsfr_
set ns [Simulator instance]
set head_ [new Connector]
set drophead_ [new Connector]
set link_ [new DelayLink]
set ttl_ [new TTLChecker]
set flow_clsfr_ [new Classifier/Flow]
set sch_ [new PktScheduler/RR]
set num_queues_ $num_queues
$head_ set link_ $self
$drophead_ target [$ns set nullAgent_]
$head_ target $flow_clsfr_
for {set i 0} {$i < $num_queues_} {incr i} {
set queue_($i) [new Queue/DropTail]
$queue_($i) target $sch_
$queue_($i) drop-target $drophead_
}
$sch_ target $link_
$link_ target $ttl_
$link_ drop-target $drophead_
$link_ set bandwidth_ $bw
$link_ set delay_ $delay
$ttl_ target [$dst entry]
$ttl_ drop-target $drophead_
}
LinkSch instproc add-flow { fid } {
$self instvar queue_ flow_clsfr_
$flow_clsfr_ install $fid $queue_($fid)
}
Simulator instproc sch-link { n1 n2 bw delay num_queues} {
$self instvar link_ queueMap_ nullAgent_ useasim_
set sid [$n1 id]
set did [$n2 id]
set link_($sid:$did) [new LinkSch $n1 $n2 $bw $delay $num_queues]
set pushback 0
$n1 add-neighbor $n2 $pushback
}
Simulator instproc add-flow { n1 n2 prio } {
$self instvar link_
set sid [$n1 id]
set did [$n2 id]
$link_($sid:$did) add-flow $prio
}
*The output of the compilation is correct. However, when I try to simulate
this tcl script:*
set num_queues [lindex $argv 0]
set ns [new Simulator]
set f [open book.tr w]
$ns trace-all $f
set n1 [$ns node]
set n2 [$ns node]
set n3 [$ns node]
$ns duplex-link $n1 $n2 5Mb 2ms DropTail
$ns duplex-link $n2 $n3 5Mb 2ms DropTail
$ns sch-link $n1 $n3 5Mb 2ms 10
$ns simplex-link $n3 $n1 5Mb 2ms DropTail
for {set i 0} {$i < $num_queues} {incr i} {
$ns add-flow $n1 $n3 $i
set tcp($i) [new Agent/TCP]
set sink($i) [new Agent/TCPSink]
set ftp($i) [new Application/FTP]
$tcp($i) set fid_ $i
$ns attach-agent $n1 $tcp($i)
$ns attach-agent $n3 $sink($i)
$ftp($i) attach-agent $tcp($i)
$ns connect $tcp($i) $sink($i)
$ns at 0.0 "$ftp($i) start"
}
proc show_tcp_seqno {} {
global tcp num_queues
for {set i 0} {$i < $num_queues} {incr i} {
puts "The final tcp($i) sequence number is
[$tcp($i) set t_seqno_]"
}
}
$ns at 10.0 "show_tcp_seqno"
$ns at 10.1 "$ns halt"
$ns run
*I get the following error:*
*
*
can't read "queue_": variable is array
while executing
"return $queue_"
(procedure "_o59" line 3)
(Link queue line 3)
invoked from within
"$link_($qn) queue"
(procedure "_o3" line 20)
(Simulator run line 20)
invoked from within
"$ns run"
(file "book.tcl" line 34)
I have notice that when I comment the following lines in ns-link.tcl file
the error disappear but I do not know if it is correct or not to do it, or
there is a smoother way to fix the problem:
#
# Also reset every queue
#
foreach qn [array names link_] {
set q [$link_($qn) queue]
$q reset
}
I use ns2 v2.34 on Ubuntu 10.04 64 bits OS.
yes, I've read the FAQ, ns-problems page, and manual and I couldn't find
the answer there.
Thanks,
--
Ricard Alegre
http://wirelessatcom.uab.es/ricardalegre.htm
--
Ricard Alegre
http://wirelessatcom.uab.es/ricardalegre.htm
