[ns] Problem:First packet always get lost under TCP when error rate is bigger than 0.01
Hello everyone,
I have a problem when simulate the ordinary FTP/TCP transmission in NS-2.28.
I add a link error model in the link. When I set the packet error reate
bigger than 0.01(for example 0.015). The first packet's t_seqno_ is 1, and
always get lost. The transmission recovered after 6 sec. Here is the trace
file:
0.05000 0 0 1 0 t_seqno_ 1
6.05000 0 0 1 0 t_seqno_ 0
6.05000 0 0 1 0 t_seqno_ 1
6.09032 0 0 1 0 t_seqno_ 2
6.09032 0 0 1 0 t_seqno_ 3
．．． ．．．
Is it a bug or something else? Dose anyone can help me? Thank you very much.
I attach my OTcl script here, you can try by yourself.
set ns [new Simulator]
#Define different colors for data flows (for NAM)
$ns color 1 Blue
#Open the Trace files
set tracefile1 [open out.tr w]
set winfile [open WinFile w]
$ns trace-all $tracefile1
#Open the NAM trace file
set namfile [open out.nam w]
$ns namtrace-all $namfile
#Define a 'finish' procedure
proc finish {} {
global ns tracefile1 namfile
$ns flush-trace
close $tracefile1
close $namfile
exec nam out.nam
exit 0
}
#Create two nodes
set n0 [$ns node]
set n1 [$ns node]
#Create links between the nodes
$ns duplex-link $n0 $n1 2Mb 20ms DropTail
set em [new ErrorModel]
$em set rate_ 0.02
$em unit pkt
$em ranvar [new RandomVariable/Uniform]
$em drop-target [new Agent/Null]
$ns link-lossmodel $em $n0 $n1
#Set Queue Size of link (n0-n1) to 20
#$ns queue-limit $n0 $n1 20
#Setup a TCP connection
set tcp [new Agent/TCP]
$ns attach-agent $n0 $tcp
set sink [new Agent/TCPSink]
$ns attach-agent $n1 $sink
$ns connect $tcp $sink
$tcp set fid_ 1
#Open the t_seqno_ trace file
$tcp trace t_seqno_
set trace_ch [open trace.txt w]
$tcp attach $trace_ch
#Setup a FTP over TCP connection
set ftp [new Application/FTP]
$ftp attach-agent $tcp
$ns at 0.05 $ftp start
$ns at 63.5 $ftp stop
#Procedure for plotting window size. Gets as arguments the name
#of the tcp source node (called tcpSource) and of output file.
proc plotWindow {tcpSource file} {
global ns
set time 0.1
set now [$ns now]
if { [$tcpSource set cwnd_][$tcpSource set window_]} {
set cwnd [$tcpSource set cwnd_]
} else {
set cwnd [$tcpSource set window_]
}
puts $file $now $cwnd
$ns at [expr $now+$time] plotWindow $tcpSource $file
}
$ns at 0.1 plotWindow $tcp $winfile
$ns at 64.0 finish
$ns run
Best Regards,
Tong Mao
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Eng Rony hi all i run simple-wireless.tcl example from Marc Greis' tutorial section IX. Running Wireless Simulations in ns and i want to know what each field in o/p trace file means, for example: s 0.029290548 _1_ RTR --- 0 message 32 [0 0 0 0] --- [1:255 -1:255 32 0] M 10.0 0 (5.00, 2.00, 0.00), (20.00, 18.00), 1.00 s 10.0 _0_ AGT --- 2 tcp 40 [0 0 0 0] --- [0:0 1:0 32 0] [0 0] 0 0 r 10.0 _0_ RTR --- 2 tcp 40 [0 0 0 0] --- [0:0 1:0 32 0] [0 0] 0 0 ..D 76.430622539 _0_ IFQ ARP 2 tcp 80 [0 0 0 800] --- [0:0 1:0 32 1] [0 0] 0 0 D 76.430622539 _0_ RTR CBK 8 tcp 80 [0 0 0 800] --- [0:0 1:0 32 1] [0 0] 0 0 s 100.337960577 _1_ RTR --- 80 ack 60 [0 0 0 0] --- [1:0 0:0 32 0] [28 0] 0 0 r 100.340096680 _0_ AGT --- 72 ack 60 [13a 0 1 800] --- [1:0 0:0 32 0] [24 0] 1 0 r 69.501265756 _1_ RTR --- 15 message 32 [0 0 800] --- [0:255 -1:255 32 0] i want to know also what means by agentTrace,RouterTrace,MacTrace thanks
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Better you refer Ch. 16 of ns-manual for good understanding. Eng Rony hi all i run simple-wireless.tcl example from Marc Greis' tutorial section IX. Running Wireless Simulations in ns and i want to know what each field in o/p trace file means, for example: s 0.029290548 _1_ RTR --- message 32 [0 0] --- [1:255 -1:255 32 0] M 10.0 (5.00, 2.00, 0.00), (20.00, 18.00), 1.00 s 10.0 _0_ AGT --- 2 tcp 40 [0 0] --- [0:0 1:0 32 0] [0 0] 0 r 10.0 _0_ RTR --- 2 tcp 40 [0 0] --- [0:0 1:0 32 0] [0 0] 0 ..D 76.430622539 _0_ IFQ ARP 2 tcp 80 [0 800] --- [0:0 1:0 32 1] [0 0] 0 D 76.430622539 _0_ RTR CBK 8 tcp 80 [0 800] --- [0:0 1:0 32 1] [0 0] 0 s 100.337960577 _1_ RTR --- 80 ack 60 [0 0] --- [1:0 0:0 32 0] [28 0] 0 r 100.340096680 _0_ AGT --- 72 ack 60 [13a 1 800] --- [1:0 0:0 32 0] [24 0] 1 0 r 69.501265756 _1_ RTR --- 15 message 32 [0 800] --- [0:255 -1:255 32 0] i want to know also what means by agentTrace,RouterTrace,MacTrace thanks
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Re: [ns] Problem with DSR modification...
I'm thinking if this has to do with the modification of the SR header:
I added an int variable, named low_energy_, which represents a flag
to tell receiving nodes that the source is finishing its energy, but
maybe this increases the size of the header too much, over its limit
(which I don't know exactly, is it 8 bytes?). I also didn't modify the
method ''int size(), to add the size of the integer variable when it
returns...
Could this be the reason, and if yes, how can I add an option to the
SR header safely?
2009/2/26 Salvo Danilo Giuffrida giuffsa...@gmail.com:
Hello, I modified the DSR implementation of NS-2, in such a way that,
when a node reaches an energy level below a certain percentage of its
initial level at the beginning of the simulation (say, 30%), it sends
a broadcast IP packet
SRPacket p;
p.src = net_id;
p.pkt = allocpkt();
hdr_sr *srh = hdr_sr::access(p.pkt);
hdr_ip *iph = hdr_ip::access(p.pkt);
hdr_cmn *cmnh = hdr_cmn::access(p.pkt);
iph-daddr() = IP_BROADCAST;
cmnh-next_hop() = IP_BROADCAST;
iph-dport() = RT_PORT;
iph-saddr() =
Address::instance().create_ipaddr(net_id.getNSAddr_t(),RT_PORT);
iph-sport() = RT_PORT;
iph-ttl() = 1;
cmnh-ptype() = PT_DSR;
cmnh-size() = size_ + IP_HDR_LEN; // add in IP header
cmnh-direction() = hdr_cmn::DOWN;
//srh-init();
srh-low_energy()=1;
Scheduler::instance().schedule(ll, p.pkt, 0);
p.pkt = NULL;
The 'valid' flag of the Source Route header is not set to 1, because
this is a broadcast, route-less packet. That 'low_energy()' method
sets a flag on the header, which I added to indicate that this is a
low energy message to neighbors nodes.
After the packet is received by neighbors, that's what happens in recv(...)
if (srh-valid() != 1) {
unsigned int dst = cmh-next_hop();
if (dst == IP_BROADCAST) {
// extensions for mobileIP --Padma, 04/99.
// Brdcast pkt - treat differently
if (p.src == net_id)
// I have originated this pkt
sendOutBCastPkt(packet);
//Lines added by me
else if (srh-low_energy()) {
ID to_id(iph-saddr(),::IP);
ID from_id(net_id.addr,::IP);
/* kill any routes we have using this link (this node-sender node of
the broadcast packet) */
route_cache-noticeDeadLink(from_id,
to_id,Scheduler::instance().clock());
flow_table.noticeDeadLink(from_id, to_id);
/* now kill all the other packets in the output queue that would
use the same next hop. */
Packet *r, *nr, *queue1 = 0, *queue2 = 0;
// pkts to be recycled
while((r = ifq-prq_get_nexthop(to_id.getNSAddr_t( {
r-next_ = queue1;
queue1 = r;
}
// the packets are now in the reverse order of how they
// appeared in the IFQ so reverse them again
for(r = queue1; r; r = nr) {
nr = r-next_;
r-next_ = queue2;
queue2 = r;
}
// now process them in order
for(r = queue2; r; r = nr) {
nr = r-next_;
undeliverablePkt(r, 1);
}
return;
} else
//hand it over to port-dmux
port_dmux_-recv(packet, (Handler*)0);
...
The idea is that receivers of this broadcast low energy packet would
clear their route caches from the link X-Y, where X it's net_id
(themselves), and Y is the low energy nodeThen, if packets with
a route having X-Y among the links are received, to be forwarded to a
certain destination, this neighbors nodes would try to savage the
package, or generate an RERR to the original sender. Hopefully, with
new RREQs, a new route, which would not pass for the low energy node,
would be selected (I made other modifications to make this more
likely). But if this node is the only possible route for a certain
destination, it would be used anyway.
What I see happening is that the broadcast packet is received by
neighbors, the link net_id-Y is cleared (I guess), but new RREQs
can't be generated by the other nodes, because for a while the other
nodes are unable to forward packets, and drop them (IFQ_FULL),
including RREQs packets. So, becuase of these dropping, links between
good nodes (nodes with enough energy, and I'm sure it's not a problem
of the interface queue size, because even with a value of 500 packets,
the problem remains).
I can send the Tcl scenario file, and/or the trace output, if anyone
is interested and willing to help.
Also, is there a way to dump the content of a mobilenode's
routecache?...I looked into the source code, and currently the 'dump'
method is unimplemented, and I didn't find in 'routecache.h' any
mention of the data structure where all routes are memorized...
Thanks a lot
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hi all it's true the node uses the carrier sense before sending the data. as per my understanding the NAV for the nodes in the carrier sense rage is updated. Nodes uses this nav to determine the time after which the it is permited to send the data. my promblem is to use the entries in nav for my work.how can i access the nav table. Neeraj Gupta Assistant Professor HOD, CSE IT Department Hindu College of Engineering Sonepat
