TDC 562/ Winter'02
Network Simulation Project: Studying the
TCP and UDP Fairness on the Internet
Jeffrey Absher
In this assignment you will do network simulation experiments to using ns to show how TCP streams of the same
traffic type (bulk vs. interactive traffic) coexist with each other. Also you will show how UDP streams impact others
and compromise the bandwidth fairness in Internet.
Initiate FTP traffic using TCP Reno from n1 to h1 and another FTP traffic that uses TCP Tahoe from n2 to h2. Each
FTP traffic use packet size of 1024 bytes. Connect n3 and h3 with a TELNET stream and n4 with h4 with an HTTP
stream. The HTTP traffic is generated between one Web client and one Web server such that HTTP request average
rate (surfing rate) is 800 ms exponentially distributed. A typical page average consists of 4 objects where the
average size of each object is 12 packets in constant distribution and the page pool size is 100 pages. The Web
server is lightly loaded which enables sending requested objects every 15 ms in average exponentially distributed
(inter-object arrival time). Finally, initiate an audio traffic using UDP from n5 to h5 such that the audio packet size
1000 bytes and the rate is 1 Mbps.
FTP1/Reno n1
h1
|
|
FTP2 n2 |1Mb
1Mb| h2
\ |
| /
1Mb\ |
|/1Mb
Telnet n3 ----- R1 ------>------ R2 ----- h3
1Mb/ | (RED/SFQ)
|\1Mb
/ |
| \
HTTP n4 |1Mb
1Mb| h4
|
|
CBR n5
h5
Running Scenario
Start the traffic as follows: TELNET at time 0, FTP1 at time 3, FTP2 at time 5, HTTP at time 15, UDP at time 25.
Stop UDP traffic at time 40 and then stop simulation and time 45.
See Appendix A for sample tcl code for Part 1; Part 2 is similar code with opt(bw2) set to 2Mb and 1Mb, Part
4 is similar to Part 1 with opt(bw2) set to 1Mb and opt(rtrq) set to .
Key Items to note:

I placed the http server on the left-hand side (n4) and the client on the right (h4) to increase the
contention for resources at router R1 and to maximize the left-to-right traffic flow. This assumes that
the server-to-client transmission is larger (which it is).

Email to grader confirmed that only the R1<->R2 link should be of different queue type, the host<>router links should remain DropTail

In the assignment, it said “A typical page average consists of 4 objects…” I took this to mean that the
number of objects in a page should be a constant distribution centered around 4.

Note the setting of ftp to 1024-byte packets for ftp0 and ftp1 in the non-default settings section
See Appendix B for the bash script used to extract data for all parts
Part (1) Plot in two graphs the throughput in Mbps and number of packet dropped for FTP1, FTP2, TELNET,
HTTP and UDP streams every 1 sec till the end of the simulation. (2 graphs – 20%)
Part 1 Throughput
1.2
1
0.8
1_ftp1_thru_mbps
1_ftp2_thru_mbps
0.6
1_telnet_thru_mbps
1_http_thru_mbps
1_udp_thru_mbps
0.4
0.2
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
9
11
7
5
3
1
Se
co
nd
s
0
Part 1 Dropped Packets
1
0.9
0.8
0.7
0.6
1_ftp1_drop
1_ftp2_drop
0.5
1_telnet_drop
1_http_drop
0.4
1_udp_drop
0.3
0.2
0.1
Se
co
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
nd
s
0
Part (2): Repeat Part(1) when L = 2 Mbps (2a) and 1 Mbps (2b) respectively (4 graphs – 40%).
Part 2a Throughput
1.2
1
0.8
2a_ftp1_thru_mbps
2a_ftp2_thru_mbps
0.6
2a_telnet_thru_mbps
2a_http_thru_mbps
2a_udp_thru_mbps
0.4
0.2
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
9
11
7
5
3
1
Se
co
nd
s
0
Part 2a Dropped Packets
4.5
4
3.5
3
2a_ftp1_drop
2a_ftp2_drop
2.5
2a_telnet_drop
2a_http_drop
2
2a_udp_drop
1.5
1
0.5
Se
co
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
nd
s
0
Part 2b Throughput
1.2
1
0.8
2b_ftp1_thru_mbps
2b_ftp2_thru_mbps
0.6
2b_telnet_thru_mbps
2b_http_thru_mbps
2b_udp_thru_mbps
0.4
0.2
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
9
11
7
5
3
1
Se
co
nd
s
0
Part 2b Dropped Packets
40
35
30
25
2b_ftp1_drop
2b_ftp2_drop
20
2b_telnet_drop
2b_http_drop
2b_udp_drop
15
10
5
Se
co
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
11
9
7
5
3
1
nd
s
0
Part (3): Make R1 and R2 use SFQ instead of RED. Repeat part(1) when link L has 1 Mbps (2 graphs – 20%).
Part 3 Throughput
1.2
1
0.8
3_ftp1_thru_mbps
3_ftp2_thru_mbps
0.6
3_telnet_thru_mbps
3_http_thru_mbps
3_udp_thru_mbps
0.4
0.2
0
co
Se
s
nd
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
Part 3 Dropped Packets
100
90
80
70
60
3_ftp1_drop
3_ftp2_drop
50
3_telnet_drop
3_http_drop
40
3_udp_drop
30
20
10
Se
co
43
41
39
37
35
33
31
29
27
25
23
21
19
17
15
13
9
11
7
5
3
1
nd
s
0
Part (4): What is your observations and conclusion about the fairness of TCP and UDP in each part above (20%)?
Part 1 had no contention and no dropped packets, therefore there was no fairness test.
In Part 2a using RED with some contention, there were some packet drops for the tcp streams as
well as some for the udp stream, When contention started, FTP2 (Tahoe) was better able to
maintain its throughput than FTP1(reno), but reno did recover somewhat. This design (under
“light” contention) maintained UDP at the expense of TCP, and dropped a similar absolute
amount of packets for each connection. So if fairness is defined as picking a packet “roundrobin” from all of the current active connections to drop, this design is fair, but if fairness is
defined as maintaining tcp at the expense of udp, or dropping a higher number of packets from
the largest resource user, or allocating bandwidth, then this design is unfair. Even the sparse http
and telnet streams experienced drops.
Part 2b using RED with high contention, shows that udp is strongly favored over tcp
connections. It appears that a udp stream can “bully” itself into being the favored stream. Also
when contention started, FTP1 and FTP2 performed approximately the same, yet FTP2(tahoe)
recovers from a slow link much more quickly. While udp did drop significantly more packets
than any other protocol, it still also successfully delivered many more packets and starved the
other tcp streams, . This is a consequence of tcp “playing nice” and having congestion control
while udp does not. Again, the sparse protocol streams http and telnet did suffer, but not greatly
with this set-up. The higher contention shows that RED is unfair to TCP streams, and to sparse
streams.
Part 3 using Stochastic Fair Queuing instead of Random Early Detection shows that SFQ
allocates bandwidth significantly more fairly than RED in the presence of udp. While there are a
few anomalies, the high network utilizers such as ftp1, ftp2, and udp, experience more dropped
packets than the others, and the sparse streams experienced no drops. As well, ftp1 and ftp2
continued to use approximately one third of the total available bandwidth when the udp was
started. For this particular experiment, I would conclude that SFQ is the fairest allocator of
bandwidth, and it fairly drops packets because the number of packets dropped is relative to
bandwidth demand.
Appendix A… Sample tcl code
#!/bin/sh
set opt(tr)
"ass3_1.tr"
set opt(namtr) ""
set opt(stop) 45
set
set
set
set
set
set
opt(bw1)
1Mb
opt(delay1)
2ms
opt(bw2)
4Mb
opt(delay2) 15ms
opt(ifq)
DropTail
opt(rtrq) RED
proc finish {} {
global env nshome pwd
global ns opt trfd
$ns flush-trace
close $trfd
exit 0
}
proc create-trace {} {
global ns opt
if [file exists $opt(tr)] {
catch "exec rm -f $opt(tr) $opt(tr)-bw [glob $opt(tr).*]"
}
set trfd [open $opt(tr) w]
$ns trace-all $trfd
if {$opt(namtr) != ""} {
$ns namtrace-all [open $opt(namtr) w]
}
return $trfd
}
proc create-topology {} {
global ns opt node
## first 5 nodes(n1-N5 = 0-4)
for {set i 0} {$i < 5} {incr i} { set node($i) [$ns node] }
## second 5 nodes (h1-h5 as 6-9)
for {set i 5} {$i < 10} {incr i} { set node($i) [$ns node] }
##routers (10 = R1, 11=R2)
set node(10) [$ns node]
set node(11) [$ns node]
##node-router links
##note I am using droptail for these links, and RED/SFQ for the Router-Router link.
for {set i 0} {$i < 5} {incr i} {
$ns duplex-link $node($i) $node(10) $opt(bw1) $opt(delay1) $opt(ifq)
}
for {set i 5} {$i < 10} {incr i} {
$ns duplex-link $node($i) $node(11) $opt(bw1) $opt(delay1) $opt(ifq)
}
##router-router link
$ns duplex-link $node(10) $node(11) $opt(bw2) $opt(delay2) $opt(rtrq)
}
proc create-traffic {} {
global ns opt node
$ns rtproto DV
set tcp0 [new Agent/TCP/Reno]
set tcp1 [new Agent/TCP]
set tcp2 [new Agent/TCP]
#set tcp3 [new Agent/TCP]
set udp4 [new Agent/UDP]
set sink0 [new Agent/TCPSink]
set sink1 [new Agent/TCPSink]
set sink2 [new Agent/TCPSink]
#set sink3 [new Agent/TCPSink]
set sink4 [new Agent/Null]
$ns attach-agent $node(0) $tcp0
$ns attach-agent $node(1) $tcp1
$ns attach-agent $node(2) $tcp2
#$ns attach-agent $node(3) $tcp3
$ns attach-agent $node(4) $udp4
$ns attach-agent $node(5) $sink0
$ns attach-agent $node(6) $sink1
$ns attach-agent $node(7) $sink2
#$ns attach-agent $node(8) $sink3
$ns attach-agent $node(9) $sink4
set
set
set
set
set
ftp0 [new Application/FTP]
ftp1 [new Application/FTP]
telnet2 [new Application/Telnet]
pgp3 [new PagePool/WebTraf]
cbr4 [new Application/Traffic/CBR]
$ftp0 attach-agent $tcp0
$ftp1 attach-agent $tcp1
$telnet2 attach-agent $tcp2
# $http3 attach-agent $tcp3
$cbr4 attach-agent $udp4
##http extras
$pgp3
$pgp3
$pgp3
$pgp3
$pgp3
set-num-server 1
set-num-client 1
set-server 0 $node(3)
set-client 0 $node(8)
set-num-session 1
set numPage 100
#interPage...hope that it is arrival of requests?
set interPage [new RandomVariable/Exponential]
$interPage set avg_ .8
#pageSize..
set pageSize [new RandomVariable/Constant]
$pageSize set val_ 4
#inter-arrival time for obj
set interObj [new RandomVariable/Exponential]
$interObj set avg_ 0.015
#avg object size in pkts
set objSize [new RandomVariable/Constant]
$objSize set avg_ 12
##non-default settings
$cbr4 set packetSize_ 1000
$cbr4 set interval_ 8ms
$ftp0 set packetSize_ 1024
$ftp1 set packetSize_ 1024
##agent connections
$ns connect $tcp0 $sink0
$ns connect $tcp1 $sink1
$ns connect $tcp2 $sink2
$pgp3 create-session 0 $numPage 15 $interPage $pageSize $interObj $objSize
$ns connect $udp4 $sink4
##start-stoptimes
$ns at 3 "$ftp0 start"
$ns at 5 "$ftp1 start"
$ns at 0 "$telnet2 start"
#$ns at 15 $pgp3 start
$ns at 25 "$cbr4 start"
$ns at 40 "$cbr4 stop"
}
## MAIN ##
set ns [new Simulator]
set trfd [create-trace]
create-topology
create-traffic
$ns at $opt(stop) "finish"
$ns run
Appendix B… Extraction bash script
#!/usr/bin/bash
for ((s=0; $s<45; s = $s+1)) do
awk '$1=="d" && int($2)=='$s' &&
awk '$1=="d" && int($2)=='$s' &&
awk '$1=="d" && int($2)=='$s' &&
awk '$1=="d" && int($2)=='$s' &&
$5=="cbr"
$5=="cbr"
$5=="cbr"
$5=="cbr"
&&
&&
&&
&&
int($9)==4
int($9)==4
int($9)==4
int($9)==4
&&
&&
&&
&&
int($10)==9
int($10)==9
int($10)==9
int($10)==9
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
1}
1}
1}
1}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_udp_drop_inpackets.txt;
ass3_2a.tr >> ass3_2a_udp_drop_inpackets.txt;
ass3_2b.tr >> ass3_2b_udp_drop_inpackets.txt;
ass3_3.tr >> ass3_3_udp_drop_inpackets.txt;
awk
awk
awk
awk
'$1=="d"
'$1=="d"
'$1=="d"
'$1=="d"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==3
int($9)==3
int($9)==3
int($9)==3
&&
&&
&&
&&
int($10)==8
int($10)==8
int($10)==8
int($10)==8
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
1}
1}
1}
1}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_http_drop_inpackets.txt;
ass3_2a.tr >> ass3_2a_http_drop_inpackets.txt;
ass3_2b.tr >> ass3_2b_http_drop_inpackets.txt;
ass3_3.tr >> ass3_3_http_drop_inpackets.txt;
awk
awk
awk
awk
'$1=="d"
'$1=="d"
'$1=="d"
'$1=="d"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==2
int($9)==2
int($9)==2
int($9)==2
&&
&&
&&
&&
int($10)==7
int($10)==7
int($10)==7
int($10)==7
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
1}
1}
1}
1}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_telnet_drop_inpackets.txt;
ass3_2a.tr >> ass3_2a_telnet_drop_inpackets.txt;
ass3_2b.tr >> ass3_2b_telnet_drop_inpackets.txt;
ass3_3.tr >> ass3_3_telnet_drop_inpackets.txt;
awk
awk
awk
awk
'$1=="d"
'$1=="d"
'$1=="d"
'$1=="d"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==1
int($9)==1
int($9)==1
int($9)==1
&&
&&
&&
&&
int($10)==6
int($10)==6
int($10)==6
int($10)==6
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
1}
1}
1}
1}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_ftp2_drop_inpackets.txt;
ass3_2a.tr >> ass3_2a_ftp2_drop_inpackets.txt;
ass3_2b.tr >> ass3_2b_ftp2_drop_inpackets.txt;
ass3_3.tr >> ass3_3_ftp2_drop_inpackets.txt;
awk
awk
awk
awk
'$1=="d"
'$1=="d"
'$1=="d"
'$1=="d"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==0
int($9)==0
int($9)==0
int($9)==0
&&
&&
&&
&&
int($10)==5
int($10)==5
int($10)==5
int($10)==5
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
1}
1}
1}
1}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_ftp1_drop_inpackets.txt;
ass3_2a.tr >> ass3_2a_ftp1_drop_inpackets.txt;
ass3_2b.tr >> ass3_2b_ftp1_drop_inpackets.txt;
ass3_3.tr >> ass3_3_ftp1_drop_inpackets.txt;
awk
awk
awk
awk
'$1=="r"
'$1=="r"
'$1=="r"
'$1=="r"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==0
int($9)==0
int($9)==0
int($9)==0
&&
&&
&&
&&
int($10)==5
int($10)==5
int($10)==5
int($10)==5
&&
&&
&&
&&
$4==5
$4==5
$4==5
$4==5
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
$6}
$6}
$6}
$6}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_ftp1_thru_inbytes.txt;
ass3_2a.tr >> ass3_2a_ftp1_thru_inbytes.txt;
ass3_2b.tr >> ass3_2b_ftp1_thru_inbytes.txt;
ass3_3.tr >> ass3_3_ftp1_thru_inbytes.txt;
awk
awk
awk
awk
'$1=="r"
'$1=="r"
'$1=="r"
'$1=="r"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==1
int($9)==1
int($9)==1
int($9)==1
&&
&&
&&
&&
int($10)==6
int($10)==6
int($10)==6
int($10)==6
&&
&&
&&
&&
$4==6
$4==6
$4==6
$4==6
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
$6}
$6}
$6}
$6}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_ftp2_thru_inbytes.txt;
ass3_2a.tr >> ass3_2a_ftp2_thru_inbytes.txt;
ass3_2b.tr >> ass3_2b_ftp2_thru_inbytes.txt;
ass3_3.tr >> ass3_3_ftp2_thru_inbytes.txt;
awk
awk
awk
awk
'$1=="r"
'$1=="r"
'$1=="r"
'$1=="r"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==2
int($9)==2
int($9)==2
int($9)==2
&&
&&
&&
&&
int($10)==7
int($10)==7
int($10)==7
int($10)==7
&&
&&
&&
&&
$4==7
$4==7
$4==7
$4==7
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
$6}
$6}
$6}
$6}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_telnet_thru_inbytes.txt;
ass3_2a.tr >> ass3_2a_telnet_thru_inbytes.txt;
ass3_2b.tr >> ass3_2b_telnet_thru_inbytes.txt;
ass3_3.tr >> ass3_3_telnet_thru_inbytes.txt;
awk
awk
awk
awk
'$1=="r"
'$1=="r"
'$1=="r"
'$1=="r"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="tcp"
$5=="tcp"
$5=="tcp"
$5=="tcp"
&&
&&
&&
&&
int($9)==3
int($9)==3
int($9)==3
int($9)==3
&&
&&
&&
&&
int($10)==8
int($10)==8
int($10)==8
int($10)==8
&&
&&
&&
&&
$4==8
$4==8
$4==8
$4==8
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
$6}
$6}
$6}
$6}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_http_thru_inbytes.txt;
ass3_2a.tr >> ass3_2a_http_thru_inbytes.txt;
ass3_2b.tr >> ass3_2b_http_thru_inbytes.txt;
ass3_3.tr >> ass3_3_http_thru_inbytes.txt;
awk
awk
awk
awk
'$1=="r"
'$1=="r"
'$1=="r"
'$1=="r"
&&
&&
&&
&&
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
int($2)=='$s'
&&
&&
&&
&&
$5=="cbr"
$5=="cbr"
$5=="cbr"
$5=="cbr"
&&
&&
&&
&&
int($9)==4
int($9)==4
int($9)==4
int($9)==4
&&
&&
&&
&&
int($10)==9
int($10)==9
int($10)==9
int($10)==9
&&
&&
&&
&&
$4==9
$4==9
$4==9
$4==9
{xmit
{xmit
{xmit
{xmit
+=
+=
+=
+=
$6}
$6}
$6}
$6}
END
END
END
END
{print
{print
{print
{print
'$s'":
'$s'":
'$s'":
'$s'":
"
"
"
"
xmit}'
xmit}'
xmit}'
xmit}'
ass3_1.tr >> ass3_1_udp_thru_inbytes.txt;
ass3_2a.tr >> ass3_2a_udp_thru_inbytes.txt;
ass3_2b.tr >> ass3_2b_udp_thru_inbytes.txt;
ass3_3.tr >> ass3_3_udp_thru_inbytes.txt;
done