ns lecture v2
TRANSCRIPT
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Introduction to NS-2
Tutorial overview of NSCreate basic NS simulation
Walk-through a simple exampleModel specification
Execution and trace analysis
http://www-net.cs.umass.edu/~honggang/ns-cs653/
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NS-2, the network simulator
Academic project over 10 years old freely distributed, open source
Currently maintained by ISI (Information
Sciences Institute)DARPA + NSF projects
~ 200K LoC, 403 page manualLarge user basemostly academics
de facto standard in networking researchMain website: http://www.isi.edu/nsnam/ns
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NS Functionality
Discrete event simulator Modeling Network Components
Traffic models and applications Web, FTP, telnet, audio, sensor nets
Transport protocols TCP (Reno, SACK, etc), UDP, multicast Routing and queueing
static routing, DV routing, multicast, ad-hoc routing queueing disciplines: drop-tail, RED, FQ
Link layer wired, wireless, satellite
Providing Infrastructure tracing, visualization, error models, etc modify or create your own modules
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NS components
NS, the simulator itself (this is all well have time for) NAM, the Network AniMator
visualize NS (or other) output GUI input simple Ns scenarios
pre-processing: traffic and topology generators
post-processing: simple trace analysis, often in Awk, Perl, or Tcl
Tutorial: http://www.isi.edu/nsnam/ns/tutorial NS by example: http://nile.wpi.edu/NS/
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NS Software Structure: C++ and OTCL
Uses two languages
C++ for the core of NS simulator per packet processing fast to run, detailed, complete control
OTCL for control [our focus]
simulation setup, configuration fast to write and change
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Steps when using NS
Create OTCL script for your network model nodes, links, traffic sources, sinks, etc.
Parameterize simulation objects
Links: queue sizes, link speeds, Transport Protocols: TCP flavor and parameters(more than 30),
Collect statisticsdump everything to trace, post process it gather stats during simulation within OTCL scriptmodify Ns source code
Run NS multiple times confidence intervals
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Create a Basic NS Simulation
1. Create event scheduler2. Create nodes and links
3. Create connections4. Create traffic sources/sinks5. Enable tracing
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Step 1: Creating Event Scheduler
Create scheduler set ns [new Simulator]
Schedule event$ns at
: any legitimate Ns/TCL commands
Start scheduler
$ns run
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Create a Basic NS Simulation
1. Create the event scheduler2. Create nodes and links
3. Create connections4. Create traffic sources/sinks5. Enable tracing
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Step 2: Creating Network (Nodes + Links)
Nodes set n0 [$ns node]
set n1 [$ns node]
Links: connect together two nodes$ns duplex-link $n0 $n1
determines propagation delay determines queueing policy
DropTail, RED, CBQ, FQ, SFQ, DRR
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Create a Basic NS Simulation
1. Create the event scheduler2. Create nodes and links
3. Create connections4. Create traffic sources/sinks5. Enable tracing
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Step 3: Create Connections
Transports:TCP, UDP, multicast, etc.
transport protocol instances attach to nodes
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Creating Transport Channels: UDP
source and sink set u_src [new Agent/UDP]
set u_dst [new Agent/NULL]
attach them to nodes, then connect to eachother$ns attach-agent $n0 $u_src
$ns attach-agent $n1 $u_dst
$ns connect $u_src $u_dst
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Creating Transport Channels: TCP
source and sink set t_src [new Agent/TCP/Newreno]
set t_dst [new Agent/TCPSink]
Newreno flavor of TCP
attach to nodes and each other$ns attach-agent $n0 $t_src
$ns attach-agent $n1 $t_dst
$ns connect $t_src $t_dst
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Create a Basic NS Simulation
1. Create the event scheduler2. Create nodes and links
3. Create connections4. Create traffic sources/sinks5. Enable tracing
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Step 4: Create Traffic Models
Traffic (applications):Web, ftp, telnet, audio, etc.
application objects attach to transport protocol
objects generates traffic into transport protocol
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Creating Traffic over TCP Channels
How to create a FTP session over TCP?
create traffic model set ftp [new Application/FTP]
default is infinite file sizeattach to TCP channel$ftp attach-agent $t_src
schedule start time$ns at $ftp start
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Creating Traffic over UDP Channels
How to create a CBR (Constant Bit Rate)model over UDP? set cbr [new Application/Traffic/CBR]
$cbr set packetSize_ 512$cbr set interval_ 0.250
$cbr attach-agent $u_src
$ns at $cbr start
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Create a Basic NS Simulation
1. Create the event scheduler2. Create nodes and links
3. Create connections4. Create traffic sources/sinks5. Enable tracing
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Tracing: dump everything into a file
Trace packets on individual link
Tracefile format: --
+ 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
- 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
r 1.00234 0 2 tcp 900 ------- 1 0.0 3.1 7 15
+ enqueue- dequeuer received drop
time
nodes involvedin this event
Node 0 Node 1enqueue
receivedequeuedrop
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Trace packets on individual links
Tracefile format: --
+ 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
- 1 0 2 tcp 900 ------- 1 0.0 3.1 7 15
r 1.00234 0 2 tcp 900 ------- 1 0.0 3.1 7 15
+ enqueue- dequeuer received drop
time
nodes involvedin this event
packettype
packetlength
packetflags
flowID source
destaddresses
seqnumber
packetID
Tracing: dump everything into a file
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Tracing via Monitors
Queue monitor: the queue to access a linkFlow monitor: particular flow within queue to specify a link, we need:
set link [$ns link $n0 $n1] to create a flow monitor:
set fmon [$ns makeflowmon Fid]
$ns attach-fmon $link $fmon
$ns at puts $fmon set pdrops_
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Introduction to NS-2:
Tutorial overview of NS
Create basic NS simulationWalk-through simple exampleModel specification
Execution and trace analysis
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Walk-through example
acks
full duplex
acks
full duplex
Node 2Node 0 Node 1
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Walk-through example
2 FTPsources
One On-OffSource (voice)
acks
12 TCP
dest
One On-Off destOne CBR dest
2 Mbps full duplex5 msec prop delay100 packet bufferDrop-tail policy
acks
1 Mbps full duplex10 msec prop delay700 packet bufferDrop-tail policy
10 FTPsources
One UDP2 TCP SACK
W_max = 32MSS = 1400
10 TCP NewReno
W_max = 32MSS = 1400Node 0 Node 1 Node 2
One UDP
One CBRsource 12 FTPdest
Two UDPdest
fat link thin link
performance
tracing
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Introduction to NS-2:
Tutorial overview of NS
Create basic NS simulationWalk-through simple exampleModel specification
Execution and trace analysis
See handout for source code
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NS Trace file (link n1->n2):NS-trace.txt
...
+ 11.533441 1 2 tcp 1440 ------- 12 1.2 2.4 96 2092
r 11.535694 1 2 tcp 1440 ------- 12 1.2 2.4 65 1527
- 11.537214 1 2 exp 180 ------- 100 0.2 2.13 284 1528
- 11.538654 1 2 cbr 1440 ------- 101 1.11 2.14 155 1530
r 11.547214 1 2 tcp 1440 ------- 12 1.2 2.4 66 1529
+ 11.54728 1 2 tcp 1440 ------- 12 1.2 2.4 97 2095r 11.548654 1 2 exp 180 ------- 100 0.2 2.13 284 1528
+ 11.55 1 2 cbr 1440 ------- 101 1.11 2.14 211 2096
- 11.550174 1 2 tcp 1440 ------- 12 1.2 2.4 67 1534
r 11.560174 1 2 cbr 1440 ------- 101 1.11 2.14 155 1530
- 11.561694 1 2 exp 180 ------- 100 0.2 2.13 285 1532
+ 11.56222 1 2 tcp 1440 ------- 12 1.2 2.4 98 2097
- 11.563134 1 2 tcp 1440 ------- 12 1.2 2.4 68 1537
r 11.571694 1 2 tcp 1440 ------- 12 1.2 2.4 67 1534
r 11.573134 1 2 exp 180 ------- 100 0.2 2.13 285 1532
- 11.574654 1 2 exp 180 ------- 100 0.2 2.13 286 1536
...
0.0114sec=180*8/(10^6)+0.01
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Flow Monitor (link n1->n2) Trace :packet-trace.txt
...
10 356 1394.6939635123624 1262 906 0 4 7 3 0
10.5 367 1575.3875777393503 1325 958 0 8 15 7 0 1 1 0 0
11 366 1759.8340061666161 1384 1018 0 8 15 7 0 1 1 0 0
11.5 370 1944.0583990191849 1448 1078 0 8 15 7 0 1 1 0 0
12 380 2131.710863713804 1512 1132 0 8 15 7 0 1 1 0 012.5 382 2325.178644727122 1558 1176 0 8 15 7 0 1 1 0 0
13 382 2516.7615454470124 1613 1231 0 8 15 7 0 1 1 0 0
13.5 395 2710.8647514290892 1676 1281 0 8 15 7 0 2 3 1 0
14 421 2912.3462186990751 1747 1326 0 16 31 15 0 2 3 1 0
14.5 432 3130.3858423193769 1805 1373 0 16 31 15 0 2 3 1 0
15 436 3344.5896974377333 1862 1426 0 16 31 15 0 2 3 1 0
15.5 462 3571.3811182311597 1937 1475 0 16 31 15 0 2 3 1 0
16 477 3804.653159658757 1995 1518 0 16 31 15 0 2 3 1 0
16.5 495 4049.5929326563519 2057 1562 0 16 31 15 0 2 3 1 0
17 531 4303.9211771379323 2136 1605 0 16 31 15 0 2 3 1 0
...
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Results - Queue Statistics
Red - instantaneous
Green - running average
Blue - average w/o transient P
urple - packet drops
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Results - Flow Statistics
Red - TCP flow 1 Green - TCP flow 2
Number of packets in queuemimics TCP Window behavior
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Results - Flow Statistics
Congestion Windows of Flow 1and Flow 2
Cumulative dropped packets ofFlow 1 and Flow 2
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Performance Queue Statistics
Multiple runs to obtain confidence intervals