Network simulator

1
Network simulator

• Lunsjkollokvium 29.10.99
• Poul Heegaard
• Brynjar Viken

2
Overview

• Otcl/C.
• Example script.
• Discrete Event Scheduler.
• Network Topology.
• Queue Management and Packet Scheduling.
• Transport agents.
• Applications.
• Packet Format.
• Routing.

• DEMO

3
otcl and C

• Object oriented simulator written in C.
• Otcl interpreter as a frontend.

C
otcl
Otcl class hierarchy
C class hierarchy
From users view a one-to-one correspondence.
4
Example Script

• set ns new Simulator
• set n0 ns node

set ftp new Application/FTP ftp attach-agent
tcp
set n1 ns node
ns connect tcp sink
ns duplex-link n0 n1 1.5Mb 10ms DropTail
ns at 0.2 "ftp start" ns at 1.2 exit" ns run
Set sink new Agent/TCPSink ns attach-agent
n1 sink
set tcp new Agent/TCP ns attach-agent n0 tcp
5
Event Scheduler

• Create scheduler
• set ns new Simulator
• Four schedulers available (linked list, heap,
  calendar queue and real-time.)
• Objects derived from Event packets and
  at-events.
• Schedule event
• ns at lttimegt lteventgt
• lteventgt any legitimate ns/tcl commands
• Start scheduler
• ns run

6
Creating Topology

• Nodes
• set n0 ns node
• set n1 ns node
• Links Queuing
• ns duplex-link n0 n1 ltbandwidthgt ltdelaygt
  ltqueue_typegt
• Packet scheduling and queue management
• FIFO queueing, Class Based Queueing (CBQ),
  Weighted Fair Queueing (WFQ), Stochastic Fair
  Queueing (SFQ), Deficit Round-Robin and RED
  buffer management.

7
Network Topology - Node
Unicast Node
8
Network Topology - Link
9
Creating Topology

• ns Supports a variety of other media
• Multi-access local area network.
• Wireless media.
• Broadcast media.
• ...

10
Creating Connection UDP

• UDP
• set udp new Agent/UDP
• set null new Agent/NULL
• ns attach-agent n0 udp
• ns attach-agent n1 null
• ns connect udp null

11
Creating Connection TCP

• TCP
• set tcp new Agent/TCP
• set tcpsink new Agent/TCPSink
• ns attach-agent n0 tcp
• ns attach-agent n1 tcpsink
• ns connect tcp tcpsink
• Support several one-way sending TCP agents and
  sinks. (Tahoe, Reno, NewReno, Sack1, Vegas and
  Fack.)

12
Transport
n0
n1
Port Classifier
Port Classifier
Addr Classifier
Addr Classifier
0
0
agents_
dmux_
dmux_
Link n0-n1
entry_
entry_
classifier_
classifier_
Link n1-n0
13
Creating Traffic Applications

• FTP
• set ftp new Application/FTP
• ftp attach-agent tcp
• Telnet
• set telnet new Application/Telnet
• telnet attach-agent tcp

14
Creating Traffic Applications

• CBR
• set src new Application/Traffic/CBR
• Exponential or Pareto on-off
• set src new Application/Traffic/Exponential
• set src new Application/Traffic/Pareto
• Traffic generation from traces.

15
Application
n0
n1
Port Classifier
Port Classifier
Addr Classifier
Agent/TCP
Addr Classifier
Agent/TCPSink
0
0
agents_
agents_
dmux_
dmux_
Link n0-n1
entry_
entry_
classifier_
classifier_
Link n1-n0
16
Packet Flow
n0
n1
Port Classifier
Port Classifier
Application/FTP
Addr Classifier
Agent/TCP
Addr Classifier
Agent/TCPSink
0
0
Link n0-n1
entry_
entry_
Link n1-n0
17
Packet Format
header
data
18
Computing routes

• Unicast
• ns rtproto lttypegt
• lttypegt Static, Session, DV, cost, multi-path
• Multicast
• ns multicast (right after new Simulator)
• ns mrtproto lttypegt
• lttypegt CtrMcast, DM, ST, BST

19
Trace and Monitoring Support

• Traces - record each individual packet as it
  arrives, departs, or is dropped at a link or
  queue.
• lteventgt lttimegt ltfromgt lttogt ltpktgt ltsizegt--ltflowidgt
  ltsrcgt ltdstgt ltseqnogt ltaseqnogt
• 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• - 1 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• r 1.00234 0 2 cbr 210 ------- 0 0.0 3.1 0 0
• Monitors - compute statistics over time intervals
  about arrivals, departures, drops and flows.

20
Class Hierarchy (Partial)
21
Visualization Tools

• nam-1 (Network AniMator Version 1)
• Nam is a Tcl/TK based animation tool for viewing
  network simulation traces and real world packet
  traces. It supports topology layout, packet level
  animation, and various data inspection tools.
• xgraph

22

• nam-1 (Network AniMator Version 1)

23
Other ns-2 Freatures

• Mathematical Support
• Network Dynamics
• Simulation Scale
• 460 nodes, 100,000 TCP connections
• Emulation Interface

24
Online Resources

• http//netweb.usc.edu/vint
• http//www-mash.cs.berkeley.edu/ns/
• Mailing lists
• ns-users_at_mash.cs.berkeley.edu
• ns-announce_at_mash.cs.berkeley.edu
• To subscribe
• majordomo_at_mash.cs.berkeley.edu

25
Credits

• UCB
• Elan Amir, Hari Balakrishnan, Tom Henderson,
  Steven McCanne, Giao Nguyen, Venkat Padmanabhan,
  Teck-Lee Tung
• USC/ISI
• Lars Eggert, Deborah Estrin, Padma Haldar, Mark
  Handley, John Heidemann, Ahmed Helmy, Polly
  Huang, Satish Kumar, Reza Rejaie, Puneet Sharma,
  Kannan Varadhan, Vikram Visweswariah, Ya Xu,
  Haobo Yu
• LBNL
• Kevin Fall, Sally Floyd
• Xerox Parc
• Sandeep Bajaj, Lee Breslau, Scott Shenker