COMPUTER NETWORK: MODELING AND SIMULATION - PowerPoint PPT Presentation

Loading...

PPT – COMPUTER NETWORK: MODELING AND SIMULATION PowerPoint presentation | free to view - id: 5e27d9-NzMzY



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

COMPUTER NETWORK: MODELING AND SIMULATION

Description:

COMPUTER NETWORK: MODELING AND SIMULATION-Abhaykumar Kumbhar Computer Science Department References: 1:Advanced Modelling and Simulation Methods for Communication ... – PowerPoint PPT presentation

Number of Views:296
Avg rating:3.0/5.0
Slides: 36
Provided by: INDU3
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: COMPUTER NETWORK: MODELING AND SIMULATION


1
COMPUTER NETWORKMODELING AND SIMULATION
  • -Abhaykumar Kumbhar
  • Computer Science Department

2
Motivation
  • Bridge between Real life application and
    Theoretical world.

3
Contents
  • Introduction.
  • Modeling.
  • Simulation.
  • How to develop a Model.
  • Classification .
  • NS simulator.
  • OPNET.
  • An Ethernet Case Study.
  • Requirements of a good Network Simulating Tool
  • Evolution.
  • Conclusion and Future Work

4
Introduction
  • Performance analysis of computer networks
    increase in size and geographical extent.
  • The size of the networks and the inherent
    complexity of network protocols complicate this
    analysis.
  • Analysis techniques such as queuing models have
    difficulty modeling dynamic behavior
    retransmission timeouts and congestion.
  • Simulation offers a better method of studying
    computer networks, since one can simulate the
    details of actual protocols.

5
  • Simulation is an analysis and evaluation tool.
  • Every simulation is tight to a model that
    represents the real world.
  • Inconsistent modeling
  • Modeling itself is a crucial step towards
    meaningful results.
  • Aim systematic modeling techniques -increase the
    quality and validity of results

6
Modeling
  • Constructing a conceptual framework that
    describes a system.

7
Modeling Taxonomy
8
Simulation
system boundary
system under study (has deterministic rules
governing its behavior)
exogenous inputs to system (the environment)
real life
observer
9
Why Simulation?
  • study system performance, operation
  • real-system not available, is complex/costly or
    dangerous (eg space simulations, flight
    simulations)
  • quickly evaluate design alternatives (eg
    different system configurations)
  • evaluate complex functions for which closed form
    formulas or numerical techniques not available

10
When to Use Simulation?
  • Whenever Mathematical Analysis Is Difficult or
    Impossible.
  • For Validating Analytic Models.
  • For Experimentation Without Disturbing an
    Operational System

11
How to develop a model
  • Determine the goals and objectives
  • Build a conceptual model
  • Convert into a specification model
  • Convert into a computational model
  • Verify
  • Validate

12
(No Transcript)
13
Simulation Model Development Methodology
14
Simulation Model Verification and Validation
15
Classification of Simulation Tools
  • GPPL General Purpose Programming Language
  • PSL Plain Simulation Language
  • SP Simulation Package

16
NS Simulator
  • Began as REAL in 1989
  • Developed by UC Berkeley
  • Public domain SP
  • Object-oriented
  • Written in C and object-oriented tcl (Otcl)
  • Network components are represented by classes

17
Ns class hierarchy
18
OPNET
  • Developed by OPNET Technologies Inc.
  • Commercial SP
  • Object-oriented
  • Totally menu-driven package
  • Built-in model libraries contain most popular
    protocols and applications
  • Simulation task made easy

19
Modeling hierarchy in OPNET
20
(No Transcript)
21
An Ethernet Case Study
  • Bridging the Gap Between Reality and Simulations
  • We set up our test-bed using two nodes connected
    by a 3 meter cross-over Ethernet cable.
  • a simple test-bed experiment and attempt to
    replicate the obtained results by simulation in
    ns-2,QualNet and OPNET.

22
  • Network details
  • set packet size of the application to 1472 bytes.
    This was to ensure that the maximum Ethernet
    frame of 1500 bytes would be transmitted

23
Delay experienced by packets in saturated case
with non-blocking sockets
  • particularly interested in the saturation
    performance of the system and we chose multiple
    rates near the maximum link bandwidth

24
  • The maximum delay of the system is experienced
    when the source bufferis full.
  • This delay is given as max delay tx delay
    buffer size in packets.
  • The transmission delay for one packet is the
    minimum delay.
  • The buffer size is then calculated as max
    delay/min delay. Hence a buffer size of 78
    packets was arrived at 94/1.2 78packets
    128KB.

25
  • Setting up simulations in QualNet
  • --the link propagation delay being negligible,
    set it to 25 µs to model test-bed network
    characteristics.
  • --queue size from its default value of 50 KB to
    117 KB, which corresponds to 78 packets of 1500
    bytes each.

26
  • Setting up simulations in OPNET
  • Ethernet Station Advanced (ESA).
  • The ESA has a traffic generator built over the
    Ethernet MAC.
  • the queue length to infinity.
  • OPNET models queues as a set of sub-queues,
    allowing the possibility of different
    application traffic to map on to different
    queues. By default only one sub-queue is created
    in the Ethernet MAC process model and this is a
    hidden parameter. This sub queue is accessed as a
    process interface of the Ethernet MAC process
    model. The sub-queue packet capacity was set to
    78 packets.

27
  • Setting up simulations in NS-2
  • configurable parameters node objects, link
    bandwidth, maximum length and type of the
    interface queue and delay.
  • queue length to 78.
  • maximum propagation delay is 25 µs for 10 Mbps.

28
  • Results
  • Figure Throughput

29
  • Figure Packet Delivery Fraction

30
  • Figure Average End-to-End Delay

31
Requirements for Network Simulation tools
  • Model development simplicity
  • Modeling flexibility
  • Fast modeling
  • Animation
  • Different kinds of implemented components
  • Component adaptability
  • Creating new components
  • Static capabilities of a simulator
  • Graphs

32
Evolution of Network Simulation Tools
  • Zeroth Generation General Purpose Languages
  • - Fortran, C/C, Pascal, Basic
  • First Generation General Purpose Queueing
    System Simulations
  • -GPSS, SLAM, SIMSCRIPT
  • Second Generation Application Specific
    Computer Systems and Wide-Area Communication
    Networks
  • Third Generation Integration of Second
    Generation Languages
  • -With a Graphics-Oriented Analysis and Modeling
    Environment
  • -SES/Workbench
  • -OPNET

33
Conclusion and Future work
  • Best way to learn Protocols.

34
References
  • 1Advanced Modelling and Simulation Methods
  • for Communication Networks Jože Mohorko, Fras
    Matjaž, Klampfer Saša.
  • 2www.sciencedirect.com
  • 3www.ieeexplore.org

35
  • THANK YOU
  • QUESTIONS??
About PowerShow.com