top-rated free essay

Computer Network

By svvota Apr 24, 2013 1789 Words
Bahçeşehir University Department of Computer Engineering
CMPE 2204 Introduction to Computer Networks Spring 2013

Chapter 1 Data Communications and Networks Overview and Protocol Layers Dr. Çağrı Güngör

1

Basic Info about the Course
• Course Content (tentative):
— Computer networks; network architectures; protocol layers; TCP/IP; principles of Internet; wireless networks; introduction to network management, etc..

• Course Objectives:
— Understand widely known network protocols, communication architectures, and wireless networks, — Learn TCP/IP and protocol layers, — Get a basic understanding of network management, etc.

Bahcesehir Univeristy CMPE 2204

2

Text Books
• J. Kurose, K. Ross, “Computer Networking: A Top Down Approach,” Addison-Wesley, 5th edition, March 2009.



W. Stallings, “Data and Computer Communications,” Prentice Hall, 8th edition, 2007. B. Forouzan, “Data Communications and Networking,” McGraw-Hill, 4th edition, 2007. Bahcesehir Univeristy CMPE 2204

3



Grading
• You will have:
— — — — 1 Midterm Quiz 1 Class Project 1 Final : : : : 25 10 25 40 % % % %

• NO MERCY ABOUT CHEATING !!!

Bahcesehir Univeristy CMPE 2204

4

Internet Infrastructure

Bahcesehir Univeristy CMPE 2204

5

Interesting Internet Appliances
Web-enabled toaster + weather forecaster

IP picture frame http://www.ceiva.com/

World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html

Internet phones
6

Bahcesehir Univeristy CMPE 2204

Networks are complex !!!
• Many “pieces”:
— Various applications, hosts, routers, protocols hardware, software

• The complexity of the communication task is reduced by using multiple protocol layers: — Each protocol is implemented independently — Each protocol is responsible for a specific subtask — Protocols are grouped in a hierarchy

• A structured set of protocols is called a communications architecture or protocol suite Bahcesehir Univeristy CMPE 2204
7

Simplified Communications Model - Diagram

Bahcesehir Univeristy CMPE 2204

8

A Communications Model
• Source
—generates data to be transmitted

• Transmitter
—Converts data into transmittable signals

• Transmission System
—Carries data

• Receiver
—Converts received signal into data

• Destination
—Takes incoming data
Bahcesehir Univeristy CMPE 2204

9

Simplified Data Communications Model

Bahcesehir Univeristy CMPE 2204

10

Examples of Communications Tasks
Transmission system utilization Interfacing Signal generation Addressing Routing Recovery

Synchronization
Exchange management Error detection and correction Flow control

Message formatting
Security Network management

Bahcesehir Univeristy CMPE 2204

11

Networking
• Point to point communication is usually not practical
—Devices are too far apart —Large set of devices would need impractical number of connections

• Solution is a communications network • Network Types:
—Wide Area Network (WAN) —Local Area Network (LAN) —Metropolitan Area Networks (MAN) Bahcesehir Univeristy CMPE 2204
12

Data Flow Types

Bahcesehir Univeristy CMPE 2204

13

Connection Types

Bahcesehir Univeristy CMPE 2204

14

Categories of Topology

Bahcesehir Univeristy CMPE 2204

15

Mesh Topology

Bahcesehir Univeristy CMPE 2204

16

Star Topology

Bahcesehir Univeristy CMPE 2204

17

Bus Topology

Bahcesehir Univeristy CMPE 2204

18

Ring Topology

Bahcesehir Univeristy CMPE 2204

19

Hybrid Topology: A star backbone with three bus networks

Bahcesehir Univeristy CMPE 2204

20

Network Types
A. Wide Area Network (WAN) B. Local Area Network (LAN) C. Metropolitan Area Networks (MAN)

Bahcesehir Univeristy CMPE 2204

21

A. Wide Area Networks
• • • • Covers large geographical area Circuits provided by a common carrier High-speed WANs use optical fiber Technologies: 1. 2. 3. 4. Circuit switching Packet switching Frame relay Asynchronous Transfer Mode (ATM)

Bahcesehir Univeristy CMPE 2204

22

1. Circuit Switching
• Dedicated communications path established for the duration of the conversation (guaranteed service) — e.g., telephone network

• Network resources (e.g., bandwidth) divided into “pieces”: — Call setup required — Pieces allocated to users

• Dividing link bandwidth into “pieces”:
— frequency division (FDM) — time division (TDM)
Bahcesehir Univeristy CMPE 2204
23

1. Circuit Switching: FDM and TDM
FDM
Example: 4 users frequency TDM time

frequency time
Bahcesehir Univeristy CMPE 2204
24

2. Packet Switching
• Data sent out of sequence • Small chunks (packets) of data at a time • Packets passed from node to node between source and destination • Used for terminal to computer and computer to computer communications Bahcesehir Univeristy CMPE 2204

25

2. Packet Switching
• Great for bursty data
—Resource sharing —Simpler, no call setup

• Excessive congestion: packet delay and loss
—Protocols needed for reliable data transfer and congestion control

• Challenge: How to provide performance QoS?
—Bandwidth guarantees needed for audio/video apps —Still an unsolved problem Bahcesehir Univeristy CMPE 2204
26

3. Frame Relay
• Packet switching systems have large overheads to compensate for errors

• Modern systems are more reliable
• Errors can be caught in end system • Most overhead for error control is stripped out

Bahcesehir Univeristy CMPE 2204

27

4. Asynchronous Transfer Mode (ATM)
• Evolution of frame relay • Little overhead for error control • Fixed packet (called cell) length • Anything from 10Mbps to Gbps • Constant data rate using packet switching technique

Bahcesehir Univeristy CMPE 2204

28

B. Local Area Networks (LAN)
• Smaller scope
—Building or small campus

• Usually owned by same organization as attached devices • Data rates much higher • Usually broadcast systems Bahcesehir Univeristy CMPE 2204
29

LAN Configurations
• Switched
—Switched Ethernet
• May be single or multiple switches

—ATM LAN —Fibre Channel

• Wireless
—Mobility —Ease of installation

Bahcesehir Univeristy CMPE 2204

30

Differences between LANs and WANs
• Scope of a LAN is smaller — LAN interconnects devices within a single building or cluster of buildings

• LAN usually owned by organization that owns the attached devices — For WANs, most of network assets are not owned by same organization • Internal data rate of LAN is much greater

Bahcesehir Univeristy CMPE 2204

31

C. Metropolitan Area Networks (MAN)
• Middle ground between LAN and WAN • Private or public network • High speed • Large area

Bahcesehir Univeristy CMPE 2204

32

The Need for MANs
• Traditional point-to-point and switched network techniques used in WANs are inadequate for growing needs of organizations • Need for high capacity and low costs over large area • MAN provides: —Service to customers in metropolitan areas —Required capacity —Lower cost and greater efficiency than equivalent service from telephone company Bahcesehir Univeristy CMPE 2204

33

Key Features of a Protocol
• Syntax —Concerns the format of the data blocks

• Semantics —Includes control information for coordination and error handling • Timing —Includes speed matching and sequencing
Bahcesehir Univeristy CMPE 2204
34

Standardized Protocol Architectures
• Required for devices to communicate • Vendors have more marketable products • Customers can insist on standards based equipment • Two standards: —OSI Reference model
• Never lived up to early promises

—TCP/IP protocol suite
• Most widely used

Bahcesehir Univeristy CMPE 2204

35

OSI Model - 1
• Open Systems Interconnection • Developed by the International Organization for Standardization (ISO) • Seven layers • A theoretical system delivered too late! • TCP/IP model is the de facto standard

Bahcesehir Univeristy CMPE 2204

36

OSI Model - 2
• A layer model • Each layer performs a subset of the required communication functions • Each layer relies on the next lower layer to perform more primitive functions • Each layer provides services to the next higher layer • Changes in one layer should not require changes in other layers Bahcesehir Univeristy CMPE 2204

37

Layers of the OSI Model
• • • • • • • Application Presentation Session Transport Network Data link Physical

Bahcesehir Univeristy CMPE 2204

38

OSI Layers
• Physical
—Physical interface between devices
• • • • Mechanical Electrical Functional Procedural

• Data Link
—Means of activating, maintaining and deactivating a reliable link —Error detection and control —Higher layers may assume error free transmission Bahcesehir Univeristy CMPE 2204
39

OSI Layers (Cont’ d.)
• Network
— Transport of information — Higher layers do not need to know about underlying technology — Not needed on direct links

• Transport
— Exchange of data between end systems — Error free — In sequence — No losses — No duplicates — Quality of service

Bahcesehir Univeristy CMPE 2204

40

OSI Layers (Cont’ d.)
• Session
—Control of dialogues between applications —Dialogue discipline —Grouping —Recovery

• Presentation
—Data formats and coding —Data compression —Encryption

• Application
—Means for applications to access OSI environment
Bahcesehir Univeristy CMPE 2204
41

Summary of OSI Layers

Bahcesehir Univeristy CMPE 2204

42

Use of a Relay

Bahcesehir Univeristy CMPE 2204

43

TCP/IP Protocol Architecture
• Developed by the US Defense Advanced Research Project Agency (DARPA) for its packet switched network (ARPANET) • Used by the global Internet • No official model but a working one. —Application layer —Transport layer (Host-to-host) —Routing layer (Internet) —Data link layer (Network Access) —Physical layer Bahcesehir Univeristy CMPE 2204

44

TCP/IP and OSI model

Bahcesehir Univeristy CMPE 2204

45

Physical Layer
• Physical interface between data transmission device (e.g. computer) and transmission medium or network • Physical layer specifies: —Characteristics of the transmission medium —The nature of the signals —The data rate

Bahcesehir Univeristy CMPE 2204

46

Data Link Layer
• Concerned with the exchange of data between an end system and the network to which it's attached

• Software used depends on type of network —Circuit switching —Packet switching (e.g., X.25) —LANs (e.g., Ethernet)

Bahcesehir Univeristy CMPE 2204

47

Routing Layer (IP)
• Uses internet protocol (IP) • Provides routing functions to allow data to traverse multiple interconnected networks • Implemented in end systems and routers

Bahcesehir Univeristy CMPE 2204

48

Transport Layer (TCP)
• Commonly uses transmission control protocol (TCP)

• Provides reliability during data exchange
—Completeness —Order

Bahcesehir Univeristy CMPE 2204

49

Application Layer
• Logic supports user applications • Uses separate modules that are peculiar to each different type of application • E.g., http, SMPT

Bahcesehir Univeristy CMPE 2204

50

Common TCP/IP Applications
• Simple mail transfer protocol (SMTP)
—Provides a basic electronic mail facility

• File Transfer Protocol (FTP)
—Allows files to be sent from one system to another

• TELNET
—Provides a remote logon capability

Bahcesehir Univeristy CMPE 2204

51

TCP/IP Architecture Dominance
• TCP/IP protocols matured quicker than similar OSI protocols —When the need for interoperability across networks was recognized, only TCP/IP was available and ready to go

• OSI model is unnecessarily complex —Accomplishes in seven layers what TCP/IP does with fewer layers Bahcesehir Univeristy CMPE 2204
52

TCP
• Usual transport layer is Transmission Control Protocol
— Reliable connection

• Connection
— Temporary logical association between entities in different systems

• TCP PDU
— Called TCP segment — Includes source and destination port (c.f. SAP) • Identify respective users (applications) • Connection refers to pair of ports

• TCP tracks segments between entities on each connection
Bahcesehir Univeristy CMPE 2204
53

UDP
• • • • • • Alternative to TCP is User Datagram Protocol Not guaranteed delivery No preservation of sequence No protection against duplication Minimum overhead Adds port addressing to IP

Bahcesehir Univeristy CMPE 2204

54

Some Protocols in TCP/IP Suite

Bahcesehir Univeristy CMPE 2204

55

Internetworking Terms
• Communication network – facility that provides a data transfer service among devices attached to the network • Internet – collection of communication networks, interconnected by bridges/routers • Intranet – internet used by an organization for internal purposes — Provides key Internet applications — Can exist as an isolated, self-contained internet

• Bandwidth – the amount of data that can pass through a network interface over time.

Bahcesehir Univeristy CMPE 2204

56

Internetworking Terms
• End System (ES) – device used to support end-user applications or services • Bridge – used to connect two LANs that use similar LAN protocols • Router – used to connect two networks that may or may not be similar

Bahcesehir Univeristy CMPE 2204

57

Cite This Document

Related Documents

  • World Without Computers Essay

    ...The router is an expert computer or network element connected more than one network running software that allows the router to move data from network to another. It does this by storing the addresses of all the networks to be able to communicate with them and to control the internet and the LAN (local area network) traffic. The internet is glob...

    Read More
  • computer

    ...Akintunde (A.K.A LAGBE) Computer package Hand Hand- Book powered by www.lagbeglobal.net What is a Computer? A computer is a programmable machine. The two principal characteristics of a principal computer are: it responds to a specific set of instructions in a well-defined manner defined and it can execute a prerecorded list of instru...

    Read More
  • Introduction to Network Concepts

    ...Introductory Network Concepts, Network Standards, and the OSI Model 1. There are many reasons for a company to network its computers, some are as follows; Share software, information with others on networks, cheaper than buying individual software and hardware for each standalone especially if the software often offers deals for amount be...

    Read More
  • Homework Network and Concept

    ...Final Exam of Computer Networks (ICE 1230) 2008.5. 27. Answer in English and Total 15 points 1. Why is it said that packet switching employs statistical multiplexing? Contrast statistical multiplexing with the multiplexing that takes place in TDM. (1 point) Answer: In a packet switched network, the packets from different sources flowing on...

    Read More
  • Network Design Proposal

    ...NETWORK DESIGN PROPOSAL for OASIS COURIER SERVICES TABLE OF CONTENTS Contents INTRODUCTION 3 The Company Needs 3 LAN Design 4 Topology 6 Media 6 VLAN 6 Internet 7 Servers 7 INTRODUCTION The purpose of this report ...

    Read More
  • Client/Server Network Design

    ...Network Technology Concepts Matthew Jarju IT 2250 Introduction to Network Technology Professor Jalinous May 29, 2011 Table of Contents Networking Technology Concepts 1 Definition 1 OSI Reference Model 4 Network Standards 5 IEEE 6 References 7 U02a1 Networking Technology Concepts Definition Network architectur...

    Read More
  • Role of the Physical Layer, Data Link Layer and Network Layer for the in Network Transmissions for Dotcom

    ...Layer and Network layer for the in Network Transmissions for DotCom The Role of the Physical Layer, Data Link Layer and Network layer for the in Network Transmissions for DotCom As the Network Manager of NotCom, my goal is to plan and implement the corporate network services strategy that is the best fit for the future needs of the org...

    Read More
  • network

    ... Network and standards protocol Professor 1.Which of the following terms is the cloaet synonym to the term computer networking? Protocol 2.Ann uses her email address, me@here.com, to send an email to bob, whose email address is you@there.com. the message contains a few paragraphs of text. Which of the following will be important t...

    Read More

Discover the Best Free Essays on StudyMode

Conquer writer's block once and for all.

High Quality Essays

Our library contains thousands of carefully selected free research papers and essays.

Popular Topics

No matter the topic you're researching, chances are we have it covered.