Lecture 1 Introduction to computer network -2013

Computer Engineering Department - MEFGI

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Computer Network150702

Hemang KothariAssistant Professor

Computer Engineering Department MEFGI, Rajkot.

Email: [email protected]


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Teaching Scheme

• 150702 - Computer Network

• Theory - 4

• Practical - 2

• Credit - 6

• Final Exam - 70

• Term work -30

• Internal Practical - 50

• Total – 150 Marks

Reference Books:

1. Computer network, Andrew S. Tanenbaum, Pearson.

2. Introduction to Data Communication and Networking, Behrouz Forouzan, TMH.

3. Computer Network, Natalia Olifer, Victor Olifer, Wiley-India edition.

4. Data and computer communication, William Stallings, Pearson.


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Expectation

• Smiling Face

• Attendance

• Interactive Session

• Enjoy the joy of learning

• Be an observer


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Methodology

• Why Need to learn

• What Definition, Meaning, is all about

• How Performance, Implementation, Simulation, Development

Do Not Worry, We have only 6 Assignment


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Computer Network

• Life without friends is boring.

• Photos without Facebook tagging is colorless.

• We love to follow Dipika Padukone & Ranbeer Kapoor love stories.

• Beating a friends on LAN Gaming is the just awesome.


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Networking ( You Can’t Live Without It)

Facebook TwitterGoogle

Yahoo !!!WhatsApp

YouTubeeBay MakeMyTrip


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You Require …


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Module 1: Introduction to Network•Uses of computer network.•Network hardware, Network software•OSI model, TCP/IP model, Comparison of OSI and

TCP/IP model, • Example network: The internet, X.25, Frame Relay,

ATM, Ethernet, Wireless LANs: 802.11.


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Use of Computer Network

•Business Applications•Home Applications•Mobile Users• Social Issues

Business Applications of Networks

• A network with two clients and one server.

Business Applications of Networks (2)• The client-server model involves requests and replies.

Home Network Applications

• Access to remote information• Person-to-person communication• Interactive entertainment• Electronic commerce

Home Network Applications (2)

• In peer-to-peer system there are no fixed clients and servers.

Home Network Applications (3)

• Some forms of e-commerce.

Mobile Network Users

• Combinations of wireless networks and mobile computing.

Network Hardware• Local Area Networks• Metropolitan Area Networks• Wide Area Networks• Wireless Networks• Home Networks• Internetworks

Types of transmission technology

• Broadcast links (Speaking loudly in a class)• Point-to-point links (Gap-sap with friend)

Classification By Scale

Local Area Networks

(a) Bus (b) Ring

Metropolitan Area Networks - Cable TV

Wide Area Networks

• Relation between hosts on LANs and the subnet.

Wide Area Networks (2)

• A stream of packets from sender to receiver.

Wireless Networks

Categories of wireless networks:• System interconnection• Wireless LANs

Wireless Networks (2)

(a) Bluetooth configuration (b) Wireless LAN


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Task we need to perform (Design Issue)• Addressing• Error Control• Flow Control• Multiplexing• Routing

Solution : Divide the work and solve the issue


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Motivation behind layer model

• To reduce the design complexity, most of the networks are organized as a series of layers or levels, each one build upon one below it. • The basic idea of a layered architecture is to divide the design into

small pieces. • Each layer adds to the services provided by the lower layers in such a

manner that the highest layer is provided a full set of services to manage communications and run the applications. • The benefits of the layered models are modularity and clear

interfaces, i.e. open architecture and comparability between the different providers' components.


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Element of layered model

• A service is a set of actions that a layer offers to another (higher) layer. • Protocol is a set of rules that a layer uses to exchange information

with a peer entity. These rules concern both the contents and the order of the messages used. • Between the layers service Interfaces are defined. The messages

from one layer to another are sent through those interfaces.


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Summary: Why Layered architecture?1. To make the design process easy by breaking unmanageable tasks

into several smaller and manageable tasks (by divide-and-conquer approach).

2. Modularity and clear interfaces, so as to provide comparability between the different providers' components.

3. Ensure independence of layers, so that implementation of each layer can be changed or modified without affecting other layers.

4. Each layer can be analyzed and tested independently of all other layers.


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Open System Interconnection Reference Model• The Open System Interconnection (OSI) reference model describes

how information from a software application in one computer moves through a network medium to a software application in another computer.

1. Application2. Presentation3. Session

4. Transport5. Network6. Data link7. Physical

Computer Engineering Department - MEFGI 32

Application Application

Presentation Presentation

Session Session

TransportTransport

Network Network

Data linkData link

Physical Physical

protocol

protocol

protocol

protocol

protocol

protocol

protocol


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Application Layer• File transfer (FTP): Connect to a remote machine and send or fetch an

arbitrary file. FTP deals with authentication, listing a directory contents, ASCII or binary files, etc. • Remote login (telnet): A remote terminal protocol that allows a user at

one site to establish a TCP connection to another site, and then pass keystrokes from the local host to the remote host. • Mail (SMTP): Allow a mail delivery agent on a local machine to connect

to a mail delivery agent on a remote machine and deliver mail. • News (NNTP): Allows communication between a news server and a

news client. • Web (HTTP): Base protocol for communication on the World Wide Web.


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Presentation Layer

• This layer is concerned with Syntax and Semantics of the information transmitted. Few of the services that Presentation layer provides are:• Encoding data in a standard agreed upon way.• It manages the abstract data structures and converts from representation

used inside computer to network standard representation and back.

MIME: Multi Purpose Internet Mail Extension


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Session Layer

• This layer manages Dialogue Control. Session can allow traffic to go in both direction at the same time, or in only one direction at one time. • Token management. For some protocols, it is required that both sides

don't attempt same operation at the same time. To manage these activities, the session layer provides tokens that can be exchanged. Only one side that is holding token can perform the critical operation. • Synchronization/Check Pointing: Session layer provides a way to

insert checkpoints into data streams, so that after a crash, only the data transferred after the last checkpoint have to be repeated.


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Transport Layer

• The transport level provides end-to-end communication between processes executing on different machines.• Negotiation of Quality and Type of Services.• Deal with congestion control• Connection establishment and termination.• Multiplexing – Demultiplexing.• Error control


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Network Layer

1. Interface between the host and the network (the network layer is typically the boundary between the host and subnet)

2. Routing 3. Congestion and deadlock 4. Internetworking (A path may traverse different network technologies

(e.g., Ethernet, point-to-point links, etc.)


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Data Link Layer

1. Group the physical layer bit stream into units called frames. Note that frames are nothing more than ``packets'' or ``messages''. By convention, we shall use the term ``frames'' when discussing DLL packets.

2. Sender calculates the checksum and sends checksum together with data. The checksum allows the receiver to determine when a frame has been damaged in transit or received correctly. This is called error detection and correction.


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Continue

3.Error control protocol returns a positive or negative acknowledgment to the sender. A positive acknowledgment indicates the frame was received without errors, while a negative acknowledgment indicates the opposite.

4.Flow control prevents a fast sender from overwhelming a slower receiver. For example, a supercomputer can easily generate data faster than a PC can consume it.


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Physical Layer

• The physical layer is concerned with transmission of raw bits over a communication channel. It specifies the mechanical, electrical and procedural network interface specifications and the physical transmission of bit streams over a transmission medium connecting two pieces of communication equipment• Number of pins and functions of each pin of the network connector

(Mechanical) • Signal Level, Data rate (Electrical) • Whether simultaneous transmission in both directions • Establishing and breaking of connection • Deals with physical transmission.


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Let’s Evaluate This !!!!!


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What we are using – TCP/IP Model

• OSI Model • TCP/IP Hierarchy • Protocols

• 7th

• Application Layer

• 6th

• Presentation Layer

• 5th

• Session Layer

• 4th

• Transport Layer

• 3rd

• Network Layer

• 2nd

• Link Layer

• 1st

• Physical Layer

• Application Layer

• Transport Layer

• Network Layer

• Link Layer


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That’s the only difference ?

• OSI • TCP / IP• Application (Layer7)

• Application• Presentation (Layer6)

• Session (Layer 5)

• Transport (Layer 4) • Transport

• Network (Layer 3) • Internet

• Data Link (Layer 2)

• Host to network layer • Physical (Layer 1)

The Upper Layers

OSI TCP / IP

Application (Layer7)

ApplicationPresentation (Layer6)

Session (Layer 5)

The Session Layer

The Session layer permits two parties to hold ongoing communications called a session across a network.• Not found in TCP/IP model• In TCP/IP, its characteristics are provided by the TCP protocol.

(Transport Layer)

The Presentation Layer

The Presentation Layer handles data format information for networked communications. This is done by converting data into a generic format that could be understood by both sides.• Not found in TCP/IP model• In TCP/IP, this function is provided by the Application Layer.

e.g. External Data Representation Standard (XDR) Multipurpose Internet Mail Extensions (MIME)

The Application Layer

The Application Layer is the top layer of the reference model. It provides a set of interfaces for applications to obtain access to networked services as well as access to the kinds of network services that support applications directly.

• OSI- File Transfer Access Method (FTAM), Virtual Terminal, MHS,DS,CMIP

• TCP/IP- FTP,SMTP,TELNET,DNS,SNMP

Comparing Transport for both Models

• The TCP/IP and OSI architecture models both employ all connection and connectionless models at transport layer.• However, the internet architecture refers to the two models in TCP/IP

as simply “connections” and datagrams. But the OSI reference model, with its penchant for “precise” terminology, uses the terms connection-mode and connection-oriented model and the term connectionless-mode for the connectionless model.

Network Vs. Internet

• Like all the other OSI Layers, the network layer provides both connectionless and connection-oriented services. As for the TCP/IP architecture, the internet layer is exclusively connectionless.

OSI TCP / IP

Network (Layer 3) Internet

Data link / Physical vs. Subnet

Data link layer The function of the Data Link Layer is “provides for the control of the physical layer, and detects

and possibly corrects errors which may occur” (IOS/IEC 7498:1984). In another words, the Data Link Layer transforms a stream of raw bits (0s and 1s) from the physical into a data frame and provides an error-free transfer from one node to another, allowing the layers above it to assume virtually error-free transmission

OSI TCP / IP

Data Link (Layer 2)Subnet (host to network layer)

Physical (Layer 1)


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Switching TechniquesLet’s Switch it !!!!!!

The Network Core

• The fundamental question: how is data transferred through net?

• Circuit switching: dedicated circuit per call: telephone net

• Packet-switching: data sent thru net in discrete “chunks”

Basic of Switching

• In large networks there might be multiple paths linking sender and receiver. Information may be switched as it travels through various communication channels. There are two typical switching techniques available for digital traffic.

• Circuit Switching • Packet Switching

Circuit Switching • Circuit switching is a technique that directly

connects the sender and the receiver in an unbroken path.

• Telephone switching equipment, for example, establishes a path that connects the caller's telephone to the receiver's telephone by making a physical connection.

• With this type of switching technique, once a connection is established, a dedicated path exists between both ends until the connection is terminated.

• Routing decisions must be made when the circuit is first established, but there are no decisions made after that time

Circuit Switching (Good Vs. Bad) End-end resources reserved

for “call”• link bandwidth, switch

capacity• dedicated resources: no

sharing• circuit-like (guaranteed)

performance• call setup required

network resources (e.g., bandwidth) divided into “pieces”• pieces allocated to calls• resource piece idle if not

used by owning call (no sharing)• dividing link bandwidth into

“pieces”• frequency division• time division

Packet Switching Each end-end data stream divided into packets• User A, B packets share network resources

• Each packet uses full link bandwidth • Resources used as needed, • There are two methods of packet switching: Datagram and virtual circuit.

Bandwidth division into “pieces”

Dedicated allocationResource reservation

Packet Switching• In both packet switching methods, a message is broken into small

parts, called packets. • Each packet is tagged with appropriate source and destination

addresses. • Since packets have a strictly defined maximum length, they can be

stored in main memory instead of disk, therefore access delay and cost are minimized.

• With current technology, packets are generally accepted onto the network on a first-come, first-served basis. If the network becomes overloaded, packets are delayed or discarded (``dropped'').

Example Networks

• The Internet

• Connection-Oriented Networks: X.25, Frame Relay, and ATM

• Ethernet

• Wireless LANs: 802:11

The ARPANET

(a) Structure of the telephone system.(b) Baran’s proposed distributed switching system.

The ARPANET – How it grows

• Growth of the ARPANET (a) December 1969. (b) July 1970.(c) March 1971. (d) April 1972. (e) September 1972.

Internet Usage1. Traditional applications (1970 – 1990) 2. E-mail3. News4. Remote login5. File transfer

Architecture of the Internet

ATM Virtual Circuits

ATM Virtual Circuits (2)

• An ATM cell.

The ATM Reference Model

• The ATM reference model.

The ATM Reference Model (2)

X.25

~ Most widely used today~ an interface between DTE and DCE for terminal operation at the packet mode on

public data network.• A packet switching protocol used in a wide area network• use virtual circuit and asynchronous TDM

X.25 Layers

• Error detection and correction in both the data link and the network layers• Network layer: establishing the connection

transferring the dataterminating the connection

Ethernet

Wireless LANs

(a) Wireless networking with a base station.(b) Ad hoc networking.

Wireless LANs (2)

• The range of a single radio may not cover the entire system.

Education

Lecture 1 Introduction to computer network -2013