Final Chapt - 1 Part - 1

8/12/2019 Final Chapt - 1 Part - 1

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Data Communication Networks and

Prof. M. S. Godase 1


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Review Topics

, ,

Network Criteria, Network Models, Categories of

Connection Oriented Networks

Connectionless Networks, Wireless LAN, Gigabit

Interconnection of Networks: Internetwork Protocol Layering, OSI Model

TCP/IP Model

OSI vs TCP/IP



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Data Communications

, , ,television, means communication at a distance (teleis Greek word

forfar).

electronic equipment.

Datarefers to information presented in whatever form is agreed upon

by the parties creating and using the data.

Data Communications are the exchange of data between two

devices via some form of transmission medium such as a wire cable.

A communication system is made up of a combination of hardware

(physical equipment) and software (programs).

ec veness o a a a commun ca on sys em epen s on our fundamental characteristics delivery, accuracy, timeliness, and

jitter.



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Data Communications

Delivery:system must deliver data to the correct destination.

Accuracy:system must deliver data accurately.

Timeliness:system must deliver data in a timely manner.

Jitter:it refers to the variation in the packet arrival time or A

henomenon in real-time traffic caused b a s between

consecutive packets at the receiver.

Components of a data communication system ata commun cat on system as ve components.



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Data Communications

1. Message: is the information (data) to be communicated.

Information includes text, numbers, pictures, audio and

v eo.

2. Sender: is the device that sends the message. It can be a

computer, workstation, telephone handset, video camera etc.

3. Receiver:is the device that receives the message. It can be a

computer, workstation, telephone handset, video camera etc.

.

message travels from sender to receiver. It can be twistedpair

wire, coaxial cable, fiber optic cable and radio waves.

. ro oco : s a se o ru es a governs a a commun ca ons.It represents an agreement between communicating devices.



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Data Communications

Information can be represented in different forms such as text,

numbers, images or pictures, audio and video.

Text: text is represented as a bit pattern, different sets of bit

patterns have been designed to represent text symbols. Each set

is calledcode, and the process of representing symbols is called

coding. For example:32 bit Unicode,ASCIIcode, etc.

Numbers: numbers are represented by bit patterns, number is

directl converted to binar number. ASCII is not used to

represent numbers.

Images:images are also represented by bit patterns. An image is

,on the resolution.

For pure black white image: 1 bit is enough to represent a pixel


:w e, : ac .


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Data Communications

Images:

If image is not pure black white image (gray scale): 2 bit patterns

are use to s ow our eve s o gray sca e : a ac p xe,

01: a dark gray pixel,10: a light gray pixel, 11: a white pixel.

For color images:RGB(red, green, blue) andYCM(yellow, cyan,

magenta met o s are use .

Audio:it refers to recording or broadcasting of sound or music.

It is continuous, not discrete. We can use microphone to changevoice or music to an electric signal (analog or digital).

Video:it refers recording or broadcasting of a picture or movie.

It can be either continuous entit b a TV camera or it can be

combination of images, each is a discrete entity, arranged to

convey the idea of motion. We can change video to a digital or


.


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Data Communications

Communication between two devices can be Simplex, Half

Duplex or Full Duplex.



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Data Communications

Simplex:communication is unidirectional, only one of the

two devices on a link can transmit; the other can only

receive. Keyboards and traditional monitors are

examples of Simplex devices.

,

not at the same time. When one device is sending, the

other can only receive, and vice versa.Walkie - talkiesan c zen an ra os are ot a up ex

systems.

Full - Du lex: both stations can transmit and receive

simultaneously, also called as Duplex. It is used when

communication in both directions is required all the time.


.


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Networks

A Network is a set of devices (often referred as nodes)connected by communication links. A node can be a computer,

printer or any other device capable of sending and / or

.

Networks allow users toshare resources, such as hardware,software, data and information.

Advantages of using a Network

Facilitates communications because people can communicate- , , ,

telephony, and videoconferencing.

Allow tight control over who has access to what data.

Reduce cost by sharing hardware (a printer) and software(using a network version or site license of a program).

Sharin data and information stored on other com uters on the


network.


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Networks

The hardware, software, and expertise required to set up a

network can be expensive.

Networks are vulnerable to security problems.

If the server fails to work, the complete network may also fail

to work.

Distributed Processing:most of the networks use distributed

processing, in which task is divided among multiplecompu ers.



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Networks

number of criteria, most important criteria are performance,

reliability, and security.

Performance:performance is measured by transit time and

response time.

Transit time is the amount of time re uired for a

message to travel from one device to another.

Response Time is the elapsed time between an enquiry.

Performance of a network depends on a number of factors

such asnumber of users,type of transmission medium,

capabilities of connected hardware an efficiency ofsoftware.

Performance is often evaluated by two networkingmetrics:


throughputanddelay.


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Networks

Reliability: in addition to accuracy of delivery, reliability is

measured by thefrequency of failure, the time it takes a link to

recover rom a ure.

Security:network security issues include protecting data from

unauthorized access, protecting data from damage and

development, and implementing polices and procedures for

recovery from breaches and data losses.



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Networks

Based on the size, distance covered and transmission

media used, networks are categorized into three types

namely: LAN, MAN, WAN.

LAN (Local Area Network):

small area such as a building, office or campus.

LANs are designed to allow resources to be shared betweenworkstations.

Covers distance up to 5 - 10 km.

- .

Today LANs have data rate/speed 100 or 1000 Mbps.



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Networks

LAN (Local Area Network)



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Networks

MAN (Metropolitan Area Network):

It covers the area inside a town or Metropolitan city.

It connects many LANs located at different offices orcampuses within a city.

.

Covers distance up to few hundred km.

It has data rate/speed in the range of 1.5 - 150 Mbps.

A good example of MAN is the part of the telephone

company network that can provide a high speedDSLline

to the customer.



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Networks

MAN (Metropolitan Area Network):



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Networks

WAN (Wide Area Network):

Used to interconnect computers over a very large

geographic area such as different cities within the country

or continent or even the whole world.

Covers distance u to few thousand km.

It has data rate/speed in the range of 1.5 Mbps to 2.4 Gbps.

An early example of Switched WAN is X.25 networkes gne to prov e connect v ty etween en users.

Today, a good example of switched WAN is ATM network.



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Networks

WAN (Wide Area Network):



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Networks

It is very rare to see a LAN, a MAN, or a WAN in isolation;

they are connected to one another.

When two or more networks are connected, they become an

Internetwork or internet.

The Internet has revolutionized man as ects of our dail lives.

It has affected the way we do business as well as the way we

spend our leisure time.

wealth of information to our fingertips and organized it for our

use.

: e wor ccess o n comp ex w c ng s a on. National ISP: National Internet Service Providers.

Re ional ISP andLocal ISP.



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Networks



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Network Models Layered Tasks:

We use the concept oflayersin our daily life. As an example, let us

consider two friends who communicate through postal mail.

Sender, Receiver, and Carrier that trans orts the letter.

There is hierarchy of tasks involved.



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Network Models: The OSI Model Established in 1947, the International Standards Organization (ISO) is a

mu t nat ona o y e cate to wor w e agreement on nternat onastandards.

AnISO standardthat covers all aspects of network communications is

t e pen ys ems n erconnec on mo e .

It was first introduced in the late 1970s.

An Open System is a set of protocols that allows any two different

systems to communicate regardless of their underlying architecture.

ISO is the organizationandOSI is the model.

An international standard that is referred by most network vendors for

their products and services.

Best tool for teaching people about sending and receiving data on a

network.

Consist of 7 layers: Physical (L1), Data Link (L2), Network (L3),Transport (L4), Session (L5), Presentation (L6) and Application (L7).

Each of the la er illustrates a articular network function.


This separation of networking functions is called layering.


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Network Models: The OSI Model Advantages of multi layered model

Reduce complexity: simplified teaching and learning.

Standardize interface, accelerate evolution.

Prevent the chan e of one la er from affectin the other la ers.

Characteristics for the 7 layer model Peer to Peer process:layer Nof one computer can communicate

.

Alayer Ngets a service from thelayer N 1and provide a service to

thelayer N + 1. ApplicationLa er 7:

Presentation

Session

Layer 6:

Layer 5:

Network

Data link

Layer 3:

Layer 2:


ayer :


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Network Models: The OSI Model The Interaction between layers in the OSI model.



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Network Models: The OSI Model Data Encapsulation: Wrapping of data with necessary protocol

information before network transit (adding header or trailer or

both).



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Network Models: The OSI Model Why Data Encapsulation?

To addcontrol information(in the form ofheader or trailer or

both) to the data being encapsulated in order to ensure accurate and

secure communication.

The data after encapsulated is calledProtocol Data Unit (PDU). Note:Headersare added to the data atlayers 7, 6, 5, 4, 3,and2.

ra ersare usua y a e on y a ayer .

The control information falls into the three categories:

Address:The address of the sender and / or receiver may beindicated.

Error-detecting code: some sort of frame check sequence.

implement the protocol functions such as priority,quality of

serviceandsecurity.



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Network Models: The OSI Model Functions of Physical Layer

Physical characteristics of interfaces and media:interface between the

devices and the transmission medium (e.g. NIC). It also defines the type of

transmission medium (e.g. Wire).

Representation of Bits:encoding the bits (0s and 1s ) into electrical or

optical signals. This layer also defines the type of encoding (e.g. ASK or

FSK).



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Network Models: The OSI Model Functions of Physical Layer

Data Rate: the transmission rate in terms of number of bit sent each

second (e.g. 56 Kb/s).

S nchronization of Bits: the sender and the receiver clocks must be

synchronized.

Line Configuration:the connection of devices to the medium (point

to ointormulti oint confi uration.

Physical Topology:the configuration for the devices to be connected to

form a network (mesh, star, ringorbus topology).

transmission between two devices: Simplex, Half-Duplex, or Full-

Duplex.

Exam le for the h sical la er rotocol: Point-to-Point Protocol PPP

Ethernet,FDDIetc.



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Network Models: The OSI Model Functions of Data Link Layer

The data link layer is responsible fornodetonode delivery, it makes the

physical layer appear error free to the upper layer (network layer). It also

take care of the following functions:

Framing:The data link layer divides the stream of bits received from the

network layer into manageable data units calledframes.

Ph sical Addressin :The data link la er adds a header to the frame to

define thephysical address (MAC)of thesender(source address) and/or

receiver(destination address) of the frame.



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Flow control:If the rate at which the data are absorbed by the receiver is

less than the rate produced in the sender, the data link layer will impose a

flow control mechanism to prevent overwhelming the receiver.

Error control:Mechanism that can detect and retransmit damaged or lost

frames and also prevent duplication of frames. Error control is normallyachieved by the trailer at the end of the frame.

Access control:When one or more devices are connected to the same link,

data link layer protocols are necessary to determine which device has

control over the link at any given time.

Data 20 62DT


Trailer Source address Destination address


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The data link layer is responsible forNodetoNode orHoptoHop

delivery.



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Network Models: The OSI Model Functions of Network Layer

The network layer is responsible for thesourcetodestinationdelivery

of a packet possibly across multiple networks, if two systems are

connected to the same link, no need for a network layer.

Logical addressing:network layer adds a header to the incoming packet

from the upper layer with a logical address of the sender. If a packet passesthe network boundary, this universal (logical) address helps to distinguish

whether the packet belong to the source or destination systems.



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Routing: Router (or gateways) connect independent networks together,

network layer routes the packet to their final destination by router

(gateway).

The figure shows the case for a computer"S" communicating with a

remote computer"D". SandDare thelogical addressesof the sourceand destination computers respectively, where 02 and79 are the local

physical addressesof the source and destination computers respectively.

S A

F

D

79DT Data S D 02 46

DT Data S D 23 09

DT Data S D 29 79

T

Router

X46

23 29

02 37

R

K

L

15

78Ring

Router

U 61

09

C


OS


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Network Layerresponsible forSourcetoDestinationdelivery.


N k M d l Th OSI M d l


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Network Models: The OSI Model Functions of Transport Layer

Responsible for SourcetoDestination (EndtoEnd) delivery of the

entire message.

Se mentation occurs and this la er also ensures the whole messa e arrives

intact and in order.

A logical path can be set up (fixed pathway) between the Source and

Destination for all ackets in a messa e for additional securit .

This layer has more control oversequencing,flowanderror detection

andcorrection.


N t k M d l Th OSI M d l


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Network Models: The OSI Model Functions of Transport Layer

Connection control:The transport layer can be eitherConnectionlessor

ConnectionOriented.

Flow control:It erform End to End flow control which differs from the

data link layer which is responsible for flow control in single link.

Error control:It performs End to End error control which make sure the

entire messa e arrives at the receivin trans ort la er without error

(damage, loss or duplication). Error correction is done by re-transmission.

Transport layer is responsible for the delivery of a message from one

process to another.




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Network Models: The OSI Model Functions of Session Layer

It is network dialog controlling layer. It establishes, maintains, and

synchronizes the interaction between communication systems.

Dialo control: It allows two s stems to enter into a dialo . The

communication between two processes can be controlled in either half-

duplex or full-duplex.

S nchronization:- It allows a rocess to addcheck ointsinto a stream

of data, when data loss during transmission occurred, more efficient re-

transmission can be performed.




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Network Models: The OSI Model Functions of Presentation Layer

The presentation layer is concerned with the syntax and semantics of the

information exchange between two systems.

Translation:It encodes the sender de endent format of the messa e into

a common format that can be readable by any receiving system.

Encryption:It can transform the original information into an encrypted

form to assure rivac .

Compression: Data compression can reduce the number of bits to be

transmitted, which is important for multimedia transmission.




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Network Models: The OSI Model Functions of Application Layer

This layer enable the user (human or software) to access the network by

user interfaces. Other services provided by this layer are:

Network virtual terminal:remote lo -in to other host in the internet.

File transfer, access, and management: store, retrieve or manage the

files from a remote computer. e.g. File Transfer Protocol (FTP).

. . .

Directory services:access for global information and services e.g.Hyper

Text Transfer Protocol (HTTP).


Network Models: The OSI Model


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Network Models: The OSI Model Summary for the functions of OSI Layers


Network Models: TCP/IP Protocol Suite


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Network Models: TCP/IP Protocol Suite TCP/IP vs OSI model:The layers in the TCP/IP protocol suite do not

exact y matc t ose n t e mo e . e or g na protoco su tewas defined as havingfour layers: host-to-network,internet,transport,

andapplication. However, whenTCP/IPis compared toOSI, we can say

, ,

network,transport, andapplication.

TCP/IP - Transmission Control Protocol / Internet Protocol.

s t e as c commun cat on anguage or protoco o t e nternet.

It can also be used as a communications protocol in the private networks

such as Intranets and Extranets. TCP/IP is a two layered program

TCP Manages the assembling of a message or file into smaller packets.

IP Handles the address part of each packet so that it gets to the right

destination.




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Network Models: TCP/IP Protocol Suite Application Layer: It contains all the higher level protocols such as

, , , , , , etc. Transport Layer: Designed to allow peer entities on the source and

destination hosts carry on a conversation. Contains protocols such as TCP,

an . an are en -to-en rotoco s.

TCP (Transmission Control Protocol):connection-oriented protocolthat manages the assembling of a message or file into smaller packets

t at are transm tte over t e nternet.

UDP (User Datagram Protocol): Connectionless protocol for

applications that do not want TCPs sequencing or flow controlpeec or eo .

SCTP (Stream Control Transmission Protocol):provides support

for newer applications such as Voice over Internet. It combines the

es ea ures o an .




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Network Models: TCP/IP Protocol Suite Internet Layer:defines an official packet format and protocol called as IP

nternet rotoco . nternet ayer e vers pac ets to w ere t ey aresupposed to go (packet routing). Contains protocols such as ARP, RARP,

ICMP, IGMP, RIP, OSPF etc.

ress eso u on ro oco : use to assoc ate t e og ca

address to physical address. RARP (Reverse Address Resolution Protocol):allows the host to

scover t s og ca a ress w en t nows on y t s p ys ca a ress.

ICMP (Internet Control Message Protocol):it is used by hosts and

gateways to send the notification of datagram problems back to sender. IGMP (Internet Group Message Protocol):it allows simultaneous

transmission of message to a group of recipients.

RIP (Routing Information Protocol):It is adistance vector route

discovery protocol. RIP broadcast their route table throughout the

network. The broadcasted information lists destination networks and

their distances from the broadcasting router in terms of hops, must be


crosse . oes no wor we n arge an comp ca e n er-ne wor s.



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Network Models: TCP/IP Protocol Suite Internet Layer: Contains protocols such as ARP, RARP, ICMP, IGMP,

, etc. OSPF (Open Shortest Path First):It was developed to address RIPs

weakness. It is a link state route discovery protocol that provides

t e a ty to scover t e networ s spec c topo ogy. t ex ts

better performance than RIP in large inter-network. Since it facilitatesClass-of-Servicebased onroutingandload balancing.

os o e wor ayer ys ca an a a n ayer : at

physical and data link layer, TCP/IP does not define any specific protocol.

Host connects to the network using relevant protocols so it can send IP

.



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Connection Oriented Networks / Service Connection-oriented services involves 5 phases:

1. Idle No Connection

2. Connection Establishment

3. Data transfer

4. Connection Release


Packet Switched Network

Idle No Connection

Connection Establishment

It provides substantial amount of care for the

user data.

Provides Acknowledgement, Flow Control and

Data Transfer

Connection Release

Error Recovery.

Involves more overheads because of many

support functions.

Idle No Connection

( ACK, Flow Control, Error Recovery )

e a e ut ower serv ce.

Example: TCPs service.



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Connectionless Networks / Service

Connectionless services involves 3 phases:



Also called as datagram networks.

Packet Switched Network

release phase.

Does not provide Acknowledgement, Flow

Control and Error Recovery.

Idle No Connection

It involves less overhead.

Faster service but unreliable Service.

Example: UDPs service.

Data Transfer

( No - ACK, Flow Control, Error Recovery )


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