Overview of Data Communications and Networking

(1)

PART I

Overview of

Data Communications and

Networking

Dr.Gihan Naguib

Behrouz A. Forouzan” Data communications and Networking 1

Dr.Gihan Naguib Behrouz A. Forouzan” Data communications and Networking

(2)

Overview

2

made up of : H.W( physical equipments )and S.W

Communicating devices (wire cable)

exchange of data between two devices via transmission medium

Data communication:

distance remote communication. (tele: far)

(telephone, television, telegraphy) means communication at a

: Tele communication remote (over distance)

sharing information. Sharing can be local (face to face) or :

Communication

Data Communication 1

. 1

Dr.Gihan Naguib BehrouzA.Forouzan” Data communications and Networking 5

(3)

delivery of audio or video packets.

Variation in the packet arrival time. It is the uneven delay in the Jitter:

•

delivered later are useless.

the system must deliver data in a timely manner. Data :

Timeliness

•

The system must deliver data accurately

: Accuracy

•

received by only intended device or user.

. Data must be correct destination

System must deliver data to :

Delivery

•

Effectiveness of data communication depends on :

Data Communication 1

. 1

6

Direction of Data Flow

•

Data Representation

•

Components

•

Data Communication 1

. 1

(4)

Components

devices may be connected but not communicating.

between the communicating devices. Without a protocol two agreement

an

is a set of rules that governs data communications. It represents Protocol:

Five components of data communication

8

(5)

1

Direction of data flow

Simplex

,

half duplex and full duplex

. Simplex:

Co communication is unidirectional. (one-way-street). Only one of the two devices on a link can transmit; the other can only receive

E x: As Keyboard (only input) and monitors (only output )

Dr.Gihan Naguib Behrouz A. Forouzan” Data communications and Networking 10

can be analog or digital signal

:

Video

represent sound by continuous (analog) signal Audio :

small dot. The size of pixel represent the resolution.

represented by matrix of pixels (picture element),

Images :

represented by bit pattern (binary number)

: Numbers

enough to represent any symbol in the world.

which is definitely ,

) symbols 216

, 536 , 65 bits pattern ( 32

: Unicode

•

0111111 to 00000000

at left from 0

bit pattern (with an extra -

:8 Extended ASCII

•

) different symbols 128

( patteren bit - 7 : ASCII

•

Text:

Text, numbers, images, audio, and video

Data representation

(6)

2

Direction of data flow

. Half duplex

:

Each station can both transmit and receive , but not at the same time. When one device is sending the other can receive and vice versa. onelane road with two direction).

3

Direction of data flow

. Full-Duplex:

Both stations can transmit and receive simultaneously. ( telephone network) Like two way street with traffic flowing in both directions at the same time.

Signals going in either direction share the capacity of the link in two ways:

 Either the link must contain two physically separate transmission paths one for sending and other for receiving.

 Capacity of the channel is divided between signals traveling in both direction

(7)

the network.

receiving data generated by other nodes on other device capable of sending and/or

can be a computer, printer, or any A node ) connected by communication links.

nodes

a set of devices (often referred to as is

Networks 2

. 1

LAN, MAN and WAN) (

Categories of Networks

physical topology Type of connection

Physical Structures

security Reliability and Performance,

Network Criteria

Networks 2

. 1

(8)

Protecting data from unauthorized access.

. Security:

3

failure, and network’s robustness in a catastrophe.

Measured by frequency of failure, the time it takes to recover from

. Reliability 2

Capabilities of connected H.W and the efficiency of software.

3.

Type of transmission media, 2.

Number of user 1.

: The performance depends on

. Performance:

1

Network criteria

(9)

of connection Type

Physical Structures:

point connection -

to - point

change T.V channel by infrared remote control is possible.

or cable to connect the two ends but other options ,such as microwave satellite are Dedicated link between two devices. Most of them uses an actual length of wire

1 . Point – to - point

16

Users take turns , it is a timeshared :

Temporally

Several devices can use link simultaneously :

Spatially

spatially or temporally.

more than two devices share a single line. The capacity is shared either

. Multipoint (multidrop) connection:

2

Type of connection Physical Structures:

(10)

Physical Structures : physical topology

 The way in which a network is laid out physically. .

 It is the geometric representation of the relationship of all the links and linking devices (nods) to one another.

input/output (I/O) ports

1 - n

Every device on the network must have



link n devices.

physical connection to

2 )/

1 - n(n

Fully connected mesh network has



point link to every other devices -

to - Every device has a dedicated point



Fully connected mesh topology (for five devices)

(11)

in finding its cause and solution.

the network manager to discover the precise location of fault and aids easy. This enables

Fault identification and fault isolation



incapacitate the entire system.

. If one link becomes unusable, it does not

A mesh is robust



occur when links must be shared by multiple devices.

guarantees that each connection can carry its own data load; that can The use of dedicated links

eliminating the traffic problems



other user from gaining access the message

line, only the intended recipient sees it. Physical boundaries prevents every message travels along a dedicated

Privacy or security

(



Advantages:

Mesh topology

20

include several other topology

connecting the main computers of a hybrid network that can

backbone

So a mesh topology is usually implemented in a limited fashion( as a The H.W required to connect each link (I/O ports and cable) expensive.



accommodate.

The sheer bulk of the wiring can be greater than the available space can



and reconnection are difficult

installation

Every device must be connected to every other device,

 : required

Related to the amount of cabling devices and the amount of I/O ports Disadvantages

Mesh topology

(12)

Star topology

Each device has a dedicated point-to-point link only to a central controller (hub)

Unlike a mesh , a star topology does not allow direct traffic between devices, if one device want to send data to another , it send it to the hub, which send it to other device

Behrouz A. Forouzan” Data communications and Networking

Dr.Gihan Naguib 22

identification and fault isolation 3.

remain active.

if one link fails, only that link affected and other links

Robustness:

•

2.

to any other devices.)

each device need only one link and I/O port to connect it

•

Easy to install and reconfigure and less expensive 1.

Advantages

Star topology

(13)

to

Tree topology : Is a variation of star

Not every device plugs directly into the central hub. The majority of devices connect secondary hub that in turn is connected to the central hub

The advantages and disadvantages

of tree topology are generally the same as those of star .The addition of secondary hubs bring more advantage:

Allow more devices to be attached to a single central hub, therefore increase the distance a signal can travel between devices.

Example of tree : Cable TV technology where the main cable from the main office is divided into main branches and each branch divided into smaller branches and so on.

Bus topology dead.

the hub goes down, the whole system is If

the hub.

The dependency of the whole topology on one single point,



Disadvantages

Star topology

24

(14)

•Multipoint connection. Acts as a backbone to link all the devices in a network.

There is a limit on the number of taps a bus can support and on the distance between those taps

As a signal travels along the backbone, some of its energy is transformed into heat, therefore, it becomes weaker and weaker as it has travel farther and farther

27 Dr.Gihan Naguib BehrouzA.Forouzan” Data communications and Networking

(15)

modification or replacement of the backbone).

It can difficult to add new devices (adding more require Reconnection

. 2

noise in both directions

damaged area reflects signals back the direction of origin, creating even between devices on the same side of the problem. The

) stops all transmissions A fault in bus cable (break

Fault

Include difficult of reconnection and fault isolation1.

Disadvantages

Easy of insulation, use less cabling than mesh or star Advantages

Bus topology

28

29 Dr.Gihan Naguib BehrouzA.Forouzan” Data communications and Networking

(16)

Ring topology

Each device has a dedicated point-to-point connection only with the two devices on either side of it

A signal is passed along the ring in one direction from device until it reaches its destination.

Each device in the ring incorporate as repeater

 Repeater :regenerates the signal

 it receives a weakened signal, creates a copy, bit for bit, at the original strength

Dr.Gihan Naguib Behrouz A. Forouzan” Data communications and Networking Behrouz A. Forouzan” Data communications and Networking

Repeater Repeater

Repeater

dual ring

. This can be solved by use

the entire network

disable

such as disabled station) can

A break in the ring

(

Unidirectional traffic.



Disadvantages

network operator to the problem and its location

signal within specified period, it can issue an alarm. The alarm alerts the A signal is circulating at all times (token) if one device does not receive a

: Fault isolation is simplified



connections 2

device requires hanging only

Each device is linked only to its immediate neighbors. To add or delete a

. Easy to install and reconfigure



Advantages:

Ring topology

(17)

Networks categories

Network category is determined by its

size

,

ownership

, the

distance it cover

and its

physical architecture.

Single building LAN

A hybrid topology: a star backbone with three bus networks

32

(18)

Used in business environments, links a workgroup of task- related computer.

LAN - building -

Multiple

(19)

G).

1 MBps(

1000 Mbps or 100 reach to

Mbps. Today Speed can 16

to 4 Traditionally LAN have data rates in the

The most common LAN topologies are bus, ring and star.

LAN use only one type of transmission medium.

S/W)

LAN size determined by licensing restrictions( No of users per copy of S/W stored on server and used as needed by the whole group.

server to other clients.

In LANs one of the computers has a large capacity drive and becomes a applications program) or data.

workstations. The resources may be H.W (e.g. printer) or S.W(

LANs designed to allow resources to be shared between PCs or campus

Privately owned and links the devices in a single office, building or

LAN

36

(20)

DSL line to the customer

A part of the telephone line network that can provide

•

offices throughout the city.

Company can use MAN to connect the LANs in all its

• Examples:

LAN.

- TO - that resources may be shared LAN

may be connected number of LANs into a large network so May be single network such as a cable television network, or it Extended over an entire city.

company) -

public company ( such as local tel.

Owned by private company or it may be a service provided by

MAN (metropolitan)

MAN

38

(21)

WAN

Provides long distance transmission of data, voice , image and video information over large areas ( country or whole world)

In contrast to LAN, WAN may utilize public or private communication equipments or combination

Interconnections of networks :internetwork

An internet (small i) is two or more networks that can communicate with each other.

Dr.Gihan Naguib Behrouz A. Forouzan” Data communications and Networking Behrouz A. Forouzan” Data communications and Networking

Behrouz A. Forouzan” Data communications and Networking

(22)

duplication of effort.

share their findings, to reduce costs and eliminating

connect computers so that the researchers they funded could department of defense was interested in finding a way to

gency (ARPA) in the A

rojects P esearch R

dvanced A

The

.:

1960 In mid of

 History ( self - reading) Brief

interconnected network.

1000 of 100 nternet is a collaboration of more than

 I

The Internet

communication between the hosts.

provided )

NCP Software called Network Control Protocol (

Institute connected via IMPs computers to form a network.

angles and Santa Barba), univ. of utah and SRI (Stand ford Research ARPANET was reality. Four nodes at the UNV. Of California,(at los

, 1969 n

1

computers (mainframe).

ARPA presented its ideas for ARPANET, small network of connected

1967 n

1

Brief history

42

(23)

. ) of internet service providers (ISPs

services devices and switching stations. Today most end users use the Made up of many wide and local area networks joined by connecting

Internet today

detection, segmentation and reassembly.

functions such as error -

level - responsible for higher

TCP:IP^:Internetworking protocol to handle datagram routing and



into two protocols:

TCP Authorities made decision to split



TCP).

rotocol ( P ontrol C

ransmission T

end delivery of packets, -

to - Protocol to achieve end

 , 1972 n 1

Brief history

(24)

Standards Organization Standards

Protocols

Protocols and Standards

44

of the stream to be the message itself.

the reset receiver and

byte to be the address of the the second

address of the sender,

byte of data to be the first

A simple protocol might expect the Example:

are presented.

Structure or format of the data, meaning the order in which they

•

Syntax:

•

Syntax, semantics and timing

Key elements of a protocol:

•

When it is communicated?

•

How it communicated?

•

What is communicated?

• Protocol defines :

Set of rules that governs data communications.

Protocols

(25)

receiver and data will be largely lost.

Mpbs, transmission will overload the 1

process data at only

Mpbs but the receiver can 100

If a sender produces data at Example:

How fast they can be sent?

•

When data to should be sent?

•

Timing:

•

destination of the message.

does an address identify the route to be taken or the final Example:

•

Refers to the meaning of each section of bits.

•

Semantics:

Protocols

46

officially recognized body.

De jure: 2.

functionality of a new product or technology use .Established by manufacturers that define the Have been adopted as standers through widespread De fact:

1.

Two categories:

communication.

necessary in today's marketplace and international

and other service provides to ensure the kind of interconnectivity Provide guidelines to manufactures, vendors, government agencies

Standers

(26)

mail)

- data transmission over public digital network (e :

series -

 Xstandards :V -series( V32, V34,V90)

Data transmission over telephone line Modems

 in general and for phone and data system in particular devoted to the research of standards for telecommunication



T) - ITU ( standard sector

. International Telecommunication Union Telecommunication 2

OSI

•

Multinational body

•

) ISO ( International Organization for Standardization 1.

Standers Organization

48

(27)

SONET) Field of Information Technology (

. Electronic Industries Association (EIA) 5

3 . 802 IEEE Ethernet ):

802 LAN (project

International standards for computing and communications

 branches of engineering

In the fields of electrical engineering, electronics and all related

 International in scoop



( IEEE )

. Institute of Electrical and Electronics Engineers 4

completely private, nonprofit corporation



. American National Standards Institute (ANSI) 3

Standers Organization