computer network introduction to pc hardware

7/31/2019 COMPUTER NETWORK Introduction to PC Hardware

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COMPUTER NETWORKING Diploma Computer Engineering semester-5

Prepared By - HOD, VIMAL ADODARIYA (AARSH MAHAVIDYALAYA) 1

What is computer network?

A computer network is a system in which computers are connected to share information and resources.

The connection can be done as peer-to-peer or client/server. This web site reviews the techniques you

can use to set up and possibly manage a network for home or a small business.

A computer network can be two computers connected:

A computer network can also consist of, and is usually made for, more than two computers:

Introduction to PC Hardware


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v What is network?

A network is a group of interconnected computer systems by means of sharedcommunication link.

When two or more computers and devices like printers are connected with each other,then it is known as computer network.

Networking is the concept of sharing resources and services. In other words, a network of computer is a group of interconnected systems sharing

resources and interacting using a shared communication link.

v Objectives /Requirement of Networking1. To provide the sharing of resources:-

resources like printer, fax, modem and data can be shared among the users.

the resources can be shared from geographically distant place.

2. To provide communication among users:-

network users even being far apart from each other can share their data easily through

networking.


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3. To improve the reliability of network:-

Through backup and redundancy if one processor breaks down, another processor in Network can

handle whole task.

4. To provide distribution of processing function:-

Distribution of processing means the whole processing task is divided into smaller

Units. So instead of single large processor, we can distribute the processing task and it

can be performed from different places.

So it is cost effective as it eliminates the need of large expensive processors.

5. To provide centralize control over whole system:-

6. To provide network users with maximum performance and minimum cost.

v Advantages/Reasons for Networking PCs1. Sharing files2. Sharing printer and other devices3. Enabling common administration and security4. Supporting network application such as electronic mail(email) and database services.

v Components/Essentials of Network

The main components of network are as follows:-

1. Something to share(Resource or data)2. The communication pathway(Transmission media)3. Set of rules for communication(Protocol)


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Network Characteristics

The following characteristics should be considered in network design and ongoing maintenance

Availability.Availability is typically measured in a percentage based on the number of minutes that exist in ayear. Therefore, uptime would be the number of minutes the network is available divided by the

number of minutes in a ye

Costincludes the cost of the network components, their installation, and their ongoing maintenance.

Reliabilitydefines the reliability of the network components and the connectivity between them. Mean

time between failures (MTBF) is commonly used to measure reliability

Securityincludes the protection of the network components and the data they contain and/or the datatransmitted between them.

Speedincludes how fast data is transmitted between network end points (the data rate).

Scalabilitydefines how well the network can adapt to new growth, including new users, applications, and

network components

Topologydescribes the physical cabling layout and the logical way data moves between components.

Many different types and locations of networks exist. You might use a network in your home or home

office to communicate via the Internet, to locate information, to place orders for merchandise, and to

send messages to friends. You might have work in a small office that is set up with a network that

connects other computers and printers in the office. You might work in a large enterprise in which many

computers, printers, storage devices, and servers communicate and store information from many

departments over large geographic areas.

Networks carry data in many types of environments, including homes, small businesses, and large

enterprises. In a large enterprise,


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Corporate office:

A Corporate or main office is a site where everyone is connected via a network and where the bulk of

corporate information is located. A Corporate office can have hundreds or even thousands of people

who depend on network access to do their jobs. A main office might use several connected networks,

which can span many floors in an office building or cover a campus that contains several buildings.

Remote locations:

A variety of remote access locations use networks to connect to the main office or to each other.

Branch offices:

In branch offices, smaller groups of people work and communicate with each other via a network.

Although some corporate information might be stored at a branch office, it is more likely that branch

offices have local network resources, such as printers, but must access information directly from themain office.

Home offices:

When individuals work from home, the location is called a home office. Home office workers often

require on-demand connections to the main or branch offices to access information or to use network

resources such as file servers.

Mobile users:

Mobile users connect to the main office network while at the main office, at the branch office, or

traveling. The network access needs of mobile users are based on where the mobile users are located.

Network Components

All of these networks share many common components. As we describe in definition that network is

basically sharing of information via network components. So network component play a major role in

designing and maintaining network. Some most essential network components listed here.


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Network Criteria:

To be considered effective and efficient, a network must meet a number of criteria. The most important

of these are performance, reliability, and security.

Performance:Performance can be measured in many ways, including transit time and response time. Transit time is

the amount of time required for a message to travel from one device to another. Response time is the

elapsed time between an enquiry and a response.

The performance of a network depends on a number of factors, including the number of users, the type

of transmission medium, the capabilities of the connected hardware, and the efficiency of the software.

Number of users:

Having a large number of concurrent users can slow response time in a network not designed to

coordinate heavy traffic loads. The design of a given network is based on an assessment of the average

number of users that will be communicating at any one time. In peak load periods, however, the actual

number of users can exceed the average and thereby decrease performance. How a network responds

to loading is measure of its performance.

Type of transmission medium:

The medium defines the speed at which data can travel through a connection. Todays networks are

moving to faster and faster transmission media, such as fiber-optic cabling, a medium that can carry

data at only 10 megabits per second. However, the speed of light imposes an upper bound on the data

rate.

Hardware:

The types of hardware included in a network affect both the speed and capacity of transmission. A

higher-speed computer with greater storage capacity provides better performance.

Software:

The software used to process data at the sender, receiver, and intermediate nodes also affects network

performance. Moving a message from node to node through a network requires processing to transform

the raw data into transmittable signals, to route these signals to the proper destination, to ensure error-

free delivery, and to recast the signals into a form the receiver can use. The software that provides these

services affects both the speed and the reliability of a network link. Well-designed software can speedthe process and make transmission more effective and efficient.

Reliability:

In addition to accuracy of delivery, network reliability is measured frequency of failure, the time it takes

a link to recover from a failure, and the networks robustness in a catastrophe.


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Frequency of failure:

All networks fail occasionally. A network that fails often, however, is of little value to a user.

Recovery time of a network after a failure:

How long does it take to restore service? A network that recovers quickly is more useful than one that

does not.

Catastrophe:

Networks must be protected from catastrophic events such as fire, earthquake, or theft. One protection

against unforeseen damage is a reliable system to back up network software.

Security:

Network security issues include protecting data from unauthorized access and viruses.

Unauthorized access:

For a network to be useful, sensitive data must be protected from unauthorized access. Protection can

be accomplished at a number of levels. At the lowest level are user identification codes and passwords.

At a higher level are encryption techniques. In these mechanisms, data are systematically altered in such

a way that if an unauthorized user intercepts them, they will be unintelligible.

Viruses:

Because a network is accessible from many points, it can be susceptible to computer viruses. A virus isan illicitly introduced code that damages the system. A good network is protected from viruses by

hardware and software designed specifically for that purpose.


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What is protocol?

In information technology, a protocol (from the Greekprotocollon, which was a leaf of paper glued to a

manuscript volume, describing its contents) is the special set of rules that end points in a

telecommunication connection use when they communicate. Protocols exist at several levels in a

telecommunication connection. For example, there are protocols for the data interchange at the

hardware device level and protocols for data interchange at the application program level. In the

standard model known as Open Systems Interconnection (OSI), there are one or more protocols at each

layer in the telecommunication exchange that both ends of the exchange must recognize and observe.

Protocols are often described in an industry or international standard.

On the Internet, there are the TCP/IP protocols, consisting of:

Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with otherInternet points at the information packet level

Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internetaddress level

Additional protocols that include the Hypertext Transfer Protocol (HTTP) and File TransferProtocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere

on the Internet

There are many other Internet protocols, such as the Border Gateway Protocol (BGP) and the Dynamic

Host Configuration Protocol (DHCP).

Set of rules for communication:-

The third requirement of networking is protocol. The set of rules for communication is called protocol. All systems on the network must follow a set of common communication rules

for sending and receiving information.

Different protocols are used according to the requirement. For example SMTP (Simple mail transfer protocol) is required for mail transfer. FTP (File transfer protocol) is required for transferring a file. TCP/IP (Transmission Control protocol/internet protocol) is required for internet.
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Standards Organizations

There is no single source for all networking standards. Usually, a standards organization coordinates the

specifications for various pieces of equipment or sets the parameters for features or functions.

However, sometimes a need for a new standard will set events in motion and eventually result in a

standard through consensus or through the action of the market place.

Most local and international network standards have originated with a limited number of organizations.

Each of these organizations defines standards for a different area of network activity. The organizations

are:

American National Standards Institute (ANSI). Comit Consultatif lnternationale de Tlgraphie et Tlphonie (CCITT). Electronics Industries Association (EIA). Institute of Electrical and Electronics Engineers (IEEE). International Organization for Standardization (ISO).

Object Management Group (OMG). Open Software Foundation (OSF). SQL Access Group (SAG).

It is important to be aware of these organizations because their acronyms have become a common

feature of the general networking vocabulary.

American National Standards Institute (ANSI)

ANSI is an organization of U.S. industry and business groups dedicated to the development of trade and

communication standards. ANSI defines and publishes standards for:

Codes. Alphabets. Signaling schemes. Communications protocols.

ANSI also represents the United States in the International Organization for Standardization (ISO) and

the International Telecommunications Union (ITU).

ANSI in Microcomputers

In the microcomputer field, ANSI is commonly encountered in the areas of programming languages and

the SCSI interface. Programming languages, such as C, conform to ANSI recommendations to eliminateproblems in transporting a program from one type of computer system or environment to another.

ANSI Specifications

Major ANSI specifications and standards include:


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ANSI 802.1-1985/IEEE 802.5 Token Ring access, protocols, cabling, and interface.

ANSI/IEEE 802.3Coaxial-cable carrier-sense multiple-access with collision detection

(CSMA/CD) for Ethernet networks.

ANSI 3.l35Structured query language (SQL) database query methods for

front-end clients and back-end database services.

ANSI 3.92 A privacy and security encryption algorithm.

ANSI 12Electronic data interchange (EDI) defining the exchange of

purchase orders, bills of lading, invoices, and other business forms.

ANSI 3T9.5 Fiber Distributed Data Interface (FDDI) specification for voice anddata transmission over fiber-optic cable at 100 Mbps.

SONET

Synchronous Optical Network, a fiber-optic specification defining a

global infrastructure for the transmission of synchronous and

isochronous (time-sensitive data such as real-time video)

information.

Comit Consultatif Internationale de Tlgraphie et Tlphonie (CCITT)

The CCITT, which is also known as the International Telegraph and Telephone Consultative Committee, is

based in Geneva, Switzerland. It was established as part of the United Nations International

Telecommunications Union (ITU), and ITU remains its parent organization. The CCITT studies and

recommends use of communications standards that are recognized throughout the world, and publishes

its recommendations every four years. Each update is distinguished by the color of its cover.

CCITT Protocols

CCITT protocols apply to:

Modems.

Networks. Facsimile transmission (faxes).


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The CCITT Study Groups

The CCITT has been divided into study groups for the 1997-2000 study period; each study group is

preparing recommendations for standards in a different subject area. These subject areas include:

SG 2 Network and service operation.

SG 3Tariff and accounting principles, including related telecommunications economic and

policy issues.

SG 4 TMN and network maintenance.

SG 5 Protection against electromagnetic effects from the environment.

SG 6 Outside plant.

SG 7 Data networks and open system communications.

SG 8 Characteristics of telematic systems.

SG 9 Television and sound transmission.

SG 10 Languages and general software aspects for telecommunication systems.

SG 11 Signaling requirements and protocols.

SG 12 End-to-end transmission performance of networks and terminals.

SG 13 General network aspects.

SG 15 Transport networks, systems, and equipment.

SG 16 Multimedia services and systems.

The V Series

The recommendations for standardizing modem design and operations (transmission over telephone

networks) are collectively called the V series. These include:


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V.22 1200 bps full-duplex modem standard.

V.22bis 2400 bps full-duplex modem standard.

V.28 Defines circuits in RS-232 interface.

V.32 Asynchronous and synchronous 4800/9600 bps standard.

V.32bis Asynchronous and synchronous standard up to 14,400 bps.

V.35 Defines high data-rates over combined circuits.

V.42 Defines error-checking standards.

V.90 Defines a standard for 56Kbps modem communication

The X Series

The series covers Open Systems Interconnection (OSI) standards including:

.200 (ISO 7498) OSI reference model.

.25 (ISO 7776) Packet-switching network interface.

.400 (ISO 10021) Message handling (e-mail).

.500 (ISO 9594) Directory services.

.700 (ISO 9595) Common Management Information Protocol (CMIP).

Electronics Industries Association (EIA)

The EIA is an organization founded in 1924 by U.S. manufacturers of electronic parts and equipment. It

develops industry standards for the interface between data processing and communications equipment

and has published many standards associated with telecommunications and computer communication.

The EIA works closely with other associations such as ANSI and ITU (CCITT).


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EIA Serial Interface Standards

The EIA standards for the serial interface between modems and computers include:

RS-232 A standard for serial connections using DB-9 or DB-25 connectors and maximum cable

lengths of 50 feet. It defines the serial connections between DTE (Data TerminalEquipmenttransmitting equipment) devices and DCE (Data Communications

Equipment receiving equipment) devices.

RS-449 A serial interface with DB-37 connections that defines the RS-422 and RS-423 as

subsets.

RS-422 Defines a balanced multipoint interface.

RS-423 Defines an unbalanced digital interface.

CCITT Equivalents

BIA standards often have CCITT equivalents. RS-232, for example, is also the CCITT V.24 standard.

Institute of Electrical and Electronics Engineers (IEEE)

The Institute of Electrical and Electronics Engineers (IEEE) is a U.S.-based society that publishes a variety

of standards including those for data communications.

The 802 Committees

A subgroup of the IEEE, the 802 committees began developing network specifications in 1980 to ensure

low-cost interfaces. These specifications are passed on to the ANSI for approval and standardization

within the United States. They are also forwarded to the ISO.

Shortly after the 802 project began, the IEEE realized that a single network standard would be

inadequate because it would not be able to account for the diverse hardware and emerging

architectures. To adequately cover the wide range of subjects, the society established committees that

were to be responsible for defining standards in different networking areas.

The 802 Committees

The 802 committees are:


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802.1 Internetworking.

802.2 Logical Link Control (LLC).

802.3 CSMA/CD NETWORK (Ethernet).

802.4 Token Bus NETWORK.

802.5 Token Ring NETWORK.

802.6 Metropolitan Area Network (MAN).

802.7 Broadband Technical Advisory Group.

802.8 Fiber-Optic Technical Advisory Group.

802.9 Integrated Voice/Data Networks.

802.10 Network Security.

802.11 Wireless Network.

802.12 Demand Priority Access NETWORK (100VG-AnyLAN).

802.13 Cable TV Access Method and Physical Layer Specification.

International Organization for Standardization (ISO)

The International Organization for Standardization (ISO) is a Paris-based organization of member

countries, each of which is represented by its leading standard-setting organization. For example, ANSI

represents the United States, and the British Standards Institution (BSI) represents the United Kingdom.

Other organizations represented at the ISO include:

Governmental bodies such as the U.S. State Department. Businesses. Educational institutes. Research organizations. CCITT.

The ISO works to establish international standardization of all services and manufactured products.

ISO Computer Communication Goals

In the area of computing, the ISO's goal is to establish global standards for communications and

information exchange. The standards will promote open networking environments that let multivendor

computer systems communicate with one another using protocols that have been accepted

internationally by the ISO membership.


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The ISO Model

The ISO's major achievement in the area of networking and communications has been to define a set of

standards, known as the OSI (Open Systems Interconnection) reference model which defines standards

for the interaction of computers connected by communications networks.

computer network introduction to pc hardware

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