Network resources

By: Rohit kumar BBS 2nd year

A resource, or system resource, is any physical or virtual component of limited availability within a computer system. Every device connected to a computer system is a resource. A network refers to an interconnected or interrelated chain, group, or system.

Network resources therefore, refer to communication media and network support that are essential for information systems in all types of business organizations.

What Are Network resources?

Telecommunication is the exchange of information in any form i.e., voice, data, text, images, audio, video, etc. over networks. Basic components of telecommunications networks include:

1) Terminals: any input/output device that uses telecommunications network to transmit or receive data. Ex: networked computers, networked personal computers, etc.

2) Telecommunications processors: These are specialized hardware components that support data transmission and reception between terminals and computers. Ex: modem, switches and routers.

3) Telecommunications channels: refer to channels over which data is transmitted and received using combinations of media such as copper wires, coaxial cables, fiber optic cables, or wireless systems like microwave carriers, etc.

Telecommunications network model

4. Computers : All sizes and types of computers can be connected to telecommunications networks.

Ex: Typical arrangement includes mainframe computer as a host for the network, a

minicomputer as a front-end processor, with a dedicated microcomputer as a network server to

a smaller local group of networked microcomputer workstations.

5. Telecommunications control software: consists of programs that control telecommunications

activities and manage the functions of telecommunications networks.

For ex: network management programs include: Telecommunications monitors (mainframes)

Network operating systems (network servers)Web browsers (microcomputers)

Structure of a telecommunications network

TelecommunicationsSoftware

TelecommunicationsSoftware

1

2 3

4

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PCs, NCs, and Other Terminals

ComputersTelecommunicationsChannels and Media

TelecommunicationsProcessors

There are many different types of networks that serve as the telecommunications infrastructure for

the internet and the intranets and extranets of inter-networked enterprises. However there are

some basic types of networks, such as:•Wide Area•Local Area

•Virtual Private•Client/Server•Peer-to-peer

Types Of Telecommunications

Networks

Telecommunication networks that covers a large geographic area are called WANs. They are

essential for the working of many business and govt. organizations and their end users. For ex:

WANs are used by many multinational companies to transmit and receive information among their

employees, customers, suppliers and other organizations across cities, regions and

countries.

Wide area network (wan)

Connects computers within a limited physical area, such as an office, classroom, or building.

LANs have become commonplace in organizations as the link end users in offices, departments etc. They use a variety of media such as, telephone wiring, wireless radio and infrared systems to interconnect microcomputer workstations and computer peripherals enabling distribution of

data files and software packages along the network. To communicate each PC has a circuit

board called network interface card.

Local area network (LAN)

Many organizations use VPN to establish secure intranets and extranets.

VPN relies on network firewalls, encryption, and other security features to build a “pipe” through

the Internet that enables to send and receive data. Advantages:

•Creates a private network without the high cost of a separate proprietary connection.

•Safe exchange of files between distant branches without risk of anyone else outside the pipe seeing

it.

Virtual private network (vpn)

In a client/server network, end user personal computers or networked computers workstations are the clients.

They are interconnected by local area networks and Network servers manage the networks. It is also called

a two-tier client server model because it interconnects LANs and WANs. Today, Larger

computer systems are being replaced with multiple client/server networks. This involves a complex and costly effort to install new application software that

replaces the software of older mainframe-based business information systems.

Client/server networks are more adaptable to a diverse range of business needs & computing workload.

Client/Server Networks

With growing reliance on computers, for many users, the network is the computer. This network computing

concept views networks as the central computing resource of any organization. In network computing, network computers and other Thin clients provide a browser-based user interface for processing applets. Thin clients include Network computers, Net PCs &

Other low-cost network devices or information appliances. It is called three-tier client/server model as

it consists of thin clients, application servers and database servers.

Network computing

Peer-to-peer networks are a powerful telecommunications networking tool for many business applications. It has two

major models:

1) Central Server Architecture: P2P file-sharing software connects all PCs to a central server that contains a directory of all the other users in the

network.When a PC requests a file, the server searches for

any user who has that file and is online at that time.Then The server sends the requesting PC a list of

links to all such active users.Clicking on one such link connects the two PCs and automatically transfers the file to the hard drive of

requesting PC.

Peer-to-Peer Networks

2) Pure Peer-to-Peer Architecture: There is no central directory or server. First, the File sharing software connects your PC to one of the online users in the network. Then an active link to your username is transmitted to all the online users in the network that first user encountered in previous sessions. In this way the more you use peer to peer the more the active links are spread.

When you request a file, the software searches every online user and sends you a list of active file names.

Clicking a link automatically transfers the file from that user’s hard drive to yours.

1)Wired technologies include twisted pair wires, coaxial cables, and fiber-optic cables, all of which

physically link the devices in a network.

2)Wireless technologies include terrestrial microwave, communication satellites, cellular phone systems, and packet and LAN radio, all of which use

microwave and other radio waves.

Telecommunications media

1)Twisted-Pair Wire-•Consists of Cu wire twisted into pairs•Wrapped or shielded in a variety of forms•Used in established communications for both voice and data transmission•Used extensively in home and office telephone systems and many local area networks•Transmission speeds range from 2mbps(unshielded) to 100mbps(shielded).

WIRED TECHNOLOGIES

2)Coaxial Cable-Consists of a sturdy Cu or Al wire wrapped with spacers to insulate and protect itInsulation minimizes interference and distortion of the signal it carriesCan be placed underground and laid on the floors of lakes and oceansTransmission speeds range from 200-500 mbpsUsed for cable T.V. systems, short distance computer connections etc.

3)Fiber Optics-•Consists of one or more hair-thin filaments of glass fiber wrapped in a protective jacket.•Conduct pulses of visible light elements at transmission rates as high as Tbps•Provide substantial size and weight reductions•Multiple fibers can be placed in the same cable•Less need for repeaters for signal retransmissions than Cu wire media

1)Terrestrial Microwave-Involves earthbound microwave systems that transmit high speed radio signals between relay stations spaced approx 30 miles apartUsually placed on top of buildings, towers, hills, and mountain peaks

WIRELESS TECHNOLOGIES

2)Communication Satellites-Use microwave radio as their telecommunication mediumHEO communications satellites are placed in stationary geosynchronous orbits approximately 22,000 miles above the equatorPowered by solar panels and transmission speeds range in several hundred MbpsServe as relay stations transmitted from earth stations and use dish antennas to beam microwave signals to satellitesUsed for voice and video transmission of large volumes of dataMany Cos use networks of small dish antennas known as VSAT to connect their stores and distant worksites via satellite

3)Wireless LANs-Its use arrives when wiring an office/building for a local area network is often a difficult and costly taskGrowing rapidly because of high speed technologiesPrime example is Wi-Fi which is faster and less expensive than other technologiesWi-Fi wireless LANs enable laptop PCs and other devices to connect easily to internet

4)Bluetooth-Short range wireless technology rapidly being built into computer and other devicesServes as a cable-free wireless connection to peripheral devicesOperates at 1Mbps with a range of 10 to 100mCable replacement technology

5)Wireless Web-Smart telephones, pagers, PDAs, other portable devices have become very thin clients in wireless networksAgreement on standard WAP has encouraged the development of many wireless web servicesTelecommunications industry’s goal is to raise wireless transmission speeds to enable streaming video and multimedia apps on mobile devices

Telecommunications processors such as modems, multiplexers, and other devices perform a variety of support functions between the terminals and computers in a telecommunications network. Let's take a look at some of these devices and their functions.

Telecommunications processor

Modems. Modems are the most common type of communications processor. They convert the digital signals from a computer or transmission terminal at one end of a communications link into analog frequencies, which can be transmitted over ordinary telephone lines.

A modem at the other end of the communications line converts the transmitted data back into digital form at a receiving terminal. This process is known as modulation and demodulation, and the word modem is a combined abbreviation of those two words.

Modems are used because ordinary telephone networks were primarily designed to handle continuous analog signals (electromagnetic frequencies), such as those generated by the human, voice over the telephone.

modems

Since data from computers are in digital form (voltage pulses), devices are necessary to convert digital signals into appropriate analog transmission frequencies and vice versa. However, digital communications networks that transmit only digital signals and do not need analog/digital conversion are becoming commonplace. Since most modems also perform a variety of telecommunications support functions, modems may still be needed in digital networks.

modems

Internetwork Processors

Telecommunications network are interconnected by special purpose communications processors called inter-network processors, which include switches, routers, hubs, and gateways.

Switches-A switch is a communications processor that makes connections between telecommunications circuits in a network. Switches are now available in managed versions with network management capabilities.

Bridge-A bridge is a device that connects two or more local area networks that use the same communication rules or protocol.

Router-A router is an intelligent communication processor that interconnects networks based on different rules or protocols, so a telecommunication message can be routed to its destination.

Hub-A hub is a port switching communications processor. Advanced versions of hubs provide automatic switching among connections called ports for shares access to a network's resources.

Gateway-Networks that use different communications architectures are interconnected by using a communications processor called a gateway.

All these devices are essential to providing connectivity and easy access between the multiple LANs within an organization and the wide area networks communications channel. In many cases, star networks take the form of hierarchical networks.

Multiplexers. A multiplexer is a communications processor that allows a single communications channel to carry simultaneous data transmissions from many terminals. Thus, a single communications line can be shared by several terminals.

Typically, a multiplexer merges the transmissions of several terminals at one end of a communications channel, while a similar unit separates the individual transmissions at the receiving end.

This is accomplished in two basic ways. In frequency division multiplexing (FDM), a multiplexer effectively divides a high-speed channel into multiple slow speed channels. In time division multiplexing (TDM), the multiplexer divides the time each terminal can use high-speed line into very short time slots, or time frames.

Multiplexers

A network topology describes the arrangement of systems on a computer network.

It defines how the computers, or nodes, within the network are arranged and connected to each other.

Network topologies

Advantages Disadvantages

Easy to implement Limits on cable length and Workstation numbers

Low Cost Difficult to isolate network faults

  A cable fault affects all workstations

 As the number of workstations increase, the speed of the network slows down

In bus network The computers that send data also attach address of the destination computer with the data. All computers connected to the bus receive the data but only that computer accept it whose address matches the address attached with data.In this topology only one computer at a time can send a data therefore the speed of network reduces as the number of computers attached to the bus increases.

In the star topology, all computers and other network devices connect to a central device called a hub or switch. Each connected device requires a single cable to be connected to the hub, creating a point-to-point connection between the device and the hub.Using a separate cable to connect to the hub allows the network to be expanded without disruption to the network. A break in any single cable will not cause the entire network to failAdvantages Disadvantages

Easy to add new workstations Hub failure cripples all workstationsconnected to that hub

Centralized control Hubs are slighty more expensive than thin-Ethernet

Centralized network/hub monitoring  

Advantages Disadvantages

Cable failures affect limited users Costly Wiring

Equal access for all users Difficult Connections

Each workstation has full access speed to the ring Expensive Adaptor Cards

As workstation numbers increaseperformance diminishes slightly  

the ring topology is a computer network configuration where each network computer and device are connected to each other forming a large circle (or similar shape). Each packet is sent around the ring until it reaches its final destination. Today, the ring topology is seldom used.