Telecommunications

and NetworksSection 2 “Telecommunications Network Alternatives”

CHAPTER 6

Lecture-8/ T. Nouf Almujally

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Telecommunications Network Alternatives

Telecommunications is a highly technical, rapidly changing field

Most business professionals don’t needdetailed technical knowledge

However, understanding basic componentsand their characteristics is necessary

Can help you make informed decisions abouttelecommunications alternatives

Telecommunications Network Model

A telecommunications network is any arrangement where… A sender transmits a message to a receiver Over a channel Consisting of some sort of medium

Key Telecommunications Network Component Categories

1. Terminals Any input/output device that uses

telecommunications networks to transmit or receive data

Example: Networked personal computers, network computers or information appliances.

Con.

2. Telecommunications processors Devices that support data transmission and

reception between terminals and computers. Control and support functions in

telecommunications network. Convert data from digital to analog and back code and decode data control the speed, accuracy, and efficiency of the

communications flow between computers and terminals in a network.

Example: modems, switches, and routers

3. Telecommunications channels Media over which data are transmitted and

received Example: copper wires, coaxial cables,

microwave, cellular systems

4. Computers All sizes and types of computers are

interconnected by telecommunications networks.

Con.

Con.

5. Telecommunications control software Controls telecommunications activities Manages the functions of

telecommunications networks

Example: network management programs of all kinds such as,

Telecommunications monitors (mainframes) Network operating systems (network servers) Web browsers (microcomputers)

Types of Communications Networks

CommunicationNetworks

Wide Area

Peer-to-Peer

Client/Server

Virtual Private

Local Area

1- Wide Area Network (WAN)

• Telecommunications networks covering a large geographic area.

• WANs are used by many multinational companies to transmit and receive information among their employees, customers, suppliers, and other organizations across cities, regions, countries, and the world.

2- Local Area Network (LAN)

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

• To communicate over the network:• each PC usually has a circuit board called

“network interface card” • Most LANs use more powerful microcomputer with

a large hard disk capacity, called “file server” or “network server”.

• It contains a network operating system program that controls telecommunications and the use and the sharing of network resources.

Local Area Network (LAN)

• LAN allows users to share hardware, software, and data resources.

3- Virtual Private Network

• VPN is used to establish secure intranets and extranets• The Internet is the main backbone network

• Relies on network firewalls, encryption, and other security features

• VPN = “pipe” travelling through the Internet

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

Virtual Private Network

4- Client/Server Network

• Clients• End user personal computers or networked

computers• Servers

• Used to manage the networks• Processing

• Shared between the clients and servers• Sometimes called a two-tier architecture

• Downsizing: Larger computer systems are being replaced with multiple client/server networks

Client/Server Network

Network Computing

• Called network centric• Views networks as the central computing

resource of the organization• Thin clients provide a browser-based user interface

for processing small application program called applets

• Thin clients include:• Network computers• Net PCs• Other low-cost network devices or information

appliances

Network Computing

• Application and database servers provide• The operating system• Application software• Applets• Databases• Database management software

• Sometimes called a three-tier client/server model because it consists of:• Thin clients• Application servers• Database servers

Network Computing

5- Peer-to-Peer Networks

Central Server Architecture

P2P file-sharing software connects all PCsto a central server

Clicking a link connects the two PCs andautomatically transfers the file to the

requesting PC

The server sends the requesting PC a list oflinks to all active peers who have the file

Peer-to-Peer Networks

Pure Peer-to-Peer Architecture

No central directory or server

File-sharing software connectsone PC to another online user

When you request a file, the softwaresearches every online user, then sends

you a list of active file names

Clicking a link automatically transfers the filefrom that user’s hard drive to yours

Peer-to-Peer Network Diagrams

Central Server Peer-to-Peer Networks

Advantages

Can better protect the integrity and security of the

content and users of the network

Disadvantages

Directory servercan be slowed or overwhelmed by

too many users or technical problems

Pure Peer-to-Peer Networks

Disadvantages

Slow response times

bogus and corrupted files

Telecommunications Media

• Telecommunications channels make use of a variety of telecommunications media.

• These include:• Wired technologies: which physically link

the devices in a network.

• Wireless technologies: which uses microwave, radio waves or infrared light to transport digital communications without wires between communication devices.

Wired Technologies

• Twisted-Pair Wire• Ordinary telephone wire

• Copper wire is twisted into pairs

• The most widely used medium for telecommunications, used in home and office telephone systems and many LANs and WANs.

• Used in established communications networks throughout the world for both voice and data transmission.

• Transmission speeds can range from 2 million bits per second (unshielded) to 100 million bits per second (shielded).

Twisted-Pair Wire

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Shielded Twisted–pair cable

Unshielded Twisted–pair cable

Wired Technologies

• Coaxial Cable• Sturdy copper or aluminum wire

wrapped with spacers to insulate and protect it.

• The cable’s cover minimize interference and distortion of the signals the cable carries.

• They allow high speed data transmission from 200 to more than 500 million bits per second (200-500 Mbps).

• Used in high-service metropolitan areas, LANs and for short distance connections of computers and peripheral devices.

Wired Technologies

• Fiber-Optic Cable• One or more hair-thin filaments of glass

fiber wrapped in a protective jacket.• Transmission rates are high (trillions of

bits per second)• Fiber-optic are not affected by and do

not generate electromagnetic radiation; therefore multiple fibers can be placed in the same cable.

• Need less repeaters for signal retransmissions.

• Expected to replace other communications media

The Problem of “The Last Mile”

• Network providers use fiber optic cable as a communications backbone.• Houses connected to the backbone are wired

with twisted pair (can’t handle the bandwidth provided by fiber)

• Users don’t benefit from the faster, better technology.

• Methods to solve this problem:• Using sophisticated technologies, only coaxial wire that

originally put there.• Bypassing the old wired network completely and provide

high speed services via a satellite or other wireless approach.

• WiMax (still under development stages)

WiMax

Wireless Technologies

TerrestrialMicrowave

Earthbound microwave systems transmit high-speed radio signals in a line-of-sight path between relay systems spaced about 30 miles apart

Antennas placed on top of buildings, towers, and mountain peaks.

Communications Satellites

Use microwave radio signals

Serve as relay stations

Earth stations beam signals to the satellites that amplify and retransmit the signals to other earth stations

Not suitable for interactive, real-time processing

Cellular andPager Systems

Use radio technologies

Geographic areas divided into cells

Each cell has low-power transmitter or radio relay antenna

Computers & other communications processors coordinate/control transmissions to/from mobile users

Wireless Technologies

Terrestrial Microwave

Communications Satellites Cellular,PCS telephone &Pager Systems

Wireless Technologies

WirelessLANS

Uses wireless radio-wave technology to connect PCs within an office or building

Wi-Fi is faster and less expensive than common wire-based LAN technologies

Bluetooth

Short-range wireless

Connects PCs to peripheral devices

Operating at 1 Mbps – range from 10 to 100 meters

Its a cable replacement technology

Wireless Web

Wireless access to the Internet is growing as more web-enabled information appliances appear.

Smart telephones, PDAs all are very thin clients in wireless networks

WAP (Wireless Application Protocol) is the foundation of wireless mobile Internet and Web Applications.

The Wireless Protocol (WAP)

Telecommunications Processors

• Telecommunication Processors:

Perform a variety of support functions between the computers and other devices in a telecommunications network.

1- Modems:

• the most common type of communications processor. Converts a digital signal to an analog frequency that can be transmitted over phone lines, then back into a digital signal (modulation and demodulation).

• Come in several forms.

• Support a variety of functions.

• Transmission error control, faxing, and Automatic dialling and answering

Telecommunications Processors

Telecommunications networks are interconnected by special-purpose communications processors called :

2. Internetwork Processors: such as Hub and Switch: makes connections between

telecommunications circuits in a network. They provide automatic switching among connections called “ports” for shared access to a network’s resources.

Bridge: connect two or more LANs that use the same communications rules or protocol.

Router: intelligent communications processor that interconnects networks based on different protocols

Telecommunications Processors

Communications Processors

3. Multiplexer:• Allows a single communications channel to carry simultaneous data transmissions from many terminals.

• Multiplexers work to increase the number of transmissions possible without increasing the number of physical data channels.

Telecommunications Software

• Telecommunications and network management SW may reside in PCs, servers, mainframes, and communications processors.• Vital part of all telecommunications networks.

• Used to manage network performance.

• Servers rely on network operating systems like Novell Netware, UNIX, Microsoft Widows Servers.

Network Management Functions

Traffic Management

Manage network resources & traffic to avoid congestion, optimize service levels

SecurityProvide authentication, encryption,

firewall, auditing.

Network Monitoring

Troubleshoot & watch over the network, alerting administrators to problems

Capacity Planning

Survey network resources, traffic patterns, and users’ needs

Determine the best way to accommodate network needs as it grows and changes

Network Topologies

Topology: The structure of a network• Star Network

• Ties end user computers to a central computer

• Ring Network• Ties local computer processors together in a ring on a

relatively equal basis

• Bus Network• Local processors share the same communications channel

• Mesh Networks• Uses direct communications lines to connect some or all

of the computers to one another.

Network Topologies

Read from Chapter 6 (Section 2)