Telecommunications and Networks Business value of networks The Internet Network components Chapter 6

Network Concepts Computer Network – An interconnected chain, group or system of computers and other devices Number of possible connections on a network is N * (N-1) – Where N = number of nodes (points of connections on the network) – Example, if there are 10 computers on a network, there are 10 * 9 = 90 possible connections This type of mathematical growth is called exponential. This term just means that the growth in number of connections is many times greater than the number of nodes. Metcalfe’s law states that the usefulness, or utility, of a network equals the square of the number of users. 6-2

Telecommunications network Telecommunications – Exchange of information in any form (voice, data, text, images, audio, video) over networks – Any arrangement where a sender transmits a message to a receiver over a channel consisting of some type of medium 6-3

Telecommunications network components Terminals: any input/output device that uses networks to transmit or receive data Telecommunications Processors: devices that support data transmission and reception Telecommunications Channels: media over which data are transmitted and received Computers: all sizes and types; Telecommunications Control Software: programs that control telecommunications activities – telecommunications monitors for mainframe, – network operatings ystems for network servers, – Web browsers for microcomputers. 6-4

Telecommunications network model 6-5

Types of Telecommunications Networks Internet, intranet, extranet, wide area, local area, client/server, peer-to-peer 6-6

The Internet the Internet is a network made up of millions of smaller private networks, each with the ability to operate independent of, and in harmony with, all the other millions of networks connected to the Internet. No central computer system No governing body No one owns it 6-7

Internet Service Provider ISP – A company that specializes in providing easy access to the Internet – For a monthly fee, you get software, user name, password and access 6-8

Popular uses of the Internet 6-9

An Intranet A network inside an organization That uses Internet technologies (such as Web browsers and servers, TCP/IP protocols, HTML, etc.) To provide an Internet-like environment within the organization For information sharing, communications, collaboration and support of business processes Protected by security measures such as passwords, encryption, and firewalls, Can be accessed by authorized users through the Internet 6-10

Enterprise Information Portal 6-11

Extranet Network links that use Internet technologies To connect the Intranet of a business with its customers, suppliers or other business partners 6-12

Extranet Uses 6-13

Wide Area Network (WAN) Telecommunications network that covers a large geographic area 6-14 Source: Courtesy of Cisco Systems Inc.

Metropolitan Area Networks a wide area network optimized a specific geographical area Such networks can range from several blocks of buildings to entire cities. A local telephone company is probably operating on a MAN. MANs will often provide means for internetworking of local area networks. 6-15

Local Area Network (LAN) Connect computers within a limited physical area such as an office, classroom, or building Most LANs use a more powerful microcomputer with a large hard disk capacity, called a file server or network server, that contains a network operating system program that controls telecommunications and the sharing of network resources. 6-16

Local Area Network (LAN) 6-17

Virtual Private Networks (VPN) A secure intranets and extranets, that uses the Internet as its backbone but relies on firewalls, encryption and other security A pipe traveling through the Internet, so we can send and receive our data without anyone outside the pipe being able to see or access our transmissions. 6-18

VPN 6-19

Client/Server networks (two-tier model) Clients (PCs or networked computers workstations) are Interconnected by LANs and share application processing with network servers. 1.Clients: Provide user interface, perform some/most processing on an application. 2.Network Servers: Shared computation, application control, distributed databases. 6-20

Client/Server networks(three-tier model) 1.Thin clients: provide a browser-based user interface for processing small application programs. 2.Application servers for multi-user operating systems, Web server software, and application software applets. 3.Database servers for Internet/intranet Web databases, operational databases, and database management software. 6-21

Client/Server Network 6-22

Peer-to-peer networks Networks that connect from one PC to another PC two major models of peer-to-peer networking technology: – The pure peer-to-peer network architecture – the central server architecture Common use is the downloading and trading of files 6-23

Peer-to-Peer Network 6-24

Telecommunications Media Wired Technologies – Twisted-Pair Wire – Coaxial Cable – Fiber Optics Wireless Technologies – Terrestrial Microwave – Communications Satellites – Cellular Systems – Wireless LANs – Bluetooth 6-25

Wired Technologies Twisted-pair wire: – Ordinary telephone wire – Copper wire twisted into pairs – the most widely used medium for telecommunications Source: Phil Degginger/Getty Images.

Wired Technologies Coaxial cable: – Sturdy copper or aluminum wire wrapped with spacers to insulate and protect it – they can be placed underground and laid on the floors of lakes and oceans. – They allow high-speed data transmission and are used instead of twisted-pair wire lines in high-service metropolitan areas, for cable television systems, and for short- distance connections of computers and peripheral devices Source: Ryan McVay/Getty Images.

Wired Technologies Fiber-optic cable: – One or more hair-thin filaments of glass fiber wrapped in a protective jacket – They can conduct pulses of visible light elements (photons) generated by lasers at transmission rates as high as trillions of bits per second. – This speed is hundreds of times faster than coaxial cable and thousands of times better than twisted-pair wire lines Source: CMCD/Getty Images.

Problem of “The Last Mile” Network providers use fiber optic to provide backbone But houses are connected to the backbone via twisted- pair Cannot get the benefit of the faster, better technology 6-29

Wireless Technologies Wireless telecommunications technologies rely on radio wave, microwave, infrared, and visible light pulses to transport digital communications without wires between communications devices. Terrestrial microwave – Earthbound microwave systems that transmit high-speed radio signals in a line-of-sight path – Between relay systems spaced approximately 30-miles apart – Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks – a popular medium for both long-distance and metropolitan area networks. Communications satellites – Satellite serves as relay stations for communications signals – Uses microwave radio signals 6-30

Wireless Technologies Cellular systems – Divide the geographic area into small areas or cells – Each cell has transmitter or radio relay antenna to send message from one cell to another Wireless LANs (WiFi) – Radio signals within an office or building – Connect PCs to networks Bluetooth – Short-range wireless technology – To connect PC to peripherals such as printer 6-31

Telecommunications Processors Modems Internetwork Processors – Hub – Switch – Router – Gateway Multiplexers 6-32

Modems Modems: Convert digital signals from a computer into Analog frequencies that can be transmitted over ordinary telephone lines. In analog systems: the quantity is as an electrical voltage or current. – For example, if the temperature being measured is 83 degrees then quantity could be 83 volt or 8.3 volt or any other voltage proportional to the temperature. In a digital systems: the quantity is expressed as a number. – For example, the 83 is the binary number , 0 could be represented by 0 volts, and 1 by 5 volts. 6-33

Internetwork Processors Hub and Switch – port switching communications processors that make connections between different network devices (computers, other processors, etc.) Router and Gateway – intelligent communications processors that interconnects networks based on different protocols and different communications architectures 6-34

Communications Processors 6-35

Telecommunications Processors Multiplexer – Allows a single communications channel to carry simultaneous data transmissions from many terminals This process is accomplished in two basic ways. 1.frequency division multiplexing (FDM): multiplexer effectively divides a high-speed channel into multiple slow-speed channels. 2.time division multiplexing (TDM): the multiplexer divides the time so each terminal can use the high- speed line into very short time slots, 6-36

Telecommunications Software Used by PCs, servers and communications processors like multiplexers and routers. to manage network performance, for example: – Network Operating Systems – Middleware: which can help diverse networks communicate with one another. 6-37

Telecommunications Software functions Traffic Management – manage network resources and traffic to avoid congestion and optimize service levels to users Security – provide authentication, encryption, firewall, auditing and enforcement Network Monitoring – troubleshoot and watch over the network, informing network administrators of potential problems before they occur 6-38

6-39 Network Topologies Topology: structure of a network Star: ties end user computers to a central computer Ring: ties local computer processors together in a ring Bus: in which local processors share the same communications channel

Network Topologies 6-40

Network Architectures & Protocols Protocol: standard set of rules and procedures for the control of communications in a network Network Model: is a standard description for how messages should be transmitted between any two points in a telecommunications network. The main idea in any network model is that the process of communication between two endpoints in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Two main type of Network Model: – OSI model – TCP/IP model 6-41

OSI & TCP/IP Models Open Systems Interconnection (OSI) – A seven-layer model that serves as a standard model for network architectures Transmission Control Protocol / Internet Protocol (TCP/IP) – A five layer telecommunications protocol used by the Internet 6-42

OSI & TCP/IP Models 6-43

Bandwidth – Frequency range of a telecommunications channel – Determines transmission rate (speed) and represents the capacity of the connection. – measured in bits per second (bps) Transmission Rates: – Narrow-band channels provide low-speed – Broadband channels provide high-speed 6-44

Transmission Speeds (bandwidth) of various network technologies. 6-45

Switching Alternatives Circuit Switching – Switch opens a circuit to establish a link between a sender and receiver – it remains open until the communication session is completed Packet Switching – Break messages into groups called packets – Transmit packets separately 6-46

Internet Telephony: Voice over IP (VoIP) Using an Internet connection to pass voice data using IP Advantage: Skips standard long-distance phone charges 6-47

Voice Over IP VoIP works by – Digitizing a voice signal, – Chopping it into packets, and – Sending them over a company’s network or the Internet – Packets are reassembled at the destination 6-48