Telecommunications and Networks Chapter 6
Telecommunications and Networks • telecommunications • the components of a telecommunications system. • several telecommunications applications. • the benefits of a network. • basic types of communications media • telecommunications hardware and the role • network topology & five alternatives.
Communications Sender Receiver • Telecommunication • The electronic transmission of signals for communications, such as telephone, radio and television • Data communications • a subset of telecommunications involving computerized data, but not voice communications. Signal
The hardware and software that transmits information from one location to another • Components: • Hardware: Modems, switches, routers, front-end processors, so on. • Media: Twisted-pair wire, cable, microwave radio, so on • Networks: Internet, intranet, wide area, local are, client/server, … • Software: Network operating systems, telecommunications software • Data communication providers: AOL, CompuServe,.. • Protocols: TCP/IP, .. • applications
Basic Communications Channel Characteristics • Simplex channel • Half-duplex • Full-duplex channel • Bandwidth • The range of frequencies that an electronic signal occupies on a given transmission medium. • The broader the bandwidth, the more information that can be carried • Broadband • Telecommunications in which a wide band of frequencies is available to transmit information, allowing more information to be transmitted in a given amount of time.
Communication Media and Channels • Anything that carries an electronic signal and interfaces between a sending device and a receiving device
Types of Media • Twisted-Pair • Coaxial Cable • Fiber-Optic Cable • Microwave Transmission
Telecommunication Signals • Analog signals • Continuous waves • Information conveyed by changing wave characteristics (amplitude and frequency) • Digital signals • Discrete pulses • Information conveyed in binary form (on or off pulses) • Easily understood by computer
Communication Processors • Hardware devices utilized in data transmission and reception • Modem • Multiplexor • Front-end processor
Modems • Analog signals: continuous • Digital signals: discrete • Modulation: translating digital data to analog • Demodulation: translating analog data to digital • Modems modulate & demodulate data
Multiplexers • devices that combine signals from several computers to allow them to be sent over a single transmission line. • Front end processors • computers that manage communications to and from a computer system. This relieves the main computer of work so that it can be free to process other tasks. Front end processors are usually mainframes or midrange computers.
Telecomm Carriers and Services • Telecomm carriers – provide telecomm technology and services for data communication • Common carriers – long-distance phone companies • Value-added carriers – companies that have developed private telecommunications systems and offer their services for a fee.
Telecomm Carriers and Services (continued) • Telecomm services • Switched lines – transmission is routed along path to destination • Dedicated lines – continuous connection is established • Wide-area Telecomm Service (WATS) – lower cost long distance telephone service, refers to the use of toll-free numbers • Integrated Services Digital Network (ISDN) – high speed data transmission over existing phone lines • Digital Subscriber Lines (DSL) - high speed digital transmission over existing phone lines • Phone & dialing services - caller ID, Intelligent dialing • T1 Carrier
What is a network? A collection of computers and devices connected by communications channels Facilitates communications among users and allows users to share resources with other users share data and information share hardware share software
Basic Processing Strategies • Centralized processing • all processing is done at one location. • When • High level of control required • Security is a key issue • Remote sites do not have expertise to operate system • Decentralized processing • different locations have their own processing devices. Devices at different locations aren’t connected together. • When • Local independence is required • Efficiency, based on local needs, is requirement • Remote sites possess individualized skills required for local computing tasks • Distributed processing • computers at different locations are connected by a communications network
Network Concepts & Considerations • Network topology • Network types • Local Area Networks • Wide Area Networks • International networks • Home & small business networks
What is a network topology? The configuration, or physical arrangement, of the devices in a communications network Networks usually use combinations of five topologies Ring Bus Star Hierarchical Hybrid
Computer Network Type Networks may be classified by size: • Local Area Networks (LANs) • Wide Area Networks (WANs) • The Internet Connections to the Internet are through: • LANS • Internet Service Providers (ISP)
Local Area Network (LAN) • Limited geographical area such as a home, school computer laboratory, office building • Any topology possible • Designs • Peer-to-peer • Client-server
Shared Database and Software Packages PC PC PC Network Server Shared Printer PC PC Internetwork Processor to Other Networks Local Area Networks
LAN Components • Network cabling – physically connects each component to the network • Hub – a device that allows cables to be connected together • Network interface card – allows network cabling to be connected to a computer • Network Operating System – software that controls the network • Bus – a main cable to which all clients and servers are connected • Ethernet - protocol for transmitting packets over a bus
What is a network operating system? The system software that organizes and coordinates the activities on a local area network Also called a network OS or NOS Functions Administration:Adding, deleting, and organizing users and performing maintenance tasks File management: locating and transferring files Printer management: Prioritizing print jobs and reports sent to specific printers on the network Security: Monitoring and, when necessary, restricting access to network resources
What is a peer-to-peer LAN? A simple, inexpensive network that typically connects less than 10 computers together Each computer on a peer-to-peer network can share the hardware, data, or information located on any other computer in the network Each computer stores files on its own storage devices network operating system and application software installed on each computer printer may be used by all computers on network
What is a client/server LAN? A network in which one or more computers act as a server and the other computers on the network can request services from the server client client client laser printer server
Wide Area Network (WAN) A network that covers a large geographic area using a communications channel that combines many types of media Can be one large network or can consist of two or more LANs connected together The Internet is the world’s largest WAN
Ontario WAN California Norway Wide Area Network Manitoba Belgium British Columbia Pennsyl- vania Japan Dominican Republic Chile
What is a metropolitan area network (MAN)? A backbone network that connects local area networks in a metropolitan area such as a city or town Handles the bulk of communications activity, or traffic, across that region
Network Types • International networks • Home and small business networks • HomePLC (powerline cable) network • Uses the same lines that bring electricity and power into your home. • Phoneline network • Uses existing telephone lines in the home. • HomeRF (radio frequency) network • Uses radio waves, instead of cables, to transmit data.
Connecting Computers in a Distributed System • Terminal-to-Host • In a terminal-to-host configuration, users have dumb terminals connected to a host computer. All file access and processing is done on the host • File Server • In a file server environment, the file or database resides on a host computer, the file server, and applications, including the database management system, run on the user’s computer. All processing is done on the user’s computer. When an application needs a record, the file server sends the whole file. • Client/Server
Client/server processing • Applications can be divided into presentation, applications, and data management components • Components can be partitioned between the server and the clients to form different implementations. • Peer-to-peer processing • Simplified form of client/server • Devices attached to network have access to all other devices • No file server involved • Simple set up and maintenance • Implemented in many operating systems such as Windows 2000 and Windows XP
Network Communication Software • Needed to provide a number of network functions: • Check for errors • Format messages • Maintain communication logs • Ensure data security and privacy • Provide message translation
Network Communication Software (continued) • Components • Network Operating System – enables all devices on network to communicate • Network Management Software – simplifies human network management tasks • Protocols – specify rules that govern device communication over the network and ensure communications among computers of different types and from different manufacturers
Network Communication Software (continued) • Types of Protocols • Ethernet • Transmission Control Protocol/Internet Protocol (TCP-IP) • SNA
Ethernet • A LAN network protocol that allows personal computers to contend for access to the network • Based on a bus topology, but can be wired in a star pattern • The most popular LAN because it is relatively inexpensive and easy to install and maintain • original Ethernet standard: not very fast by today’s standards, but works well for small to medium networks • Fast Ethernet: transmits data and information at speeds up to 10 times faster than the original standard • Gigabit Ethernet: provides an even higher speed of transmission, with speeds up to 10 times faster than Fast Ethernet
TCP/IP(Transmission Control Protocol/Internet Protocol) • Sends large files accurately over different systems • The primary communications protocol of the Internet • A technology that manages the transmission of data by breaking it up into packets • Packets :Data is divided into small pieces called packets • Routers: Devices that direct packets along the fastest available path • packet switching: Technique of breaking a message into packets, sending the packets, and then reassembling the data
Switching and Routing • Circuit Switching • Physical end-to-end circuit • Phone voice service • Packet Switching • Connectionless • Division of data into packets • Packets have data and addressing information • Packets handled individually by routers • Data is reassembled at the destination
Packet Switching To: Algae Gush <email@example.com> From: Gal Bore <firstname.lastname@example.org> Congratulations on your victory, chump! 125.99.3333 To: Algae Gush <email@example.com> From: Gal Bore <firstname.lastname@example.org> Congratulations on your victory, chump! 125.99.3333 gushmemo25#1 125.99.3333 gushmemo25#2 125.99.3333 gushmemo25#3 125.99.3333 gushmemo25#4
SNA • Systems Network Architecture (SNA) • Introduced by IBM in 1974 • IBM proprietary communications architecture and protocols. • The structure of SNA is a layered architecture much like OSI. But it does not provide full scale support of the OSI protocols.
Communication Between Protocols • Open Systems Interconnection (OSI) model • A standard model for network architectures that divides data communications functions into seven distinct layers to promote the development of modular networks that simplify the development, operation, and maintenance of complex telecommunications networks
Open Systems Interconnection (OSI) model • Application Layer • Presentation Layer (HTTP) • Session Layer • Transport Layer (TCP) • Network Layer (Internet Protocol) • Data Link Layer • Physical Layer (Packet switching, Router)