Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Wireless USB wikipedia , lookup
Deep packet inspection wikipedia , lookup
Internet protocol suite wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Wireless security wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
List of wireless community networks by region wikipedia , lookup
Policies promoting wireless broadband in the United States wikipedia , lookup
Managing Telecommunications Chapter 6 Information Systems Management In Practice 5E McNurlin & Sprague How are telecommunications analogous to highway systems? The flow of information within and among the corporate office, departments, and individuals analogous to traffic on a highway. Building of systems - IS department responsible for designing, building, and maintaining IS in same way as government is for the streets, roads, and highways. Managed by users - both systems are managed by users, not builders. Standards - must be issued for highway (enforced by police) and message traffic Copyright 2002 by Prentice Hall, Inc. 6-2 The Evolving Telecommunications Scene New telecommunications infrastructure is being built The telecom industry is being transformed Copyright 2002 by Prentice Hall, Inc. 6-3 The Internet is the Network of Choice The Internet has arrived for business use: Beginning in 1994, because of the invention of WWW - a hyperlinked graphical layer of the Net. Funded by DOD in 1960, intended for electronic shipment of large scientific and research files. Built as a distributed network, without a controlling node. Copyright 2002 by Prentice Hall, Inc. 6-4 OSI Reference Model Copyright 2002 by Prentice Hall, Inc. The worldwide telephone system has been so effective in connecting people because it has been based on common standards worldwide. Closed vs. open networks: closed network - one that is offered by one supplier and to which only the products of that supplier can be attached. Open networks are based on international standards so products of many manufacturers can be attached. Seven layer OSI reference model guides the development for computer networks. 6-5 OSI Reference Model Analogy of mailing a letter: - see Figure 6-2 Control information (address and type of delivery) is on the envelope - determines the services provided by the next lower layer and addressing information for next lower layer. When a layer receives a “message” from the next higher layer, it performs the requested services and “wraps” the message in its own layer of control information. It passes the “bundle” to the layer directly below it. On the receiving end, a layer receiving a bundle from a lower layer unwraps the outermost layer of control information, interprets the information, and acts on it. 6-6 Copyright 2002 by Prentice Hall, Inc. OSI Reference Model: The Seven Layers 7 - Application Layer: contains the protocols embedded in the applications used, e.g., HTTP, FTP for transferring files in Internet, X.500 Directory Services, X.400 Mail Handling, postscript 6 - Presentation: translate data to and from language and format of 7; e.g. NetBIOS to communicate among peripherals 5 - Session: control the dialog for a session and acts as a moderator and sees that messages are sent as directed; e.g., Secure Sockets Layer (SSL) to provide Internet security Copyright 2002 by Prentice Hall, Inc. 6-7 OSI Reference Model: The Seven Layers 4- Transport Layer: handle flow control and ensure integrity of each message, resequencing portions of data packets to ensure reliable packet delivery; TCPTransmission Control Protocol 3- Network Layer: route packets to their destination; IP- Internet Protocol, allows packets to traverse an “Internet” Copyright 2002 by Prentice Hall, Inc. 6-8 OSI Reference Model: The Seven Layers Copyright 2002 by Prentice Hall, Inc. 2 - Logical Link: protocols do error correction; LAN protocols, such as Ethernet and Token Ring, work here 1 - Physical Layer: defines the physical connection of the devices to the network; defines electrical and mechanical characteristics of connections, characteristics of transmission wires (e.g., DS1, coax) 6-9 Wireless is the Next Frontier Wireless will be the leading access technology because people are mobile, PC may be next era cell phone Personal area networks (PANs) LANs The last mile Long distance M-commerce Copyright 2002 by Prentice Hall, Inc. 6-10 Wireless is the Next Frontier: Personal Area Networks (PANs) To connect a laptop computer to a cell phone or to connect computers in a room creating an ad hoc LAN or to create a PAN in one’s office PAN is a short distance network (30 ft.) Uses: Copyright 2002 by Prentice Hall, Inc. Synchronize a laptop and a PDA Dispense money to a toll booth 6-11 Wireless is the Next Frontier: LANs Advantage: used in hazardous environments, where no wiring ducts available, disaster recovery, and temporary installations. 1. Infrared light LANs - transmit at frequencies in the lowest frequency in the light spectrum. Transmitters and receivers in sight with each other. Wide BW. Can be licensed anywhere. 2. Narrowband radio frequency (RF) - transmit on a center frequency. RF transmitters must be licensed, government regulates radio signals. Copyright 2002 by Prentice Hall, Inc. 6-12 Wireless is the Next Frontier: LANs Spread Spectrum LANs use RF bands that are allocated to wireless nets by FCC, signal is spread by transmitting a chirp pattern, receiver accepts signals it can decode. RF-noisy environment. Wireless LANs topologies - see Figure 6.5 1. Peer Level System: Each unit communicated with every other unit. Low cost and no master control needed. Breaks down as traffic grows. 2. Centrally Controlled System (client-server): Central controller is linked to a wired LAN. Control unit handles all communications, and has centralized network management and access control. Copyright 2002 by Prentice Hall, Inc. 6-13 Wireless is the Next Frontier: Wireless Local Loops Uses RF technology between a home or business and a telephone company’s central office. Also called “fixed wireless,” this technology is being used in developing countries and remote locations in place of wire line. Copyright 2002 by Prentice Hall, Inc. Networks are rapidly deployed Less costly 6-14 Wireless is the Next Frontier: Wireless Long Distance The most familiar wide area wireless technology is cell phones. Standards Copyright 2002 by Prentice Hall, Inc. Global Systems for Mobile Communications (GMS) Time division for Multiple Access (TDMA) Code Division Multiple Access (CDMA) 6-15 Wireless is the Next Frontier: Wireless Long Distance Technologies: 1G, first generation cell phones used analog technology and circuit switching 2G, second generation cell phones use Digital technology and circuit switching Carry data and messages using short messaging service (SMS) 2.5G Upcoming, will extend 2G digital technologies (GSM, CDMA and TDMA) 3G Upcoming, will provide WANs for PCs and multimedia Copyright 2002 by Prentice Hall, Inc. 6-16 Wireless is the Next Frontier: M-Commerce M-Commerce stands for “Mobile Commerce” Objective: Being able to conduct commerce digitally from wireless devices Technology: Cellular radio technology at higher frequencies than cell phones. Transmitters and receivers have lower power, thus cells are smaller. Copyright 2002 by Prentice Hall, Inc. 6-17 Is Wireless Safe? Wireless services used for LANs and PCSs are in the microwave range. Are they safe for humans? Copyright 2002 by Prentice Hall, Inc. 6-18 The Role of the IS Department The IS Department plays three roles: 1. Create the telecom architecture for the enterprise Connectivity Interoperability 2. Operate the network 3. Stay close to the forefront of the field Copyright 2002 by Prentice Hall, Inc. 6-19 Conclusion The Telecom world is: Big and getting bigger Complex The telecom world has caused a great impact in the new economy E-mail, Web sites, transactions, and business Generations of Internet economy Copyright 2002 by Prentice Hall, Inc. Wired Unwired 6-20