Communication Networks
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Communication Networks Reading: Laudon & Laudon chapter 6 Additional Reading: Brien & Marakas chapter 6 COMP 5131 1 Outline Telecommunication and Networking Current Trends Computer Network Key Digital Networking Technologies Communication Network Topologies The Global Internet Addressing and Architecture Governance Future Trends Internet and E-commerce COMP 5131 2 Hyatt Hotels – Wireless Networking ¾ HRO 500 Guest Rooms, 28 floors Distance from central Osaka ¾ Problems Pressures to adapt in a competitive industry Outdated communication methods ¾ Solutions Implement a mobile wireless LAN to provide integrated voice and data coverage across the entire hotel Wireless Handheld or Notebook PCs → Ability to access the info online anywhere in hotel and respond accurately and immediately Provide immediate/before service from past record, memorable service Savings → 60 hrs per year per staff member or total 4800 hrs annually Intel Centrino and Intel XScale technologies capable of handling phone calls as well as data communication allowed employees to access information from anywhere in the hotel Demonstrates IT’s role in hastening the communication and flow of information Illustrates digital technology’s role contemporary networking COMP 5131 3 Trends – Networking and Telecom ¾ Convergence Telephone Networks and Computer Networks Single digital network using Internet standards Cable companies providing voice service ¾ Broadband More than 60% U.S. Internet users → Broadband Cost of Service ↓ ¾ Broadband Wireless Voice and data communication as well as Internet access are increasingly taking place over broadband wireless platforms Mobile Wireless Access → Fastest growing form of internet access (2008 – 96% ↑) COMP 5131 4 Trends – Networking and Telecom ¾ Internet2 Next generation of the Internet – Network of Networks 1996 to 2006 High-performance backbone network – different infrastructure BW → 2.5 - 9.6 Gbps 200 universities, scientific institutions, communications corporations → Part of Internet2 Never, Not intended to replace Internet, test bed Purpose → Develop roadmap, next stage of innovation for current internet New addressing protocol, satellite quality video Most Connections → Abilene Network backbone, 10 Gbps Video Conferencing, Multicasting, Remote Applications, Speed ↑ & BW ↑ ¾ IPv6 Internet population growth, Out of available IP address – 2013 New version, 128 bit addresses, more than new quadrillion (2^128) possible addresses, IPv4 – 32bits Roughly 5,000 addresses for every square micrometer of the earth's surface, sufficiently large for the indefinite future COMP 5131 5 Network Concept ¾ Network An interconnected chain, group or system ¾ Number of possible connections (N → Nodes) N*(N-1) If 10 computers on a network → 10 * 9 = 90 possible connections ¾ Metcalfe’s Law The usefulness of a network equals the square of number of users On a small network, a change in technology affects technology only On a large network like the Internet, a change in technology affects social, political and economic systems COMP 5131 6 Computer Network ¾ Two or More Connected Computers ¾ Major Components in Simple Network Client computer Server computer Network interfaces (NICs) Connection medium Network operating system Routes & manages communication on network Coordinates network resources Example → Server software’s, Novell NetWare, Linux, Microsoft Windows Server Hub Sends packet of data to all connected devices Switch More intelligence, can filter and forward data to specified destination on network ¾ Routers Device used to route packets of data through different networks, ensuring that data sent gets to the correct address COMP 5131 7 Computer Network ¾Switch Makes connections between telecommunications circuits in a network ¾Router Intelligent communications processor that interconnects networks based on different protocols ¾Gateway Connects networks using different communications Connection medium COMP 5131 8 Computer Network ¾Switch Makes connections between telecommunications circuits in a network ¾Router Intelligent communications processor that interconnects networks based on different protocols ¾Gateway Connects networks using different communications Connection medium COMP 5131 9 Network in Large Companies ¾Can Include Hundreds of local area networks (LANs) linked to firmwide corporate network Various powerful servers Web site Corporate intranet, extranet Backend systems Mobile wireless LANs (Wi-Fi networks) Videoconferencing system Telephone network Wireless cell phones COMP 5131 10 Network in Large Companies COMP 5131 11 Key Network Technologies ¾ Client/Server Computing Clients → End user personal computers or networked computers Servers → Manage Networks Interconnected by LANs, Distributed computing model Processing shared between clients and servers Server sets rules of communication for network and provides every client with an address so others can find it on the network Has largely replaced centralized mainframe computing The Internet → Largest implementation of client/server computing COMP 5131 12 Key Network Technologies ¾ Packet Switching Method of slicing digital messages into parcels (packets) Sends packets along different communication paths as they become available, and then reassembling packets at destination Previous circuit-switched networks required assembly of complete point-to-point circuit Expensive, Wasted communication capacity Packet switching more efficient use of network’s communications capacit COMP 5131 13 Key Network Technologies ¾ Packet Switching Communication Data are grouped into small packets, transmitted independently over various Communications channels Reassembled at their final destination COMP 5131 14 Computer Network ¾Network Topologies (Structure of Network) Star → ties end user computers to a central computer Ring → ties local computer processors together in a ring on a relatively equal basis Bus → local processors share the same comm channel COMP 5131 15 Key Network Technologies ¾ Open Systems Interconnection Model (OSI) A seven-layer model that serves as a standard model for network architectures Model for how messages should be transmitted between two points in a network Each layer adds functions ¾ TCP/IP and Connectivity Connectivity between computers enabled by protocols Protocols → Different components in network communicate with each other by adhering to common set of rules Transmission Control Protocol/Internet Protocol Common worldwide standard that is basis for Internet TCP → Movement of data between computes, establish connection, sequences transfer of packets, acknowledges packet sent IP → Responsible for delivery of packets, disassembling and reassembling of packets A five layer telecommunications protocol used by the Internet COMP 5131 16 Key Network Technologies ¾ OSI (7 layer) Communication Network ¾ TCP/IP (5 layer) COMP 5131 17 Key Network Technologies ¾TCP/IP Postal system → finds your house addresses, delivers your mail (packets) IP4 → Current IP addressing protocol, 32 bit Internet address value First Part identifies the network on which the host resides Second part identifies the particular host on network Four decimal numbers separated by period Valid addresses can range from 0.0.0.0 to 255.255.255.255 (4.3 billion addresses) COMP 5131 18 Key Network Technologies ¾ TCP/IP (IP4) Class E addresses Reserved → Research Organizations, Experiments Limited broadcast address → 255.255.255.255 One sender to many recipients, all the nodes on LAN Loopback IP address → 127.0.0.1, Adapter intercepts and sends back to application, network behavior Private Addresses (reserved range for intranet, free usage) COMP 5131 19 Key Network Technologies ¾ IPv6 128 bit address Generally written in hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh:hhhh E3D7:0000:0000:0000:51F4:9BC8:C0A8:6420 Shorthand Notation → E3D7::51F4:9BC8:C0A8:6420 Mixed Notation → E3D7::51F4:9BC8:158.132.11.186 Only two reserved addresses in IPv6 0:0:0:0:0:0:0 → Internal for protocol implementation 0:0:0:0:0:0:1 → Loopback address (similar to 127.0.0.1 in IPv4) COMP 5131 20 Key Network Technologies ¾Internet Over 46 million servers (2004) 710 – 945 million users (2004) No central computer system No governing body No one owns it COMP 5131 21 The Global Internet ¾ What is Internet? ¾ Internet Addressing and Architecture The Domain Name System Hierarchical structure Top-level domains ¾ Internet Architecture and Governance No One Owns Internet! Worldwide Internet Policies → Professional & Government Bodies IAB, ICANN, W3C COMP 5131 22 The Global Internet ¾ Domain Name System The Domain Name System is a hierarchical system with a root domain, top-level domains, second-level domains, and host computers at the third level. COMP 5131 23 The Global Internet ¾Internet Services E-mail Chatting and instant messaging Newsgroups Telnet File Transfer Protocol (FTP) World Wide Web VoIP Virtual private network (VPN) COMP 5131 24 The Global Internet ¾Client/Server Computing on Internet Client computers running Web browser and other software can access an array of services on servers over the Internet. These services may all run on a single server or on multiple specialized servers. COMP 5131 25 The Global Internet ¾How Voice over IP Works? An VoIP phone call digitizes and breaks up a voice message into data packets that may travel along different routes before being reassembled at the final destination. A processor nearest the call’s destination, called a gateway, arranges the packets in the proper order and directs them to the telephone number of the receiver or the IP address of the receiving computer. COMP 5131 26 Virtual Private Network ¾ A secure network that uses the Internet as its backbone but relies on firewalls, encryption and other security ¾ A pipe traveling through the Internet COMP 5131 27 The Global Internet ¾Virtual Private Network Using Internet This VPN is a private network of computers linked using a secure “tunnel” connection over the Internet. It protects data transmitted over the public Internet by encoding the data and “wrapping” them within the Internet Protocol (IP). By adding a wrapper around a network message to hide its content, organizations can create a private connection that travels through the public Internet. COMP 5131 28 Network Computing ¾ Thin Clients Network computers and other clients provide a browser-based user interface COMP 5131 29 Case Study – Monitoring Employees People Monitoring Employees on Networks: Unethical or Good Business? ¾ Question - Should managers monitor employee e-mail and Internet usage? Why or why not? Corporate misuse, abuse of email for personal reasons is exploding Employees who use company resources for work not related to the company are, in essence, engaged in “service theft.” Companies are in business to generate profits for their shareholders. Managers certainly should be concerned with the loss of time and employee productivity, the additional traffic it creates on their networks that inhibits the efficiency for real business purposes, lost revenue or missed opportunities, as well as overcharging clients because of lost employee efficiencies. The company itself is responsible for the use of its resources and what employees do while using them Adverse publicity can seriously affect a company and could even result in very expensive lawsuits Companies also fear e-mail leakage of trade secrets. Other legal and regulatory problems involve the safe keeping of all e-mails that are generated on corporate equipment. This information must be retained for specific time periods and may be requested as evidence in a lawsuit COMP 5131 30 Case Study – Monitoring Employees ¾ Describe an effective e-mail and Web use policy for a company Effective e-mail and Web use policy must be carefully designed and clearly communicated to all persons who use these corporate resources There are a number of different policies - Some companies allow absolutely no personal use of corporate networks whereas others allow some degree of activity that is easily monitored A good policy will detail exactly what type of activity is acceptable and what is not allowed Clearly articulate sanctions that will be followed for any and all offenses in relation to the policy Most of all, rules for Internet usage should be tailored to specific business needs and organizational cultures COMP 5131 31 Case Study – Monitoring Employees Explore the Web site of online employee monitoring software such as SpectorSoft, NetVizor, SpyTech, or Activity Monitor and answer the following questions ¾ What employee activities does this software track? What can an employer learn about an employee by using this software? SpectorSoft Web site - The Spector Pro keylogger will instantly inform you whenever they type, or even simply view, any alert words or phrases that you specify Spector Pro continuously looks for alert words in everything they type, every web site they visit, all chats/Instant Messages and in each email sent or received. Every time a keyword is detected, Spector Pro will immediately email you a detailed report of when, where and how the keyword was used COMP 5131 32 Case Study – Monitoring Employees ¾ How can businesses benefit from using this software? Testimonials → With Spector Pro, we were immediately able to discover which employees were non-productive. Not only has Spector Pro helped us weed out lazy workers, it also helped to uncover fraud in some of our departments In addition, this program has also allowed us to realize and resolve training issues we've experienced with our internal software Spector Pro is very stealthy, has no noticeable effect on system performance and provides excellent return on investment COMP 5131 33 World Wide Web ¾ Hypertext Markup Language (HTML): Formats documents for display on Web ¾ Hypertext Transfer Protocol (HTTP): Communications standard used for transferring Web pages ¾ Uniform resource locators (URLs): Addresses of Web pages Example → http://www.megacorp.com/content/features/082602.html ¾ Web servers Software for locating and managing Web pages COMP 5131 34 World Wide Web ¾ Search Engines Started in early 1990s as relatively simple software programs using keyword indexes In 1994 two Stanford students → Hand selected list of web pages Yet Another Hierarchical Officious Oracle – Yahoo! In 1998, two another Stanford students released first version of Google Not only index each page’s word but also ranked search results → PageRank Also combination of key words → Foundation of Google Major source of Internet advertising revenue via search engine marketing, using complex algorithms and page ranking techniques to locate results ¾ Shopping Bots Use intelligent agent software for searching Internet for shopping information MySimon or Google Product Search Filter and retrieve info about products of interest, negotiate price/delivery terms, evaluate competitive products using criteria ¾ Semantic Web Collaborative effort to make Web searching more efficient by reducing the amount of human involvement in searching for and processing Web information COMP 5131 35 World Wide Web ¾ How Google Works? The Google search engine is continuously crawling the Web, indexing the content of each page, calculating its popularity, and storing the pages so that it can respond quickly to user requests to see a page. The entire process takes about one-half second. COMP 5131 36 World Wide Web ¾ Major Web Search Engines Google is the most popular search engine on the Web, handling 56 percent of all Web searches. COMP 5131 37 World Wide Web ¾ Web 2.0 Started in early 1990s as relatively simple software programs using keyword indexes Second-generation interactive Internet-based services for people to collaborate, share information, and create new services online Blogs → Chronological, informal Web sites created by individuals using easy-to-use weblog publishing tools RSS (Really Simple Syndication) → Syndicates Web content so aggregator software can pull content for use in another setting or viewing later, mashups Wikis → Collaborative web sites where visitors can add, delete, or modify content on the site COMP 5131 38 The Global Internet ¾Intranet Use existing network infrastructure with Internet connectivity standards software developed for the Web Create networked applications that can run on many types of computers Protected by firewalls ¾Extranet Allow authorized vendors and customers access to an internal intranet Used for collaboration Also subject to firewall protection COMP 5131 39 The Wireless Revolution ¾Wireless Devices PDAs, BlackBerry, smart phones Instant availability of Info from field – Inventory level ↓ ¾Cellular Systems Competing standards for cellular service United States → CDMA Most of rest of world → GSM Third-generation (3G) networks Higher transmission speeds suitable for broadband Internet access 384 Kbps (Mobile), 2Mbps (Stationary), Available in HK, Japan, S. Korea, Taiwan, Singapore, N. Europe, Not yet in USA(?) COMP 5131 40 The Wireless Revolution ¾ Bluetooth Network (PAN) Short-range wireless technology To connect PC to peripherals such as printer Within a small 30-foot (10-meter) area COMP 5131 41 The Wireless Revolution ¾ Wireless Computer Network and Access Bluetooth (802.15) Links up to 8 devices in 10-m area using low-power, radio-based communication Useful for personal networking (PANs) FedEx drivers, handheld → computers → cellular No docking of handheld units in transmitters, saves 20 million $ year Wi-Fi (802.11) Set of standards: 802.11a, 802.11b, 802.11g, 802.11n Used for wireless LAN and wireless Internet access Also known as Wi-Fi → Wireless for Fidelity Use access points → Device with radio receiver/transmitter for connecting wireless devices to a wired LAN Hotspots → One or more access points in public place to provide maximum wireless coverage for a specific area Weak security features, Susceptibility to Interference (n, MIMO) COMP 5131 42 The Wireless Revolution ¾An 802.11 Wireless LAN Radio waves to transmit network signals from the wired network to the client adapters COMP 5131 43 The Wireless Revolution ¾Wireless Computer Network and Access WiMax (802.16) Wi-Fi range < 300 feet from base stations WiMax → Worldwide Interoperability for Microwave Access 802.16 → 75 Mbps, Robust Security & QOS Links Wireless access range of 31 miles Require WiMax (Rooftop) antennas Broadband Cellular Wireless Many cell services offer Wi-Fi capabilities for Internet access No Wi-Fi hotspot?, Small card (Laptop) → 3G, 300-500 Kbps COMP 5131 44 The Wireless Revolution ¾Wireless Sensor Networks Networks of hundreds or thousands of interconnected wireless devices embedded into physical environment to provide measurements of many points over large spaces Used to monitor building security, detect hazardous substances in air, monitor environmental changes, traffic, or military activity Devices have built-in processing, storage, and radio frequency sensors and antennas Require low-power, long-lasting batteries and ability to endure in the field without maintenance COMP 5131 45 The Wireless Revolution ¾ Wireless Sensor Networks The small circles represent lower-level nodes and the larger circles represent high-end nodes. Lower-level nodes forward data to each other or to higher-level nodes, which transmit data more rapidly and speed up network performance. COMP 5131 46
