10Base2 refers to the specifications for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate maximum segment length being 200 meters.10Base5 refers to the specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum segment length being 500 meters. Thick coaxial cable has an extra protective plastic cover that helps keep moisture away from the center conductor. This makes thick coaxial a great choice when running longer lengths in a linear bus network. One disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
IntranetIntranet is a private computer network using Internet Protocol technology to securely share organization's information within that organization. Intranet refers only to the organization's internal website, therefore it is not exposed to the general public and is accessed only by authorized persons (Miller,2009). Moreover, an intranet can be understood as a private extension of the Internet.By storing information on an Internal Web Server and providing each computer on the network with browser software such as Internet Explorer, and a network data access application, anyone on the network can view information located on the Intranet Server (Yusof & Saat, n.d.). This allows for easy and inexpensive distribution of internal corporate information, an essential ingredient in today's fast-moving competitive environment.FeaturesIntranet can enhance communication and collaboration by using the same common standards, technologies, protocols of the internet, such as HTTP (web services), SMTP (e-mail), and FTP (file transfer protocol). However, the computer servers of the intranet are accessible only from internal computers within the organization. intranet comes standard with free technical support and hassle-free Web-accessibility so you can focus on your core business in order to increase productivity and keep IT costs low (Turner & Weickgenannt, 2009).Advantages (Kos, 2011).- Reduce printing, paper costs- the computers and servers can communicate much faster than they could over the internet- Useful for sharing information throughout an organization while still keeping it private.- inexpensive to use (once it is set up)Disadvantages (Kos, 2011).- It is an evolving technology that requires upgrades and could have software incompatibility problems- Security features can be inadequate- Maintaining content can be time consuming- Some employees may not have PCs at their desksRole of IntranetThere are four types of applications which provide by intranet (Wood & Varey’s, 1999).1. Communication and collaborationMany companies situate at several different locations across a country or even differentcountries. IntranetpromotesCommunication and collaboration between groups in different locations by sending and receiving e-mail, voice mail and virtual team meeting.2. Web publishingIntranet is often used to implement paperless office. Companies use intranet to publish company newsletters, product catalogs and policy manuals.3. Business operationAn intranet supports functions including order processing, inventory control and management information systems.4. Intranet managementIntranet is a tool that allows users access to a variety of internal and external business. Also, it is used to centrally administer all network functions.SecurityIntranet security focuses on the various ways in which intranet delivers information within the enterprise and to its partners, and protecting it from unauthorized outsiders. This means that the security capabilities of intranet technologies enable companies to control the availability of information and the authenticity of that information. For example, the new security architecture SESAME, which builds on the Kerberos authentication system, adding to it both public-key technology and a role-based access control service, and modern security technologies such as PGP, Secure Shell, Secure Sockets Layer. Other technologies are also included such as requiring a password, firewall and limiting access (Chin,2005).Intranet vs. Extranet and InternetAn "intranet" is the generic term for a collection of private computer networks within an organization. An "extranet" is a computer network that allows controlled access from the outside for specific business or educational purposes. Intranets and extranets are communication tools designed to enable easy information sharing within workgroups. The Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services, such as electronic mail, online chat, file transfer, and the interlinked Web pages and other documents of the World Wide Web. (shahidpages ,2009)There's one major distinction between an intranet and the Internet: The Internet is an open, public space, while an intranet is designed to be a private space. An intranet may be accessible from the Internet, but as a rule it's protected by a password and accessible only to employees or other authorized users. The Extranet is a portion of an organization's Intranet that is made accessible to authorized outside users without full access to an entire organization's intranet.An example of intranetAs an example of Intranet, Air New Zealand Intranet has the following main functions:• News, events & Press Release• Company Policies & Announcements• Classified Ads & Staff Offers• Share Price• Search & Links• Publishers- Training document- Manuals & Standards- IT Service- Travel
UNIT 3Network & E – Commerce
Networks A network can be defined as two or more computers connected together in such a way that they can share resources. The purpose of a network is to share resources. A network is simply a collection of computers or other hardware devices that are connected together, either physically or logically, using special hardware and software, to allow them to exchange information and cooperate. Networking is the term that describes the processes involved in designing, implementing, upgrading, managing and otherwise working with networks and network technologies.
Why networking? Sharing information Sharing hardware or software Sharing an Internet Connection Centralize administration and support
Computer Network Uses of Computer NetworkCompanies People Social IssuesResource Sharing Access to remote News-groups informationGeography Person To Person Bulletin Boards communication & e- mailHigh reliability: Interactivereplication EntertainmentSaving money on the flowClient-server modelScalability: Ability toincrease systemperformance graduallyas the workload grows.
Advantages of networking Connectivity and Communication Data Sharing Hardware Sharing Internet Access Internet Access Sharing Data Security and Management Performance Enhancement and Balancing Entertainment
Disadvantages Network Hardware, Software and Setup Costs Hardware and Software Management and Administration Costs Undesirable Sharing Illegal or Undesirable Behavior Data Security Concerns
Network Classifications Based on network size: LAN WAN MAN Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) Wireless Based on management method: Peer-to-peer Client/Server
Network Size Local Area Networks (LANs) Wide Area Networks (WANs) Metropolitan Area Network (MAN)
LAN A local area network (LAN) is a computer network covering a small geographic area, like a home, office, or group of buildings Limited by no. of computers and distance covered Usually one kind of technology throughout the LAN Serve a department within an organization
WAN Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries). The largest and most well-known example of a WAN is the Internet. WANs are used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations
MAN A metropolitan area network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large local area network (LAN) but smaller than the area covered by a wide area network (WAN). The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a wide area network). It is also used to mean the interconnection of several local area networks by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.
Classification on the basis of management Peer to peer Client- server
Peer-to-Peer Networks Peer-to-peer network is also called workgroup No hierarchy among computers - all are equal No administrator responsible for the network Peer-to-peer 15
• Advantages of peer-to-peer networks: • Low cost • Simple to configure • User has full accessibility of the computer Disadvantages of peer-to-peer networks: • May have duplication in resources • Difficult to uphold security policy • Difficult to handle uneven loading Where peer-to-peer network is appropriate: • 10 or less users • No specialized services required • Security is not an issue • Only limited growth in the foreseeable future 16
Clients and Servers Network Clients (Workstation) Computers that request network resources or services Network Servers Computers that manage and provide network resources and services to clients Usually have more processing power, memory and hard disk space than clients Run Network Operating System that can manage not only data, but also users, groups, security, and applications on the network Servers often have a more stringent requirement on its performance and reliability 17
Advantages of client/server networks Facilitate resource sharing – centrally administrate and control Facilitate system backup and improve fault tolerance Enhance security – only administrator can have access to Server Support more users – difficult to achieve with peer-to- peer networks Disadvantages of client/server networks High cost for Servers Need expert to configure the network Introduce a single point of failure to the system 18
Classification on the basis of typology Bus Ring Star Mesh
Network topology A topology is a way of ―laying out‖ the network. Topologies can be either physical or logical. Physical topologies describe how the cables are run. Logical topologies describe how the network messages travel
Bus Topology A bus is the simplest physical topology. It consists of a single cable that runs to every workstation This topology uses the least amount of cabling, but also covers the shortest amount of distance. Each computer shares the same data and address path. With a logical bus topology, messages pass through the trunk, and each workstation checks to see if the message is addressed to itself. If the address of the message matches the workstation’s address, the network adapter copies the message to the card’s on-board memory.
Bus topology Advantages Simple Low Cost Easy to find errors Disadvantage It is difficult to add a workstation If any one of the cables breaks, the entire network is disrupted. Passive topology Congestion Less no. of users
Star Topology A physical star topology branches each network device off a central device called a hub. Very easy to add a new workstation. Also, if any workstation goes down it does not affect the entire network. But if the central device goes down, the entire network goes down.
Star topology Advantages Easy to install. Prevents data collision & congestion If one devices breakdowns, whole network is not affected Disadvantages Star topologies are more expensive to install than bus networks One point failure
Ring Topology Each computer connects to two other computers, joining them in a circle creating a unidirectional path where messages move workstation to workstation. Each entity participating in the ring reads a message, then regenerates it and hands it to its neighbor on a different network cable.
Ring topology Advantages Avoids data collision Every computer serves as a repeater to boost signals Disadvantages Difficult to add new computers More expensive If one computer fails, whole network fails
Mesh topology (cont.) The mesh topology is the simplest logical topology in terms of data flow, but it is the most complex in terms of physical design. Each device is connected to every other device This topology is rarely found in LANs, mainly because of the complexity of the cabling. If there are x computers, there will be (x × (x–1)) ÷ 2 cables in the network. For example, if you have five computers in a mesh network, it will use 5 × (5 – 1) ÷ 2, which equals 10 cables. This complexity is compounded when you add another workstation.
Mesh topology Advantages High fault tolerance There will always be a way of getting the data from source to destination. Disadvantages Very expensive to install and maintain. Becomes inefficient with five or more entities.
Advantages and Disadvantages ofNetwork Topologies Topology Advantages Disadvantages Bus Cheap. Easy to install. Difficult to reconfigure. Break in bus disables entire network. Star Cheap. Easy to install. More expensive than bus. Easy to reconfigure. Fault tolerant. Ring Efficient. Easy to install. Reconfiguration difficult. Very expensive. Mesh Simplest. Most fault tolerant. Reconfiguration extremely difficult. Extremely expensive. Very complex.
Based on Transmission Two main categories: Guided ― wires, cables Unguided ― wireless transmission, e.g. radio, microwave, infrared, sound, sonar Guided media Twisted-Pair cables: Unshielded Twisted-Pair (UTP) cables Shielded Twisted-Pair (STP) cables Coaxial cables Fiber-optic cables
Twisted-Pair Cables Twisted pair cabling is a form of wiring in which two conductors are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources If the pair of wires are not twisted, electromagnetic noises from, e.g., motors, will affect the closer wire more than the further one, thereby causing errors The least expensive media Capable of handling up to 100 Mbps
Unshielded Twisted-Pair (UTP) Unshielded twisted pair (UTP) is the most popular The quality of UTP may vary from telephone-grade wire to extremely high-speed cable. Each pair is twisted with a different number of twists per inch to help eliminate interference from adjacent pairs and other electrical devices. The tighter the twisting, the higher the supported transmission rate and the greater the cost per foot. It is the least expensive cable but may be susceptible to radio and electrical frequency interference
Categories of UTP CablesEIA classifies UTP cables according to the quality: Category 1 ― the lowest quality, only good for voice, mainly found in very old buildings, not recommended now Category 2 ― good for voice and low data rates (up to 4Mbps for low-speed token ring networks) Category 3 ― at least 3 twists per foot, for up to 10 Mbps (common in phone networks in residential buildings) Category 4 ― up to 16 Mbps (mainly for token rings) Category 5 (or 5e) ― up to 100 Mbps (common for networks targeted for high-speed data communications)
Shielded Twisted Pair cable If you cable is placed in environments with lots of potential interference shielded twisted pair is the solution. Shielded cables can also help to extend the maximum distance of the cables. STP cabling includes metal shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interferences).
Coaxial Cables Coaxial cabling has a single copper conductor at its center. A plastic layer provides insulation between the center conductor and a braided metal shield The metal shield helps to block any outside interference from fluorescent lights, motors, and other computers.
Although coaxial cabling is difficult to install, it is highly resistant to signal interference. It can support greater cable lengths between network devices than twisted pair cable. The two types of coaxial cabling are Thin coaxial cable is also referred to as thinnet. (10Base2) Thick coaxial cable is also referred to as thicknet. (10Base5) In general, coaxial cables, or coax, carry signals of higher freq (100KHz–500MHz) than UTP cables Outer metallic wrapping serves both as a shield against noise and as the second conductor that completes the circuit
Fiber-Optic Cables Light travels at 3 108 ms-1 in free space and is the fastest possible speed in the Universe Light slows down in denser media, e.g. glass Refraction occurs at interface, with light bending away from the normal when it enters a less dense medium Beyond the critical angle total internal reflection
Fiber optic cabling consists of a center glass core surrounded by several layers of protective materials. It transmits light rather than electronic signals eliminating the problem of electrical interference. This makes it ideal for certain environments that contain a large amount of electrical interference. It has also made it the standard for connecting networks between buildings, due to its immunity to the effects of moisture and lighting. Fiber optic cable has the ability to transmit signals over much longer distances than coaxial and twisted pair. It also has the capability to carry information at vastly greater speeds. 42
This capacity broadens communication possibilities to include services such as video conferencing and interactive services. The cost of fiber optic cabling is comparable to copper cabling; however, it is more difficult to install and modify. The center core of fiber cables is made from glass or plastic fibers A plastic coating then cushions the fiber center, and kevlar fibers help to strengthen the cables and prevent breakage. The outer insulating jacket made of teflon or PVC. There are two common types of fiber cables -- single mode and multimode. Multimode cable has a larger diameter; however, both cables provide high bandwidth at high speeds. Single mode can provide more distance, but it is more expensive.
Advantages of Optical Fiber: Noise immunity: RFI and EMI immune (RFI - Radio Frequency Interference, EMI -Electromagnetic Interference) Security: cannot tap into cable. Large Capacity due to BW (bandwidth) No corrosion Longer distances than copper wire Smaller and lighter than copper wire Faster transmission rate Disadvantages of optical fiber: Physical vibration will show up as signal noise! Limited physical arc of cable. Bend it too much and it will break! Difficult to splice
Transmissionmedium Total data rate Bandwidth RepeaterspacingTwisted pair 4 Mbps 3 MHz 2 to 10 kmCoaxial Cable 500 Mbps 350 MHz 1 to10 kmOptical fiber 2 Gbps 2 GHz 10 to 100 km
Electromagnetic spectrum for telecommunicationsFrequenc 2 103 104 105 106 107 108 109 1010 1011 1012 1013y (hertz) 10 1014 ELF 1015 VF VLF LF MF HF VHF UHF SHF EHF Power and Radio Microwave Infrared visible telephone Rotating Radios and Radar Lasers light generators televisions Microwave guided Musical Electronic tubes antennas missiles instruments Integrated circuits Magnetrons Rangefinders Voice microphone Twisted Pair Coaxial optical Cable fiber AM Radio FM Terrestrial Radio and and TV Satellite Transmissio 10 6 105 104 103 102 101 100 n 10-1 10-2 10-3 10-4 10-5Wavelength inspace (meters) -6 10
Unguided transmission media Unguided transmission media is data signals that flow through the air. They are not guided or bound to a channel to follow. Types Radio waves Microwave Satellite
RF Propagation Ground wave propagation follows the curvature of the Earth. Ground waves have carrier frequencies up to 2 MHz. AM radio is an example of ground wave propagation.
RF Propagation Ionospheric propagation bounces off of the Earths ionospheric layer in the upper atmosphere. It is sometimes called double hop propagation. It operates in the frequency range of 30 - 85 MHz. Because it depends on the Earths ionosphere, it changes with the weather and time of day. The signal bounces off of the ionosphere and back to earth.
RF Propagation Line of sight propagation transmits exactly in the line of sight. The receive station must be in the view of the transmit station. It is limited by the curvature of the Earth for ground- based stations (100 km, from horizon to horizon). Reflected waves can cause problems. Examples of line of sight propagation are: FM radio, microwave and satellite.
What is data communication? Not to be confused with telecommunication— Any process that permits the passage from a sender to one or more receivers of information of any nature, delivered in any easy to use form by any electromagnetic system. Data communication- Defined as a subset of telecommunication involving the transmission of data to and from computers and components of computer systems. More specifically data communication is transmitted via mediums such as wires, coaxial cables, fiber optics, or radiated electromagnetic waves such as broadcast radio, infrared light, microwaves, and satellites.
Features of Communication Four things required Sender, receiver, medium, and message Types of messages File Request Response Status Control Correspondence
Business Data Communication Applications Major data communication applications include: E-mail Groupware Knowledge management systems E-commerce and e-business applications Wireless applications
Moving Bits through the Network A n a lo g S ig n a l 1 0 D ig ita l S ig n a l 1 1 1 0 0 0 digital analog digital C om puter M odem M odem C om puter telephone lines
Direction of Data Flow Simplex Half Duplex Duplex (or Full duplex)
Intranet A network based on TCP/IP protocols belonging to an organization, usually a corporation, accessible only by the organizations members, employees, or others with authorization. Intranet is a private extension of the Internet, but the firewall surrounding an intranet fends off unauthorized access. Used to securely share organizations information within that organization. Organizations internal website, therefore it is not exposed to the general public and is accessed only by authorized persons
Secure intranets are now the fastest-growing segment of the Internet because they are much less expensive to build and manage than private networks based on proprietary protocols Advantages Reduce printing, paper costs the computers and servers can communicate much faster than they could over the internet- Useful for sharing information throughout an organization while still keeping it private. Disadvantages It is an evolving technology that requires upgrades and could have software incompatibility problems- Security features can be inadequate Maintaining content can be time consuming
Functions of intranet Knowledge sharing Collaboration Publishing: E,g, homepages, newsletters, documents, employee directories. Searching: The intranet can integrate different search functions, e.g. through a search engine or using a system of categorization. Transacting: Allows user to make transactions with other web/intranet homepages. Interacting: Collaborative applications and other groupware, expert finders, directories, etc. Recording: It can be used as a storage medium for such elements as procedures, best practices, and FAQs
Extranet An intranet that is partially accessible to authorized outsiders. An extranet provides various levels of accessibility to outsiders. You can access an extranet only if you have a valid username and password, and your identity determines which parts of the extranet you can view. Extranets are becoming a very popular means for business partners to exchange information. An extranet implies an ―extended intranet‖, which uses TCP/IP protocol networks (like the Internet) to link intranets in different locations. Extranet transmissions are conducted over the Internet to save money.
The Extranet (cont.) Extranet Suppliers Intranet VPN FirewallDistributors VPN Tunneling Internet Intranet VPNCustomers Firewall 64
Functions of Extranet Enhanced Communications Improved internal communications Improved business partnership channels Effective marketing, sales, and customer support Collaborative activities support Productivity Enhancements Just-in-time (JIT) information delivery Productive collaboration between workgroups Training on demand
Business Enhancements Faster time to market Simultaneous engineering potential Lower design and production costs Improved client relationships New business opportunities. Cost Reduction Reduced errors Improved comparison shopping Reduced travel and meetings expenses Reduced administrative and operational costs Elimination of paper publishing costs
Information Delivery Low-cost publishing Leveraging of legacy systems Standard delivery systems Ease of implementation and maintenance Elimination of paper publishing and mailing costs
Internet The Internet is a public and global communication network that provides direct connectivity to anyone via a Local Area Network (LAN) and an Internet Service provider (ISP). It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. Access to the Internet is not restricted to anyone. Wide and unlimited scope
Internet Advantages Unlimited information Free unrestricted access Better communication Increased productivity Disadvantages This lack of control may result in an information overload. Due to its vast scope and openness, the information is difficult to locate. Users need effective and efficient search engines to navigate the sea of information . There is no centralized control of network and information. Cyber Crimes
How the Internet Works Transport control protocol (TCP) A protocol that operates at the transport layer and is used in combination with IP by most Internet applications Backbone An Internet high-speed, long distance communications links (like a bus; wire that connects nodes) Uniform resource locator (URL) An assigned address on the Internet for each computer E.g., http://www.yorku.ca/
Internet Service Providers Any company that provides individuals or companies with access to the Internet Thousands of providers including large communications companies Need an account with the ISP and software that links with TCP/IP
The World Wide Web World Wide Web A collection of tens of thousands of independently-owned computers that work together as one in an Internet service WWW terminologies Home page The cover page for a Web site that has graphics, titles, coloured text, etc. Hypermedia Tools that connect the data on Web pages, allowing users to access topics in whatever order they wish Hypertext markup language (HTML) The standard page description language for Web pages Web browser Software that creates a unique hypermedia-based menu on your computer screen and provides a graphical interface to the Web Web page A screen of information sent to a requesting user and presented through a browser
Internet, Intranet, and Extranet Network Typical Type of Type Users Access Information Internet Any individual with Unlimited, publi General, public dial-up access or c; no and advertisement LAN restrictions Intranet Authorized Private and Specific, corporate and employees ONLY restricted proprietary Extranet Authorized groups Private and Shared in authorized from collaborating outside collaborating group companies authorized partners
Electronic commerce Is a set of technologies, applications, and business processes that link business, consumers, and communities. For buying, selling, and delivering products and services For integrating and optimizing processes within and between businesses. It is a general concept covering any form of business transaction or information exchange executed using information and communication technologies (ICT’s) It includes electronic trading of goods, services and electronic material. It takes place between companies, between companies and their customers, or between companies and public administrations.
With the birth of dot-com sites such as Expedia.com, Priceline.com, and Travelocity.com the hospitality industry has had to change how they do business. Technology has been useful in assisting companies in understanding their customers and potential customers on an individual level and developing marketing to their specific wants.
eTourism Business • Management • Marketing • Finance eTouris m IT Tourism • IT tools and • Accessibility technologies • Accommodation • Hardwares • Attractions • Softwares • Ancillary Services