Internet Technology and Web Programming
Total Page:16
File Type:pdf, Size:1020Kb
INTERNET TECHNOLOGY AND WEB PROGRAMMING 1 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 CONTENTS LESSON I: Introduction to Networking · Networking concepts and Technology (LANs and WANs) . · Serial Networking (SLIP, PPP) . · Internet Protocol (IP) and Domain Name System (DNS) . · What is the Internet . LESSON II: Internet Access Hardware and Media · HARDWARE: Modems, Terminal Adapters, Routers . · MEDIA: PTSN, ISDN, Kilostream . LESSON III: Internet Services · Electronic Mail; Newsgroups . · File Transfer Protocol (FTP) and Hypertext Transfer Protocol (HTTP) . · Internet databases: WAIS, Archie, gopher, WWW search databases . LESSON IV: Using E-Mail and other Clients · Electronics Mail . · Other Internet Clients . · FTP . · Newsgroups . · Telnet . LESSON V: Media & Active Content · Object & Active Content . · Types of Browser Plug-ins . 2 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 · Additional Media File Formats . · Images File Formats . LESSON VI: Internetworking Servers · Server Implementation . · Content Servers . · Performance Servers . · Database Servers . · Mirrored Servers . · Popular Server Products . LESSON VII: Web Servers and Databases · Databases . · Introduction to Database Gateways for Web Servers . · Common Gateway Interface (CGI) . · Server Application Programming Interfaces (SAPIs) . · JavaScript . · ASP . · PHP . · HTML . · Java & Java Service . · JSP . · ColdFusion . · Database Connectivity 3 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 · ODBC . · JDBC . LESSON VIII: Internet Security · What is Security? . · The cracker Process . · Types of Attacks . · Defending Your Networks . · Firewalls . · Defending Your Computer . · Defending Your Transmitted Data . Lesson I: (Introduction to Networking) 1. Network concepts and Technology (LANs and WANs) 4 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 LANs, WANs, and Other Area Networks Computer networks come in many different shapes and sizes. Over the years, the networking industry has coined terms like "LAN" and "WAN" attempting to define sensible categories for the major types of network designs. The precise meaning of this terminology remains lost on the average person, however. Area Networks For historical reasons, the industry refers to nearly every type of network as an "area network." The most commonly-discussed categories of computer networks include the following - · Local Area Network (LAN) · Wide Area Network (WAN) · Metropolitan Area Network (MAN) · Storage Area Network (SAN) · System Area Network (SAN) · Server Area Network (SAN) · Small Area Network (SAN) · Personal Area Network (PAN) · Desk Area Network (DAN) · Controller Area Network (CAN) · Cluster Area Network (CAN) LANs and WANs were the original flavors of network design. The concept of "area" made good sense at this time, because a key distinction between a LAN and a WAN involves the physical distance that the network spans. A third category, the MAN, also fit into this scheme as it too is centered on a distance-based concept. 5 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 · LAN Basics A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs, and occasionally a LAN will span a group of nearby buildings. In IP networking, one can conceive of a LAN as a single IP subnet (though this is not necessarily true in practice). Besides operating in a limited space, LANs include several other distinctive features. LANs are typically owned, controlled, and managed by a single person or organization. They also use certain specific connectivity technologies, primarily Ethernet and Token Ring. · WAN Basics As the term implies, a wide-area network spans a large physical distance. A WAN like the Internet spans most of the world! A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address. WANs differ from LANs in several important ways. Like the Internet, most WANs are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs use technology like ATM, Frame Relay and X.25 for connectivity. LANs and WANs at Home Home net workers with cable modem or DSL service already have encountered LANs and WANs in practice, though they may not have noticed. A cable/DSL router like those in the Links family join the home LAN to the WAN link maintained by one's ISP. The ISP provides a WAN IP address used by the router, and all of the computers on the home network use private LAN addresses. On a home network, like many LANs, all computers can communicate directly with each other, but they must go through a central gateway location to reach devices outside of their local area. What About MAN, SAN, PAN, DAN, and CAN? Future articles will describe the many other types of area networks in more detail. After LANs and WANs, one will most commonly encounter the following three network designs: A Metropolitan Area Network (MAN) connects an area larger than a LAN but smaller than a WAN, such as a city, with dedicated or high-performance hardware. A Storage Area Network (SAN) connects servers to data storage devices through a technology like Fibre Channel. A System Area Network (SAN) connects high-performance computers with high-speed connections in a cluster configuration. 6 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 Conclusion To the uninitiated, LANs, WANs, and the other area network acronyms appear to be just more alphabet soup in a technology industry already drowning in terminology. The names of these networks are not nearly as important as the technologies used to construct them, however. A person can use the categorizations as a learning tool to better understand concepts like subnets, gateways, and routers. A Simple Computer Network for File Sharing Illustration: 1 This diagram illustrates the simplest possible kind of computer network. In a simple network, two computers (or other networkable devices) make a direct connection with each and communicate over a wire or cable. Simple networks like this have existed for decades. A common use for these networks is file sharing. A Local Area Network (LAN) 7 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 Illustration: 2 This diagram illustrates a typical local area network (LAN) environment. Local area networks often feature a group of computers located in a home, school, or part of an office building. Like a simple network, computers on a LAN share files and printers. Computers on one LAN can also share connections with other LANs and with the internet. A Hypothetical Wide Area Network Illustration: 3 This diagram illustrates a hypothetical wide area network (WAN) configuration that joins LANs in three metropolitan locations. Wide area networks cover a large geographic area like a city, a country or multiple countries. WANs normally connect multiple LANs and other smaller-scale area networks. WANs are built by large telecommunication companies and other corporations using highly-specialized equipment not found in consumer stores. The Internet is an example of a WAN that joins local and metropolitan area networks across most of the world. 8 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 Wiring in Computer Networks Illustration: 4 This diagram illustrates s e v e r a l c o m m o n forms of wiring in computer networks. In many homes, twisted-pair Ethernet cables are often used to connect computers. Phone or cable TV lines in turn connect the home LAN to the Internet Service Provider (ISP). ISPs, larger schools and businesses often stack their computer equipment in racks (as shown), and they use a mix of different kinds of cable to join this equipment to LANs and to the Internet. Much of the Internet uses high-speed fiber optic cable to send traffic long distances underground, but twisted pair and coaxial cable can also be used for leased lines and in more remote areas. Network Topologies Bus, ring, star, and all the rest In networking, the term topology refers to the layout of connected devices on a network. This article introduces the standard topologies of computer networking. Topology in Network Design One can think of a topology as a network's "shape" . This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle, but it would be highly unlikely to find an actual ring topology there. Network topologies are categorized into the following basic types: · bus · ring · star 9 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 · tree · mesh More complex networks can be built as hybrids of two or more of the above basic topologies. Illustration: 5 Bus Topology diagram Bus Topology Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium, that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast 10 F.C Ledesma Avenue, San Carlos City, Negros Occidental Tel. #: (034) 312-6189/(034) 729-4327 message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message. Ethernet bus topologies are relatively easy to install and don't require much cabling compared to the alternatives. 10Base-2 ("ThinNet") and 10Base-5 ("ThickNet") both were popular Ethernet cabling options years ago.