History of the Internet
- The history of the internet has three main phases:
- 1969, ARPANET (Advanced Research Projects Agency Networks). Created by the U.S. department of defense as a communications infrastructure that would withstand nuclear attack.
- 1986, NSFNET (National Science Foundation NET). Created to enable the research community to access supercomputer centers.
- 1990, ANS (Advanced Network and Services). Over time the private sector increased its participation in NFSNET and ANS started managing the NSFNET backbone. Commercial traffic took the internet.
- Since 1995 the following internet structure has been in effect:
- 3-tiered hierarchy of national backbone, regional networks and campus networks but NSFNET backbone is dismantled.
- Federal agency networks and commercial NSPs (network service providers) are interconnected through four NAPs (network access points) in Chicago, N.Y., S.F. and Washington. These NSPs carry the traffic of regional networks, which connect to the NAPs.
- Educational and research institutions are forging ahead with their own Internet II.
- The internet has evolved from military/research use to business and private use (initially mostly for e-mail and file sharing to now e-commerce etc.).
- Because the internet is essentially a decentralized network of networks, standards are key. Standards are set by informal bodies – primarily IETF (Internet Engineering Task Force) and the W3C (World Wide Web Consortium), and the standard setting process is based on cooperation, problem solving and technical excellence. Published standards are open standards (i.e. anyone can use them).
Elements of Internet Technology
- The internet is a network of interconnected LANs (Local Area Networks), MANs (Metropolitan Area Networks) and WANs (Wide Area Networks). To move data across these networks they must all follow the same communication protocols.
- Packet switching: the basic communication technology used to exchange data. At the sending computer data is divided into packets that also contain info. about the destination. The packets are sent independently (packet transmission) and reassembled at the destination. Bandwidth is only used when a package is transmitted as opposed to (circuit switching) as we know it from phone lines where the line is “blocked” for the entire duration of the connection.
- Internet and communication protocols: Communication protocols define the network standards that enable computers to “talk and understand each other”. The Internet Protocol is one of two key communication protocols of the internet and defines the format of data packets, a common addressing scheme and the rules for routing.
- IP Address: To make routing and delivery possible all internet host computers are assigned a unique numeric IP address.
- Transmission control protocol: Is the other key communication protocol of the internet. Resends lost data packets, assembles data packets at the destination and eliminates useless copies.
- Domain name system: Numeric IP addresses are inconvenient so people use domain names for this. Each domain name corresponds to an IP address. The Domain Name System enable the translation from domain name to IP address through Domain Name Servers.
- Router: computer used to interconnect the communication lines.
- Bandwidth: the speed/transmission capacity of the communication lines. Is measured in bits per second.
- ISPs: Internet Service Providers (e.g. AOL) through which you access the internet.
- Security: Security is becoming increasingly important with e-commerce, money transfers etc. A number of technologies are used to increase security; e.g. PINs, Passwords, Firewalls (a pair of routers with a host between them – the router on the internet side lets the host communicate freely with the internet while the other router prevents unwanted traffic from reaching the host), Application Layer Gateway (requires users to authenticate themselves), Encryption (plain text is encrypted into ciphertext before it’s sent and only the recipient has the key to undo the encryption and get plain text), Virtual Private Networks (a secure path through the internet on which all data is encrypted before transmission).
- Distinction is made between dial up (access is established with a phone call when internet connection is needed) and dedicated/leased lines (provide permanent internet access) and Cable modems (enable the use of cable TV lines for internet connectivity).
- Intranet: restricted company specific “internets”.
- Extranet: extends the intranet to a network of partners
- Congestion problems: the increasing use of the internet causes delays, connection problems etc. and bandwidth capacity is becoming an increasingly important issue. A structural solution may eventually be necessary, or/and a shift from connection based pricing to a pricing system based on use of bandwidth.
- E-mail, File Transfer Protocol (basic service for transferring and copying files efficiently), Telnet (allows a user to login to a remote computer and use it as a local computer), Mailing lists and bulletin boards.
- World Wide Web: a user friendly layer on top of the internet that provides an easier to use way of organizing and delivering information. Data on WWW servers is accessed through software called a browser and the browser interfaces with internet services such as e.g. e-mail and search engines like Yahoo!. The WWW is a collection of linked multimedia documents that can be reached through mouse clicks, and, more technically, WWW is a collection of servers linked to the internet and communicating through HTTP (Hyper Text Transport Protocol). Hypertext is text with built in links that allow users to jump from one document to another. Web pages are written in HTML (Hyper Text Markup Language), which is a language that specifies to the browser how to visually structure the page. Sometimes the browser needs “help” (additional programs) to display a page – e.g. help from Adobe’s Acrobat – but this help is automatically invoked by the click of the mouse.
- URLs: Resources on the web are identified by their URL (Universal Resource Locator), which is a unique code that identifies the location of the resource and the protocol needed to access it.
- Client-Server Computing Model: Classifies each program as either a client or a server. When a user (client) clicks on a link the browser translates the link into HTTP so that the server knows exactly what the client is requesting. The server then replies to the client via the browser displaying the pages the client requested.
- CGI and Java: The need for interaction between users and web sites has grown with e-commerce. To manage such interaction (e.g. filling out a credit card form) CGI (Common Gateway Interface) was developed, but no longer suffices as the degree of required interaction has increased. To meet the need for greater interaction JAVA was developed. JAVA allows the client to interact directly with the program on the screen (CGI only allowed transmission of “forms”) and is platform independent so it can run on many kinds of computers and operating systems. JAVA also allows users to search databases and the internet in much more sophisticated ways than CGI or HTML.
- Search Engines and Portals: Search engines such as Yahoo! are among the most widely used internet portals – a portal is a gateway to the internet.