Internet
From Saferpedia
Internet is a global system of interconnected computer networks using the TCP / IP standard to connect billions of users all over the world. The Internet is a crowd of networks (private, public, business, academic, governmental, etc.) connected trough a series of technological equipments.
The origins of the Internet date since 1960s when United States financed research projects of its military agencies to build robust and fault tolerant networks. Starting with 2009 it was estimated that over a quarter of Earth population use Internet services.
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Terminology
The terms "Internet" and "World Wide Web (WWW)" are often used in day to day conversation without making a big difference between them although Internet and WWW are not the same thing. Internet is a global data communication system, an infrastructure of hardware equipments and software offering connectivity between computers. WWW is one of the services offered with the help of Internet, a collection of interconnected documents and other resources connected trough hyperlinks and URls.
Protocols
The complex Internet communication infrastructure consists of hardware components and a system of software layers controlling certain aspects of the architecture. The design and the strict standardization process of the software architecture are the foundation for scalability. The responsibility for architectural design of software systems for Internet was delegated to IETF (Internet Engineering Task Force). IETF lead groups of establishing work standards regarding certain aspects of Internet architecture. The discussions and final standards are published in RFC (Request for Comments) available for free on IETF's site.
There have been developed several architectural models but the most used are the TCP/IP (Transmission Control Protocol/Internet Protocol) model and the OSI (Open System Internconnection) model.
TCP/IP model
The TCP/IP model was created by the US DoD (US Department of Defence) in the necessity of a network able to survive any conditions. DoD wanted that as long as the source machine and the destination machine were working the connection to stay intact even if a part of machines or transmission lines were damaged. These necessities led to choosing for levels for the TCP/IP model: Application, Transport, Network (or Internet) and Network Access.
Application level
It refers to high level protocols used in most applications like Telnet, FTP and SMTP. These protocols are DNS, NNTP pr HTTP
Transport level
It deals with safety issues, flux control and error correction. It is designed to allow conversations between pair entities from the source and destination hosts. For these there have been defined two end-to-end protocols: TCP/IP and UDP (User Datagram Protocol). TCP/IP is a connection oriented protocol allowing a flux of bytes sent from a machine to reach without errors on any other machine in the network. UDP is an unsafe protocol without connections destined for applications wishing to use their own sequencing and flux control.
Network level
It's initial purpose was to ensure packages' routing inside a single network, but in time there have been added features of communication between a source network and a destination one.
Network Access level
Deals with all the transmission problems of an IP package including aspects about technologies and transmission environments.
OSI model
The OSI model is a hierarchical communication structure often used to represent a network. OSI is a standard of the International Standardization Organization issued in 1984.
The OSI model proposes some general criteria to realize computers communication in order for these to exchange information whatever the systems' particularities (producer, OS, country, etc.). The OSI model divides the complex issue of communication in 7 layers ordered in a hierarchical structure. Each layer has well determined functions and communicates only with the neighbor layers. These 7 layers are: Application, Presentation, Session, Transport, Network, Data Link, Physical.
Application level
It realizes the interface with the user and with applications and manages the communication between applications. This layer is not a stand alone application but the interface between applications and computer's components.
Presentation level
Transforms data in formats understood by each application and computers, ensures data compression and encryption.
Session level
Controls communications between applications: establishes, maintains, manages and closes connections.
Transport level
It ensures the reliable transportation between two terminal systems of a certain communication. It supplies errors control and data flux control between two terminal points ensuring the correct order of data packages. It offers a data transportation service isolating the upper levels of any specifications about the way data transportation is realized.
Network level
Determines optimal ways to realize information transfer in a network with several segments by fragmenting and reassembling the information.
Data Link level
Deals with physical addressing, network topology, network access, direction and errors announcing and physical flow control. It supplies a safe, reliable data transportation on a physical link, realizing:
- Communication errors controls;
- Data flow control;
- Link control;
- Frame level synchronization.
Physical level
Defines electric, mechanic, procedural and functional specifications for activating, maintaining and deactivating physical links between systems.
- Mechanical (shape and size of the connectors, number of pins);
- Electric (modulation, binary flow, codings, maximal lengths for communication channels);
- Functional (each pin's function);
- Procedural (the succession of procedures to activate a service).
Social impact
Internet allowed new social interaction forms, activities and organizations. Users have the possibility to interact with each other on social networks like Facebook and MySpace, they have the possibility to share personal information, common interests, etc.
Internet also can be used as a politic tool leading to site censoring in some states. For example Howard Dean's presidential campaign in 2004 in USA was notable for its success in asking online donations. Many political groups use Internet to obtain a new method of organization. Some of them in order to fulfill their mission founded Internet activism. So some governments like Iran, North Korea, Myanmar, Popular Republic of China and Saudi Arabia restrict users' access to the Internet especially for politic and religious contents.
Many people use Internet to access news, weather reports, sport information, holidays planning or other interests. People use chat rooms, instant messaging and e-mails to keep in touch with the world.
