Internet and internet services

OSI model

By specialized function

By network topology

By functional relationship

By range

Classification of computer networks.

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A computer network is a system for communication among two or more computers. Computer networks can be categorized by range, functional relationship, network topology and specialized function.

• personal area network (PAN)

• wireless PAN

• local area network (LAN)

• wireless LAN

• metropolitan area network (MAN)

• wide area network (WAN)

• client-server

• multitier architecture

• Peer-to-peer

• bus network

• star network

• ring network

• grid network

• toroidal networks and hypercubes

• tree and hypertree networks

• Storage area networks

• Server farms

• Process control networks

• Value added network

• SOHO network

• Wireless community network

a) The Open Systems Interconnection model (OSI model) is a method of thinking of computer networking in terms of abstraction layers. Different communication technologies with similar functions are grouped into different logical layers on the OSI Model. Each layer of the OSI Model makes use of functions provided by the layers below it and provides functions that are used by the layers above it.

According to the standard OSI Model there are seven layers. Each layer is dependent upon the layers below it to function. Some aspects of computer networking, such as management and security, use or are used on every layer.

Layer 1: physical layer

Layer 2: data link layer

Layer 3: network layer

Layer 4: transport layer

Layer 5: session layer

Layer 6: presentation layer

Layer 7: Application layer

Internet. It is an international network of networks that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies.

The Internet was created in the United States by the "United States Department of Defense Advanced Research Projects Agency" (ARPA). It was first connected in October, 1969. The World Wide Web was created at CERN in Switzerland in 1989 by a British (UK) man named Tim Berners-Lee. Today, people can pay money to access the Internet from Internet Service Providers. Some services on the Internet cost nothing to use.

Services on the Internet. The Internet carries an extremely large number of network services, including the World Wide Web, electronic mail, Internet phone, audio, video and file transfer services.

The most used service on the Internet is the World Wide Web (which is also called the "Web"). The Web contains websites, blogs, and also wikis like Wikipedia. Webpages on the Web can be seen and read by anyone (unless the page needs a password, or it is blocked). The second major use of the Internet is to send and receive e-mail. E-mail is private and goes from one user to another. Instant messaging (such as AIM or ICQ) is similar to email, but allows two or more people to chat to each other much faster.

Дата добавления: 2014-12-16