The Internet is the worldwide "network of networks" that links millions of computers together via copper wires, fiber-optic cables, wireless connections, and other telecommunications channels. This publicly accessible network of interconnected computer networks communicate using a set of protocols and standards, the most basic of which are TCP/IP.
The Internet and the World Wide Web are everywhere. They can provide answers to questions and hours of entertainment. The Internet can allow people from all over the world to talk to each other. But what exactly are the Internet and the World Wide Web?
This resource is intended to function as a general overview of the workings of the Internet, which may cover social, economic, historical and other aspects. For a more detailed and step by step approach to learning about networking, consider visiting the topic on computer networking.
The internet started out as a US Department of Defence project called ARPANET, which slowly expanded with the integration of packet switching networks over circuit switching networks. ARPANET could be considered the original heart of the internet, with additional bits and pieces being added on until certain standards were needed to unify them all. These standards eventually came to be known as Protocols.
As of July 2008, there were close to 600 million hosts connected to the World Wide Web, linked together by a series of switches and communication links.
A protocol is a definition of the format and order of messages that are exchanged between two or more hosts. For example, if person A wanted to know the time from person B in England, person A may approach person B and ask "What is the time?". Person B may then reply with the current time. Some important things to note in this example is that both assume they will be communicating in English, and have a concept of time. While these are things that we as human beings may take for granted, machines have no idea what and how they will be communicating with each other until a set of rules is specified. As mentioned above, one of the most original and common protocols in use today is the TCP/IP protocol.
TCP/IP consists of the Transmission Control Protocol in conjunction with the Internet Protocol. Other protocols such as DHCP, DNS, FTP, HTTP, IRC, MIME, POP3, SMTP, SSH, TELNET, RTP and many more help hold the whole thing together.
Protocols are only a subset of the entire design of the internet. Proposals for existing and new standards are made through Requests for Comments (RFCs), hosted by the Internet Engineering Task Force. RFCs are highly technical and detailed documents that specify each and every operation of the standard being proposed. Comments (hence the name) are sought after regarding the standard and the process carries on until most are satisfied. The standard is then published.
A popular way to visualize the complexity of the Internet is to see it as a stack of layers known as the OSI model, short for Open Systems Interconnection model.
- Layer 7: Application Layer – the main interface for the user(s) to interact with the application and therefore the network
- Layer 6: Presentation Layer – transforms data to provide a standard interface for the Application layer
- Layer 5: Session Layer – controls the dialogues (sessions) between computers
- Layer 4: Transport Layer – provides transparent transfer of data between end users and machines
- Layer 3: Network Layer – provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks
- Layer 2: Data Link Layer – provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer
- Layer 1: Physical Layer – defines all the electrical and physical specifications for devices and the communications media
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