The Internet is essentially defined by its interconnections and routing policies. In an often-cited, if perhaps gratuitously mathematical definition, Seth Breidbart once described the Internet as "the largest equivalence class in the reflexive, transitive, symmetric closure of the relationship 'can be reached by an IP packet from'". Something that satisfies all three (RST) conditions is considered mathematically isomorphic or "the same".

Other, more social definitions, are often used, but they usually refer to some combination of the services offered using the Internet, from some set of terminals, in some language. With the spread of hundred dollar laptops and mesh networks and any worn device able to do at least a few IP-based services, it seems unlikely that any one social definition could be of value.

works over any physical layer

Unlike older communications systems, the Internet protocol or IP suite was deliberately designed to be independent of the underlying physical medium. Any communications network, wired or wireless, that can carry two-way digital data can carry Internet traffic.

Thus, Internet packets flow through wired networks like copper wire (dialup), coaxial cable, and fiber optic; and through wireless networks like Wi-Fi. Together, all these networks, sharing the same high-level protocols, form the Internet.

protocol standardization

From a process and quality management point of view, the Internet can be viewed as a process by which IP-based protocols become global standards.

The Internet protocols originate from discussions within the Internet Engineering Task Force (IETF) and its working groups, which are open to public participation and review. These committees produce documents that are known as Request for Comments documents (RFCs). These are accepted on the basis of "rough consensus and working code".

Some RFCs are raised to the status of Internet Standard by the Internet Architecture Board (IAB). See Internet governance on this.


Some of the most used protocols in the Internet protocol suite are IP itself, TCP, UDP, DNS, PPP, SLIP, ICMP, POP3, IMAP, SMTP, HTTP, HTTPS, SSH, Telnet, FTP, LDAP, SSL, and TLS.

Some of the popular services on the Internet that make use of these protocols are e-mail, Usenet newsgroups, file sharing, Instant Messenger/IM or IRC/chat, the World Wide Web, Gopher, session access, WAIS, finger, IRC, MUDs, and MUSHs. Of these, e-mail and the World Wide Web are clearly the most used, and many other services are built upon them, such as mailing lists and blogs. Some services such as yahoogroups or google groups integrate multiple of the standard services - adding web services to email and newsgroups respectively.

The Internet also makes it possible to provide real-time services such as Internet radio and webcasts that can be accessed from anywhere in the world. To podcast has become very simple and typically involves just posting descriptions as XML and the audio material as MP3s.

Some other popular services of the Internet were not created this way, but were originally based on proprietary systems. These include the chat media IRC, ICQ and AIM, and the Gnutella protocol that lets users share files.

Web services to the public are the most user privacy sensitive and rely typically on DNS to look up domain names, SMTP to deliver email, HTTP for web services and HTTPS for secure web services, e.g. credit card or PayPal use.


There have been many analyses of the Internet and its structure. For example, it has been determined that the Internet IP routing structure and hypertext links of the World Wide Web are examples of scale-free networks.


The Internet is notorious for having no semantics at all. However, the World Wide Web has many weak ontology requirements including its RESTful HTTP protocol. Building on many prior hypertext systems, there have been many attempts to impose one typed link structure on the entire Web. This has reliably failed.

Interwiki, the open politics web and GFDL corpus are three attempts to rigorize a much smaller subset of the web's total content.


refer link http://en.wikipedia.org/wiki/Internet en: wikipedia: Internet