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Internet Protocol

Internet protocol

Internet protocol may refer to:
- The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork.
- The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs.

Internet protocol

Packet switched

In computer networking and telecommunications, packet switching is the now-dominant communications paradigm, in which packets (units of information carriage) are individually routed between nodes over data links which might be shared by many other nodes. This contrasts with the principal other paradigm, circuit switching, which sets up a dedicated connection between the two nodes for their exclusive use for the duration of the communication. Packet switching is used to optimize the use of the bandwidth available in a network, to minimize the transmission latency (i.e. the time it takes for data to pass across the network), and to increase robustness of communication. Basically, a file is broken up into smaller groups of data known as packets. Such "packets" carry with them information with regard to their origin, destination and sequence within the original file. This sequence is needed for re-assembly at the file's destination.

Packets

A packet is a block of data (called a payload) with address and administrative information attached to allow a network of nodes to deliver the data to the destination, e.g., as in IPv6. A packet is analogous to a letter sent through the mail with the address written on the outside.

Packet routing

Packets are routed to their destination through the most expedient route (as determined by some routing algorithm). Not all packets travelling between the same two nodes will necessarily follow the same route. One data connection will usually carry a stream of packets from several nodes. The destination node reassembles the packets into their appropriate sequence. Consequently packets sent between a pair of nodes may arrive in an order different from the order in which they were sent. Packet switching influenced the development of the Actor model of concurrent computation in which messages sent to the same address may be delivered in an order different from the order in which they were sent.

Packet switching in the Internet

The most well-known use of the packet switching model is the Internet, which is a packet-switched network, running the Internet Protocol layer 3 protocol over a variety of other network technologies. Ethernet, X.25 and Frame relay are international standard layer 2 packet switching networks. Newer mobile phone technologies such as GPRS and i-mode also employ packet switching. Packet switching is also called connectionless networking, because it is the opposite of circuit switched or connection-oriented networking, although technologies such as MPLS are beginning to blur the boundaries between the two. ATM is another hybrid technology, which uses cell relay instead of packet switching. Fast packet switching is a packet switching technique that increases the throughput by eliminating overhead.

Controversy over invention of packet switching

There is controversy over the invention of packet switching.

Work at MIT

In Internet Society publication A Brief History of the Internet, Barry M. Leiner, Vinton G. Cerf, David D. Clark, Robert E. Kahn, Leonard Kleinrock, Daniel C. Lynch, Jon Postel, Larry G. Roberts, Stephen Wolff stated :"Leonard Kleinrock at MIT published the first paper on packet switching theory in July 1961 and the first book on the subject in 1964. Kleinrock convinced Roberts of the theoretical feasibility of communications using packets rather than circuits, which was a major step along the path towards computer networking. The other key step was to make the computers talk together. To explore this, in 1965 working with Thomas Merrill, Roberts connected the TX-2 computer in Mass. to the Q-32 in California with a low speed dial-up telephone line creating the first (however small) wide-area computer network ever built. The result of this experiment was the realization that the time-shared computers could work well together, running programs and retrieving data as necessary on the remote machine, but that the circuit switched telephone system was totally inadequate for the job. Kleinrock's conviction of the need for packet switching was confirmed."

Work at RAND

According to Larry Roberts in The Evolution of Packet Switching, :"The first published description of what we now call packet switching was an 11-volume analysis, On Distributed Communications, prepared by Paul Baran of the Rand Corporation in August 1964. This study was conducted for the Air Force, and it proposed a fully distributed packet switching system to provide for all military communications, data, and voice. The study also included a totally digital microwave system and integrated encryption capability. The Air Force's primary goal was to produce a totally survivable system that contained no critical central components. Not only was this goal achieved by Rand's proposed packet switching system, but even the economics projected were superior, for both voice and data transmissions. Unfortunately, the Air Force took no follow-up action, and the report sat largely ignored for many years until packet switching was rediscovered and applied by others." Baran described two key ideas: first, use of a decentralized network with multiple paths between any two points; and second, dividing complete user messages into what he called message blocks (later called packets) before sending them into the network. This first allowed the elimination of single points of failure, and enabled the network to automatically and efficiently work around any failures. A summary paper describing the entire scheme was published in 1964.

Work at National Physical Laboratory

According to Larry Roberts in The Evolution of Packet Switching, :"Almost immediately after the 1965 meeting, Donald Davies conceived of the details of a store-and-forward packet switching system, and in a June 1966 description of his proposal coined the term "packet" to describe the 128-byte blocks being moved around inside the network. Davies circulated his proposed network design throughout the U.K. in late 1965 and 1966. It was only after this distribution that he discovered Paul Baran's 1964 report. :The first open publication of the NPL proposal was in October 1967 at the A.C.M. Symposium in Gatlinburg, TN. In nearly all respects, Davies' original proposal, developed in late 1965, was similar to the actual networks being built today. His cost analysis showed strong economic advantages for the packet approach, and by all rights, the proposal should have led quickly to a U.K. project. However, the communications world was hard to convince, and for several years, nothing happened in the U.K. on the development of a multi-node packet switching network. :Donald Davies was able, however, to initiate a local network with a single packet switch at the NPL. By 1973 this local network was providing an important distribution service within the laboratory. This project, plus the strong conviction and continued effort by those at NP1. (Davies, Barber, Scantlebury, Wilkinson, and Bartlett), did gradually have an effect on the U.K. and much of Europe." Davies had begun working with related concepts in 1965, after a conference in the United Kingdom on time-sharing brought up the inadequacies of existing circuit-switched networks. His work was originally carried out independently from Baran's work, although Davies learned of it after he gave a seminar on his ideas at NPL in 1966. Prior to his death, Davies contested the claim that Leonard Kleinrock invented packet switching pointing out that Kleinrock's research was actually in queueing theory, which is a key theoretical underpinning to packet switching. Davies claimed that Kleinrock's published works nowhere prominently mention breaking a user's message up into segments, and sending the segments through the network separately, which he said was the key innovation.

Simultaneous Development

As with many other inventions, it can be said that the research groups developed simultaneously. Thus, the ideas that were to become the ARPANET came from three research centers: MIT, the RAND Corporation, and National Physical Laboratory.

Reference

- Leonard Kleinrock, [http://www.lk.cs.ucla.edu/LK/Bib/REPORT/PhD/ Information Flow in Large Communication Nets], (MIT, Cambridge, May 31, 1961) Proposal for a Ph.D. Thesis
- Leonard Kleinrock. Information Flow in Large Communication Nets (RLE Quarterly Progress Report, July 1961)
- Leonard Kleinrock. Communication Nets: Stochastic Message Flow and Delay (Mcgraw-Hill, New York, 1964)
- Paul Baran et al., [http://www.rand.org/publications/RM/baran.list.html On Distributed Communications, Volumes I-XI] (RAND Corporation Research Documents, August, 1964)
- Paul Baran, [http://www.rand.org/publications/RM/RM3420/ On Distributed Communications: I Introduction to Distributed Communications Network]] (RAND Memorandum RM-3420-PR. August 1964)
- Paul Baran, On Distributed Communications Networks (IEEE Transactions on Communications Systems, March 1964)
- D. W. Davies, K. A. Bartlett, R. A. Scantlebury, and P. T. Wilkinson, A digital communications network for computers giving rapid response at remote terminals (ACM Symposium on Operating Systems Principles. October 1967)
- R. A. Scantlebury, P. T. Wilkinson, and K. A. Bartlett, The design of a message switching Centre for a digital communication network (IFIP 1968)
- Larry Roberts and Tom Merrill, Toward a Cooperative Network of Time-Shared Computers (Fall AFIPS Conference. October 1966)
- Lawrence Roberts, [http://www.packet.cc/files/ev-packet-sw.html The Evolution of Packet Switching] (Proceedings of the IEEE, November, 1978)

External links

- [http://www.rand.org/about/history/baran.html Paul Baran and the Origins of the Internet]
- [http://www.computer.org/internet/v1n3/kleinrock9702.htm Len Kleinrock on the Origins] (subscribers only)
- [http://www.isoc.org/internet/history/brief.shtml A Brief History of the Internet]
- [http://www.ziplink.net/~lroberts/InternetChronology.html Internet Chronology by Larry Roberts]
- [http://www.zakon.org/robert/internet/timeline/ Hobbes' Internet Timeline v7.0] Category:Computer networks Category:Packets Category:Telecommunications ja:パケット通信

Internet protocol suite

The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. It is sometimes called the TCP/IP protocol suite, after the two most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two defined. The Internet protocol suite can be described by analogy with the OSI model, which describes the layers of a protocol stack, not all of which correspond well with internet practice. In a protocol stack, each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the higher layers. Higher layers are logically closer to the user and deal with more abstract data, relying on lower layers to translate data into forms that can eventually be physically manipulated. The Internet model was produced as the solution to a practical engineering problem. The OSI model, on the other hand, was a more theoretical approach. Therefore, some consider the OSI model as easier to understand, and the TCP/IP model as the one that fits with actual use. Some consider it helpful to have an understanding of the OSI model before learning TCP/IP, as the same principles apply, but are easier to understand in the OSI model.

Layers in the TCP/IP stack

There is some discussion about how to map the TCP/IP model onto the OSI model. Since the TCP/IP and OSI protocol suites do not match precisely, there is no one correct answer. In addition, the OSI model is not really rich enough at the lower layers to capture the true layering; there needs to be an extra layer (the Internetworking layer) between the Transport and Network layers. Protocols specific to a particular network type, but which are run on top of the basic hardware framing, ought to be at the Network layer. Examples of such protocols are ARP and the Spanning Tree Protocol (used to keep redundant bridges idle until they are needed). However, they are local protocols and operate beneath the internetwork functionality. Admittedly, placing both groups (not to mention protocols which are logically part of the internetwork layer, but run on top of the internetwork protocol, such as ICMP) all at the same layer can be confusing, but the OSI model is not complex enough to do a better job. The following diagram attempts to show where various TCP/IP and other protocols would reside in the original OSI model: Commonly, the top three layers of the OSI model (Application, Presentation and Session) are considered as a single Application Layer in the TCP/IP suite. Because the TCP/IP suite has a comparatively lightweight session layer, consisting of opening and closing connections under TCP and RTP and providing different port numbers for different applications under TCP and UDP, these functions may be augmented by individual applications. Similarly, IP is designed around the idea of treating the network below it as a black box so it can be considered as a single layer for the purposes of discussing TCP/IP.

The link layer

The Link layer is not really part of the Internet protocol suite, but is the method used to pass packets from the Internet layer of one device to the Internet layer of another. This process can be controlled both in the software device driver for the network card, as well as on firmware or specialist chipsets. These will perform data link functions such as adding a packet header to prepare it for transmission, then actually transmit the frame over a physical medium. On the other end, the link layer will receive data frames, strip off the packet headers, and hand the received packets to the Internet layer. However, the link layer is not always so simple. It may also be a Virtual private network (VPN) or tunnel, where packets from the Internet layer, instead of being sent over a physical interface, are sent using a tunneling protocol and another (or the same) protocol suite. The VPN or tunnel is usually established ahead of time, and has special characteristics that direct transmission out a physical interface does not (for example, it may encrypt the data going over it). This recursive use of the protocol suite can be confusing since the link "layer" is now an entire network. But it is an elegant method for implementing often complex functions. (though care is needed to prevent a packet that is wrapped and sent through a tunnel being repeatedly re-wrapped and sent down the tunnel again).

The Internetwork layer

As originally defined, the Network layer solves the problem of getting packets across a single network. Examples of such protocols are X.25, and the ARPANET's Host/IMP Protocol. With the advent of the concept of internetworking, additional functionality was added to this layer, namely getting data from the source network to the destination network. This generally involves routing the packet across a network of networks, known as an internet. In the internet protocol suite, IP performs the basic task of getting packets of data from source to destination. IP can carry data for a number of different higher level protocols; these protocols are each identified by a unique IP Protocol Number. ICMP and IGMP are protocols 1 and 2, respectively. Some of the protocols carried by IP, such as ICMP (used to transmit diagnostic information about IP transmission) and IGMP (used to manage multicast data) are layered on top of IP but perform internetwork layer functions, illustrating an incompatibility between the internet and OSI models. All routing protocols, such as BGP, OSPF, and RIP are also really part of the internetwork layer, although they might seem to belong higher in the stack.

The transport layer

The protocols at the Transport layer can solve problems like reliability ("did the data reach the destination?") and ensure that data arrives in the correct order. In the TCP/IP protocol suite, transport protocols also determine which application any given data is intended for. The dynamic routing protocols which technically fit at this layer in the TCP/IP Protocol Suite (since they run over IP) are generally considered to be part of the Network layer; an example is OSPF (IP protocol number 89). TCP (IP protocol number 6) is a "reliable", connection-oriented, transport mechanism providing a reliable byte stream, which makes sure data arrives complete, undamaged, and in order. TCP tries to continuously measure how loaded the network is and throttles its sending rate in order to avoid overloading the network. Furthermore, TCP will attempt to deliver all data correctly in the specified sequence. These are its main differences from UDP, and can become disadvantageous in real-time streaming or routing applications with high internetwork layer loss rates. The newer SCTP is also a "reliable", connection-oriented, transport mechanism. It is record rather than byte oriented, and provides multiple sub-streams multiplexed over a single connection. It also provides multi-homing support, in which a connection end can be represented by multiple IP addresses (representing multiple physical interfaces), such that if one fails the connection is not interrupted. It was developed initially for telephony applications (to transport SS7 over IP), but can also be used for other applications. UDP (IP protocol number 17) is a connectionless datagram protocol. It is a "best effort" or "unreliable" protocol - not because it is particularly unreliable, but because it does not verify that packets have reached their destination, and gives no guarantee that they will arrive in order. If an Application requires these characteristics, it must provide them itself, or use TCP. UDP is typically used for applications such as streaming media (audio and video, etc) where on-time arrival is more important than reliability, or for simple query/response applications like DNS lookups, where the overhead of setting up a reliable connection is disproportionately large. DCCP is currently under development by IETF. It provides TCP's flow control semantics, while keeping UDP's datagram service model visible to the user. Both TCP and UDP are used to carry a number of higher-level applications. The applications at any given network address are distinguished by their TCP or UDP port number. By convention certain well known ports are associated with specific applications. RTP is a datagram protocol that is designed for real-time data such as streaming audio and video. RTP is a session layer that uses the UDP packet format as a basis yet is said to sit within the transport layer of the Internet protocol stack.

The application layer

The Application layer is the layer that most common network-aware programs use in order to communicate across a network with other programs. Processes that occur in this layer are application specific; data is passed from the network-aware program, in the format used internally by this application, and is encoded into a standard protocol. Some specific programs are considered to run in this layer. They provide services that directly support user applications. These programs and their corresponding protocols include HTTP (The World Wide Web), FTP (File transport), SMTP (Email), SSH (Secure remote login), DNS (Name <-> IP Address lookups) and many others. Once the data from an application has been encoded into a standard application layer protocol it will be passed down to the next layer of the IP stack. At the Transport Layer, applications will most commonly make use of TCP or UDP, and server applications are often associated with a well-known port number. Ports for server applications are officially allocated by the Internet Assigned Numbers Authority (IANA) but developers of new protocols today often choose the port numbers themselves. As it is rare to have more than a few server applications on the same system, problems with port conflicts are rare. Application software also generally allows users to specify arbitrary port numbers as runtime parameters. Client applications connecting out generally use a random port number assigned by the operating system. Applications that listen on a port and then send that port to another copy of the application via a server to set up a peer-peer link (e.g. dcc file transfers on IRC). may also use a random port but the applications usually allow specification of a specific port range to allow the ports to be mapped inwards through a router that implements network address translation.

Development

The Internet protocol suite came from work done by DARPA in the early 1970s. After doing the pioneering ARPANET, DARPA started work on a number of other data transmission technologies, including packet radio, and satellite links. Wanting to be able to communicate across them, Robert E. Kahn of DARPA recruited Vint Cerf of Stanford University to work with him on the problems of connecting multiple networks, using different access protocols. By the summer of 1973, they had soon worked out a fundamental reformulation, where the differences between network protocols were hidden by using a common internetwork protocol, and instead of the network being responsible for reliability, as in the ARPANET, the hosts became responsible. (Cerf credits Hubert Zimmerman and Louis Pouzin (designer of the CYCLADES network) with important influences on this design.) With the role of the network reduced to the bare minimum, it became possible to join almost any networks together, no matter what their characteristics were, thereby solving Kahn's initial problem. (One popular saying has it that TCP/IP, the eventual product of Cerf and Kahn's work, will run over "two tin cans and a string".) A computer called a gateway (later changed to router to avoid confusion with other types of gateway) is provided with an interface to each network, and forwards packets back and forth between them. The idea was worked out in more detailed form by Cerf's networking research group at Stanford in the 1973–74 period. (The early networking work at Xerox PARC, which produced the PARC Universal Packet protocol suite, much of which was contemporaneous, was also a significant technical influence; people moved between the two.) DARPA agreed to fund development of prototype software, and after several years of work, the first somewhat crude demonstration of what had by then become TCP/IP occurred in July 1977. On 9 November 2005 Kahn and Cerf were presented with the Presidential Medal of Freedom for their contribution to American culture. [http://news.bbc.co.uk/1/hi/technology/4415326.stm]

Implementation

- KA9Q PPJ

External links

- [http://www.showip.org/ Show your IP address]
- [http://www.itprc.com/tcpipfaq/ TCP/IP FAQ]
- [http://www.columbia.edu/~rh120/other/tcpdigest_paper.txt A Study of the ARPANET TCP/IP Digest]
- [http://www.eventhelix.com/RealtimeMantra/Networking/ TCP/IP Sequence Diagrams]
- [http://cng.ateneo.edu/cng/wyu/classes/cs197/ Ateneo Network Research Group] TCP/IP research at the Ateneo de Manila University Internet protocol suite ja:TCP/IP

Protocol stack

A protocol stack is a particular software implementation of a computer networking protocol suite. The terms are often used interchangeably. Strictly speaking, the suite is the definition of the protocols and the stack is the software implementation of them. Individual protocols within a suite are often designed with a single purpose in mind. This modularisation makes design and evaluation easier. Because each protocol module usually communicates with two others, they are commonly imagined as layers in a stack of protocols. The lowest protocol always deals with "low-level", physical interaction of the hardware. Every higher layer adds more features. User applications habitually deal only with the topmost layers. See also OSI model. In practical implementation, protocol stacks are often divided into three major sections for media, transport, and applications. A particular operating system or platform will often have two well-defined software interfaces, one between the media and transport layers, and one between the transport layers and applications. The media-to-transport interface defines how transport protocol software makes use of particular media and hardware types ("card drivers"). For example, this interface level would define how TCP/IP transport software would talk to Ethernet hardware. Examples of these interfaces include ODI and NDIS in the Microsoft Windows and DOS world. The application-to-transport interface defines how application programs make use of the transport layers. For example, this interface level would define how a web browser program would talk to TCP/IP transport software. Examples of these interfaces include Berkeley sockets and System V streams in the Unix world, and Winsock in the Microsoft world. General protocol suite description: T ~ ~ ~ T [A] [B]_____[C] Imagine three computers A, B, and C. A and B both have radio equipment, and can communicate via the airwaves using a suitable network protocol like IEEE 802.11. B and C are connected via a cable, exchanging data over that - again with the help of a protocol (for example Ethernet). However, neither of these two protocols will be able to transport information from A to C, because these computers are conceptually on different networks. One therefore needs an inter-network protocol to "connect" them. One could combine our two protocols to form a powerful third mastering both cable and wireless transmission, but we would need a different super-protocol for each possible combination of protocols. It is easier to leave the base protocols alone, and design a protocol that can work on top of any of them (the Internet Protocol is an example). This will make two stacks of two protocols each. The inter-network protocol will communicate with each of the base protocol in their simpler language. The base protocols will not talk directly to each other. A request on computer A to send a chunk of data to C is taken by the upper protocol, which (through whatever means) knows that C is reachable through B. It therefore instructs the wireless protocol to transmit the data packet to B. On this computer, the lower layer handlers will pass the packet up to the inter-network protocol, which, on recognizing that B is not the final destination, will again invoke lower-level functions. This time, the cable protocol is used to send the data to C. There the received packet is again passed to the upper protocol, which (with C being the destination) will pass it on. Often an even higher-level protocol will sit on top, and incur further processing. A commonly used protocol stack looks like this: +- - - - - -+ | HTTP | +- - - - - -+ | TCP | +- - - - - -+ | IP | +- - - - - -+ | Ethernet | +- - - - - -+ See also: Network protocol design principles Category:Computing

Internet

:For the more general networking concept, see internetworking. The Internet, or simply the Net, is the worldwide system of interconnected computer networks which makes information stored on it accessible. This information is transmitted by packet switching using a standardized Internet Protocol (IP) and many other protocols. It is made up of thousands of smaller commercial, academic, domestic and government networks. It carries various information and services, such as electronic mail, online chat, and the interlinked web pages and other documents of the World Wide Web.

Creation of the Internet

During the 1950s, several communications researchers realized that there was a need to allow general communication between users of various computers and communications networks. This led to research into decentralized networks, queuing theory, and packet switching. The subsequent creation of ARPANET in the United States in turn catalyzed a wave of technical developments that made it the basis for the development of the Internet. Contrary to popular myth, the DoD did not create the ARPANET so that they could communicate to the US Government after a nuclear war. The first TCP/IP wide area network was operational in 1984 when the United States' National Science Foundation (NSF) constructed a university network backbone that would later become the NSFNet. It was then followed by the opening of the network to commercial interests in 1995. Important separate networks that offered gateways into, then later merged into the Internet include Usenet, Bitnet and the various commercial and educational X.25 networks such as Compuserve and JANET. The ability of TCP/IP to work over these pre-existing communication networks allowed for a great ease of growth. Use of Internet as a phrase to describe a single global TCP/IP network originated around this time. The collective network gained a public face in the 1990s. In August 1991 CERN in Switzerland publicized the new World Wide Web project, two years after Tim Berners-Lee had begun creating HTML, HTTP and the first few web pages at CERN in Switzerland. In 1993 the Mosaic web browser version 1.0 was released, and by late 1994 there was growing public interest in the previously academic/technical Internet. By 1996 the word "Internet" was common public currency, but it referred almost entirely to the World Wide Web. Meanwhile, over the course of the decade, the Internet successfully accommodated the majority of previously existing public computer networks (although some networks such as FidoNet have remained separate). This growth is often attributed to the lack of central administration, which allows organic growth of the network, as well as the non-proprietary open nature of the Internet protocols, which encourages vendor interoperability and prevents any one company from exerting too much control over the network.

Today's Internet

FidoNets, FTP client, and Telnet client]] Apart from the complex physical connections that make up its infrastructure, the Internet is held together by bi- or multi-lateral commercial contracts (for example peering agreements) and by technical specifications or protocols that describe how to exchange data over the network. Indeed, 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'". Unlike older communications systems, the Internet protocol 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, 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. 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). Some RFCs are raised to the status of Internet Standard by the Internet Architecture Board (IAB). Some of the most used protocols in the Internet protocol suite are IP, 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, 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. The Internet makes it possible to provide real-time services such as Internet radio and webcasts that can be accessed from anywhere in the world. Some other popular services of the Internet were not created this way, but were originally based on proprietary systems. These include IRC, ICQ, AIM, and Gnutella. 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. Similar to how the commercial Internet providers connect via Internet exchange points, research networks tend to interconnect into large subnetworks such as:
- GEANT
- Internet2
- GLORIAD These in turn are built around relatively smaller networks. See also the list of academic computer network organizations In network schematic diagrams, the Internet is often represented by a cloud symbol, into and out of which network communications can pass.

Internet culture

The Internet is also having a profound impact on work, leisure, knowledge and worldviews. worldviews]]

ICANN

The Internet Corporation for Assigned Names and Numbers (ICANN) is the authority that coordinates the assignment of unique identifiers on the Internet, including domain names, Internet protocol addresses, and protocol port and parameter numbers. A globally unified namespace (i.e., a system of names in which there is one and only one holder of each name) is essential for the Internet to function. ICANN is headquartered in Marina del Rey, California, but is overseen by an international board of directors drawn from across the Internet technical, business, academic, and non-commercial communities. The US government continues to have a privileged role in approving changes to the root zone file that lies at the heart of the domain name system. Because the Internet is a distributed network comprising many voluntarily interconnected networks, the Internet, as such, has no governing body. ICANN's role in coordinating the assignment of unique identifiers distinguishes it as perhaps the only central coordinating body on the global Internet, but the scope of its authority extends only to the Internet's systems of domain names, Internet protocol addresses, and protocol port and parameter numbers.

The World Wide Web

Through keyword-driven Internet research using search engines like Google, millions worldwide have easy, instant access to a vast and diverse amount of online information. Compared to encyclopedias and traditional libraries, the World Wide Web has enabled a sudden and extreme decentralization of information and data. Some companies and individuals have adopted the use of 'weblogs' or blogs, which are largely used as easily-updatable online diaries. Some commercial organizations encourage staff to fill them with advice on their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information, and be attracted to the corporation as a result. One example of this practice is Microsoft, via whose product developers publish their personal blogs in order to pique the public's interest in their work. For more information on the distinction between the World Wide Web and the Internet itself — as in everyday use the two are sometimes confused — see Dark internet where this is discussed in more detail.

Remote access

The Internet allows computer users to connect to other computers and information stores easily, wherever they may be across the world. They may do this with or without the use of security, authentication and encryption technologies, depending on the requirements. This is encouraging new ways of working from home, collaboration and information sharing in many industries. An accountant sitting at home can audit the books of a company based in another country, on a server situated in a third country that is remotely maintained by IT specialists in a fourth. These accounts could have been created by home-working book-keepers, in other remote locations, based on information e-mailed to them from offices all over the world. Some of these things were possible before the widespread use of the Internet, but the cost of private, leased lines would have made many of them infeasible in practice. An office worker away from his or her desk, perhaps the other side of the world on a business trip or a holiday, can open a remote desktop session into his or her normal office PC using a secure Virtual Private Network (VPN) connection via the Internet. This gives him or her complete access to all their normal files and data, including e-mail and other applications, while they are away.

Collaboration

This low-cost and nearly instantaneous sharing of ideas, knowledge and skills has revolutionized some, and given rise to whole new, areas of human activity. One example of this is the collaborative development and distribution of Free/Libre/Open-Source Software (FLOSS) such as Linux, Mozilla and OpenOffice.org. See Collaborative software.

File-sharing

A computer file can be e-mailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or FTP server for easy download by others. It can be put into a "shared location" or onto a file server for instant use by colleagues. The load of bulk downloads to many users can be eased by the use of "mirror" servers or peer-to-peer networking. In any of these cases, access to the file may be controlled by user authentication; the transit of the file over the Internet may be obscured by encryption and money may change hands before or after access to the file is given. The price can be paid by the remote charging of funds from, for example a credit card whose details are also passed - hopefully fully encrypted - across the Internet. The origin and authenticity of the file received may be checked by digital signatures or by MD5 message digests. These simple features of the Internet, over a world-wide basis, are changing the basis for the production, sale and distribution of many types of product, wherever they can be reduced to a computer file for transmission. This includes all manner of office documents, publications, software products, music, photography, video, animations, graphics and the other arts. This in turn is causing seismic shifts in each of the existing industry associations, such as the RIAA and MPAA, that previously controlled the production and distribution of these products.

Streaming media and VoIP

Many existing radio and television broadcasters have provided Internet 'feeds' of their live audio and video streams (for example, the BBC). They have been joined by a range of pure Internet 'broadcasters' who never had on-air licences. This means that an Internet-connected device, such as a computer or something more specific, can be used to access on-line media in much the same way as was previously possible only with a TV or radio receiver. The range of material is much wider, from pornography to highly specialised technical web-casts. The simplest equipment can allow anybody, with little censorship or licencing control, to broadcast on a worldwide basis. Time-shift viewing or listening is not a problem as the BBC have shown with their Preview, Classic Clips and Listen Again features. Web-cams can be seen as an even lower-budget extension of this phenomenon. In this case the picture may update only slowly - perhaps once every few seconds or slower, but Internet users can watch animals around an African waterhole, ships in the Panama Canal or the traffic at a local roundabout live and in real time. Video chat rooms, video conferencing, and remote controllable webcams have become popular. Some people install webcams in their bedrooms that can be accessed by other voyeurs, often with two-way sound. VoIP stands for Voice over IP, where IP refers to the Internet Protocol that underlies all Internet communication. This phenomenon began as an optional two-way voice extension to some of the Instant Messaging systems that took off around the turn of the millennium. In recent years many people and organizations have made VoIP systems as easy to use and as convenient as a normal telephone. The benefit is that, as the actual voice traffic is carried by the Internet, VoIP is free or costs much less than an actual telephone call, especially over long distances and especially for those with always-on ADSL or DSL Internet connections anyway. The disadvantages are that it is still difficult to initiate a call with someone, unless they also have a VoIP phone or are at their computer and that there are still several competing standards that are mitigating against universal acceptance. In all of these cases, existing large organisations, that have grown accustomed to regular incomes for their services, are finding increased competition in their service areas, coming directly from the Internet. While newcomers strive to make these inroads, the traditional industries are having to adapt, adopt, complain or suffer. Meanwhile the consumer in each case most probably benefits from the increased range of services and possible price reductions. Some worry about censorship and control while others see a continuing globalisation of culture and norms.

Language

Main article: English on the Internet The most prevalent language for communication on the Internet is English. This may be due to the Internet's origins or to the growing role of English as an international language. It may also be related to the poor capability of early computers to handle characters other than those in the basic Latin alphabet (see Unicode). After English (32 % of web visitors) the most-requested languages on the world wide web are Chinese 13 %, Japanese 8 %, Spanish 6 %, German 6 % and French 4 %. (From [http://www.internetworldstats.com/stats7.htm Internet World Stats]) By continent, 33 % of the world's Internet users are based in Asia, 29 % in Europe and 23 % in North America.[http://www.internetworldstats.com/stats.htm] The Internet's technologies have developed enough in recent years that good facilities are available for development and communication in most widely used languages. However, some glitches such as mojibake still remain.

Cultural awareness

From a cultural awareness perspective, the Internet has been both an advantage and a liability. For people who are interested in other cultures it provides a significant amount of information and an interactivity that would be unavailable otherwise. However, for people who are not interested in other cultures there is some evidence indicating that the Internet enables them to avoid contact to a greater degree than ever before.

Censorship

Some countries, such as Iran and the People's Republic of China, restrict what people in their countries can see on the Internet, especially unwanted political and religious content. In the Western world, it is Germany that has the highest rate of censorship. Internet Service Providers are required by law to block some sites that contain child pornography or Nazi or Islamist propaganda. Censorship is sometimes done through government sponsored censoring filters, or by means of law or culture, making the propagation of targeted materials extremely hard. At the moment most Internet content is available regardless of where one is in the world, so long as one has the means of connecting to it.

Internet access

Germany Common methods of home access include dial-up, landline broadband (over coaxial cable, fiber optic or copper wires), Wi-Fi, satellite and cell phones. Public places to use the Internet include libraries and Internet cafes, where computers with Internet connections are available. There are also Internet access points in many public places like airport halls, in some cases just for brief use while standing. Various terms are used, such as "public Internet kiosk", "public access terminal", and "Web payphone". Many hotels now also have public terminals, though these are usually fee based. Wi-Fi provides wireless access to computer networks, and therefore can do so to the Internet itself. Hotspots providing such access include Wi-Fi-cafes, where a would-be user needs to bring their own wireless-enabled devices such as a laptop or PDA. These services may be free to all, free to customers only, or fee-based. A hotspot need not be limited to a confined location. The whole campus or park, or even the entire city can be enabled. Grassroots efforts have led to wireless community networks. Apart from Wi-Fi, there have been experiments with proprietary mobile wireless networks like Ricochet, various high-speed data services over cellular or mobile phone networks, and fixed wireless services. These services have not enjoyed widespread success due to their high cost of deployment, which is passed on to users in high usage fees. New wireless technologies such as WiMAX have the potential to alleviate these concerns and enable simple and cost effective deployment of metropolitan area networks covering large, urban areas. There is a growing trend towards wireless mesh networks, which offer a decentralized and redundant infrastructure and are often considered the future of the Internet. Broadband access over power lines was approved in 2004 in the United States in the face of stiff resistance from the amateur radio community. The problem with modulating a carrier signal onto power lines is that an above-ground power line can act as a giant antenna and jam long-distance radio frequencies used by amateurs, seafarers and others. Countries where Internet access is available to a majority of the population include Germany, India, China, Chile, Iceland, Finland, Sweden, Greece, Italy, Australia, Denmark, the United States, Canada, the United Kingdom, The Netherlands, Japan, Singapore, Taiwan, Thailand, South Korea and Norway. The use of the Internet around the world has been growing rapidly over the last decade, although the growth rate seems to have slowed somewhat after 2000. The phase of rapid growth is ending in industrialized countries, as usage becomes ubiquitous there, but the spread continues in Africa, Latin America, the Caribbean and the Middle East. However, there are still problems for many. ADSL and other broadband access are rare or nonexistent in most developing countries. Even in developed countries, high prices, mediocre performance and access restrictions often limit its uptake. Within individual countries, wide differences may exist between larger cities (often having multiple providers of broadband access) and some rural areas, where no broadband access may be available at all. The expansion of the availability of Internet access is a way to bridge the so-called digital divide.

Capitalization conventions

In formal usage, Internet is traditionally written with a capital first letter. The Internet Society, the Internet Engineering Task Force, the Internet Corporation for Assigned Names and Numbers, the World Wide Web Consortium, and several other Internet-related organizations all use this convention in their publications. In English grammar, proper nouns are capitalized. Most newspapers, newswires, periodicals, and technical journals also capitalize the term. Examples include the New York Times, the Associated Press, Time, The Times of India, Hindustan Times and Communications of the ACM. In other cases, the first letter is often written small (internet), and many people are not aware of any convention of using a capital letter. Some argue that internet is the correct form. Since 2000, a significant number of publications have switched to using internet. Among them are The Economist, the Financial Times, the London Times, and the Sydney Morning Herald. As of 2005, most publications using internet appear to be located outside of North America although one American news source, Wired News, has adopted the lowercase spelling.

Leisure

The Internet has been a major source of leisure since before the World Wide Web, with entertaining social experiments such as MOOs being conducted on university servers, and humor-related USENET groups receiving much of the main traffic. Today, many Internet forums have sections devoted to neta; short cartoons in the form of Flash movies are also popular. The pornography and gambling industries have both taken full advantage of the World Wide Web, and often provide a significant source of advertising revenue for other Web sites. Although many governments have attempted to put restrictions on both industries' use of the Internet, this has generally failed to stop their widespread popularity. One main area of leisure on the Internet is multiplayer gaming. This form of leisure creates communities, bringing people of all ages and origins to enjoy the fast-paced world of multiplayer games. These range from MMORPG to first-person shooters, from role-playing games to online gambling. This has revolutionized the way many people interact and spend their free time on the Internet. Online gaming began with services such as GameSpy and MPlayer, which players of games would typically subscribe to. Non-subscribers were limited to certain types of gameplay or certain games. With the release of Diablo by Blizzard Entertainment, gamers were treated to a built in online game service that was free of charge. With Blizzard's next game, StarCraft, the gaming world saw an explosion in the numbers of players using the Internet to play multi-player games. StarCraft may have been the first non-MMO game in which most players utilized the online gameplay as opposed to the single-player gameplay. Online gaming has progressed so much in the last 10 years that gamers earn a living from being a professional at the subject by winning tournaments and prizes as well as signing sponsor deals. Because there is a large support for certain online games, a new community has been born for people modding games, where users edit games to add a whole new element to it. This is how games such as Counter-Strike were born from the Half-Life Gaming Engine. Cyberslacking has become a serious drain on corporate resources; the average UK employee spends 57 minutes a day surfing, according to a study by Peninsula Business Services[http://news.scotsman.com/topics.cfm?tid=914&id=1001802003].

A complex system

Many computer scientists see the Internet as a "prime example of a large-scale, highly engineered, yet highly complex system" (Willinger, et al). The Internet is extremely heterogeneous. (For instance, data transfer rates and physical characteristics of connections vary widely.) The Internet exhibits "emergent phenomena" that depend on its large-scale organization. For example, data transfer rates exhibit temporal self-similarity.

Marketing

The Internet has also become a big market, and the biggest companies today have grown by taking advantage of the efficient low-cost advertising and commerce through the Internet. It is the fastest way to spread information to a vast community of people all at once. The Internet has revolutionized shopping –– a person can order a CD online and receive it in the mail within a couple of days, or download it directly in some cases.

Criticism

Many hyperlinks are outdated as time takes its toll on the existence of URL weblinks. These weblinks are often times defunct and are retained as hyperlinks for extended timeframes as a result of laziness or being busy enough to be sidetracked away from updating webpages. This is a common hoax for people who are fans in the field of what those links provide them with/to.

External links

General

- [http://www.channel101.com/ Internet TV Stations]
- [http://www.isoc.org/ The Internet Society (ISOC)]
- [http://www.techterms.org/internet.php Internet Dictionary] - Definitions of Internet-related terms
- [http://www.experienced-people.co.uk/1099-webmaster-glossary/ The Alternate Internet Glossary] (Humor)
- A [http://www.illusivecreations.com Calgary Web Design] company that has put together over 300 articles about the internet and web development. You can view them by going [http://www.illusivecreations.com/articles/ here].
- [http://www.clickz.com/stats/sectors/geographics/article.php/5911_151151 Internet access stats]
- [http://www.sharpened.net/glossary/ Glossary of Computer and Internet Terms]
- [http://scoreboard.keynote.com/scoreboard/Main.aspx?Login=Y&Username=public&Password=public Internet Health Report] from Keynote
- [http://www.internetworldstats.com/stats.htm Internet World Stats]

Articles

- [http://www.iht.com/articles/2005/09/29/business/net.php "EU and U.S. clash over control of the Net" - International Herald Tribune article by Tom Wright]
- [http://www.wired.com/wired/archive/13.08/intro.html "10 Years that changed the world" - WiReD looks back at the evolution of the Internet over last 10 years]
- [http://www.fourmilab.ch/documents/digital-imprimatur/ John Walker: The Digital Imprimatur]
- [http://www.addressingtheworld.info addressingtheworld.info] - website accompanying a book (ISBN 0742528103) on the history of DNS
- [http://computer.howstuffworks.com/internet-infrastructure.htm How Stuff Works explanation of the Infrastructure of the Internet]
- [http://www.searchandgo.com/articles/internet/net-explained-1.php Internet Explained] Seven part article explaining the origins to the present and a future look at the Internet.
- [http://www.wired.com/news/culture/0,1284,64596,00.html?tw=wn_tophead_7 "It's Just the 'internet' Now" - Wired.com article by Tony Long]

History

- [http://www.isoc.org/internet/history/brief.shtml The Internet Society History Page]
- [http://www.internetvalley.com/archives/mirrors/cerf-how-inet.txt How the Internet Came to Be]
- [http://www.zakon.org/robert/internet/timeline/ Hobbes' Internet Timeline v7.0]
- [http://www.ciolek.com/PAPERS/e-scholarship2000.html Futures and Non-futures for Scholarly Internet. ]
- [http://www.lk.cs.ucla.edu/internet_history.html History of the Internet links]
- [http://www.ietf.org/rfc/rfc801.txt RFC 801, planning the TCP/IP switchover]
- [http://www.archive.org/ Internet Archive] - A searchable database of old cached versions of websites dating back to 1996
- A list of lectures, some of which relate to the Internet, from the Massachusetts Institute of Technology is available [http://ocw.mit.edu/OcwWeb/Comparative-Media-Studies/CMS-930Media--Education--and-the-MarketplaceFall2001/VideoLectures/index.htm here]. Of particular interest is lecture #3 The Next Big Thing: Video Internet which is delivered in Real Player format. The lecture gives a brief history of networking; discusses convergence between the internet/telephone/television networks; the expansion of broadband access; makes predictions about the future of delivery of video over the internet.

References

- Walter Willinger, Ramesh Govindan, Sugih Jamin, Vern Paxson, and Scott Shenker. (2002). Scaling phenomena in the Internet. In Proceedings of the National Academy of Sciences, 99, suppl. 1, 2573 – 2580. Category:Communication Category:Digital media Category:Internet Category:Digital Revolution Category:Technology Category:Computer networks Category:Networks ko:인터넷 ms:Internet ja:インターネット simple:Internet th:อินเทอร์เน็ต fiu-vro:Internet

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130px 130px 130px 130px 130px #Wikipedia là bách khoa toàn thư bao gồm những yếu tố của bách khoa toàn thư tổng quát, bách khoa toàn thư về chuyên môn, và niên lịch. Wikipedia không phải là kho đựng tài liệu nguồn (xem Wikisource), bục để diễn giả, tờ báo, a free host, a webspace provider, a series of vanity articles, a memorial collection, an experiment in anarchy or democracy, or a grouping of links (whether internal or external). It is also not the place to insert your own opinions, experiences, or arguments — all editors must follow our no original research policy. All editors must strive for accuracy. #Wikipedia sử dụng "thái độ trung lập", which means we strive for articles that advocate no single point of view. Sometimes this requires representing multiple points of view; presenting each point of view accurately; providing context for any given point of view, so that readers understand whose view the point represents; and presenting no one point of view as "the truth" or "the best view". It means citing verifiable, authoritative sources whenever possible, especially on controversial topics. When a conflict arises as to which version is the most neutral, declare a cool-down period and tag the article as disputed; hammer out details on the talk page and follow dispute resolution. #Wikipedia chỉ có nội dung mở, có sẵn dưới Giấy phép Văn bản Tự do GNU (GFDL) hay thuộc phạm vi công cộng, and may be distributed or linked accordingly. Recognize that articles can be changed by anyone and no individual controls any specific article; therefore, any writing you contribute can be mercilessly edited and redistributed at will by the community. Do not submit copyright infringements or works licensed in a way incompatible with the GFDL. #Wikipedia theo quy tắc ứng xử: Respect your fellow Wikipedians even when you may not agree with them. Be civil. Avoid making personal attacks or sweeping generalizations. Stay cool when the editing gets hot; avoid lame edit wars by following the three-revert rule; remember that there are articles on the English Wikipedia to work on and discuss. Act in good faith by never disrupting Wikipedia to illustrate a point, and assume the same of others in the absence of compelling evidence to the contrary. Don't use sockpuppets to do wrong or circumvent policy. Be open, welcoming, and inclusive. #Wikipedia không có nguyên tắc nghiêm ngặt trừ ra năm nguyên tắc tổng quát ở đây. Be bold in editing, moving, and modifying articles, because the joy of editing is that perfection isn't required. And don't worry about messing up. All prior versions of articles are kept (unless a page is deleted by an administrator), so there is no way that you can accidentally damage Wikipedia or irretrievably destroy content. But remember—whatever you write here may be preserved for posterity.

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Internet protocol

Internet protocol

Packet switched

Packets

Packet routing

Packet switching in the Internet

Controversy over invention of packet switching

Work at MIT

Work at RAND

Work at National Physical Laboratory

Simultaneous Development

See also

Further reading

Reference

External links

Internet protocol suite

Layers in the TCP/IP stack

The link layer

The Internetwork layer

The transport layer

The application layer

Development

Implementation

See also

External links

Protocol stack

Internet

Creation of the Internet

Today's Internet

Internet culture

ICANN

The World Wide Web

Remote access

Collaboration

File-sharing

Streaming media and VoIP

Language

Cultural awareness

Censorship

Internet access

Capitalization conventions

Leisure

A complex system

Marketing

Criticism

See also

External links

General

Articles

History

References

Wikipedia:Năm cột trụ

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