UNIT 3 Notes for Students_2

UNIT -III

Computer Network Overview Computer networking or data communication is a most important part of the information technology. Today every business in the world needs a computer network for smooth operations, flexibly, instant communication and data access. Just imagine if there is no network communication in the university campuses, hospitals, multinational organizations and educational institutes then how difficult are to communicate with each other. In this article you will learn the basic overview of a computer network. The targeted audience of this article is the people who want to know about the network communication system, network standards and types. A computer network is comprised of connectivity devices and components. To share data and resources between two or more computers is known as networking. There are different types of a computer network such as LAN, MAN, WAN and wireless network. The key devices involved that make the infrastructure of a computer network are Hub, Switch, Router, Modem, Access point, LAN card and network cables. LAN stands for local area network and a network in a room, in a building or a network over small distance is known as a LAN. MAN stands for Metropolitan area network and it covers the networking between two offices within the city. WAN stands for wide area network and it cover the networking between two or more computers between two cities, two countries or two continents. There are different topologies of a computer network. A topology defines the physical layout or a design of a network. These topologies are star topology, bus topology, mesh topology, star bus topology etc. In a star topology each computer in a network is directly connected with a centralized device known as hub or switch. If any computer gets problematic in star topology then it does not affect the other computers in a network. There are different standards and devices in computer network. The most commonly used standard for a local area network is Ethernet. Key devices in a computer network are hub, switch, router, modem and access point etc. A router is used to connect two logically and physical different networks. All the communication on the internet is based on the router. Hub/Switch is used to connect the computers in local area network. Hopefully, in this article you may have learnt that what a computer network is, how important it is in our lives, what are different network devices, standards, topologies and communication types.

Types of Computer Network One way to categorize the different types of computer network designs is by their scope or scale. For historical reasons, the networking industry refers to nearly every type of design as some kind of area network. Common examples of area network types are: •LAN - Local Area Network •WLAN - Wireless Local Area Network •WAN - Wide Area Network •MAN - Metropolitan Area Network •SAN - Storage Area Network, System Area Network, Server Area Network, or sometimes Small Area Network •CAN - Campus Area Network, Controller Area Network, or sometimes Cluster Area Network •PAN - Personal Area Network •DAN - Desk Area Network LAN and WAN were the original categories of area networks, while the others have gradually emerged over many years of technology evolution. Note that these network types are a separate concept from network topologies such as bus, ring and star. LAN - Local Area Network A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs (perhaps one per room), and occasionally a LAN will span a group of nearby buildings. In TCP/IP networking, a LAN is often but not always implemented as a single IP subnet. In addition to operating in a limited space, LANs are also typically owned, controlled, and managed by a single person or organization. They also tend to use certain connectivity technologies, primarily Ethernet and Token Ring. WAN - Wide Area Network As the term implies, a WAN spans a large physical distance. The Internet is the largest WAN, spanning the Earth. A WAN is a geographically-dispersed collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address. A WAN differs from a LAN in several important ways. Most WANs (like the Internet) are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs tend to use technology like ATM, Frame Relay and X.25 for connectivity over the longer distances. LAN, WAN and Home Networking

Residences typically employ one LAN and connect to the Internet WAN via an Internet Service Provider (ISP) using a broadband modem. The ISP provides a WAN IP address to the modem, and all of the computers on the home network use LAN (so-called private) IP addresses. All computers on the home LAN can communicate directly with each other but must go through a central gateway, typically a broadband router, to reach the ISP. Other Types of Area Networks While LAN and WAN are by far the most popular network types mentioned, you may also commonly see references to these others: •Wireless Local Area Network - a LAN based on WiFi wireless network technology •Metropolitan Area Network - a network spanning a physical area larger than a LAN but smaller than a WAN, such as a city. A MAN is typically owned an operated by a single entity such as a government body or large corporation. •Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus. •Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel. •System Area Network - links high-performance computers with high-speed connections in a cluster configuration. Also known as Cluster Area Network. Computer network A computer network, often simply referred to as a network, is a collection of computers and devices interconnected by communications channels that facilitate communications among users and allows users to share resources. Networks may be classified according to a wide variety of characteristics. A computer network allows sharing of resources and information among interconnected devices. History Early networks of communicating computers included the military radar system Semi-Automatic Ground Environment (SAGE) and its relative the commercial airline reservation system Semi-Automatic Business Research Environment (SABRE), starting in the late 1950s.[1][2] In the 1960s, the Advanced Research Projects Agency (ARPA) started funding the design of the Advanced Research Projects Agency Network (ARPANET) for the United States Department of Defense. Development of the network began in 1969, based on designs developed during the 1960s.[3] The ARPANET evolved into the modern Internet. Purpose Computer networks can be used for a variety of purposes:
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Facilitating communications. Using a network, people can communicate efficiently and easily via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.

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Sharing hardware. In a networked environment, each computer on a network may access and use hardware resources on the network, such as printing a document on a shared network printer. Sharing files, data, and information. In a network environment, authorized user may access data and information stored on other computers on the network. The capability of providing access to data and information on shared storage devices is an important feature of many networks. Sharing software. Users connected to a network may run application programs on remote computers. Information preservation. Security. Speed up.

Network classification The following list presents categories used for classifying networks. Connection method Computer networks can be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as optical fiber, Ethernet, wireless LAN, HomePNA, power line communication or G.hn. Ethernet as it is defined by IEEE 802 utilizes various standards and mediums that enable communication between devices. Frequently deployed devices include hubs, switches, bridges, or routers. Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium. ITU-T G.hn technology uses existing home wiring (coaxial cable, phone lines and power lines) to create a high-speed (up to 1 Gigabit/s) local area network. Wired technologies
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Twisted pair wire is the most widely used medium for telecommunication. Twisted-pair cabling consist of copper wires that are twisted into pairs. Ordinary telephone wires consist of two insulated copper wires twisted into pairs. Computer networking cabling consist of 4 pairs of copper cabling that can be utilized for both voice and data transmission. The use of two wires twisted together helps to reduce crosstalk and electromagnetic induction. The transmission speed ranges from 2 million bits per second to 100 million bits per second. Twisted pair cabling comes in two forms which are Unshielded Twisted Pair (UTP) and Shielded twisted-pair (STP) which are rated in categories which are manufactured in different increments for various scenarios. Coaxial cable is widely used for cable television systems, office buildings, and other worksites for local area networks. The cables consist of copper or aluminum wire wrapped with insulating layer typically of a flexible material

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with a high dielectric constant, all of which are surrounded by a conductive layer. The layers of insulation help minimize interference and distortion. Transmission speed range from 200 million to more than 500 million bits per second.
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Optical fiber cable consists of one or more filaments of glass fiber wrapped in protective layers. It transmits light which can travel over extended distances. Fiber-optic cables are not affected by electromagnetic radiation. Transmission speed may reach trillions of bits per second. The transmission speed of fiber optics is hundreds of times faster than for coaxial cables and thousands of times faster than a twisted-pair wire.[citation needed]

Wireless technologies
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Terrestrial microwave – Terrestrial microwaves use Earth-based transmitter and receiver. The equipment look similar to satellite dishes. Terrestrial microwaves use low-gigahertz range, which limits all communications to lineof-sight. Path between relay stations spaced approx, 30 miles apart. Microwave antennas are usually placed on top of buildings, towers, hills, and mountain peaks. Communications satellites – The satellites use microwave radio as their telecommunications medium which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically 22,000 miles (for geosynchronous satellites) above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals. Cellular and PCS systems – Use several radio communications technologies. The systems are divided to different geographic areas. Each area has a lowpower transmitter or radio relay antenna device to relay calls from one area to the next area. Wireless LANs – Wireless local area network use a high-frequency radio technology similar to digital cellular and a low-frequency radio technology. Wireless LANs use spread spectrum technology to enable communication between multiple devices in a limited area. An example of open-standards wireless radio-wave technology is IEEE. Infrared communication , which can transmit signals between devices within small distances not more than 10 meters peer to peer or ( face to face ) without any body in the line of transmitting.

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Scale Networks are often classified as local area network (LAN), wide area network (WAN), metropolitan area network (MAN), personal area network (PAN), virtual private network (VPN), campus area network (CAN), storage area network (SAN), and others, depending on their scale, scope and purpose, e.g., controller area network (CAN) usage, trust level, and access right often differ between these types of

networks. LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations, such as a building, while WANs may connect physically separate parts of an organization and may include connections to third parties. Functional relationship (network architecture) Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., active networking, client– server and peer-to-peer (workgroup) architecture. Network topology Main article: Network topology Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network. Network topology is the coordination by which devices in the network are arranged in their logical relations to one another, independent of physical arrangement. Even if networked computers are physically placed in a linear arrangement and are connected to a hub, the network has a star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks. Types of networks based on physical scope Common types of computer networks may be identified by their scale. Local area network A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. Each computer or device on the network is a node. Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITU-T G.hn also provide a way to create a wired LAN using existing home wires (coaxial cables, phone lines and power lines).[4]

Typical library network, in a branching tree topology and controlled access to resources All interconnected devices must understand the network layer (layer 3), because they are handling multiple subnets (the different colors). Those inside the library, which have only 10/100 Mbit/s Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer 3 switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers. The defining characteristics of LANs, in contrast to WANs (Wide Area Networks), include their higher data transfer rates, smaller geographic range, and no need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies operate at speeds up to 10 Gbit/s. This is the data transfer rate. IEEE has projects investigating the standardization of 40 and 100 Gbit/s.[5] Personal area network A personal area network (PAN) is a computer network used for communication among computer and different information technological devices close to one person. Some examples of devices that are used in a PAN are personal computers, printers, fax machines, telephones, PDAs, scanners, and even video game consoles. A PAN may include wired and wireless devices. The reach of a PAN typically extends to 10 meters.[6] A wired PAN is usually constructed with USB and Firewire connections while technologies such as Bluetooth and infrared communication typically form a wireless PAN. [edit] Home area network A home area network (HAN) is a residential LAN which is used for communication between digital devices typically deployed in the home, usually a small number of personal computers and accessories, such as printers and mobile computing devices. An important function is the sharing of Internet access, often a broadband service through a CATV or Digital Subscriber Line (DSL) provider. It can also be referred to as an office area network (OAN). Wide area network A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Campus network

A campus network is a computer network made up of an interconnection of local area networks (LAN's) within a limited geographical area. The networking equipments (switches, routers) and transmission media (optical fiber, copper plant, Cat5 cabling etc.) are almost entirely owned (by the campus tenant / owner: an enterprise, university, government etc.). In the case of a university campus-based campus network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. [edit] Metropolitan area network A Metropolitan area network is a large computer network that usually spans a city or a large campus.

Sample EPN made of Frame relay WAN connections and dialup remote access.

Sample VPN used to interconnect 3 offices and remote users Enterprise private network

An enterprise private network is a network build by an enterprise to interconnect various company sites, e.g., production sites, head offices, remote offices, shops, in order to share computer resources. Virtual private network A virtual private network (VPN) is a computer network in which some of the links between nodes are carried by open connections or virtual circuits in some larger network (e.g., the Internet) instead of by physical wires. The data link layer protocols of the virtual network are said to be tunneled through the larger network when this is the case. One common application is secure communications through the public Internet, but a VPN need not have explicit security features, such as authentication or content encryption. VPNs, for example, can be used to separate the traffic of different user communities over an underlying network with strong security features. VPN may have best-effort performance, or may have a defined service level agreement (SLA) between the VPN customer and the VPN service provider. Generally, a VPN has a topology more complex than point-to-point. Internetwork An internetwork is the connection of two or more private computer networks via a common routing technology (OSI Layer 3) using routers. The Internet is an aggregation of many internetworks, hence its name was shortened to Internet. Backbone network A Backbone network (BBN) A backbone network or network backbone is part of a computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks.[1][2] A backbone can tie together diverse networks in the same building, in different buildings in a campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it. A large corporation that has many locations may have a backbone network that ties all of the locations together, for example, if a server cluster needs to be accessed by different departments of a company that are located at different geographical locations. The pieces of the network connections (for example: ethernet, wireless) that bring these departments together is often mentioned as network backbone. Network congestion is often taken into consideration while designing backbones. Backbone networks should not be confused with the Internet backbone. Global area network A global area network (GAN) is a network used for supporting mobile communications across an arbitrary number of wireless LANs, satellite coverage areas, etc. The key challenge in mobile communications is handing off the user

communications from one local coverage area to the next. In IEEE Project 802, this involves a succession of terrestrial wireless LANs.[7] Internet The Internet is a global system of interconnected governmental, academic, corporate, public, and private computer networks. It is based on the networking technologies of the Internet Protocol Suite. It is the successor of the Advanced Research Projects Agency Network (ARPANET) developed by DARPA of the United States Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW). Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing system (IP addresses) administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol (BGP), forming a redundant worldwide mesh of transmission paths. Intranets and extranets Intranets and extranets are parts or extensions of a computer network, usually a local area network. An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information. An extranet is a network that is limited in scope to a single organization or entity and also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities—a company's customers may be given access to some part of its intranet—while at the same time the customers may not be considered trusted from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although an extranet cannot consist of a single LAN; it must have at least one connection with an external network. Overlay network An overlay network is a virtual computer network that is built on top of another network. Nodes in the overlay are connected by virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network.

A sample overlay network: IP over SONET over Optical For example, many peer-to-peer networks are overlay networks because they are organized as nodes of a virtual system of links run on top of the Internet. The Internet was initially built as an overlay on the telephone network .[8] Overlay networks have been around since the invention of networking when computer systems were connected over telephone lines using modem, before any data network existed. Nowadays the Internet is the basis for many overlaid networks that can be constructed to permit routing of messages to destinations specified by an IP address. For example, distributed hash tables can be used to route messages to a node having a specific logical address, whose IP address is known in advance. Overlay networks have also been proposed as a way to improve Internet routing, such as through quality of service guarantees to achieve higher-quality streaming media. Previous proposals such as IntServ, DiffServ, and IP Multicast have not seen wide acceptance largely because they require modification of all routers in the network.[citation needed] On the other hand, an overlay network can be incrementally deployed on end-hosts running the overlay protocol software, without cooperation from Internet service providers. The overlay has no control over how packets are routed in the underlying network between two overlay nodes, but it can control, for example, the sequence of overlay nodes a message traverses before reaching its destination. For example, Akamai Technologies manages an overlay network that provides reliable, efficient content delivery (a kind of multicast). Academic research includes End System Multicast and Overcast for multicast; RON (Resilient Overlay Network) for resilient routing; and OverQoS for quality of service guarantees, among others. A backbone network or network backbone is a part of computer network infrastructure that interconnects various pieces of network, providing a path for the exchange of information between different LANs or subnetworks.[1][2] A backbone can tie together diverse networks in the same building, in different buildings in a

campus environment, or over wide areas. Normally, the backbone's capacity is greater than the networks connected to it. Basic hardware components All networks are made up of basic hardware building blocks to interconnect network nodes, such as Network Interface Cards (NICs), Bridges, Hubs, Switches, and Routers. In addition, some method of connecting these building blocks is required, usually in the form of galvanic cable (most commonly Category 5 cable). Less common are microwave links (as in IEEE 802.12) or optical cable ("optical fiber"). Network interface cards A network card, network adapter, or NIC (network interface card) is a piece of computer hardware designed to allow computers to communicate over a computer network. It provides physical access to a networking medium and often provides a low-level addressing system through the use of MAC addresses. Each network interface card has its unique id. This is written on a chip which is mounted on the card. Repeaters A repeater is an electronic device that receives a signal, cleans it of unnecessary noise, regenerates it, and retransmits it at a higher power level, or to the other side of an obstruction, so that the signal can cover longer distances without degradation. In most twisted pair Ethernet configurations, repeaters are required for cable that runs longer than 100 meters. Repeaters work on the Physical Layer of the OSI model. Hubs A network hub contains multiple ports. When a packet arrives at one port, it is copied unmodified to all ports of the hub for transmission. The destination address in the frame is not changed to a broadcast address.[9] It works on the Physical Layer of the OSI model.. Bridges A network bridge connects multiple network segments at the data link layer (layer 2) of the OSI model. Bridges broadcast to all ports except the port on which the broadcast was received. However, bridges do not promiscuously copy traffic to all ports, as hubs do, but learn which MAC addresses are reachable through specific ports. Once the bridge associates a port and an address, it will send traffic for that address to that port only. Bridges learn the association of ports and addresses by examining the source address of frames that it sees on various ports. Once a frame arrives through a port, its source address is stored and the bridge assumes that MAC address is associated

with that port. The first time that a previously unknown destination address is seen, the bridge will forward the frame to all ports other than the one on which the frame arrived. Bridges come in three basic types:
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Local bridges: Directly connect local area networks (LANs) Remote bridges: Can be used to create a wide area network (WAN) link between LANs. Remote bridges, where the connecting link is slower than the end networks, largely have been replaced with routers. Wireless bridges: Can be used to join LANs or connect remote stations to LANs.

Switches A network switch is a device that forwards and filters OSI layer 2 datagrams (chunks of data communication) between ports (connected cables) based on the MAC addresses in the packets.[10] A switch is distinct from a hub in that it only forwards the frames to the ports involved in the communication rather than all ports connected. A switch breaks the collision domain but represents itself as a broadcast domain. Switches make forwarding decisions of frames on the basis of MAC addresses. A switch normally has numerous ports, facilitating a star topology for devices, and cascading additional switches.[11] Some switches are capable of routing based on Layer 3 addressing or additional logical levels; these are called multi-layer switches. The term switch is used loosely in marketing to encompass devices including routers and bridges, as well as devices that may distribute traffic on load or by application content (e.g., a Web URL identifier). Routers A router is an internetworking device that forwards packets between networks by processing information found in the datagram or packet (Internet protocol information from Layer 3 of the OSI Model). In many situations, this information is processed in conjunction with the routing table (also known as forwarding table). Routers use routing tables to determine what interface to forward packets (this can include the "null" also known as the "black hole" interface because data can go into it, however, no further processing is done for said data). Firewalls Firewalls are the most important aspect of a network with respect to security. A firewalled system does not need every interaction or data transfer monitored by a human, as automated processes can be set up to assist in rejecting access requests from unsafe sources, and allowing actions from recognized ones. The vital role firewalls play in network security grows in parallel with the constant increase in 'cyber' attacks for the purpose of stealing/corrupting data, planting viruses, etc. Internet: "The Big Picture"

Welcome to "The Big Picture" of connecting through the Internet to reach online resources. The purpose of this page is to answer the question: "What are the major pieces of the Internet, and who are the major players in each segment?" If some of these links don't make sense, it's because you are not an "alumni" of my internet courses ;-) This page displays the main pieces of the Internet from a User's PC... extending all the way through to the online content. Each section mentions the most significant parts of the Internet's architecture. I also provide links to the top "couple of vendors" in each category, and then an external link to a more extensive lists of vendors. In creating this one web page to describe the "entire Internet", I split the diagram based on the function being performed. I recognize that a company may perform several of these functions. I've included several "leading edge" components as well, such as LMDS for the local loop (This page is intended to be forward-looking). I also recognize that there are many additional details that could be added to this page, but I am trying to adhere to a 90/10 rule. If this page identifies 90% of the mainstream pieces and players, that should be sufficient to convey "the big picture". (The remaining 10% details would probably triple the size & complexity of this one meta-diagram.) I welcome any comments you have to improve this page especially if I've omitted anything significant. Russ Haynal. These are the Main Sections:
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User PC - Multi-Media PCs equipped to send and receive all variety of audio and video User Communication Equipment - Connects the Users' PC(s) to the "Local Loop" Local Loop Carrier - Connects the User location to the ISP's Point of Presence ISP's POP - Connections from the user are accepted and authenticated here. User Services - Used by the User for access (DNS, EMAIL, etc). ISP Backbone - Interconnects the ISP's POPs, AND interconnects the ISP to Other ISP's and online content. Online Content - These are the host sites that the user interacts with. Origins Of Online Content - This is the original "real-world" sources for the online information. User PC - A Multi-Media PC equipped to send and receive all variety of audio and video. 1. Sound Board /Microphone/Speakers for telephony, MIDI ,Creative Labs/SoundBlaster, Yahoo's List for Sound Cards. 2. Video/Graphics for 3D graphics, video, playback . Matrox, Diamond Multimedia, Yahoo's List for Video Cards. 3. Video camera - Connectix, Yahoo's List for Video Conferencing, Yahoo's List for

Manufacturers. 4. Voice recognition - Yahoo's List for Voice Recognition. User's Communication Equipment - This is the communication equipment located at the User's location(s) to connect the Users' PC(s) to the "Local Loop" (aka Customer Premise equipment - CPE) 1. Phone line - Analog Modem (v.90=56K) US Robotics , Rockwell, Yahoo's List for Modems. 2. Phone line -ISDN(128K) Yahoo's list for ISDN. 3. Phone Line - DSL (6 MB) , Yahoo's list for DSL., ADSL Forum. 4. Cable Modem (27 MB) Cable Modem University (and their neat table of Modem Vendors) 5. Electric Line (1 MB) Digital PowerLine by Nortel 6. Satellite (400 Kb) DirecPC 7. LAN - 3com, Yahoo's list of Network Hardware. 8. Routers - Cisco, Ascend, Bay Networks, Yahoo's list. 9. Firewalls - TBD Vendors, Yahoo's list for firewalls. User services - Many corporations also provide "User services" to their employees such as DNS, Email, Usenet, etc. Links for these services are described further down this diagram in the user services section. Local Loop Carrier - Connects the User location to the ISP's Point of Presence 1. Communication Lines -RBOCS: (Ameritech, Bell Atlantic, Bell South, Cincinnati Bell, NYNEX, Pacific Bell, Southwestern Bell, US West),GTE, LEC's, MFS, TCG, Brooks, 2. Cable - List of Cable ISP's. 3. Satellite - DirecPC. 4. Power line - Digital PowerLine by Nortel. 5. Wireless - Wireless Week, Wireless Access Tech Magazine, Yahoos' List for Wireless networking. Equipment Manufacturers: Nortel, Lucent, Newbridge, Siemens.

ISP POP- This is the edge of the ISP's network. Connections from the user are accepted and authenticated here. 1. Remote ports Ascend (Max Product), US Robotics (3com), Livingston (Portmaster), Cisco, Yahoo's List for Routing Technology. User Services - these are the services that most users would use along with Internet Access. (These may be hosted within a large corporate LAN) (Webhosting is discussed under the online content section) 1. Domain Name Server - BIND, DNS Resources Directory. 2. Email Host -,Sendmail ,Microsoft Exchange 3. Usenet Newsgroups (NNTP) - INN, 4. Special services such as quake, telnet, FTP 5. User Web Hosting - See the online content section for details. 6. These servers require fast interfaces and large/fast storage. ISP Backbone - The ISP backbone interconnects the ISP's POPs, AND interconnects the ISP to Other ISP's and online content. 1. Backbone Providers - Russ Haynal's ISP Page. 2. Large Circuits - fiber Circuit carriers, AT&T, SPRINT, MCI, Worldcom (MFS, Brooks), RBOC's, C&W, Qwest, 3. Routers - Cisco, Ascend, Bay Networks, Yahoo's list. 4. ATM Switches - Fore, Newbridge, Lucent, Ascend, Yahoo's List of ATM Manufacturers. 5. Sonet/SDH Switches - Nortel, Fujitsu, Alcatel.Tellabs , Lucent and Positron Fiber Systems. 6. Gigaswitch - Gigaswitch from Dec, Yahoo's List. 7. Network Access Points - Russ Haynal's ISP Page The Broadband guide (links to 4,000 vendors)

Online Content - These are the host sites that the user interacts with. 1. Web Server platforms - Netsite, Apache, Microsoft, Yahoo's List of web servers. 2. Hosting Farms- Many online resources are hosted at well-connection facilities 3. These servers require fast interfaces and large/fast storage. Origins of online content - This is the original "real-world" sources for the online information. 1. Existing electronic information is being connected from legacy systems. 2. Traditional print resources are being scanned and converted into electronic format 3. Many types of video and audio programming is being broadcast via the internet. For example, look at Radio_locator. 4. Internet telephony is growing on the Internet Start with VON and then explore this list from Yahoo. 5. Look at this list of interesting devices connected to the Internet. Other Resources: Internet Architecture Fortunately, nobody owns the Internet, there is no centralized control, and nobody can turn it off. Its evolution depends on rough consensus about technical proposals, and on running code. Engineering feed-back from real implementations is more important than any architectural principles. RFC 1958; B. Carpenter; Architectural Principles of the Internet; June, 1996. What is the Internet architecture? It is by definition a meta-network, a constantly changing collection of thousands of individual networks intercommunicating with a common protocol. The Internet's architecture is described in its name, a short from of the compound word "inter-networking". This architecture is based in the very specification of the standard TCP/IP protocol, designed to connect any two networks which may be very different in internal hardware, software, and technical design. Once two networks are interconnected, communication with TCP/IP is enabled end-to-end, so that any node on the Internet has the near magical ability to communicate with any other no matter where they are. This openness of design has enabled the Internet architecture to grow to a global scale.

In practice, the Internet technical architecture looks a bit like a multi-dimensional river system, with small tributaries feeding medium-sized streams feeding large rivers. For example, an individual's access to the Internet is often from home over a modem to a local Internet service provider who connects to a regional network connected to a national network. At the office, a desktop computer might be connected to a local area network with a company connection to a corporate Intranet connected to several national Internet service providers. In general, small local Internet service providers connect to medium-sized regional networks which connect to large national networks, which then connect to very large bandwidth networks on the Internet backbone. Most Internet service providers have several redundant network cross-connections to other providers in order to ensure continuous availability. The companies running the Internet backbone operate very high bandwidth networks relied on by governments, corporations, large organizations, and other Internet service providers. Their technical infrastructure often includes global connections through underwater cables and satellite links to enable communication between countries and continents. As always, a larger scale introduces new phenomena: the number of packets flowing through the switches on the backbone is so large that it exhibits the kind of complex non-linear patterns usually found in natural, analog systems like the flow of water or development of the rings of Saturn (RFC 3439, S2.2). Each communication packet goes up the hierarchy of Internet networks as far as necessary to get to its destination network where local routing takes over to deliver it to the addressee. In the same way, each level in the hierarchy pays the next level for the bandwidth they use, and then the large backbone companies settle up with each other. Bandwidth is priced by large Internet service providers by several methods, such as at a fixed rate for constant availability of a certain number of megabits per second, or by a variety of use methods that amount to a cost per gigabyte. Due to economies of scale and efficiencies in management, bandwidth cost drops dramatically at the higher levels of the architecture. Resources. The network topology page provides information and resources on the real-time construction of the Internet network, including graphs and statistics. The following references provide additional information about the Internet architecture: IP address An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address. Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.

The four numbers in an IP address are used in different ways to identify a particular network and a host on that network. Four regional Internet registries -- ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses from the following three classes. •Class A - supports 16 million hosts on each of 126 networks •Class B - supports 65,000 hosts on each of 16,000 networks •Class C - supports 254 hosts on each of 2 million networks The number of unassigned Internet addresses is running out, so a new classless scheme called CIDR is gradually replacing the system based on classes A, B, and C and is tied to adoption of IPv6. ISP Short for Internet Service Provider, it refers to a company that provides Internet services, including personal and business access to the Internet. For a monthly fee, the service provider usually provides a software package, username, password and access phone number. Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. For broadband access you typically receive the broadband modem hardware or pay a monthly fee for this equipment that is added to your ISP account billing. In addition to serving individuals, ISPs also serve large companies, providing a direct connection from the company's networks to the Internet. ISPs themselves are connected to one another through Network Access Points (NAPs). ISPs may also be called IAPs (Internet Access Providers). URL Abbreviation of Uniform Resource Locator, the global address of documents and other resources on the World Wide Web. The first part of the address is called a protocol identifier and it indicates what protocol to use, and the second part is called a resource name and it specifies the IP address or the domain name where the resource is located. The protocol identifier and the resource name are separated by a colon and two forward slashes. For example, the two URLs below point to two different files at the domain pcwebopedia.com. The first specifies an executable file that should be fetched using the FTP protocol; the second specifies a Web page that should be fetched using the HTTP protocol: •ftp://www.pcwebopedia.com/stuff.exe •http://www.pcwebopedia.com/index.html

Domain Name
Domain names are used to identify one or more IP addresses. For example, the domain name microsoft.com represents about a dozen IP addresses. Domain names are used in URLs to identify particular Web pages. For example, in the URL http://www.pcwebopedia.com/index.html, the domain name is pcwebopedia.com.

Every domain name has a suffix that indicates which top level domain (TLD) it belongs to. There are only a limited number of such domains. For example: •gov - Government agencies •edu - Educational institutions •org - Organizations (nonprofit) •mil - Military •com - commercial business •net - Network organizations •ca - Canada •th - Thailand Because the Internet is based on IP addresses, not domain names, every Web server requires a Domain Name System (DNS) server to translate domain names into IP addresses.

Browser
short for Web browser, a software application used to locate and display Web pages. The two most popular browsers are Microsoft Internet Explorer and Firefox. Both of these are graphical browsers, which means that they can display graphics as well as text. In addition, most modern browsers can present multimedia information, including sound and video, though they require plug-ins for some formats.

Protocol
An agreed-upon format for transmitting data between two devices. The protocol determines the following: •the type of error checking to be used data compression method, if any •how the sending device will indicate that it has finished sending a message how the receiving device will indicate that it has received a message There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster. From a user's point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers. The protocol can be implemented either in hardware or in software.

Search engine
A program that searches documents for specified keywords and returns a list of the documents where the keywords were found. Although search engine is really a general class of programs, the term is often used to specifically describe systems like Google, Alta Vista and Excite that enable users to search for documents on the World Wide Web and USENET newsgroups. Typically, a search engine works by sending out a spider to fetch as many documents as possible. Another program, called an indexer, then reads these

documents and creates an index based on the words contained in each document. Each search engine uses a proprietary algorithm to create its indices such that, ideally, only meaningful results are returned for each query.

e-mail
Short for electronic mail, the transmission of messages over communications networks. The messages can be notes entered from the keyboard or electronic files stored on disk. Most mainframes, minicomputers, and computer networks have an e-mail system. Some electronic-mail systems are confined to a single computer system or network, but others have gateways to other computer systems, enabling users to send electronic mail anywhere in the world. Companies that are fully computerized make extensive use of e-mail because it is fast, flexible, and reliable. Most e-mail systems include a rudimentary text editor for composing messages, but many allow you to edit your messages using any editor you want. You then send the message to the recipient by specifying the recipient's address. You can also send the same message to several users at once. This is called broadcasting. Sent messages are stored in electronic mailboxes until the recipient fetches them. To see if you have any mail, you may have to check your electronic mailbox periodically, although many systems alert you when mail is received. After reading your mail, you can store it in a text file, forward it to other users, or delete it. Copies of memos can be printed out on a printer if you want a paper copy. All online services and Internet Service Providers (ISPs) offer e-mail, and most also support gateways so that you can exchange mail with users of other systems. Usually, it takes only a few seconds or minutes for mail to arrive at its destination. This is a particularly effective way to communicate with a group because you can broadcast a message or document to everyone in the group at once. Although different e-mail systems use different formats, there are some emerging standards that are making it possible for users on all systems to exchange messages. In the PC world, an important e-mail standard is MAPI. The CCITT standards organization has developed the X.400 standard, which attempts to provide a universal way of addressing messages. To date, though, the de facto addressing standard is the one used by the Internet system because almost all email systems have an Internet gateway. Another common spelling for e-mail is email.

FTP
Short for File Transfer Protocol, the protocol for exchanging files over the Internet. FTP works in the same way as HTTP for transferring Web pages from a server to a user's browser and SMTP for transferring electronic mail across the Internet in that, like these technologies, FTP uses the Internet's TCP/IP protocols to enable data transfer. FTP is most commonly used to download a file from a server using the Internet or to upload a file to a server (e.g., uploading a Web page file to a server).

Telnet
(tel´net) (n.) A terminal emulation program for TCP/IP networks such as the Internet. The Telnet program runs on your computer and connects your PC to a server on the network. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. To start a Telnet session, you must log in to a server by entering a valid username and password. Telnet is a common way to remotely control Web servers.

gopher
A system that pre-dates the World Wide Web for organizing and displaying files on Internet servers. A Gopher server presents its contents as a hierarchically structured list of files. With the ascendance of the Web, many gopher databases were converted to Web sites which can be more easily accessed via Web search engines. Gopher was developed at the University of Minnesota and named after the school's mascot. Two systems, Veronica and Jughead, let you search global indices of resources stored in Gopher systems.

WWW
The World Wide Web, abbreviated as WWW and commonly known as the Web, is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them via hyperlinks. Using concepts from earlier hypertext systems, English engineer and computer scientist Sir Tim Berners-Lee, now the Director of the World Wide Web Consortium, wrote a proposal in March 1989 for what would eventually become the World Wide Web.[1] At CERN in Geneva, Switzerland, Berners-Lee and Belgian computer scientist Robert Cailliau proposed in 1990 to use "HyperText ... to link and access information of various kinds as a web of nodes in which the user can browse at will",[2] and publicly introduced the project in December.[3] "The World-Wide Web (W3) was developed to be a pool of human knowledge, and human culture, which would allow collaborators in remote sites to share their ideas and all aspects of a common project."[4] Contents [] 1 History 2 Function 2.1 Linking 2.2 Dynamic updates of web pages 2.3 WWW prefix 3 Privacy 4 Security 5 Standards 6 Accessibility 7 Internationalization

8 Statistics 9 Speed issues 10 Caching 11 See also 12 Notes 13 References 14 External links HistoryMain article: History of the World Wide Web In the May 1970 issue of Popular Science magazine Arthur C. Clarke was reported to have predicted that satellites would one day "bring the accumulated knowledge of the world to your fingertips" using a console that would combine the functionality of the Xerox, telephone, television and a small computer, allowing data transfer and video conferencing around the globe.[5] In March 1989, Tim Berners-Lee wrote a proposal that referenced ENQUIRE, a database and software project he had built in 1980, and described a more elaborate information management system.[6] With help from Robert Cailliau, he published a more formal proposal (on November 12, 1990) to build a "Hypertext project" called "WorldWideWeb" (one word, also "W3") as a "web" of "hypertext documents" to be viewed by "browsers" using a client–server architecture.[2] This proposal estimated that a read-only web would be developed within three months and that it would take six months to achieve "the creation of new links and new material by readers, [so that] authorship becomes universal" as well as "the automatic notification of a reader when new material of interest to him/her has become available." See Web 2.0 and RSS/Atom, which have taken a little longer to mature. The proposal was modeled after the Dynatext SGML reader by Electronic Book Technology, a spin-off from the Institute for Research in Information and Scholarship at Brown University. The Dynatext system, licensed by CERN, was technically advanced and was a key player in the extension of SGML ISO 8879:1986 to Hypermedia within HyTime, but it was considered too expensive and had an inappropriate licensing policy for use in the general high energy physics community, namely a fee for each document and each document alteration. This NeXT Computer used by Tim Berners-Lee at CERN became the first web server The CERN datacenter in 2010 housing some www serversA NeXT Computer was used by Berners-Lee as the world's first web server and also to write the first web browser, WorldWideWeb, in 1990. By Christmas 1990, Berners-Lee had built all the tools necessary for a working Web:[7] the first web browser (which was a web editor as well); the first web server; and the first web pages,[8] which described the project itself. On August 6, 1991, he posted a short summary of the World Wide Web project on the alt.hypertext newsgroup.[9] This date also marked the debut of the Web as a publicly available service on the Internet. The first photo on the web was uploaded by Berners-Lee in 1992, an image of the CERN house band Les Horribles Cernettes.

Web as a "Side Effect" of the 40 years of Particle Physics Experiments. It happened many times during history of science that the most impressive results of large scale scientific efforts appeared far away from the main directions of those efforts... After the World War 2 the nuclear centers of almost all developed countries became the places with the highest concentration of talented scientists. For about four decades many of them were invited to the international CERN's Laboratories. So specific kind of the CERN's intellectual "entire culture" (as you called it) was constantly growing from one generation of the scientists and engineers to another. When the concentration of the human talents per square foot of the CERN's Labs reached the critical mass, it caused an intellectual explosion The Web -- crucial point of human's history -- was born... Nothing could be compared to it... We cant imagine yet the real scale of the recent shake, because there has not been so fast growing multidimension social-economic processes in human history... [10] The first server outside Europe was set up at SLAC to host the SPIRES-HEP database. Accounts differ substantially as to the date of this event. The World Wide Web Consortium says December 1992,[11] whereas SLAC itself claims 1991.[12] [13] This is supported by a W3C document entitled A Little History of the World Wide Web.[14] The crucial underlying concept of hypertext originated with older projects from the 1960s, such as the Hypertext Editing System (HES) at Brown University, Ted Nelson's Project Xanadu, and Douglas Engelbart's oN-Line System (NLS). Both Nelson and Engelbart were in turn inspired by Vannevar Bush's microfilm-based "memex", which was described in the 1945 essay "As We May Think".[citation needed] Berners-Lee's breakthrough was to marry hypertext to the Internet. In his book Weaving The Web, he explains that he had repeatedly suggested that a marriage between the two technologies was possible to members of both technical communities, but when no one took up his invitation, he finally tackled the project himself. In the process, he developed a system of globally unique identifiers for resources on the Web and elsewhere: the Universal Document Identifier (UDI), later known as Uniform Resource Locator (URL) and Uniform Resource Identifier (URI); the publishing language HyperText Markup Language (HTML); and the Hypertext Transfer Protocol (HTTP).[15] The World Wide Web had a number of differences from other hypertext systems that were then available. The Web required only unidirectional links rather than bidirectional ones. This made it possible for someone to link to another resource without action by the owner of that resource. It also significantly reduced the difficulty of implementing web servers and browsers (in comparison to earlier systems), but in turn presented the chronic problem of link rot. Unlike predecessors such as HyperCard, the World Wide Web was non-proprietary, making it possible to develop servers and clients independently and to add extensions without licensing restrictions. On April 30, 1993, CERN announced[16] that the World Wide Web would be free to anyone, with no fees due. Coming two months after the announcement that the Gopher protocol was no longer free to use, this produced a rapid shift away from Gopher and towards the Web. An early popular web browser was ViolaWWW, which was based upon HyperCard.

Scholars generally agree that a turning point for the World Wide Web began with the introduction[17] of the Mosaic web browser[18] in 1993, a graphical browser developed by a team at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign (NCSA-UIUC), led by Marc Andreessen. Funding for Mosaic came from the U.S. High-Performance Computing and Communications Initiative, a funding program initiated by the High Performance Computing and Communication Act of 1991, one of several computing developments initiated by U.S. Senator Al Gore.[19] Prior to the release of Mosaic, graphics were not commonly mixed with text in web pages and the Web's popularity was less than older protocols in use over the Internet, such as Gopher and Wide Area Information Servers (WAIS). Mosaic's graphical user interface allowed the Web to become, by far, the most popular Internet protocol. The World Wide Web Consortium (W3C) was founded by Tim Berners-Lee after he left the European Organization for Nuclear Research (CERN) in October, 1994. It was founded at the Massachusetts Institute of Technology Laboratory for Computer Science (MIT/LCS) with support from the Defense Advanced Research Projects Agency (DARPA), which had pioneered the Internet; a year later, a second site was founded at INRIA (a French national computer research lab) with support from the European Commission DG InfSo; and in 1996, a third continental site was created in Japan at Keio University. By the end of 1994, while the total number of websites was still minute compared to present standards, quite a number of notable websites were already active, many of which are the precursors or inspiration for today's most popular services. Connected by the existing Internet, other websites were created around the world, adding international standards for domain names and HTML. Since then, BernersLee has played an active role in guiding the development of web standards (such as the markup languages in which web pages are composed), and in recent years has advocated his vision of a Semantic Web. The World Wide Web enabled the spread of information over the Internet through an easy-to-use and flexible format. It thus played an important role in popularizing use of the Internet.[20] Although the two terms are sometimes conflated in popular use, World Wide Web is not synonymous with Internet.[21] The Web is an application built on top of the Internet. FunctionThe terms Internet and World Wide Web are often used in every-day speech without much distinction. However, the Internet and the World Wide Web are not one and the same. The Internet is a global system of interconnected computer networks. In contrast, the Web is one of the services that runs on the Internet. It is a collection of interconnected documents and other resources, linked by hyperlinks and URLs. In short, the Web is an application running on the Internet. [22] Viewing a web page on the World Wide Web normally begins either by typing the URL of the page into a web browser, or by following a hyperlink to that page or resource. The web browser then initiates a series of communication messages, behind the scenes, in order to fetch and display it. First, the server-name portion of the URL is resolved into an IP address using the global, distributed Internet database known as the Domain Name System (DNS). This IP address is necessary to contact the Web server. The browser then requests

the resource by sending an HTTP request to the Web server at that particular address. In the case of a typical web page, the HTML text of the page is requested first and parsed immediately by the web browser, which then makes additional requests for images and any other files that complete the page image. Statistics measuring a website's popularity are usually based either on the number of page views or associated server 'hits' (file requests) that take place. While receiving these files from the web server, browsers may progressively render the page onto the screen as specified by its HTML, Cascading Style Sheets (CSS), or other page composition languages. Any images and other resources are incorporated to produce the on-screen web page that the user sees. Most web pages contain hyperlinks to other related pages and perhaps to downloadable files, source documents, definitions and other web resources. Such a collection of useful, related resources, interconnected via hypertext links is dubbed a web of information. Publication on the Internet created what Tim Berners-Lee first called the WorldWideWeb (in its original CamelCase, which was subsequently discarded) in November 1990.[2] Linking Graphic representation of a minute fraction of the WWW, demonstrating hyperlinksOver time, many web resources pointed to by hyperlinks disappear, relocate, or are replaced with different content. This makes hyperlinks obsolete, a phenomenon referred to in some circles as link rot and the hyperlinks affected by it are often called dead links. The ephemeral nature of the Web has prompted many efforts to archive web sites. The Internet Archive, active since 1996, is one of the best-known efforts. Dynamic updates of web pagesMain article: Ajax (programming) JavaScript is a scripting language that was initially developed in 1995 by Brendan Eich, then of Netscape, for use within web pages.[23] The standardized version is ECMAScript.[23] To overcome some of the limitations of the page-by-page model described above, some web applications also use Ajax (asynchronous JavaScript and XML). JavaScript is delivered with the page that can make additional HTTP requests to the server, either in response to user actions such as mouse-clicks, or based on lapsed time. The server's responses are used to modify the current page rather than creating a new page with each response. Thus the server only needs to provide limited, incremental information. Since multiple Ajax requests can be handled at the same time, users can interact with a page even while data is being retrieved. Some web applications regularly poll the server to ask if new information is available.[24] WWW prefixMany domain names used for the World Wide Web begin with www because of the long-standing practice of naming Internet hosts (servers) according to the services they provide. The hostname for a web server is often www, in the same way that it may be ftp for an FTP server, and news or nntp for a USENET news server. These host names appear as Domain Name System (DNS) subdomain names, as in www.example.com. The use of 'www' as a subdomain name is not required by any technical or policy standard; indeed, the first ever web server was called nxoc01.cern.ch,[25] and many web sites exist without it. Many established websites still use 'www', or they invent other subdomain names such as 'www2',

'secure', etc. Many such web servers are set up such that both the domain root (e.g., example.com) and the www subdomain (e.g., www.example.com) refer to the same site; others require one form or the other, or they may map to different web sites. The use of a subdomain name is useful for load balancing incoming web traffic by creating a CNAME record that points to a cluster of web servers. Since, currently, only a subdomain can be cname'ed the same result cannot be achieved by using the bare domain root. When a user submits an incomplete website address to a web browser in its address bar input field, some web browsers automatically try adding the prefix "www" to the beginning of it and possibly ".com", ".org" and ".net" at the end, depending on what might be missing. For example, entering 'microsoft' may be transformed to http://www.microsoft.com/ and 'openoffice' to http://www.openoffice.org. This feature started appearing in early versions of Mozilla Firefox, when it still had the working title 'Firebird' in early 2003.[26] It is reported that Microsoft was granted a US patent for the same idea in 2008, but only for mobile devices.[27] The scheme specifier (http:// or https://) in URIs refers to the Hypertext Transfer Protocol and to HTTP Secure respectively and so defines the communication protocol to be used for the request and response. The HTTP protocol is fundamental to the operation of the World Wide Web, and the encryption involved in HTTPS adds an essential layer if confidential information such as passwords or banking information are to be exchanged over the public Internet. Web browsers usually prepend the scheme to URLs too, if omitted. In English, www is pronounced by individually pronouncing the name of characters (double-u double-u double-u). Although some technical users pronounce it dub-dubdub this is not widespread. The English writer Douglas Adams once quipped in The Independent on Sunday (1999): "The World Wide Web is the only thing I know of whose shortened form takes three times longer to say than what it's short for," with Stephen Fry later pronouncing it in his "Podgrammes" series of podcasts as "wuh wuh wuh." In Mandarin Chinese, World Wide Web is commonly translated via a phono-semantic matching to wàn wéi wǎng (万维网), which satisfies www and literally means "myriad dimensional net",[28] a translation that very appropriately reflects the design concept and proliferation of the World Wide Web. Tim BernersLee's web-space states that World Wide Web is officially spelled as three separate words, each capitalized, with no intervening hyphens.[29] PrivacyComputer users, who save time and money, and who gain conveniences and entertainment, may or may not have surrendered the right to privacy in exchange for using a number of technologies including the Web.[30] Worldwide, more than a half billion people have used a social network service,[31] and of Americans who grew up with the Web, half created an online profile[32] and are part of a generational shift that could be changing norms.[33][34] Facebook progressed from U.S. college students to a 70% non-U.S. audience, and in 2009 estimated that only 20% of its members use privacy settings.[35] In 2010 (six years after co-founding the company), Mark Zuckerberg wrote, "we will add privacy controls that are much simpler to use".[36]

Privacy representatives from 60 countries have resolved to ask for laws to complement industry self-regulation, for education for children and other minors who use the Web, and for default protections for users of social networks.[37] They also believe data protection for personally identifiable information benefits business more than the sale of that information.[37] Users can opt-in to features in browsers to clear their personal histories locally and block some cookies and advertising networks[38] but they are still tracked in websites' server logs, and particularly web beacons.[39] Berners-Lee and colleagues see hope in accountability and appropriate use achieved by extending the Web's architecture to policy awareness, perhaps with audit logging, reasoners and appliances.[40] In exchange for providing free content, vendors hire advertisers who spy on Web users and base their business model on tracking them.[41] Since 2009, they buy and sell consumer data on exchanges (lacking a few details that could make it possible to de-anonymize, or identify an individual).[42][41] Hundreds of millions of times per day, Lotame Solutions captures what users are typing in real time, and sends that text to OpenAmplify who then tries to determine, to quote a writer at The Wall Street Journal, "what topics are being discussed, how the author feels about those topics, and what the person is going to do about them".[43][44] Microsoft backed away in 2008 from its plans for strong privacy features in Internet Explorer,[45] leaving its users (50% of the world's Web users) open to advertisers who may make assumptions about them based on only one click when they visit a website.[46] Among services paid for by advertising, Yahoo! could collect the most data about users of commercial websites, about 2,500 bits of information per month about each typical user of its site and its affiliated advertising network sites. Yahoo! was followed by MySpace with about half that potential and then by AOL– TimeWarner, Google, Facebook, Microsoft, and eBay.[47] SecurityThe Web has become criminals' preferred pathway for spreading malware. Cybercrime carried out on the Web can include identity theft, fraud, espionage and intelligence gathering.[48] Web-based vulnerabilities now outnumber traditional computer security concerns,[49][50] and as measured by Google, about one in ten web pages may contain malicious code.[51] Most Web-based attacks take place on legitimate websites, and most, as measured by Sophos, are hosted in the United States, China and Russia.[52] The most common of all malware threats is SQL injection attacks against websites.[53] Through HTML and URIs the Web was vulnerable to attacks like cross-site scripting (XSS) that came with the introduction of JavaScript[54] and were exacerbated to some degree by Web 2.0 and Ajax web design that favors the use of scripts.[55] Today by one estimate, 70% of all websites are open to XSS attacks on their users.[56] Proposed solutions vary to extremes. Large security vendors like McAfee already design governance and compliance suites to meet post-9/11 regulations,[57] and some, like Finjan have recommended active real-time inspection of code and all content regardless of its source.[48] Some have argued that for enterprise to see security as a business opportunity rather than a cost center,[58] "ubiquitous, always-on digital rights management" enforced in the infrastructure by a handful of organizations must replace the hundreds of companies that today secure data and

networks.[59] Jonathan Zittrain has said users sharing responsibility for computing safety is far preferable to locking down the Internet.[60] StandardsMain article: Web standards Many formal standards and other technical specifications and software define the operation of different aspects of the World Wide Web, the Internet, and computer information exchange. Many of the documents are the work of the World Wide Web Consortium (W3C), headed by Berners-Lee, but some are produced by the Internet Engineering Task Force (IETF) and other organizations. Usually, when web standards are discussed, the following publications are seen as foundational: Recommendations for markup languages, especially HTML and XHTML, from the W3C. These define the structure and interpretation of hypertext documents. Recommendations for stylesheets, especially CSS, from the W3C. Standards for ECMAScript (usually in the form of JavaScript), from Ecma International. Recommendations for the Document Object Model, from W3C. Additional publications provide definitions of other essential technologies for the World Wide Web, including, but not limited to, the following: Uniform Resource Identifier (URI), which is a universal system for referencing resources on the Internet, such as hypertext documents and images. URIs, often called URLs, are defined by the IETF's RFC 3986 / STD 66: Uniform Resource Identifier (URI): Generic Syntax, as well as its predecessors and numerous URI scheme-defining RFCs; HyperText Transfer Protocol (HTTP), especially as defined by RFC 2616: HTTP/1.1 and RFC 2617: HTTP Authentication, which specify how the browser and server authenticate each other. AccessibilityMain article: Web accessibility Access to the Web is for everyone regardless of disability including visual, auditory, physical, speech, cognitive, or neurological. Accessibility features also help others with temporary disabilities like a broken arm or the aging population as their abilities change.[61] The Web is used for receiving information as well as providing information and interacting with society, making it essential that the Web be accessible in order to provide equal access and equal opportunity to people with disabilities.[62] Tim Berners-Lee once noted, "The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect."[61] Many countries regulate web accessibility as a requirement for websites.[63] International cooperation in the W3C Web Accessibility Initiative led to simple guidelines that web content authors as well as software developers can use to make the Web accessible to persons who may or may not be using assistive technology. [61][64] InternationalizationThe W3C Internationalization Activity assures that web technology will work in all languages, scripts, and cultures.[65] Beginning in 2004 or 2005, Unicode gained ground and eventually in December 2007 surpassed both ASCII and Western European as the Web's most frequently used character encoding. [66] Originally RFC 3986 allowed resources to be identified by URI in a subset of US-

ASCII. RFC 3987 allows more characters—any character in the Universal Character Set—and now a resource can be identified by IRI in any language.[67] StatisticsAccording to a 2001 study, there were a massive over 550 billion documents on the Web, mostly in the invisible Web, or deep Web.[68] A 2002 survey of 2,024 million Web pages[69] determined that by far the most Web content was in English: 56.4%; next were pages in German (7.7%), French (5.6%), and Japanese (4.9%). A more recent study, which used Web searches in 75 different languages to sample the Web, determined that there were over 11.5 billion Web pages in the publicly indexable Web as of the end of January 2005.[70] As of March 2009[update], the indexable web contains at least 25.21 billion pages.[71] On July 25, 2008, Google software engineers Jesse Alpert and Nissan Hajaj announced that Google Search had discovered one trillion unique URLs.[72] As of May 2009[update], over 109.5 million websites operated.[73] Of these 74% were commercial or other sites operating in the .com generic top-level domain.[73] Speed issuesFrustration over congestion issues in the Internet infrastructure and the high latency that results in slow browsing has led to a pejorative name for the World Wide Web: the World Wide Wait.[74] Speeding up the Internet is an ongoing discussion over the use of peering and QoS technologies. Other solutions to reduce the congestion can be found at W3C.[75] Standard guidelines for ideal Web response times are:[76] 0.1 second (one tenth of a second). Ideal response time. The user doesn't sense any interruption. 1 second. Highest acceptable response time. Download times above 1 second interrupt the user experience. 10 seconds. Unacceptable response time. The user experience is interrupted and the user is likely to leave the site or system. CachingIf a user revisits a Web page after only a short interval, the page data may not need to be re-obtained from the source Web server. Almost all web browsers cache recently obtained data, usually on the local hard drive. HTTP requests sent by a browser will usually only ask for data that has changed since the last download. If the locally cached data are still current, it will be reused. Caching helps reduce the amount of Web traffic on the Internet. The decision about expiration is made independently for each downloaded file, whether image, stylesheet, JavaScript, HTML, or whatever other content the site may provide. Thus even on sites with highly dynamic content, many of the basic resources only need to be refreshed occasionally. Web site designers find it worthwhile to collate resources such as CSS data and JavaScript into a few site-wide files so that they can be cached efficiently. This helps reduce page download times and lowers demands on the Web server. There are other components of the Internet that can cache Web content. Corporate and academic firewalls often cache Web resources requested by one user for the benefit of all. (See also Caching proxy server.) Some search engines also store cached content from websites. Apart from the facilities built into Web servers that can determine when files have been updated and so need to be re-sent, designers of dynamically generated Web pages can control the HTTP headers sent back to requesting users, so that transient or sensitive pages are not cached. Internet banking and news sites frequently use this facility. Data requested with an HTTP

'GET' is likely to be cached if other conditions are met; data obtained in response to a 'POST' is assumed to depend on the data that was POSTed and so is not cached. -------Intranet Show me everything on Win Development Resources definition An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet includes connections through one or more gateway computers to the outside Internet. The main purpose of an intranet is to share company information and computing resources among employees. An intranet can also be used to facilitate working in groups and for teleconferences. An intranet uses TCP/IP, HTTP, and other Internet protocols and in general looks like a private version of the Internet. With tunneling, companies can send private messages through the public network, using the public network with special encryption/decryption and other security safeguards to connect one part of their intranet to another. Typically, larger enterprises allow users within their intranet to access the public Internet through firewall servers that have the ability to screen messages in both directions so that company security is maintained. When part of an intranet is made accessible to customers, partners, suppliers, or others outside the company, that part becomes part of an extranet. extranet Show me everything on Cloud computing and SaaS definition An extranet is a private network that uses Internet technology and the public telecommunication system to securely share part of a business's information or operations with suppliers, vendors, partners, customers, or other businesses. An extranet can be viewed as part of a company's intranet that is extended to users outside the company. It has also been described as a "state of mind" in which the Internet is perceived as a way to do business with other companies as well as to sell products to customers. An extranet requires security and privacy. These can include firewall server management, the issuance and use of digital certificates or similar means of user authentication, encryption of messages, and the use of virtual private networks (VPNs) that tunnel through the public network. Companies can use an extranet to: •Exchange large volumes of data using Electronic Data Interchange (EDI) •Share product catalogs exclusively with wholesalers or those "in the trade" •Collaborate with other companies on joint development efforts •Jointly develop and use training programs with other companies •Provide or access services provided by one company to a group of other companies, such as an online banking application managed by one company on behalf of affiliated banks •Share news of common interest exclusively with partner companies ------------------

VoIP Voice over Internet Protocol (VoIP) is the family of technologies that allow IP networks to be used for voice applications, such as telephony, voice instant messaging, and teleconferencing. VoIP entails solutions at almost every layer of an IP network--from specialized voice applications (like Skype) all the way down to lowlevel quality measures that keep those applications running smoothly. In this Article The VoIP Technology Why VoIP Now? VoIP in Action How IP Telephony Fits In VoIP-Based Services What's Next for VoIP? Unless you've been sleeping under a very big rock for the last year, you've certainly heard the phrase "Voice over IP" uttered. Perhaps you've seen those hilarious Vonage commercials that feature painful and embarrassing accidents caught on tape, promising to let you dump your local phone company in order save big on your phone bill. You may also have seen the Cisco telephones that are curiously inserted in prime-time shows like 24. What is all the hubbub about, anyway? Why, VoIP, of course! VoIP, the fabulous secret ingredient in Vonage, Skype, Cisco CallManager, and a host of other revolutionary technology products you may have already encountered on TV, in the news, or in person. But what makes these products so revolutionary? What is it about VoIP that is such a big deal? The VoIP Technology Voice over Internet Protocol is a family of technologies that enable voice communications using IP networks like the internet. Inventive developers and entrepreneurs have created an industry around VoIP technology in its many forms: desktop applications, telephone services, and corporate phone systems. VoIP is a core technology that drives everything from voice-chat software loaded on a desktop PC to Mac full-blown IP-based telecommunications networks in large corporations. To the Wall Street speculator, VoIP is a single technology investment with many revenue streams. To the enterprise network engineer, it's a way to simplify the corporate network and improve the telephony experience for users of the network. To the home user, it's a really cool way to save money on the old phone bill. But how? What makes VoIP do all this awesome stuff? Read on. Why VoIP Now? The concept isn't actually that new: VoIP has been touted as a long-distance killer since the later 1990s, when goofy PC products like Internet Phone were starting to show up. But the promise of Voice over IP was lost in the shuffle of buggy applications and the slow-to-start broadband revolution. Without broadband connections, VoIP really isn't worthwhile. So early adopters of personal VoIP software like CUSeeMe and NetMeeting were sometimes frustrated by bad sound quality, and the first generation of VoIP products ultimately failed in the marketplace.

Fast forward to Fall 2005. Suddenly, everybody is talking about VoIP again. Why? There may be no greater reason than the sudden success of a freeware VoIP chat program called Skype. VoIP in Action Skype is an instant messaging program that happens to have a peer-to-peer (modeled after Kazaa) global voice network at its disposal, so you can use it to call people on your buddy list using your PC or Mac. All you need is broadband, a microphone, and a pair speakers or headphones. Voice calling alone doesn't set Skype apart from other IM applications like AIM or Windows Messenger--they also support voice. But Skype supports voice calling in a way that those applications can only dream of: Skype works in almost any broadband-connected network environment, even networks with firewalls that often break other voice-chatting apps. Plus, Skype's variable-bitrate sound codec makes it less prone to sound quality issues than its predecessors. In a nutshell, Skype just works. Perhaps that's why Skype's official slogan is "Internet Telephony that Just Works." The world has noticed. 150 million downloads later, Skype now offers the ability for its users to call regular phone numbers from their PCs, a feature known as SkypeOut. Skype also offers a voicemail service and can route incoming calls to a certain phone number right to a user's desktop PC. There's even a Skype API that allows Windows and Mac programmers to integrate the Skype client with other applications. Videoconferencing add-ons, Outlook integration, and personal answering machines are just some of the cool software folks have developed using the Skype API. How IP Telephony Fits In But Skype can't take all of the credit for the recent growth of Voice over IP. A number of enterprise telephone system vendors have heavily promoted what they call "IP telephony"--the art of building corporate phone systems using Ethernet devices and host-based servers instead of old-fashioned PBX chassis and legacy technology. Cisco Systems and Avaya were two of the earliest players in the VoIPphone-system arena, and their stubborn support of IP-based voice technology is beginning to pay off. More and more corporate customers are integrating IP phones and servers, and upgrading their IP networks to support voice applications, interested primarily in the productivity boost and long-term cost savings of running a single converged network instead of maintaining legacy voice equipment. This transition is a lot like the move from mainframes and minicomputers to personal computers a generation ago. On two fronts--the corporate phone system and that of the home user--VoIP is transforming the global communications matrix. Instead of two separate notions of a global network (one for voice calling and one for Internet Protocol), a single converged network is arising, carrying both voice and data with the same networking protocol, IP. Steadily, corporations and domestic phone subscribers are migrating their voice services from the old voice plane to the new one, and nextgeneration, IP-based phone companies have rushed in to help them make the move.

VoIP-Based Services By now you've probably seen ads for companies like Vonage and Packet8. These services promise ultra-cheap voice calling service via your broadband internet connection. Some offer calling packages as low as $9.95 per month. Their secret weapon is VoIP. Voice over IP service providers use the internet to carry voice signals from their networks to your home phone. Because VoIP telecommunication isn't regulated the way traditional phone line telecommunication is, VoIP providers like Vonage can offer drastically lower calling rates. The catch? You've got to put up with the occasional hiccup in your voice service, caused by the one thing legacy telephone technology has built-in that VoIP doesn't: guaranteed quality. Because VoIP uses packets to transmit data like other services on the internet, it cannot provide the quality guarantees of old-fashioned, nonpacket-based telephone lines. But this is changing, too. Efforts are underway on all fronts (service providers, Internet providers, and VoIP solution makers) to adapt quality-of-service techniques to VoIP services, so that one day, your VoIP calls may sound as good as (or better than) your regular land-line calls. Today, if you want to build a fully quality-enabled private VoIP network, you can. Cisco, Foundry Networks, Nortel, and other network equipment makers all support common quality-of-service standards, meaning corporate networks are only an upgrade away from effective convergence of voice and data. But it will be quite some time before the internet itself is quality-enabled. Indeed, the internet may never be fully quality-enabled. This hasn't stopped enterprising network gearheads like me from trying to connect calls over the internet, of course. Hey, if Skype works so well, why can't corporate phone calls? Enterprise phone administrators have found that it is actually very easy to equip mobile users with VoIP phones to place calls on the company phone system by connecting to it over the internet--from hotel rooms or home offices--but the quality of these calls is sort of hit or miss, like a cell phone when you drive through a "dead zone" in the cell network. What's Next for VoIP? A host of brand new, VoIP-enabled cell phones will soon be ready for action. Imagine driving to work, receiving a call on your cell phone from a client, and then continuing that call on the corporate Wi-Fi network as you walk into the front office. all without any interruption to your call-in-progress. The cell network will just "hand off" the call to your Wi-Fi network. This sort of technology exists today, and will be a commonplace feature of corporate phone systems in years to come. Cost savings, uber-slick telephony features, network convergence--VoIP is the technology at the root of all these trends, and you should expect to see a lot more news about VoIP in the coming months and years. If you haven't used Voice over IP products yet, try out a broadband phone service like Broadvox Direct or Vonage, and download a copy of Skype or the Gizmo Project, two excellent VoIP PC calling applications.

To learn more, you can visit VoIPFan.com or browse O'Reilly's growing selection of books about IP telephony, including the book that's been dubbed the "Voice over IP of reason:" Switching to VoIP. Wireless Network Wireless Network Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes are implemented without the use of wires.[1] Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, such as radio waves, for the carrier and this implementation usually takes place at the physical level or "layer" of the network.[2] Contents [] 1 Types of wireless connections 1.1 Wireless PAN 1.2 Wireless LAN 1.3 Wireless MAN 1.4 Wireless WAN 1.5 Mobile devices networks 2 Uses 3 Environmental concerns and health hazard 4 See also 5 References 6 Further reading 7 External links Types of wireless connections Wireless PANWireless Personal Area Networks (WPANs) interconnect devices within a relatively small area, generally within reach of a person. For example, Bluetooth and Infrared rays provides a WPAN for interconnecting a headset to a laptop. ZigBee also supports WPAN applications.[3] Wi-Fi PANs are also getting popular as vendors have started integrating Wi-Fi in variety of consumer electronic devices. Intel My WiFi and Windows 7 virtual Wi-Fi capabilities have made Wi-Fi PANs simpler and easier to set up and configure.[4] Wireless LAN: Wireless LAN A wireless local area network (WLAN) links two or more devices using a wireless distribution method (typically spread-spectrum or OFDM radio), and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network. Wi-Fi: Wi-Fi is increasingly used as a synonym for 802.11 WLANs, although it is technically a certification of interoperability between 802.11 devices. Fixed Wireless Data: This implements point to point links between computers or networks at two locations, often using dedicated microwave or laser beams over line of sight paths. It is often used in cities to connect networks in two or more buildings without physically wiring the buildings together.

Wireless MANWireless Metropolitan Area Networks are a type of wireless network that connects several Wireless LANs. WiMAX is a type of Wireless MAN and is described by the IEEE 802.16 standard.[5] Wireless WANwireless wide area networks are wireless networks that typically cover large outdoor areas. These networks can be used to connect branch offices of business or as a public internet access system. They are usually deployed on the 2.4 GHz band. A typical system contains base station gateways, access points and wireless bridging relays. Other configurations are mesh systems where each access point acts as a relay also. When combined with renewable energy systems such as photo-voltaic solar panels or wind systems they can be stand alone systems. Mobile devices networksFurther information: mobile telecommunications With the development of smart phones, cellular telephone networks routinely carry data in addition to telephone conversations: Global System for Mobile Communications (GSM): The GSM network is divided into three major systems: the switching system, the base station system, and the operation and support system. The cell phone connects to the base system station which then connects to the operation and support station; it then connects to the switching station where the call is transferred to where it needs to go. GSM is the most common standard and is used for a majority of cell phones.[6] Personal Communications Service (PCS): PCS is a radio band that can be used by mobile phones in North America and South Asia. Sprint happened to be the first service to set up a PCS. D-AMPS: Digital Advanced Mobile Phone Service, an upgraded version of AMPS, is being phased out due to advancement in technology. The newer GSM networks are replacing the older system. Uses This section is written like a personal reflection or essay and may require cleanup. Please help improve it by rewriting it in an encyclopedic style. (September 2010) An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI Wi-Fi card widely used by wireless Internet service providers (WISPs) in the Czech Republic.Wireless networks have continued to develop and their uses have grown significantly. Cellular phones are part of huge wireless network systems. People use these phones daily to communicate with one another. Sending information overseas is possible through wireless network systems using satellites and other signals to communicate across the world. Emergency services such as the police department utilize wireless networks to communicate important information quickly. People and businesses use wireless networks to send and share data quickly whether it be in a small office building or across the world. Another important use for wireless networks is as an inexpensive and rapid way to be connected to the Internet in countries and regions where the telecom infrastructure is poor or there is a lack of resources, as in most developing countries.

Compatibility issues also arise when dealing with wireless networks. Different components not made by the same company may not work together, or might require extra work to fix these issues. Wireless networks are typically slower than those that are directly connected through an Ethernet cable. A wireless network is more vulnerable, because anyone can try to break into a network broadcasting a signal.[citation needed] Many networks offer WEP - Wired Equivalent Privacy - security systems which have been found to be vulnerable to intrusion. Though WEP does block some intruders, the security problems have caused some businesses to stick with wired networks until security can be improved. Another type of security for wireless networks is WPA - Wi-Fi Protected Access. WPA provides more security to wireless networks than a WEP security set up. The use of firewalls will help with security breaches which can help to fix security problems in some wireless networks that are more vulnerable. Environmental concerns and health hazardStarting around 2009, there have been increased concerns about the safety of wireless communications, despite little evidence of health risks so far.[7] The president of Lakehead University refused to agree to installation of a wireless network citing a California Public Utilities Commission study which said that the possible risk of tumors and other diseases due to exposure to electromagnetic fields (EMFs) needs to be further investigated. [8] ----------------Last Mile The "last mile" or "last kilometer" is the final leg of delivering connectivity from a communications provider to a customer. The phrase is therefore often used by the telecommunications and cable television industries. The actual distance of this leg may be considerably more than a mile, especially in rural areas. It is typically seen as an expensive challenge because "fanning out" wires and cables is a considerable physical undertaking. Because the last mile of a network to the user is also the first mile from the user to the world, the term "first mile" is sometimes used. To solve the problem of providing enhanced services over the last mile, some firms have been mixing networks for decades. One example is Fixed Wireless Access, where a wireless network is used instead of wires to connect a stationary terminal to the wireline network. Various solutions are being developed which are seen as an alternative to the "last mile" of standard incumbent local exchange carriers: these include WiMAX and BPL (Broadband over Power Line) applications. Contents [] 1 Business "last mile" 2 Existing delivery system problems 3 Economical information transfer 4 Existing last mile delivery systems 4.1 Wired systems (including optical fiber) 4.2 Wireless delivery systems 4.3 Intermediate system

4.4 Courier 4.5 Line aggregation ("bonding") 5 References 6 See also Business "last mile"Connectivity from the local telephone exchanges to the customer premises is also called the "last mile". In many countries this is often an ISDN30 connection, delivered through either a copper or fibre cable. This ISDN30 can carry 30 simultaneous telephone calls and many direct dial telephone numbers, (DDI's). When leaving the telephone exchange, the ISDN30 cable can be buried in the ground, usually in ducting, at very little depth. This makes any business telephone lines vulnerable to being dug up during streetworks, liable to flooding during heavy storms and general wear and tear due to natural elements. Loss, therefore, of the "last mile" will cause the failure to deliver any calls to the business affected. Business continuity planning often provides for this type of technical failure. Any business with ISDN30 type of connectivity should provide for this failure within its business continuity planning. There are many ways to achieve this, as documented CPNI. 1. Dual Parenting. This is where the telephone carrier provides the same numbers from two different telephone exchanges. If the cable is damaged from one telephone exchange to the customer premises most of the calls can be delivered from the surviving route to the customer. 2. Diverse Routing. This is where the carrier can provide more than one route to bring the ISDN 30’s from the exchange, or exchanges, (as in dual parenting), but they may share underground ducting and cabinets. 3. Separacy. This is where the carrier can provide more than one route to bring the ISDN 30’s from the exchange, or exchanges, (as in dual parenting), but they may not share underground ducting and cabinets, and therefore should be absolutely separate from the telephone exchange to the customer premises. 4. Exchange based solutions. This is where a specialist company working in association with the carriers offers an enhancement the to ability to divert ISDN30’s upon failure to any other number or group of numbers. Carrier diversions are usually limited to all of the ISDN30 DDI numbers being delivered to 1 single number. In the UK, GemaTech offers this service in association with all of the carriers other than Verizon. By being in the exchanges, the GemaTech version offers a part diversion service if required and voice recording of calls if required. 5. Non-exchange based diversion services.

This is where a specialist company working in association with BT offers an enhancement to the ability to divert ISDN30’s upon failure to any other number or group of numbers. Carrier diversions are usually limited to all of the ISDN30 DDI numbers being delivered to 1 single number. In the UK Teamphone offers this service in association with BT. By not being in the exchanges, the Teamphone version offers an all or nothing diversion service if required and but does not offer voice recording of calls. 6. Ported number services. This is where customers numbers can be ported to a specialist company where the numbers are pointed to the ISDN30 DDI numbers during business as usual and delivered to alternative numbers during a business continuity need. These are generally carrier independent and there are a number of companies offering such solutions in the UK. 7. Hosted numbers. This is where the carriers or specialist companies can host the customers numbers within their own or the carriers networks and deliver calls over an IP network to the customers sites. When a diversion service is required, the calls can be pointed to alternative numbers. 8. Inbound numbers, (08 type services). This is where the carriers or specialist companies can offer 08/05/03 prefixed numbers to deliver to the ISDN30 DDI numbers and can point them to alternative numbers in the event of a diversion requirement. Both carriers and specialist companies offer this type of service in the UK Existing delivery system problemsThe increasing worldwide demand for rapid, lowlatency and high-volume communication of information to homes and businesses has made economical information distribution and delivery increasingly important. As demand has escalated, particularly fueled by the widespread adoption of the Internet, the need for economical high-speed access by end-users located at millions of locations has ballooned as well. As requirements have changed, existing systems and networks which were initially pressed into service for this purpose have proven to be inadequate. To date, although a number of approaches have been tried and used, no single clear solution to this problem has emerged. This problem has been termed "The Last Mile Problem". As expressed by Shannon's equation for channel information capacity, the omnipresence of noise in information systems sets a minimum signal-to-noise ratio requirement in a channel, even when adequate spectral bandwidth is available. Since the integral of the rate of information transfer with respect to time is information quantity, this requirement leads to a corresponding minimum energy per bit. The problem of sending any given amount of information across a channel can therefore be viewed in terms of sending sufficient Information-Carrying Energy (ICE). For this reason the concept of an ICE "pipe" or "conduit" is relevant and useful for examining existing systems.

The distribution of information to a great number of widely separated end-users can be compared to the distribution of many other resources. Some familiar analogies are: blood distribution to a large number of cells over a system of veins, arteries and capillaries water distribution by a drip irrigation system to individual plants, including rivers, aqueducts, water mains etc. Nourishment to a plants leaves through roots, trunk and branches All of these have in common conduits which carry a relatively small amount of a resource a short distance to a very large number of physically separated endpoints. Also common are conduits supporting more voluminous flow which combine and carry the many individual portions over much greater distances. The shorter, lowervolume conduits which individually serve only one or a small fraction of the endpoints, may have far greater combined length than the larger capacity ones. These common attributes are shown to the right. The high-capacity conduits in these systems tend to also have in common the ability to efficiently transfer the resource over a long distance. Only a small fraction of the resource being transferred is either wasted, lost, or misdirected. The same cannot necessarily be said of the lower-capacity conduits. One reason for this has to do with the efficiency of scale. These conduits which are located closer to the endpoint, or end-user, do not individually have as many users supporting them. Even though they are smaller, each has the overhead of an "installation;" obtaining and maintaining a suitable path over which the resource can flow. The funding and resources supporting these smaller conduits tend to come from the immediate locale. This can have the advantage of a "small-government model." That is, the management and resources for these conduits is provided by local entities and therefore can be optimized to achieve the best solutions in the immediate environment and also to make best use of local resources. However, the lower operating efficiencies and relatively greater installation expenses, compared with the transfer capacities, can cause these smaller conduits, as a whole, to be the most expensive and difficult part of the complete distribution system. These characteristics have been displayed in the birth, growth, and funding of the Internet. The earliest inter-computer communication tended to be accomplished with direct wireline connections between individual computers. These grew into clusters of small Local Area Networks (LANs). The TCP/IP suite of protocols was born out of the need to connect several of these LANs together, particularly as related to common projects among the defense department, industry and some academic institutions. ARPANET came into being to further these interests. In addition to providing a way for multiple computers and users to share a common inter-LAN connection, the TCP/IP protocols provided a standardized way for dissimilar computers and operating systems to exchange information over this inter-network. The funding and support for the connections among LANs could be spread over one or even several LANs. As each new LAN, or subnet, was added, the new subnet's constituents enjoyed access to the greater network. At the same time the new subnet made a contribution of access to any network or networks with which it was already networked. Thus the growth became a mutually inclusive or "win-win" event.

In general, economy of scale makes an increase in capacity of a conduit less expensive as the capacity is increased. There is an overhead associated with the creation of any conduit. This overhead is not repeated as capacity is increased within the potential of the technology being utilized. As the Internet has grown in size, by some estimates doubling in number of users every eighteen months, economy of scale has resulted in increasingly large information conduits providing the longest distance and highest capacity backbone connections. In recent years, the capacity of fiber-optic communication, aided by a supporting industry, has resulted in an expansion of raw capacity, so much so that in the United States a large amount of installed fiber infrastructure is not being used because it is currently excess capacity "dark fiber". This excess backbone capacity exists in spite of the trend of increasing per-user data rates and overall quantity of data. Initially, only the inter-LAN connections were high speed. End-users used existing telephone lines and modems which were capable of data rates of only a few hundred bit/s. Now almost all end users enjoy access at 100 or more times those early rates. Notwithstanding this great increase in user traffic, the high-capacity backbones have kept pace, and information capacity and rate limitations almost always occur near the user. The economy of scale along with the fundamental capability of fiber technology have kept the highcapacity conduits adequate but have not solved the appetite of the home users. The last mile problem is one of economically serving an increasing mass of end-users with a solution to their information needs. Economical information transferBefore considering the characteristics of existing last-mile information delivery mechanisms, it is important to further examine what makes information conduits effective. As the Shannon-Hartley theorem shows, it is a combination of bandwidth and signal-to-noise ratio which determines the maximum information rate of a channel. The product of the average information rate and time yields total information transfer. In the presence of noise, this corresponds to some amount of transferred information-carrying energy. Therefore the economics of information transfer may be viewed in terms of the economics of the transfer of ICE. Effective last-mile conduits must: 1.Deliver signal power, S — (must have adequate signal power capacity). 2.Low loss (low occurrence of conversion to unusable energy forms). 3.Support wide transmission bandwidth. 4.Deliver high signal-to-noise ratio (SNR) — low unwanted-signal (Noise) power, N. 5.Provide nomadic connectivity. In addition to these factors, a good solution to the last-mile problem must provide each user: 1.High availability and reliability. 2.Low latency, latency must be small compared with required interaction times. 3.High per-user capacity.

1.A conduit which is shared among multiple end-users must provide a correspondingly higher capacity in order to properly support each individual user. This must be true for information transfer in each direction. 2.Affordability, suitable capacity must be financially viable. Existing last mile delivery systems Wired systems (including optical fiber)Wired systems provide guided conduits for Information-Carrying Energy (ICE). They all have some degree of shielding which limits the susceptibility to external noise sources. These transmission lines have losses which are proportional to length. Without the addition of periodic amplification, there is some maximum length beyond which all of these systems fail to deliver adequate S/N to support information flow. Dielectric optical fiber systems support heavier flow, at higher cost. Local area networks (LAN) Traditional wired local area networking systems require copper coaxial cable or twisted pair to be run between or among two or more of the nodes in the network. Common systems operate at 100 Mbit/s and newer ones also support 1000 Mbit/s or more. While length may be limited by collision detection and avoidance requirements, signal loss and reflections over these lines also set a maximum distance. The decrease in information capacity made available to an individual user is roughly proportional to the number of users sharing a LAN. Telephone In the late 20th century, improvements in the use of existing copper telephone lines increased their capabilities if maximum line length is controlled. With support for higher transmission bandwidth and improved modulation, these digital subscriber line schemes have increased capability 20-50 times as compared to the previous voiceband systems. These methods are not based on altering the fundamental physical properties and limitations of the medium which, apart from the introduction of twisted pairs, are no different today than when the first telephone exchange was opened in 1877 by the Bell Telephone Company. The history and long life of copperbased communications infrastructure is both a testament to our ability to derive new value from simple concepts through technological innovation – and a warning that copper communications infrastructure is beginning to offer diminishing returns on continued investment.[1] CATV Community Access Cable Television Systems, also known simply as "cable", have been expanded to provide bidirectional communication over existing physical cables. However, they are by nature shared systems and the spectrum available for reverse information flow and achievable S/N are limited. As was done for the initial unidirectional (TV) communication, cable loss is mitigated through the use of periodic amplifiers within the system. These factors set an upper limit on per-user information capacity, particularly when many users share a common section of cable or access network. Optical fiber Fiber offers high information capacity and after the turn of the 21st century became the deployed medium of choice given its scalability in the face of increasing bandwidth requirements of modern applications.

In 2004, according to Richard Lynch, EVP and CTO of telecom giant Verizon, they saw the world moving toward vastly higher bandwidth applications as consumers loved everything broadband had to offer, and eagerly devoured as much as they could get, including two-way, user-generated content. Copper and coaxial networks wouldn’t – in fact, couldn’t – satisfy these demands, which precipitated Verizon's aggressive move into Fiber-to-the-home via FiOS.[2] Fiber is a future-proof technology that meets the needs of today's users, but unlike other copper-based and wireless last-mile mediums, also has the capacity for years to come, by upgrading the end-point optics and electronics, without changing the fiber infrastructure. The fiber itself is installed on existing pole or conduit infrastructure and most of the cost is in labor, providing good regional economic stimulus in the deployment phase and providing a critical foundation for future regional commerce. Wireless delivery systemsMobile CDN coined the term the 'mobile mile' to categorize the last mile connection when a wireless systems is used to reach the customer. In contrast to wired delivery systems, wireless systems use unguided waves to transmit ICE. They all tend to be unshielded and have a greater degree of susceptibility to unwanted signal and noise sources. Because these waves are not guided but diverge, in free space these systems have attenuation following an inverse-square law, inversely proportional to distance squared. Losses thus increase more slowly with increasing length than for wired systems whose loss increases exponentially. In a free space environment, beyond some length, the losses in a wireless system are less than those in a wired system. In practice, the presence of atmosphere, and especially obstructions caused by terrain, buildings and foliage can greatly increase the loss above the free space value. Reflection, refraction and diffraction of these waves can also alter their transmission characteristics and require specialized systems to accommodate the accompanying distortions. Wireless systems have an advantage over wired systems in last mile applications in not requiring lines to be installed. However, they also have a disadvantage that their unguided nature makes them more susceptible to unwanted noise and signals. Spectral reuse can therefore be limited. Lightwaves and free-space optics Visible and infrared light waves are much shorter than radio frequency waves. Their use to transmit data is referred to as free-space optical communication. Being short, light waves can be focused or collimated with a small lens/antenna and to a much higher degree than radio waves. Thus, a greater portion of the transmitted signal can be recovered by a receiving device. Also because of the high frequency, a high data transfer rate may be available. However, in practical last mile environments, obstructions and de-steering of these beams, and absorption by elements of the atmosphere including fog and rain, particularly over longer paths, can greatly restrict their use for last-mile wireless communications. Longer (redder) waves suffer less obstruction but may carry lesser data rates. See RONJA. Radio waves

Radio frequencies (RF), from low frequencies through the microwave region, have wavelengths much longer than visible light. Although this means that it is not possible to focus the beams nearly as tightly as for light, it also means that the aperture or "capture area" of even the simplest, omni-directional antenna is greatly larger than that of a lens in any feasible optical system. This characteristic results in greatly increased attenuation or "path loss" for systems that are not highly directional. In actuality, the term path loss is something of a misnomer because no energy is actually lost on a free-space path. Rather, it is merely not received by the receiving antenna. The apparent reduction in transmission, as frequency is increased, is actually an artifact of the change in the aperture of a given type of antenna. Relative to the last-mile problem, these longer wavelengths have an advantage over light waves when omni-directional or sectored transmissions are considered. The larger aperture of radio antennas results in much greater signal levels for a given path length and therefore higher information capacity. On the other hand, the lower carrier frequencies are not able to support the high information bandwidths which are required by Shannon's equation, when the practical limits of S/N have been reached. For the above reasons, wireless radio systems have the advantage of being optimal for lower-information-capacity broadcast communications delivered over longer paths. For high-information capacity, highly-directive point-to-point over short ranges, wireless light-wave systems are most useful. One-way (broadcast) radio and television communications Historically, most high-information-capacity broadcast has used lower frequencies, generally no higher than the UHF television region, with television itself being a prime example. Terrestrial television has generally been limited to the region above 50 MHz where sufficient information bandwidth is available, and below 1000 MHz, due to problems associated with increased path loss as mentioned above. Two-way wireless communications Two-way communication systems have primarily been limited to lower-informationcapacity applications, such as audio, facsimile. or radio teletype. For the most part, higher-capacity systems, such as two-way video communications or terrestrial microwave telephone and data trunks, have been limited and confined to UHF or microwave and to point-point paths. Higher capacity systems such as thirdgeneration, 3G, cellular telephone systems require a large infrastructure of more closely spaced cell sites in order to maintain communications within typical environments, where path losses are much greater than in free space and which also require omni-directional access by the users. Satellite communications For information delivery to end-users, satellite systems, by nature, have relatively long path lengths, even for low earth-orbiting satellites. They are also very expensive to deploy and therefore each satellite must serve many users. Additionally, the very long paths of geostationary satellites cause information latency that makes many real-time applications unusable. As a solution to the lastmile problem, satellite systems have application and sharing limitations. The ICE

which they transmit must be spread over a relatively large geographical area. This causes the received signal to be relatively small, unless very large or directional terrestrial antennas are used. A parallel problem exists when a satellite is receiving. In that case, the satellite system must have a very great information capacity in order to accommodate a multitude of sharing users and each user must have large antenna size, with attendant directivity and pointing requirements, in order to obtain even modest information-rate transfer. These requirements render highinformation-capacity, bi-directional information systems uneconomical. This is a reason that the Iridium satellite system was not more successful. Broadcast versus point-to-point For both terrestrial and satellite systems, economical, high-capacity, last-mile communications requires point-to-point transmission systems. Except for extremely small geographic areas, broadcast systems are only able to deliver large amounts of S/N at low frequencies where there is not sufficient spectrum to support the large information capacity needed by a large number of users. Although complete "flooding" of a region can be accomplished, such systems have the fundamental characteristic that most of the radiated ICE never reaches a user and is wasted. As information requirements increase, broadcast "wireless mesh" systems (also sometimes referred to as microcells or nano-cells) which are small enough to provide adequate information distribution to and from a relatively small number of local users, require a prohibitively large number of broadcast locations or "points of presence" along with a large amount of excess capacity to make up for the wasted energy. Intermediate systemRecently a new type of information transport which is midway between wired and wireless systems has been discovered. Called E-Line, it uses a single central conductor but no outer conductor or shield. The energy is transported in a plane wave which, unlike radio, does not diverge while like radio, has no outer guiding structure. This system exhibits a combination of the attributes of wired and wireless systems and can support high information capacity utilizing existing power lines over a broad range of frequencies from RF through microwave. See BPL (Broadband over Power Line). CourierWizzy Digital Courier is a project to distribute useful data to places with no Internet connection. Primarily for e-mail, it also carries web content (stored locally in a web cache). In an implementation of a sneakernet, its delivery mechanism is USB flash drive. The USB stick uses the UUCP protocol, carrying information to and from a betterconnected location - perhaps a school or local business, which acts as the dropoff for Email, and fetches web content by proxy. The email and web content is repackaged as a UUCP transaction, and ferried back on the USB flash drive. Line aggregation ("bonding")Aggregation is a method of "bonding" multiple lines to achieve a faster, more reliable connection. Some companies[3] believe that ADSL aggregation (or "bonding") is the solution to the UK's last mile problem[4]. ---------------------Types of Internet hosting service Full-featured hosting

Virtual private server Dedicated hosting Colocation centre Cloud hosting Web hosting Free hosting · Shared Clustered · Reseller · FFmpeg Application-specific web hosting Blog · Guild hosting · Image Video · Wiki farms · Application Social network Other types File · Remote backup Game server · DNS · E-mail v · d · e An example of "rack mounted" servers.A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own or lease for use by their clients as well as providing Internet connectivity, typically in a data center. Web hosts can also provide data center space and connectivity to the Internet for servers they do not own to be located in their data center, called colocation or Housing as it is commonly called in Latin America or France. The scope of hosting services varies widely. The most basic is web page and smallscale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with little processing. Many Internet service providers (ISPs) offer this service free to their subscribers. People can also obtain Web page hosting from other, alternative service providers. Personal web site hosting is typically free, advertisementsponsored, or inexpensive. Business web site hosting often has a higher expense. Single page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, Ruby on Rails, ColdFusion, and ASP.NET). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also highly recommended. The host may also provide an interface or control panel for managing the Web server and installing scripts as well as other services like e-mail. Some hosts specialize in certain software or services (e.g. e-commerce). They are commonly used by larger companies to outsource network infrastructure to a hosting company. Contents [] 1 Hosting reliability and uptime 2 Types of hosting

3 Obtaining hosting 4 See also 5 External links Hosting reliability and uptime This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2009) Multiple racks of servers.Hosting uptime refers to the percentage of time the host is accessible via the internet. Many providers state that they aim for at least 99.9% uptime (roughly equivalent to 45 minutes of downtime a month, or less), but there may be server restarts and planned (or unplanned) maintenance in any hosting environment, which may or may not be considered part of the official uptime promise. Many providers tie uptime and accessibility into their own service level agreement (SLA). SLAs sometimes include refunds or reduced costs if performance goals are not met. Types of hosting A typical server "rack," commonly seen in colocation centres.Internet hosting services can run Web servers; see Internet hosting services. Many large companies who are not internet service providers also need a computer permanently connected to the web so they can send email, files, etc. to other sites. They may also use the computer as a website host so they can provide details of their goods and services to anyone interested. Additionally these people may decide to place online orders. Free web hosting service: offered by different companies with limited services, sometimes supported by advertisements, and often limited when compared to paid hosting. Shared web hosting service: one's website is placed on the same server as many other sites, ranging from a few to hundreds or thousands. Typically, all domains may share a common pool of server resources, such as RAM and the CPU. The features available with this type of service can be quite extensive. A shared website may be hosted with a reseller. Reseller web hosting: allows clients to become web hosts themselves. Resellers could function, for individual domains, under any combination of these listed types of hosting, depending on who they are affiliated with as a reseller. Resellers' accounts may vary tremendously in size: they may have their own virtual dedicated server to a collocated server. Many resellers provide a nearly identical service to their provider's shared hosting plan and provide the technical support themselves. Virtual Dedicated Server: also known as a Virtual Private Server (VPS), divides server resources into virtual servers, where resources can be allocated in a way that does not directly reflect the underlying hardware. VPS will often be allocated resources based on a one server to many VPSs relationship, however virtualisation may be done for a number of reasons, including the ability to move a VPS container

between servers. The users may have root access to their own virtual space. Customers are sometimes responsible for patching and maintaining the server. Dedicated hosting service: the user gets his or her own Web server and gains full control over it (root access for Linux/administrator access for Windows); however, the user typically does not own the server. Another type of Dedicated hosting is Self-Managed or Unmanaged. This is usually the least expensive for Dedicated plans. The user has full administrative access to the box, which means the client is responsible for the security and maintenance of his own dedicated box. Managed hosting service: the user gets his or her own Web server but is not allowed full control over it (root access for Linux/administrator access for Windows); however, they are allowed to manage their data via FTP or other remote management tools. The user is disallowed full control so that the provider can guarantee quality of service by not allowing the user to modify the server or potentially create configuration problems. The user typically does not own the server. The server is leased to the client. Colocation web hosting service: similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes. Cloud Hosting: is a new type of hosting platform that allows customers powerful, scalable and reliable hosting based on clustered load-balanced servers and utility billing. Removing single-point of failures and allowing customers to pay for only what they use versus what they could use. Clustered hosting: having multiple servers hosting the same content for better resource utilization. Clustered Servers are a perfect solution for high-availability dedicated hosting, or creating a scalable web hosting solution. A cluster may separate web serving from database hosting capability. Grid hosting: this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes. Home server: usually a single machine placed in a private residence can be used to host one or more web sites from a usually consumer-grade broadband connection. These can be purpose-built machines or more commonly old PCs. Some ISPs actively attempt to block home servers by disallowing incoming requests to TCP port 80 of the user's connection and by refusing to provide static IP addresses. A common way to attain a reliable DNS hostname is by creating an account with a dynamic DNS service. A dynamic DNS service will automatically change the IP address that a URL points to when the IP address changes. Some specific types of hosting provided by web host service providers: File hosting service: hosts files, not web pages Image hosting service Video hosting service Blog hosting service One-click hosting Pastebin Hosts text snippets Shopping cart software

E-mail hosting service Obtaining hostingWeb hosting is often provided as part of a general Internet access plan; there are many free and paid providers offering these A customer needs to evaluate the requirements of the application to choose what kind of hosting to use. Such considerations include database server software, scripting software, and operating system. Most hosting providers provide Linuxbased web hosting which offers a wide range of different software. A typical configuration for a Linux server is the LAMP platform: Linux, Apache, MySQL, and PHP/Perl/Python. The webhosting client may want to have other services, such as email for their business domain, databases or multi-media services for streaming media. A customer may also choose Windows as the hosting platform. The customer still can choose from PHP, Perl, and Python but may also use ASP .Net or Classic ASP. Web hosting packages often include a Web Content Management System, so the end-user doesn't have to worry about the more technical aspects.