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The first part of “Learning Web Technologies With Sri” will be on “Internet Basics”. I choose this topic to give brief idea about internet & history about it, so that you know what is Internet, how & why it makes so powerful tool for making this communication between each computer or devices unique. So let’s get started. When you hear the word INTERNET, the first question that would arise in mind is What is Internet?
Internet is the largest computer network in the world, connecting millions of computers. A network is a group of two or more computer systems linked together.
So before going further with more details of internet, like different types of network etc.. let me give you brief history of internet. In 1969, the US Department of Defense started a project to allow researchers and military personnel to communicate with each other in an emergency. The project was called ARPANET (Advanced Research Projects Agency Network ) and it is the foundation of the INTERNET.
While mostly military personnel and scientists used it in early days, the advent of the WORLD WIDE WEB in the early 1990’s changed all that. Today, the internet is not owned or operated by any one entity. This worldwide computer network allows us all to communicate and exchange information in new ways. Just for information, according to www.commerce.net, in April 1999, there were 92.2 million internet users over the age of 16 in the United States and Canada. By 2005, it was predicted 75% of the total US population will be online & later it was found that, it well went past the percentage predicted!!.
ok then let’s talk about different computer networks. Common types of computer networks may be identified by their scale.
Personal Area Network (PAN)
A personal area network 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 connections between devices. The reach of a PAN typically extends to 10 meters. Wired PAN Network is usually constructed with USB and firewire while wireless with Bluetooth and Infrared.
Local Area Network (LAN)
A local area network 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).
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 network’s connecting to 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.
Home Area Network (HAN)
A home area network 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 is shared among all the personal computers present in home.
Campus Area Network (CAN)
A campus area network is a computer network made up of an interconnection of local area networks (LANs) within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.
In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network (WAN) (in some cases).
The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN (metropolitan area network), but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller 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.
Metropolitan Area Network (MAN)
A metropolitan area network is a network that connects two or more local area networks or campus area networks together but does not extend beyond the boundaries of the immediate town/city. Routers, switches and hubs are connected to create a metropolitan area network.
Wide Area Network (WAN)
A wide area network 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.
Global Area Network (GAN)
A global area network is a model 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 local area networks (WLAN).
Virtual Private Network (VPN)
A virtual private network 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.
A 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.
A VPN allows computer users to appear to be editing from an IP address location other than the one which connects the actual computer to the Internet.
An Internetwork is the connection of two or more distinct computer networks via a common routing technology. The result is called an internetwork (often shortened to internet). Two or more networks connect using devices that operate at the Network Layer (Layer 3) of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
The Internet is a global system of interconnected governmental, academic, 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 U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web (WWW). The ‘Internet’ is most commonly spelled with a capital ‘I’ as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
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 (e.g., a company’s customers may be given access to some part of its intranet creating in this way an extranet, 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, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
So the next question that would arise is What is a Server & Client?
All computers on the Internet (a wide area network, or WAN) can be lumped into two groups: servers and clients. In a network, clients and servers communicate with one another.
A server is the common source that provides shared services (for example, network security measures) with other machines and manages resources (for example, one printer many people use) in a network.
The term server is often used to describe the hardware (computer), but the term also refers to the software (application) running on the computer. Many servers are dedicated, meaning they only perform specific tasks.
- An email server is a computer that has software running on it allowing it to “serve” email-related services.
- A web server has software running on it that allows it to “serve” web-related services.
Independent computers connected to a server are called clients. Most likely, your home or office computer does not provide services to other computers. Therefore, it is a client. Clients run multiple client software applications that perform specific functions. For example,
- An email application such as Microsoft Outlook is client software.
- Your web browser (such as Internet Explorer or Firefox or Chrome) is client software.
Next question that would arise at this point is how do Servers & Clients Communicate
- Your computer (client hardware) is running a web browser such as Internet Explorer (client software).
- When you want to surf the web, your browser connects to a remote server and requests a web page.
- The remote server (server hardware) runs web server software (server software).
- The web server sends the web page to your computer’s web browser.
- Your web browser displays the page.
So in this session of Part 1 of series “Learning Web Technologies With Sri – Internet Basics”, we have covered
- Definition of Internet
- What is a Network
- Different Types of Networks
- What is a Server
- What is a Client
- How do Server & Client Communicate to each other.
In the next session, I will talk more about servers[not hardware] especially Web Server & Application Server. So stay tuned.