Part I : THEORY GUIDE Network

Key Terms: 

1. Bridge: A Device that connects two LAN (Local Area Network)s, or two segments of the same LAN. 
2. Domain: A method of identifying Network addresses on the Internet. Typically the name of an institution or unit followed by a dot (.) and an abbreviation, e.g., ‘.gov’ for governments, ‘.edu’ for educational institutions, ‘.com’ for companies, ‘.net’ for Networks or ‘.org’ for organizations and so on. 
3. E-mail (Electronic Mail): It's like a letter, a message that one person can send and have received almost instantly (immediately) by someone anywhere in the world through Networks and Modems using telephone lines. 
4. Home Page: A Web screen that acts as a starting point. A user can go from a Home Page to multiple sites across the world’s Computer Networks. 
5. HTTP (Hypertext Transfer Protocol): The Internet standard that enables information to be distributed across the Web using HTML (Hypertext Markup Language) to upload information. 
6. Internet: Abbreviation for InterNetwork. Internet is the world’s largest Computer Network. The Internet was originally established to meet the research needs of the US Defence industry, but it has grown into a huge Global Network serving universities, academic researches, commercial interests and government agencies, all over the world. The Internet uses TCP/IP (Transmission Control Protocol/Internet Protocol) and many of the Internet Host runs most of the NOS (Network Operating System). Many of the commercial Online Services give some level of Internet Access. The most popular uses of the Net are E-mail and the World Wide Web. 
7. Intranet: An Intranet is a private Network that uses Internet Protocols and Network connectivity to securely share part of an organization's information or operations with its employees. Sometimes the term refers only to the most visible service, the internal Website. The same concepts and technologies of the Internet such as Clients and Servers running on the Internet Protocol suite are used to build an Intranet. HTTP (Hypertext Transfer Protocol) and other Internet Protocols are commonly used as well, such as FTP (File Transfer Protocol). 
8. Logging On: Connecting to a Computer Network.
9. On line: On or actively connected to a Computer Network. 
10. Packet: A Packet is the fundamental unit of information transport in all modern Computer Networks, and increasingly in other communications Networks as well. 
11. Subnet: A Subnet or SubNetwork that uses the Internet Protocol. It is a range of logical addresses within the address space that is assigned to an organization. The addresses of all nodes in a Subnet start with the same binary sequence, which is the Subnet’s Network ID and Subnet ID. 
12. URL (Universal/Uniform Resource Locators): URL contains Information about the access method to use and also about the Resource itself and are used by Web Browsers to connect directly to a specific Document or Page on the WWW (World Wide Web) without having to know where that Resource is located Physically. 
13. Web Browser: Enables users of the Internet to discover, retrieve and display documents and data available on the WWW. Web Browsers allow the user to view selectively Hypertext documents, access powerful text-searching tools, listen to sound files and view graphics, animation and video across the Internet. 
14. WWW (World Wide Web): Introduced in 1991. Also known as W3C (World Wide Web Consortium), developed by Timothy John who is also known as Tim Berners Lee. WWW is a huge collection of HyperText Pages on the Internet. The first Web Site was http://www.info.cern.ch, first uploaded at 6th August 1991. It provided an explanation (description) about the World Wide Web. World Wide Web concepts were developed in Switzerland by the European Laboratory for Practical Physics, known as CERN (Conseil Européen pour la Recherche Nucléaire),  but the Web is not just a tool for scientists; it is one of the most flexible and exciting tools in existence for surfing the Internet. 

Network 

Network is a process of sharing data and shared resources between two or more connected Computers. The shared resources can include Printer, Fax Modem, Hard Disk, CD/DVD ROM, Database and the data files. A Network can be divided into a small or LAN (Local Area Network, a Networking between Computers in a building of a office (LAN), medium sized Network (MAN), a Network between two offices in a city and Wide Network (WAN) a Computer between the Networks, one is locally and the other can be thousands of miles away in any other country of the world.

WAN connectivity is done by a Network device known as “Router”. The internet is the world’s largest WAN Network, where millions of Computers from all over the globe and connected with each other.

The Network connectivity can be wired or wireless and TCP/IP Protocol can work both types of Network. A Network can be categorized in different ways, depends on the geographical area.

There are two main types of the Network Client-Server & Peer to Peer. In the Client Server Networking, a Computer plays a major role known as Server, where the files, data in the form of Web Pages, docs or spread sheet files, video, database & resources are placed. All the other Computers in the Client/Server Network are called Clients and they get the data from the Server Computer. In the Peer-to-Peer Network all the Computers play the same role and no Computers act as a Centralized Server. In the major businesses around the world Client-Server Network model is in major use.

A Network Topology defines the structure, design or layout of a Network. There are different topologies like Bus, Ring, Star, Mesh, Hybrid & so on. The star Topology is most commonly used Network Topology. 

In the Network, a common communication language is used by the Computers and the Network devices and this language is known as Protocols. The most commonly used and popular Protocols on the internet and in the home and other Network is called TCP/IP. TCP/IP is not a single Protocol but it is a suite of several Protocols. There are different kinds of protocols used in Networks such as POP3 protocols, FTP Protocols & so on.

Classification of Network

1. On the Basis of Media: - On the Basis of Media there are two kinds of Network.

• Wired (Guided) Media: On the Wired guided media, we can establish the Network physically with the help of coaxial cable twisted pair cable, NIC, RJ 45, RJ 11, Fiber Optic cable etc.
• Unwired (Unguided) Media: This type of Network is created with the help of WAP (Wireless Access Protocol). The wireless media uses USB, NIC, Infrared, Radio wave, Bluetooth and Router etc.

2. On the Basis of Scope: - On the Basis of Scope there are three kinds of Network. This is also called the Network on geographical base. They are as follows:

• LAN (Local Area Network): A Local Area Network is a Network that covers a small space and provides services to a small number of people. Depending on the number of people that use a Local Area Network, a Peer-to-Peer or Client-Server method of Networking may be used. A Peer-to-Peer Network is where each Client shares their resources with other Workstations in the Computer. Examples of Peer-to-Peer Networks are: Small office Networks where resource use is minimal. A Client-Server Network is where every Client is connected to the Server and each other. Client-Server Networks use Servers in different capacities. Computers are linked through Ethernet Cable, can be joined either directly (One Computer to another), or through a Network hub that allows multiple connections. LAN covers 500 meters long distance with the maximum of 254 Computers. A LAN can be both the wired and unwired.
• MAN (Metropolitan Area Network): A MAN (Metropolitan Area Network) is a Network that interconnects users with Network resources in a geographic area or region larger than that covered by even a large LAN but smaller than the area covered by a WAN (Wide Area Network). The term is applied to the interconnection of Computers in a city into a single larger Network. It is also used to mean the interconnection of several Local Area Networks by bridging them with backbone lines such as Repeater, Router etc.
• WAN (Wide Area Network): A wide area Network is a Network where a wide variety of resources are deployed across a large domestic area or internationally. An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is a Networked Computer consist of many smaller Networks. The Internet is considered the largest Network in the world. The PSTN (Public Switched Telephone Network) also is an extremely large Network that is converging to use Internet technologies, although not necessarily through the public Internet. A Wide Area Network involves communication through the use of a wide range of different technologies. These technologies include Point-to-Point WANs such as PPP (Point-to-Point Protocol) & HDLC (High-Level Data Link Control), Frame Relay, ATM (Asynchronous Transfer Mode) and SONet (Synchronous Optical Network). The difference between the WAN technologies is based on the switching capabilities they perform and the speed at which sending and receiving bits of information (data) occur.

3. On the Basis of Function/Model: - On the basis of function there are two kinds of Network:

1. Peer to Peer Network: A Network of personal Computers, each of which acts as both Client & Sever, so that each can exchange files and E-mail directly with every other Computer on the Network. Each Computer can access any of the others. Peer-to-Peer Networks are less expensive than Client/Server Networks but less efficient when large amounts of data need to be exchanged. In this Network, all the Computers are Administrated or managed individually. 
2. Client Server Network: A Computer in which one centralized, powerful Computer (Called the Server) is a hub to which many less powerful personal Computers or Workstations than Server (Called Clients) are connected. The Clients run programs and access data that are stored on the Server. In this Network, the main Computer which provides or blocks the services uses Server Operating System also called Domain Controller. And other Computers are known as Client Computers which uses Client Operating System. These Computers are Administrated and managed by the Domain Controller. Here, all the Client user accounts are created in the Domain Controller. The Client Computers are also called Domain Members. The Client/ Server starts different kinds of facilities such as Active Directory, FTP (File Transfer Protocol), DNS (Domain Name Server/System), IIS (Internet Information Service), DHCP (Dynamic Host Configuration Protocol), etc.

TOPOLOGY

In Networking, Topology refers to the layout of connected devices such as Network, Hub, Switch, Router, Printers, Scanners and so on. Any particular Network Topology is determined only by the graphical mapping of the configuration of physical or logical connections between nodes. The study of Network Topology uses graph theory. Distances between nodes, physical interconnections, transmission rates, and signal types may differ in two Networks and yet their topologies may be identical. There are different types of Topology listing below:

1. Bus Topology: It is a Network architecture in which a set of Clients are connected through a shared communications line, called a Bus. In Bus Topology, maximum 30 Computers with 100 meters of coaxial cable can be connected. Terminator Cap at the end of the both side of the coaxial cable used to block the flow of information. In this Topology, BNC connector, ‘T’ connector, LAN Card, Terminator, are used to connect the Computers on the Network. If the main cable will fail, it will affect the entire Network. 

2. Ring Topology: In the Ring Topology, all the Computers are connected in circular form same as ring. Its data flows in only one direction. If one Computer fails, the remaining Computer on its anti clock wise direction cannot access the data same as Bus Topology. Maximum 30 Computers with 100 meters of coaxial cable can be connected. The terminator connectors are not used. 

3. Star Topology: In Star Topology, all the Computers are connected with the help of Switch or Hub for the local LAN. Repeater Router to connect the different LANs of Star Topology. In this Topology, if one Computer fails it will not affect another Computer on the Network. But if central connectivity device fails, it will affect the entire Network. Twisted pair cable, NIC, RJ-45, Switch/Hub are used to connect the Computers on the Network.

4. Hybrid Topology: With the Hybrid Topology, two or more topologies are combined to form a complete Network. For example, a Hybrid Topology could be the combination of a Star, Bus or Ring Topology. These are also the most common in use.

5. Mesh Topology: The Mesh Topology includes a unique Network design in which each Computer on the Network connects to every other, creating a Point-to-Point connection between every device on the Network. If one Network cable fails, the data always has an alternative path to get to its destination.