TYPES OF NETWORKS

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 ethenet 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 Adress 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 NETWORKING-BASICS

A network is any collection of independent computers that communicate with one another over a shared network medium.A computer network is a collection of two or more connected computers. When these computers are joined in a network, people can share files and peripherals such as modems, printers, tape backup drives, or CD-ROM drives. When networks at multiple locations are connected using services available from phone companies, people can send e-mail, share links to the global Internet, or conduct video conferences in real time with other remote users. As companies rely on applications like electronic mail and database management for core business operations, computer networking becomes increasingly more important.

Every network includes:

• At least two computers Server or Client workstation.
• Networking Interface Card's (NIC)
• A connection medium, usually a wire or cable, although wireless communication between networked computers and peripherals is also possible.
• Network Operating system software, such as Microsoft Windows NT or 2000, Novell NetWare, Unix and Linux.

DIFFERENCE B/W A HUB,SWITCH AND ROUTER

Hubs, switches, and routers are all devices that let you connect one or more computers to other computers, networked devices, or to other networks. Each has two or more connectors called ports into which you plug in the cables to make the connection. Varying degrees of magic happen inside the device, and therein lies the difference. I often see the terms misused so let's clarify what each one really means.

A hub is typically the least expensive, least intelligent, and least complicated of the three. Its job is very simple: anything that comes in one port is sent out to the others. That's it. Every computer connected to the hub "sees" everything that every other computer on the hub sees. The hub itself is blissfully ignorant of the data being transmitted. For years, simple hubs have been quick and easy ways to connect computers in small networks.

A switch does essentially what a hub does but more efficiently. By paying attention to the traffic that comes across it, it can "learn" where particular addresses are. For example, if it sees traffic from machine A coming in on port 2, it now knows that machine A is connected to that port and that trafficto machine A needs to only be sent to that port and not any of the others. The net result of using a switch over a hub is that most of the network traffic only goes where it needs to rather than to every port. On busy networks this can make the network significantly faster.

A quick note on one other thing that you'll often see mentioned with these devices and that's network speed. Most devices now are capable of both 10mps (10 mega-bits, or million bits, per second) as well as 100mbs and will automatically detect the speed. If the device is labeled with only one speed then it will only be able to communicate with devices that also support that speed. 1000mbs or "gigabit" devices are starting to slowly become more common as well. Similarly many devices now also include 802.11b or 802.11g wireless transmitters that simply act like additional ports to the device.

A router is the smartest and most complicated of the bunch. Routers come in all shapes and sizes from the small four-port broadband routers that are very popular right now to the large industrial strength devices that drive the internet itself. A simple way to think of a router is as a computer that can be programmed to understand, possibly manipulate, and route the data its being asked to handle. For example, broadband routers include the ability to "hide" computers behind a type of firewall which involves slightly modifying the packets of network traffic as they traverse the device. All routers include some kind of user interface for configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown programming language to describe how they should operate as well as the ability to communicate with other routers to describe or determine the best way to get network traffic from point A to point B.

BASICS OF ROUTER

It’s a layer 3 device that connects 2 different networks and routes packets of data from one network to another. It breaks up Broadcast domain as well as Collision Domain.

Advantages of Router

1.Router don’t forward Broadcasts by default.

2.Perform access control on the traffic that flows through the router i.e. Packet Filtering.

3.Network Address Translation.

4.Quality of Service for particular network traffic.

5.Can be used as a DHCP relay agent.

7.Connects different VLAN’s.

DCE-Data Communications Equipment

The DCE supplies the physical connection to the network, forwards traffic, and provides a clocking signal to synchronize data transmission between DTE and DCE devices.

DTE-Data Terminal Equipment

Any device located at the end user i.e. network interface serving as a destination or source or both. DTE includes devices such as Multiplexers, routers, protocol translators and computers.

Different Modes for configuring a router

1.User Mode- some basic commands like ping, telnet can be done. Prompt will be Router >

2.Execution or Privilege or Enable Mode- can view all configuration details, minimal commands like ping, telnet, and clock setting. Prompt will be Router #

3.Global Configuration Mode- where all configurations are done. Prompt will be Router(config)#

Sub Configuration Modes

1.Interface configuration mode, prompt will be Router(config-if)#

2.Router configuration mode, prompt will be Router(config-router)#

3.Line configuration mode, prompt will be Router(config-line)#