Computer Network Defined
A computer network is a set of computers connected together for the purpose of sharing resources. The most common resource shared today is connection to the Internet. Other shared resources can include a printer or a file server.
A computer network is a group of computer systems and other computing hardware devices that are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Networks are commonly categorized based on their characteristics.A computer network is a set of connected computers. Computers on a network are called nodes. The connection between computers can be done via cabling, most commonly the Ethernet cable, or wirelessly through radio waves. Connected computers can share resources, like access to the Internet, printers, file servers, and others. A network is a multipurpose connection, which allows a single computer to do more.
Types of Network Connections
Computer networks can be broken down historically into topologies, which is a technique of connecting computers. The most common topology today is a collapsed ring. This is due to the success of a network protocol called the Ethernet. This protocol, or a network language, supports the Internet, Local Area Networks, and Wide Area Networks.
Star Topology
A star topology is a design of a network where a central node extends a cable to each computer on the network. On a star network, computers are connected independently to the center of the network. If a cable is broken, the other computers can operate without problems. A star topology requires a lot of cabling.
Bus Topology
A bus topology is another type of design where a single cable connects all computers and the information intended for the last node on the network must run through each connected computer. If a cable is broken, all computers connected down the line cannot reach the network. The benefit of a bus topology is a minimal use of cabling.
Collapsed Ring Topology
A similar topology is called a ring. In this design, computers are connected via a single cable, but the end nodes also are connected to each other. In this design, the signal circulates through the network until it finds the intended recipient. If a network node is not configured properly, or it is down temporarily for another reason, the signal will make a number of attempts to find its destination.
A collapsed ring is a topology where the central node is a network device called a hub, a router, or a switch. This device runs a ring topology internally and features plugins for cables. Next, each computer has an independent cable, which plugs into the device. Most modern offices have a cabling closet, or a space containing a switch device that connects the network. All computers in the office connect to the cabling closet and the switch. Even if a network plug is near a desk, the plug is connected via a cable to the cabling closet.
Mesh Topology
A network setup where each computer and network device is interconnected with one another, allowing for most transmissions to be distributed, even if one of the connections go down. This topology is not commonly used for most computer networks as it is difficult and expensive to have redundant connection to every computer. However, this topology is commonly used for wireless networks. Below is a visual example of a simple computer setup on a network using a mesh topology.
TREE Topology
It has a root node and all other nodes are connected to it forming a hierarchy. It is also called hierarchical topology. It should at least have three levels to the hierarchy.
HYBRID Topology
It is two different types of topologies which is a mixture of two or more topologies. For example if in an office in one department ring topology is used and in another star topology is used, connecting these topologies will result in Hybrid Topology (ring topology and star topology).
Advantage of Computer networks
• Sharing of Devices such as printer and scanner
• Sharing program / software
• Sharing files
• Sharing data
• Sharing information
• Sharing of single high-speed internet connection
• Better communication using internet services such as email, mailing list and internet Relate chat (IRC)
Disadvantage of Computer Network
• The larger network becomes, the more difficult it is to manage.
• If the network stops operating system, then it may not be possible to access various resources
• Computer Viruses: If any computer system in a network gets affected by computer virus, there is a possible threat of other systems getting affected too.
Types of Network
Metropolitan Area Network (MAN) is high speed network that connect local area network in Metropolitan Area such as city or town and handles bulk of communication activity across the region.
A MAN typically includes one or more LAN but covers a smaller geographically area than a WAN.
Wide Area Network (WAN) is a network that covers a large geographically area such country or the world. WAN combines many types of media such as telephone lines, cables and radio wave.
Network Architecture
Network Architecture is the overall design of a computer network that describes how a computer network is configured and what strategies are being used. It also known as network model or network design.
ETHERNET CABLING
You’ll need a sufficient number of Ethernet cables to connect all devices in your network. Most modern networks use Category 5 or 6 cabling, and you can purchase the cables in a variety of lengths. You can even buy cables in different jacket colors to distinguish network devices in a large network. For instance, you can use blue cables for PCs, red ones for servers, and so on.
MODEM
Your ISP usually provides a modem when you sign up for service, although you can usually purchase your own from a list of approved devices if you choose. A modem exists at the edge of your network and provides bidirectional communication between your ISP and the devices inside your network. Modems come in various forms depending on your service. A DSL modem, for example, connects to your ISP via a telephone line, while a cable modem uses a coaxial link. Most modems also have one or more Ethernet ports that you can use to connect the device to a router, switch, or directly to a computer.
ROUTERS AND SWITCHES
A router or switch connects to your modem via an Ethernet cable and provides connectivity to multiple devices. Unlike switches, routers enable you to connect two networks together. For example, if you have one or more branch offices, you can use a VPN-enabled router to provide a secure connection to those offices. Routers and switches with a DSU/CSU provide T1 links to branch offices. Routers have built-in firewalls and advanced features such as Web filtering. Switches are mainly used for facilitating communication within a single office network, although some contain such router-like features as the ability to create virtual local area networks (VLANs). You can also purchase unmanaged switches that need no configuration and work right out of the box.
Mac Address
- hardware address
- It is hardwired or hard-coded onto your computer's network interface card (NIC) and is unique to it
Communication Devices
1. Hub
- A non-intelligent device, and has no decision making capability
- Take the input data from one of the ports and broadcast the information to all the other ports connected to the network.
2. Repeaters
- A repeater is a device similar to the Hub, but has additional features.
- Used in places where amplification of input signal is necessary
- Regenerates Faded Signals
3. Switch
- A switch is an intelligent device
- Has a decision making capacity
4. Bridges
- A device that connects two local-area networks (LANs), or two segments of the same LAN that use the same protocol
5. Routers
- A router is a device that forwards data packets along networks. A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP's network.
6. NIC(Network Interface Card)
- So that the computer can be connected to a network.
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