9.1: Introduction to Computer Networks by Nida Siddiqi

Network:

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A computer network is formed when two or more computers are connected

Local area networks (LANs)

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In a LAN, computers are close together, typically in the same building or office.

Wide area networks (WANs)

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When connected computers are far apart—in different buildings, different cities, or even different countries.

Intranet:

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which is a private network that looks and acts a lot like the Internet but is available only to the employees of the organization.

Extranet:

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If a company decides to allow certain customers or other “outsiders” to access areas of its intranet, those areas of the network are then called an extranet.

Network operating system (NOS)

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The NOS controls access to the network and everything about how the network is used.

Network protocols:

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Classrooms also have rules; for example, students typically raise their hands and take turns speaking. With computer networks, the rules of initiating, interrupting, and continuing communication are known as network protocols.

Bandwidth:

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The bandwidth is the number of bits that can be transmitted or received per second.

Network interface cards(NICs):

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A network interface card makes it possible for a computer to send data to and receive data from another computer. A NIC has a port that extends outside the computer, usually in the back.

Cable

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The transmission medium by which computers in a network usually send and receive data.

Ethernet twisted-pair:

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The most common cable used in LANs today is Ethernet twisted-pair cabling. Industry-standard specifications categorize cables according to performance characteristics and test requirements.

Category 5 (CAT5)

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Category 5 (CAT5) cable sends signals at 100 megabits per second; CAT5e cable is an enhanced version of CAT5 that reduces interference.

Fiber-optic

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You may also come across fiber-optic cable, which uses light guided through thin glass tubes to send data.

Wireless networking

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as its name implies, doesn’t use cables. Instead, it uses radio frequencies to send data. Wireless networking is limited by its ability to send signals over short distances only, and certain walls and structures can prevent signals from being sent and received at all

Hub

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A hub is the central point where all of the computers on a network connect. All data is sent first to the hub, which then sends it on to the other computers on the network.

Switch

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A switch is a type of hub that uses a table to keep track of destinations so that the message from Computer 1 to Computer 23 is sent directly to Computer 23, and not to every other computer on the network, too.

Router

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A router links computers to the Internet, so users can share the connection. A router acts as a dispatcher, choosing the best path for information to travel so that it’s received quickly.

Wi-fi

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Although a wired connection is still a very good option for optimum speed and security, some new Wi-Fi technologies are faster than traditional cable.

Connection speed

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A fast cabled or wireless connection will still be limited by the connection speed provided by the service provider.

Client/Server System

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Many LANs operate using an architecture called a client/server system. In this arrangement, one computer or one set of computers, the servers, are assigned a specific task—to handle all email,

Clients

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The other machines on the network, called clients, communicate with the server(s) but do not communicate with each other.

Virtual private network (VPN)

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Virtual private networks (VPNs) can also be considered a type of WAN, although they don’t stand on their own. VPNs are built using another network, but they may have their own security settings and modifications to user connectivity.

Packets

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Computer networks use packet switching. When you send information, the data must first be broken down into smaller bits of information called packets.

Collision

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what happens when more than one transmitter tries to pass data along at once. .

Protocol

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Complicated and fine-tuned routing protocols are used to make sure data goes across the network as efficiently as possible.