Introduction to Computer

Networks
A computer network is a system that connects two or more computing
devices to transmit and share information.
• A computer network is defined as a system that connects two or
more computing devices for transmitting and sharing information.
• Computing devices include everything from a mobile phone to a
server. These devices are connected using physical wires such as fiber
optics, but they can also be wireless.
• The first working network, called ARPANET, was created in the late
1960s and was funded by the U.S. Department of Defense.
Government researchers used to share information at a time when
computers were large and difficult to move.
• Today’s world revolves around the internet, which is a network of
networks that connects billions of devices across the world.
Organizations of all sizes use networks to connect their employees’
devices and shared resources such as printers.
Key Components of a Computer Network:
• From a broader lens, a computer network is built with two basic
blocks: nodes or network devices and links. The links connect two or
more nodes with each other.
• The way these links carry the information is defined by
communication protocols. The communication endpoints, i.e., the
origin and destination devices, are often called ports.
Network Devices:
• Network devices or nodes are computing devices that need to be
linked in the network. Some network devices include:
• Computers, mobiles, and other consumer devices: These are end
devices that users directly and frequently access. For example, an
email originates from the mailing application on a laptop or mobile
phone.
• Servers: These are application or storage servers where the main
computation and data storage occur. All requests for specific tasks or
data come to the servers.
• Routers: Routing is the process of selecting the network path through
which the data packets traverse. Routers are devices that forward
these packets between networks to ultimately reach the destination.
They add efficiency to large networks.
Links:
• Links are the transmission media which can be of two types:
• Wired: Examples of wired technologies used in networks include
coaxial cables, phone lines, twisted-pair cabling, and optical fibers.
Optical fibers carry pulses of light to represent data.
• Wireless: Network connections can also be established through radio
or other electromagnetic signals. This kind of transmission is called
‘wireless’. The most common examples of wireless links include
communication satellites, cellular networks, and radio.
Communication protocols:
• A communication protocol is a set of rules followed by all nodes
involved in the information transfer.
• Some common protocols include the internet protocol suite (TCP/IP),
IEEE 802, Ethernet, wireless LAN, and cellular standards. TCP/IP is a
conceptual model that standardizes communication in a modern
network.
Network Defense:
• While nodes, links, and protocols form the foundation of a network, a
modern network cannot exist without its defenses. Security is critical
when unprecedented amounts of data are generated, moved, and
processed across networks.
• A few examples of network defense tools include firewall, intrusion
detection systems (IDS), intrusion prevention systems (IPS), network
access control (NAC), content filters and proxy servers.