Networks: Evolution & Types

What is a computer network?

A computer network is a group of two or more computers and devices connected to each other – by wires or wirelessly – so that they can share data and resources. Your mobile on Wi-Fi, a school lab and the Internet are all networks.

Why do we need networks?

Basic terms

• Node – any device on a network (computer, printer, phone, router).
• Host – a computer that provides or uses services.
• Server – a powerful computer that provides services (files, web pages, mail) to others.
• Client – a computer that requests services from a server.
• Network interface (NIC) – hardware that connects a device to the network; it has a unique MAC address.

Evolution of networking

Types of networks

Networks are classified by the geographical area they cover.

# Which network type? (rough rule of thumb by area covered)
def network_type(distance_m):
    if distance_m <= 10:
        return 'PAN'
    elif distance_m <= 1000:
        return 'LAN'
    elif distance_m <= 50_000:
        return 'MAN'
    return 'WAN'
for place, d in [('Phone to earbuds', 5), ('School computer lab', 200),
                 ('City cable TV network', 30_000), ('Delhi to London', 6_700_000)]:
    print(place.ljust(24), network_type(d))

PAN – Personal Area Network

Connects devices around one person within about 10 metres – a phone with a smartwatch, earbuds or laptop via Bluetooth, USB or a mobile hotspot.

LAN – Local Area Network

Connects computers in a room, building or campus. It is privately owned, fast (100 Mbps to 10 Gbps) and uses Ethernet cables or Wi-Fi. A school lab or office network is a LAN.

MAN – Metropolitan Area Network

Covers a city or town by joining several LANs. Cable TV networks and a city-wide Wi-Fi are examples.

WAN – Wide Area Network

Connects networks across states, countries or continents using telephone lines, optical fibre, undersea cables and satellites. The Internet is the largest WAN; a bank connecting all its branches also uses a WAN.

Comparison