A computer network is a set of computers sharing resources located on other network nodes, which can be personal computer, servers, networking hardware (like routers and switches) or other general purposes hosts, and they are identified by a network address.
Host, PCs and Servers are categorized as terminal devices, while routers are used to connect a network to other networks, and switcher connect different different terminal devices.
Computers that are made to be publicly accessible (like servers) usually also have an hostname, which are memorable labels (e.g. google.com)
The nodes in the network communicate with common protocols over digital interconnections, which are made up of telecommunication technologies based on physically wired, optical and wireless radio-frequency methods that are arranged in a variety of Network Topologies.
Types of computer networks
Local Area Network (LAN)
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.
It has an unique address that identifies it.
Nowadays, most LAN networks use an interconnection switch to which each device connects. This switch is able to recognize the destination address and send the packet to the recipient without passing through other devices (as it used to be). The switch allows multiple pairs of devices to connect simultaneously with each other.
Wide Area Network (WAN)
A Wide Area Network (WAN) is (like the LAN) an interconnection of devices capable of communicating. Differently from the LAN, its extension can cover an entire city, a nation, or the entire world.
While a LAN interconnects only terminal systems, a WAN can also interconnect switches, routers, and modems. It is managed and created by an Internet Service Provider (ISP), which provides services to organizations that use it.
LAN and WAN networks are connected to each other in an internetwork (or internet). For example, a company with two LANs in two offices in Rome and Milan uses a point-to-point WAN, renting it from an ISP, to allow employees in different cities to communicate. In this way, the company has created a private network (internetwork).
Here is an example of a LAN with connection to a WAN
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