A LAN (Local Area Network) is the most basic form of infrastructure that allows communication between two or more computers. A LAN can be constructed with or without servers and is typically restricted, through the limits of network equipments, by physical location. Any system that allows communication between multiple LAN is called a WAN (Wide Area Network), of which the biggest existing one is the World Wide Web, also known as the Internet.
Networking hardware is a switch that allows a computer to communicate to more than one other computer simultaneously. It can be physically wired through network cables or otherwise (e.g. Wi-Fi). A computer participating in the LAN similarly requires the correct equipment such as network adapters installed. Wired network provides better speed and security compared with wireless. A LAN can also consist of both. Depending on the number of clients in the LAN, functionality and complexity, multiple switches, routers and servers might be required.
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A higher-intelligent switch can allow control over QoS (Quality of Service) over different network segments of the LAN, allowing only selected computers to have certain access, run only specific applications as well as speed limitation.
A server is the central system that contains data, application or both. A server is accessed by all clients simultaneously and, as such, requires higher computing power. It typically comes with a data-protection system such as hard disk redundancy, scheduled backup and load-balancing to prevent data loss. Certain applications such as those for sending and retrieving emails can only be run via a server. Multiple servers in a LAN can run individually or as a server-farm, a collection of multiple servers operating as one logical host.
Other types of servers include hardware, security, management, proxy server and web servers, where all websites on the Internet reside.
Typical Network Infrastructure
A LAN is typically hidden from the outside world via a router. It communicates internally through its own range of IP (Internet Protocol) addresses. A NAT (Network Address Translation) is required for these clients to communicate beyond the LAN (e.g. accessing the Internet) through the gateway.
From the Internet, a connected LAN will appear as just one host or one IP address, giving no indication how many computers are inside and protected by one or more firewalls. These can be directly accessed on the outside via a VLAN (Virtual LAN) or via the Internet with the use of VPN (Virtual Private Network).
A web server that allows all unsolicited access by the Internet normally resides in the DMZ (Demilitarized Zone) area of the LAN, with limited security measures.