Introduction of Network

 Α network is simply defined as something that connects things together for a specific purpose. The term network is used in a variety of contexts, including telephone, television, computer, or even people networks.

A computer network connects two or more devices together to share a nearly limitless range of information and services, including: 

• Documents 
• Email and messaging 
• Websites 
• Databases 
• Music 
• Printers and faxes 
• Telephony and videoconferencing

 Protocols are rules that govern how devices communicate and share information across a network. 

Examples of protocols include: 

• IP – Internet Protocol 

• HTTP - Hyper Text Transfer Protocol 

• SMTP – Simple Mail Transfer Protocol 

Multiple protocols often work together to facilitate end-to-end network communication, forming protocol suites or stacks. Protocols are covered in great detail in other guides. Network reference models were developed to allow products from different manufacturers to interoperate on a network. 

 Network Types 

Network types are often defined by function or size. The two most common categories of networks are:

 • LANs (Local Area Networks) 

• WANs (Wide Area Networks) 

A LAN is generally a high-speed network that covers a small geographic area, usually contained within a single building or campus. A LAN is usually under the administrative control of a single organization. Ethernet is the most common LAN technology. 

A WAN can be defined one of two ways. 

The book definition of a WAN is a network that spans large geographical locations, usually to connect multiple LANs. This is a general definition, and not always accurate. A more practical definition of a WAN is a network that traverses a public or commercial carrier, using one of several WAN technologies. A WAN is often under the administrative control of several organizations (or providers), and does not necessarily need to span large geographical distances. 

A MAN (Metropolitan Area Network) is another category of network, though the term is not prevalently used. A MAN is defined as a network that connects LAN’s across a city-wide geographic area. 

An internetwork is a general term describing multiple networks connected together. The Internet is the largest and most well-known internetwork. 

Some networks are categorized by their function, as opposed to their size. A SAN (Storage Area Network) provides systems with high-speed, lossless access to high-capacity storage devices.

 A VPN (Virtual Private Network) allows for information to be securely sent across a public or unsecure network, such as the Internet. Common uses of a VPN are to connect branch offices or remote users to a main office.