Network Infrastructure Link to heading

varies greatly in terms of:

Size of the area covered
Number of users connected
Number and types of services available
Area of responsibility

Common Types Link to heading

Local Area Network (LAN) - provides access to users and end devices in a small geographical area, which is typically an enterprise, home, or small business network owned and managed by an individual or IT department.
Wide Area Network (WAN) - provides access to other networks over a wide geographical area, which is typically owned and managed by a telecommunications service provider.

Local Area Networks (LANs) Link to heading

a network infrastructure that spans a small geographical area.

As technologies evolve, the definition of local has evolved as well. Not only can a LAN consist of one group of users on one floor, but it can comprise all users on a multibuilding campus.

Specific features of LANs include:

LANs interconnect end devices in a limited area such as a home, school, office building, or campus.
A LAN is usually administered by a single organisation or individual. The administrative control that governs the security and access control policies are enforced on the network level.
LANs provide high speed bandwidth to internal end devices and intermediary devices.

Each LAN will have a router as its gateway connecting the LAN to other networks. Inside the LAN will be one or more hubs or switches to connect the end devices to the LAN.

Wide Area Networks (WANs) Link to heading

a network infrastructure that spans a wide geographical area.

The sole purpose of WANs is to connect LANs, and there are no end users on WANs.

WANs are typically managed by service providers (SPs).

Specific features of WANs include:

WANs interconnect LANs over wide geographical areas such as between cities, states, provinces, countries, or continents.
WANs are usually administered by multiple service providers.
WANs typically provide slower speed links between LANs.

If a company has offices in different cities, it will contract with a telecommunications service provider (TSP) to provide data lines between LANs in each city. The leased lines will vary in service and bandwidth, depending on the terms of the contract. The TSP is responsible for the intermediary devices on the WAN that transports messages, while LANs at both ends are controlled by the company.

Internetwork Link to heading

(data networks or networks) - a collection of two or more LANs interconnected by WANs.

The most popular internetwork is the Internet, which is open to public use.

The Internet Link to heading

a worldwide collection of interconnected networks.

Although there are benefits to using a LAN or a WAN, most individuals need to communicate with a resource on another network, outside of the local network within the home, campus, or organisation. This is then done using the Internet.

LANs are connected to each other through a WAN connection. WANs are then connected to each other through copper wires, fibre optic cables, or wireless transmissions. The Internet is a collection of interconnected LANs and WANs.

Note: The term internet (with a lower case “i”) is used to describe multiple networks interconnected. When referring to the global system of interconnected computer networks or the World Wide Web, the term Internet (with a capital “I”) is used.

Intranets Link to heading

a private collection of networks over LANs and WANs that belong to an company.

It is designed to be accessible only by the company’s members, employees, or others with authorisation.

For example, many companies use intranets to share company information and training across the globe to far-away employees. Documents are shared and projects are managed securely over great distances on an intranet.

Extranets Link to heading

part of a company’s intranet that is extended to users outside the company (normally over the Internet).

It provides as-needed access for external vendors and customers to a secure, limited corporate network.

Examples of extranets include:

A company that is providing access to outside suppliers and contractors.
A hospital that is providing a booking system to doctors so they can make appointments for their patients.
A local office of education that is providing budget and personnel information to the schools in its district.

Internet Service Providers (ISPs) Link to heading

also telecommunications service providers (TSPs), connect their customers to the Internet. The customer can be a home user, a company, or a government institution.

All Internet users access the web through ISPs. The ISPs cooperate with TSPs and other ISPs to make sure that all users have access to the web.

This involves implementing rules and standards that enable any user to communicate with any other user regardless of location and equipment type. connections between routers.

Internet Access Technologies Link to heading

There are many different ways to connect users and organisations to the Internet.

SOHO users and teleworkers typically require a connection to an ISP to access the Internet. Connection options vary greatly between ISP and geographical location. However, popular choices include broadband cable, broadband digital subscriber line (DSL), wireless WANs, and mobile services.

Organisations typically require access to other company sites and the Internet. Fast connections are required to support business services including IP phones, video conferencing, and data centre storage.

Business-class interconnections are usually provided by SPs. Popular business-class services include business DSL, leased lines, and Metro Ethernet.

Small Office and Home Office (SOHO) Internet Connections Link to heading

Common connection options for SOHO users include:

Cable - typically offered by cable television service providers, the Internet data signal is carried on the same cable that delivers cable television. It provides a high bandwidth, always on, connection to the Internet.
Digital Subscriber Lines (DSL) - provide a high bandwidth, always on, connection to the Internet. DSL runs over a telephone line. In general, SOHO users connect using Asymmetrical DSL (ADSL), which means that the download speed is faster than the upload speed.
Cellular - uses a cell phone network to connect. Wherever you can get a cellular signal, you can get cellular Internet access. Performance will be limited by the capabilities of the phone and the cell tower to which it is connected.
Satellite - its availability of is a real benefit in those areas that would otherwise have no Internet connectivity at all. Satellite dishes require a clear line of sight to the satellite.
Dial-up Telephone - An inexpensive option that uses any phone line and a modem. The low bandwidth provided by a dial-up modem connection is usually not sufficient for large data transfer, although it is useful for mobile access while travelling.

Many homes and small offices are more commonly being connected directly with fibre optic cables. This enables an ISP to provide higher bandwidth speeds and support more services, such as Internet, phone, and TV.

The choice of connection varies depending on geographical location and service provider availability.

Business Internet Connections Link to heading

Businesses require higher bandwidth, dedicated bandwidth, and managed services than SOHO.

The availability of connection options varies depending geographical location and SPs located nearby.

Dedicated Leased Line - Leased lines are actually reserved circuits within the service provider’s network that connect geographically separated offices for private voice and/or data networking. The circuits are typically rented at a monthly or yearly rate, which can be expensive.
Ethernet WAN - extends LAN access technology into the WAN.
DSL - Business DSL is available in various formats. A popular choice is Symmetric Digital Subscriber Lines (SDSL) which is similar to the consumer version of DSL, but provides uploads and downloads at the same speeds.
Satellite - Similar to SOHO users, satellite service can provide a connection when a wired solution is not available.

LANs, WANs, and the Internet

Table of Contents Link to heading