General networking definitions


Ethernet is the probably most widely-installed Local Area Network (LAN) technology and is specified in the IEEE 802.3 standard.

An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol.

Fast Ethernet or 100BASE-T provides transmission speeds up to 100 megabits per second and is typically used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second). 10-Gigabit Ethernet provides up to 10 billion bits per second

See Ethernet basics for more detailed information and Ethernet glossary for a collection of commonly used networking terms.

Ethernet is also used in wireless LANs (WLAN).

Local Area Network (LAN)

A Local Area Network (LAN) is a group of computers and associated devices that share a common communications line or wireless link and typically share the resources of a single processor or server within a small geographic area (for example, within an office building). A LAN may serve as few as two or three users (e.g in a home network) or as many as thousands of users (for example, in an FDDI network).

Wide Area Network (WAN)

A Wide Area Network (WAN) is a geographically dispersed telecommunications network. The term distinguishes a broader telecommunication structure from a Local Area Network (LAN). A WAN may be privately owned or rented, but the term usually connotes the inclusion of public (shared user) networks and an example would be the Internet. An intermediate form of network in terms of geography is a metropolitan area network (MAN).

Metropolitan Area Network (MAN)

A Metropolitan Area Network (MAN) is a network that interconnects users with computer resources in a geographic area or region larger than that covered by even a large LAN but smaller than the area covered by a WAN. The term is applied to the interconnection of networks in a city into a single larger network (which may then also offer efficient connection to a WAN). It is also used to mean the interconnection of several LANs by bridging them with backbone lines. The latter usage is also sometimes referred to as a campus network.

Examples of metropolitan area networks of various sizes can be found in the metropolitan areas of London, England; Lodz, Poland; and Geneva, Switzerland. Large universities also sometimes use the term to describe their networks.

A recent trend is the installation of wireless MANs.

Wireless Local Area Network (WLAN)

A wireless LAN is one in which a mobile user can connect to a LAN through a wireless (radio) connection. A standard, IEEE 802.11, specifies the technologies for wireless LANs. There are now several variants offering differing speeds and functionality. The WLAN list provides more details on this topic.

The standard includes encryption methods such as the Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA) algorithms.

Port Forwarding

Allows you to forward specific ports or ranges of ports to private IP addresses (computers) on the LAN. This enables a computer(s) to host web services such as web servers, ftp servers, e-mail servers, or other specialised applications. If there is no plan to hosting any services or games then it is not necessary to use port-forwarding.

Port numbers for port-forwarding is a list ports used by a number of applications in widespread use. The site is also useful in that it describes how port-forwarding is set-up on a vast array of SOHO routers from numerous manufacturers.

Port Triggering

An advanced feature that can be used for gaming and other Internet applications. Port Triggering monitors outbound traffic, if the router detects traffic on the specified outbound port. It will remember the IP address of the computer that sent the data and triggers the incoming port. Incoming traffic on the triggered port is then forwarded to the computer that send the data. When the data transmission is over, the port will be closed.

UPnP (Universal Plug and Play)

Is all about making home networking simple and affordable for users. UPnP allows UPnP enabled applications such Microsoft MSN Messenger 6.0 to automatically pass through the router without any configuration from the user - thus providing plug'n'play functionality. If your application requires UPnP, then you will need a router that supports it.

Demilitarized Zone (DMZ)

Allows one private IP address (computer) to be exposed to the Internet. DMZ is ideal for some applications which require multiple ports to be open for special Internet applications such as Internet gaming and videoconferencing. Where as port forwarding can only forward a maximum specific ranges of ports, DMZ forwards all the ports for one computer at the same time. Everdently, forwarding all ports to a computer opens up risks to hackers gaining access.


A firewall is a set of related programs, located at a network gateway server, that protects the resources of a private network from users on other networks.

Basically, a firewall, working closely with a router program, examines each network packet to determine whether to forward it toward its destination. A firewall also includes or works with a proxy server that makes network requests on behalf of workstation users. A firewall is often installed in a specially designated computer separate from the rest of the network so that no incoming request can get directly at private network resources.

There are examples of both hardware and software firewalls. The most common example of the former is the NAT-router type of firewall, while the most frequent example of the latter is the Personal Firewall.

Personal Firewall

A personal firewall (sometimes called a desktop firewall) is a software application used to protect a single Internet-connected computer from intruders. Personal firewall protection is especially useful for users with "always-on" connections such as broadband DSL or cable modems.

Stateful Packet Inspection (SPI) firewall

Provides the highest form of protection for routers. An SPI firewall incorporates Packet Filtering while automatically provides rigorous inspections of all inbound and outbound communications. This protects your network against malicious attacks that flood your network with inappropriate packets/data. Normally SPI Firewalls come with DoS and Intrusion Detection enhancing security even further.

Packet Filtering firewall

Isn't as advanced or secure as an SPI firewall. Packet Filtering firewalls work in conjunction with NAT firewalls. The NAT stops unauthorised inbound requests while the Packet Filtering allows you to filter inbound & outbound ports allowing you to control which applications you want access /or deny.

NAT firewall

The most basic form of security a Broadband router provides. NAT was originally designed to allow you to share a single IP address among all the computers in your home or business. However NAT mode also acts as a basic firewall that rejects any unsolicited data that tries to travel from the Internet to a computer on your LAN.

Additional Security

DoS (Denial of Service) Protection

Stops hackers from deliberately preventing you to access the Internet. A DoS attack floods a Broadband connection with an overwhelming amount of traffic, slowing its response time for legitimate traffic or grinding it to a halt completely.

Intrusion detection

Allows you to be notified when your broadband router is under attack. The most common way is to for the router to notify you by email.

Content Filtering

Allows you to screen and exclude access or availability of Web pages that is deemed objectionable. Content filtering is ideal for home computer owners, especially by parents to screen the content their children have access to from a computer. However it is a farily basic tool given it is based on simple string-matching. e.g. enter "COM" as a keyword and every .com site on the planet will be blocked!

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