User Datagram Protocol (UDP)

UDP is a lightweight transport built on top of IP. UDP squeezes extra performance from IP by not implementing some of the features a more heavyweight protocol like TCP offers. Specifically, UDP allows individual packets to be dropped (with no retries) and UDP packets to be received in a different order than they were sent.

UDP is often used in videoconferencing applications or games where optimal performance is preferred over guaranteed message delivery. UDP is one of the oldest network protocols, introduced in 1980 in RFC document 768.

Universal Naming Convention (UNC)

UNC is a naming convention used primarily to specify and map network drives in Microsoft Windows. Support for UNC also appears in other operating systems via technologies like Samba. UNC names are most commonly used to reach file servers or printers on a LAN. UNC names identify network resources using a specific notation. UNC names consist of three parts - a server name, a share name, and an optional file path. These three elements are combined using backslashes as follows: \\server\share\file_path

Universal Plug and Play (UPnP)

UPnP is a technology framework for simplifying the connection of network devices. The UPnP Forum is an industry body coordinating activities related to UPnP standardization and adoption.

UPnP is based on Internet Protocol (IP) addressing and Dynamic Host Configuration Protocol (DHCP). UPnP does not require any particular type of network connection; it works with Ethernet, Wi-Fi, Bluetooth and other physical media. UPnP also is designed to work across many different types of network devices and operating systems.

Uniform Resource Identifier (URI)

A URI is a standard global identifier for an Internet resource that may be local or remotely-accessible. URIs follow the same general syntax as URLs; in fact, URLs are one type of URI.

Whereas URLs always refer to network addresses (including a protocol specification, host name or address, and local path), a URI does not necessarily refer to a remote resource. For example, the URI file:///c:/ specifies a local directory. Because file does not refer to any specific network protocol, this URI is not also a URL.

Uniform Resource Locator (URL)

A URL is a specially-formatted text string that defines a location on the Internet. URL strings contain three parts or substrings:

1. network protocol
2. host name or address
3. file location

The network protocol substring determines the underlying Internet protocol to be used in reaching the location. These strings consist of a standard protocol name followed by the :// characters. Typical protocols found in URLs include http://, ftp://, and mailto://.

The host substring immediately follows the protocol definition. Hosts may be defined by Internet-standard naming (DNS) or by IP address. For example, a URL of http://www.rmit.edu.au or, equivalently, http://131.170.40.30 contains the protocol and host information needed to access this Web site.

The file location portion of a URL defines the location of a network resource. Resources are files that can be plain text files, documents, graphics, or programs, and resource names are relative to a local root directory. Technically, a URL like http://www.rmit.edu.au contains an implied file location of /, that Web servers like Apache automatically translate to a specific file name like index.htm.

Universal Serial Bus (USB)

USB is a high-performance serial bus communication technology. Most new computers and associated peripheral devices like printers and scanners contain built-in support for this technology. USB hubs for file and printer sharing also exist. USB and FireWire are the most popular, competing standards for networking computer peripherals.

Very High Bit Rate DSL (VDSL)

VDSL was developed to support exceptionally high-bandwidth applications such as High-Definition Television (HDTV). VDSL is not as widely deployed as other forms of DSL service. However, VDSL can achieve data rates up to approximately 51,840 Kbps, making it the fastest available form of DSL.

To perform at this speed, VDSL relies on fiber optic cabling. VDSL is designed to work more as a business service that uses ATM internetworking rather than as a consumer service that utilizes IP. VDSL supports both voice and data communication on the same line, like other forms of DSL.

Virus

viruses are malicious software programs, a form of malware. By definition, viruses exist on local disk drives and spread from one computer to another through sharing of "infected" files. Common methods for spreading viruses include floppy disks, FTP file transfers, and copying files between shared network drives.

Once installed on a computer, a virus may modify or remove application and system files. Some viruses render a computer inoperable; others merely display startling screen messages to unsuspecting users.

Virtual Network Computing (VNC)

VNC is a technology for remote desktop sharing. VNC enables the desktop display of one computer to be remotely viewed and controlled over a network connection. This technology is useful on home computers, allowing someone to access their desktops from another part of the house or while traveling. It is also useful for network administrators in business environments.

VNC works similarly to the Remote Desktop appplication built into newer versions of Microsoft Windows. Unlike Windows Remote Desktop, VNC runs on older Windows computers, Linux/Unix and other non-Windows operating systems. VNC applications, however, are generally regarded as slower and offering fewer features and security options than Windows Remote Desktop.

Voice over Internet Protocol (VoIP)

VoIP is a technology that allows telephone calls to be made over computer networks like the Internet. VoIP converts analog voice signals into digital data packets and supports real-time, two-way transmission of conversations using Internet Protocol (IP).

VoIP calls can be made on the Internet using a VoIP service provider and standard computer audio systems. Alternatively, some service providers support VoIP through ordinary telephones that use special adapters to connect to a home computer network. Many VoIP implementations are based on the H.323 technology standard.

Virtual Private Network (VPN)

A VPN utilizes public telecommunications networks to conduct private data communications. Most VPN implementations use the Internet as the public infrastructure and a variety of specialized protocols to support private communications through the Internet.

VPN follows a client and server approach. VPN clients authenticate users, encrypt data, and otherwise manage sessions with VPN servers utilizing a technique called tunneling.

VPN clients and VPN servers are typically used in these three scenarios:

1. to support remote access to an intranet,
2. to support connections between multiple intranets within the same organization, and
3. to join networks between two organizations, forming an extranet.

The main benefit of a VPN is the lower cost needed to support this technology compared to alternatives like traditional leased lines or remote access servers.

VPN users typically interact with simple graphical client programs. These applications support creating tunnels, setting configuration parameters, and connecting to and disconnecting from the VPN server. VPN solutions utilize several different network protocols including PPTP, L2TP, IPsec, and SOCKS.

VPN servers can also connect directly to other VPN servers. A VPN server-to-server connection extends the intranet or extranet to span multiple networks.

Wide Area Network (WAN)

A WAN spans a large geographic area, such as a state, province or country. WANs often connect multiple smaller networks, such as local area networks (LANs) or metro area networks (MANs).

The world's most popular WAN is the Internet. Some segments of the Internet, like VPN-based extranets, are also WANs in themselves. Finally, many WANs are corporate or research networks that utilize leased lines.

WANs generally utilize different and much more expensive networking equipment than do LANs. Key technologies often found in WANs include SONET, Frame Relay, and ATM.

Wireless Application Protocol (WAP)

WAP - the Wireless Application Protocol - defines a network architecture for content delivery over wireless networks. Central to the design of WAP is a network stack based on the OSI model. WAP implements several new networking protocols that perform functions similar to the well-known Web protocols HTTP, TCP, and SSL.

WAP includes the concepts of browsers, servers, URLs, and gateways. WAP browsers are intended to be implemented on small mobile devices such as cell phones, pagers, and PDAs. Instead of developing content in HTML and JavaScript, WAP developers use WML and WMLScript.

Wired Equivalent Privacy (WEP)

WEP is a protocol that adds security to wireless local area networks (WLANs) based on the 802.11 Wi-Fi standard. WEP is an OSI Data Link layer (Layer 2) security technology that can be turned "on" or "off." WEP was designed to give wireless networks the equivalent level of privacy protection as a comparable wired network.

WEP is based on a security scheme called RC4 that utilizes a combination of secret user keys and system-generated values. The original implementations of WEP supported so-called 40-bit encryption, having a key of length 40 bits and 24 additional bits of system-generated data (64 bits total). Research has shown that 40-bit WEP encryption is too easy to decode, and consequently product vendors today employ 128-bit encryption (having a key length of 104 bits, not 128 bits) or better (including 152-bit and 256-bit WEP systems).

When communicating over the wire, wireless network equipment uses WEP keys to encrypt the data stream. The keys themselves are not sent over the network but rather are generally stored on the wireless adapter or in the Windows Registry.

Wireless Fidelity (Wi-Fi)

Wi-Fi is the industry name for wireless LAN (WLAN) communication technology related to the IEEE 802.11 family of wireless networking standards. To some, the term Wi-Fi is synonymous with 802.11b, as 802.11b was the first standard in that family to enjoy widespread popularity. Today, however, Wi-Fi can refer to any of the established standards: 802.11a, 802.11b, 802.11g and 802.11n.

WiMax

WiMax is the industry term for a long-range wireless networking standard. WiMax technology has the potential to deliver high-speed Internet access to rural areas and other locations not serviced by cable or DSL technology. WiMax also offers an alternative to satellite Internet services.

WiMax technology is based on the IEEE 802.16 WAN communications standard. WiMax signals can function over a distance of several miles / kilometers. Data rates for WiMax can reach up to 75 megabits per second (Mb/s). A number of wireless signaling options exist ranging anywhere from the 2 GHz range up to 66 GHz.

WiMax equipment exists in two forms. WiMax base stations are installed by service providers to deploy the technology in a coverage area. WiMax antennas must be installed at the home or other receiving location. As WiMax evolves, these antennas will change from being mounted outdoors, to smaller varieties set up indoors, and then finally to built-in versions integrated inside mobile computers. Similar to other types of Internet access, consumers will subscribe and pay a recurring fee to connect to the Internet via WiMax.

Windows Internet Naming Service (WINS)

The Windows Internet Naming Service (WINS) supports name resolution, the automated conversion of computer names to network addresses, for Windows networks. Specifically, WINS converts NetBIOS names to IP addresses on a LAN or WAN.

Windows Sockets (WinSock)

WinSock is the standard sockets programming API for the Windows operating system. WinSock has been the standard sockets library shipped with all versions of Windows starting with Windows 95.

WinSock was created to allow different Microsoft Windows TCP/IP software applications to communicate. WinSock borrowed and expanded on the concept of sockets and socket programming first made popular on Unix computer systems in the 1980s. WinSock most closely matches the Berkeley implementation of Unix sockets.

Two major versions of WinSock exist for Windows. All implementations of WinSock are packaged in a single Windows dynamic-link library (DLL). The current version of Windows WinSock, version 2.2, is contained in the WS2_32.DLL library. Older Winsock version 1 libraries are named either WINSOCK.DLL or WSOCK32.DLL. Newer releases of Windows WinSock have retained backward compatibility with the older WinSock versions.

Wireless Internet Service Provider (WISP)

A WISP offers public wireless network services. WISPs typically install Wi-Fi wireless hotspots in airports, hotels and other public business places. These hotspots provide Internet access and local area network (LAN) printing for mobile network devices like laptops, handheld computer and cell phones.

Wireless LAN (WLAN)

WLANs provide wireless network communication over short distances using radio or infrared signals instead of traditional network cabling.

A WLAN typically extends an existing wired local area network. WLANs are built by attaching a device called the access point (AP) to the edge of the wired network. Clients communicate with the AP using a wireless network adapter similar in function to a traditional Ethernet adapter.

Wireless Markup Language (WML)

WML is a tag-based markup language designed after the model of HTML for Web content. The designers of WML (and its companion scripting language, WMLScript) created an environment that demands less memory and processing power from browsers than HTML and JavaScript. WML also includes features that tailor it for the relatively small display sizes of today's wireless devices.

WML and HTML differ in significant ways. Although WML strips some features from HTML and co-opts others, WML also incorporates some powerful programming constructs not found in HTML like variables, tasks, and events. WML implements a stricter tag syntax than HTML and includes a DTD for use with XML parsers.

Worm

Computer worms are malicious software applications designed to spread via computer networks. Computer worms are one form of malware along with viruses and trojans. A person typically installs worms by inadvertently opening an email attachment or message that contains executable scripts.

Once installed on a computer, worms spontaneously generate additional email messages containing copies of the worm. They may also open TCP ports to create networks security holes for other applications, and they may attempt to "flood" the LAN with spurious Denial of Service (DoS) data transmissions.

Being embedded inside everyday network software, computer worms easily penetrate most firewalls and other network security measures. Antivirus software applications attempt to combat worms as well as viruses.

Wi-Fi Protected Access (WPA)

WPA is a security technology for wireless networks. WPA improves on the authentication and encryption features of WEP (Wired Equivalent Privacy). In fact, WPA was developed by the networking industry in response to the shortcomings of WEP.

One of the key technologies behind WPA is the Temporal Key Integrity Protocol (TKIP). TKIP addresses the encryption weaknesses of WEP. Another key component of WPA is built-in authentication that WEP does not offer. With this feature, WPA provides roughly comparable security to VPN tunneling with WEP, with the benefit of easier administration and use.

One variation of WPA is called WPA Pre Shared Key or WPA-PSK for short. WPA-PSK is a simplified but still powerful form of WPA most suitable for home Wi-Fi networking. To use WPA-PSK, a person sets a static key or "passphrase" as with WEP. But, using TKIP, WPA-PSK automatically changes the keys at a preset time interval, making it much more difficult for hackers to find and exploit them.

World Wide Web (WWW)

T he term WWW refers to the World Wide Web or simply the Web. The World Wide Web consists of all the public Web sites connected to the Internet worldwide, including the client devices (such as computers and cell phones) that access Web content. The WWW is just one of many applications of the Internet and computer networks.

The World Web is based on these technologies:

• HTML - Hypertext Markup Language
• HTTP - Hypertext Transfer Protocol
• Web servers and Web browsers

Researcher Tim Berners-Lee led the development of the original World Wide Web in the late 1980s and early 1990s. He helped build prototypes of the above Web technologies and coined the term WWW. Web sites and Web browsing exploded in popularity during the mid-1990s.

X.25

X.25 is a standard suite of protocols used for packet switching across computer networks. The X.25 protocols works at the physical, data link, and network layers (Layers 1 to 3) of the OSI model.

Each X.25 packets contains up to 128 bytes of data. The X.25 network handles packet assembly at the source device, delivery, and then disassembly at the destination. X.25 packet delivery technology includes not only switching and network-layer routing, but also error checking and re-transmission logic should delivery failures occur. X.25 supports multiple simultaneous conversations by multiplexing packets and using virtual communication channels.

X.25 was originally designed more than 25 years ago to carry voice over analog telephone lines (dialup networks). Typical applications of X.25 today include automatic teller machine networks and credit card verification networks. X.25 also supports a variety of mainframe terminal/server applications.

With the widespread acceptance of Internet Protocol (IP) as a standard for corporate networks, many X.25 applications are now being migrated to cheaper solutions using IP as the network layer protocol and replacing the lower layers of X.25 with Ethernet or ATM hardware.

XML – RPC

XML-RPC is a network programming technique for making remote procedure calls (RPC) to software running on remote devices. XML-RPC uses XML coding for calls and sends messages using the Hypertext Transfer Protocol (HTTP).

XML-RPC serves a similar function to Simple Object Access Protocol (SOAP), that supports remote object method invocations using XML over HTTP.