Glossary

ACK: ACK is TCP flag that acknowledges receipt of a TCP segment.
Advanced Research Projects Agency Network: ARPANET was early network established in 1972 between a few research nstitutes and universities in the USA that evolved into the Internet
applet: Java program that can be embedded in an HTML page. They have security restrictions and cannot access file system, launch processes or make system calls on the local computer.
application layer: Level of network reference model that interfaces below with transport layer and above with user.
application programming interface: API is set of procedures, methods, types and so on defining a set of application services and how to invoke and handle them from a programming language.
Asymmetric Digital Subscriber Line: ADSL is version of Digital Subscriber Line that uses most of the channel to transmit to the user.
Asynchronous Transfer Mode: ATM is a connection oriented, high speed switching technology that organises digital data into 53 byte cells to transmit them over physical media. Cells can be rapidly processed asynchronously by hardware and multiplexed in transmission.
authentication: Authentication is process of determining that an entity is who or what it claims to be.
authorisation: Authorisation is process of determining what services and resources an entity can use.
bastion: A bastion is a firewall that is the gateway between a LAN and the Internet.
bluetooth: Wireless technology standard for small-form factor, low-cost, short range radio links between mobile PCs, mobile phones and other portable devices based on spread spectrum radio communications.
BOOTP: BOOTP is the Bootstrap protocol used by by discless hosts to discover their IP address, the location of the boot server and to start system download over tftp prior to booting.
bridge: Device connecting two networks at the data link layer level that filters and forwards packets across divide both ways but doesn't alter format or contents of packets passed.
broadcast: Broadcast is an IP packet sent to all interfaces connected to the same network.
broadcast network: Type of network in which all connected hosts share a single communication channel. It is the opposite of a point to point network.
broker: Intermediaries in network applications that add value to the provision of services. Brokers may find servers for clients or refine service requests for clients. Unlike proxies, brokers don't mask their role as intermediaries between clients and servers.
Browsing: Looking for resources of interest in a reactive process of exploration where the seeker has no precise search objective. It can be contrasted with searching.
bus: Shared communications link interconnecting multiple local devices that pairs of communicating parties must take turns using.
byte code: Compiled form of a program in a language such as Java which can be executed on an emulator for that code such as a Java Virtual Machine. Java byte code is stored in ".class" files.
cache: Fast access storage units placed on communication links to improve effective bandwidth from remote sites. They exploit locality of reference by storing recent copies of previously fetched data and let the cache try to service data fetches first.
cache consistency protocol: Protocol for ensuring that the data stored in a cache is a valid copy of the data it purports to be a copy of.
CERT: CERT stands for Computer Emergency Response Team, an information coordination centre and Internet security emergency prevention centre formed at Carnegie Mellon.
chain: Chain is a list of rules defining what packets can come in and go out through a network interface.
chaining: Recursive forwarding of a X.500 directory service query to directory service agents able to process the various parts of it and the subsequent marshalling of these replies into its own reply.
checksum: Checksum is a number produced by arithmetic on each byte in a file or packet so that if the file or packet is changed or corrupted, the same checksum will no longer be produced.
circuit-switched: Type of network infrastructure that establishes point to point connections to communicate along in the style of telephone calls. Opposite of packet-switched.
Common Gateway Interface: CGI is RFC 3875 standard used by web servers to interface web clients to programs. It is primarily used to process forms and return results and as a gateway to third tier applications such as databases
client: Hardware or software acting as service consumer usually using a client server model of computing
client pull: Term for push technology application on the web in which the client regularly or irregularly pulls data from a web server.
client server model: Model of distributed computing based upon a passive service provider or server waiting to receive requests from one or more active service consumers or clients to which it responds by providing service.
communication domain: Socket addressing scheme which is either Internet domain or Unix domain. Internet domain addressing uses Internet domain names or IP addresses and port numbers and has the scope of the Internet. Unix domain addressing uses local file names and has the scope of the local host.
Common Object Request Broker Architecture: CORBA is powerful programming language and operating system neutral API for realising distributed systems of objects that is being developed by OMG
conferencing: Computer based realisation of synchronous or asynchronous multiparty communication.
connection-oriented communication: Communication is connection-oriented if identity of each endpoint is established at start of communication, is maintained at each end for presentation at any time, and is not transmitted with each packet of data sent.
context switch: Switching of processor from executing one thread or process to executing another.
cookie: Small item of persistent data stored by a web browser on local filespace of client's host in accordance with <a href="cookie_spec.html">Netscape</a> or RFC 2965 standards.
COPS: Computer Oracle and Password Systems or COPS is a suite of programs that check for security vulnerabilities on UNIX operating systems.
Crosspost: Posting of news article on news service to several different newsgroups.
Cascading Style Sheets: CSS is stylesheet language for HTML and XML documents that controls their layout and formatting.
daemon: Process providing network or operating system services on demand.
datagram: Packet of data.
datagram socket: Socket suitable for datagram communication in a connectionless, unreliable manner where each communication packet must be addressed and may be duplicated, reordered or lost in transit. It is realised by use of the UDP transport protocol.
data link layer: Data link layer is the second layer in the OSI reference model that handles point to point data delivery between two adjacent network devices.
denial-of-service attack: Denial-Of-Service attack is an attack based on flooding a network or host with packets so as to disrupt or seriously impair network performance or that host's performance.
deny-all: Deny-all is a policy for packet filters that drops all packets.
Dynamic Host Configuration Protocol: DHCP is a protocol used to assign IP addresses to hosts without them. It also supplies server and router information.
Dynamic HyperText Markup Language: DHTML denotes the combined use of JavaScript, CSS and the DOM to create animation and interaction by manipulating styles and HTML documents.
Digital Subscriber Line: DSL is standard for high bandwidth communications on existing phone lines that is continuously available. It also accommodates voice on same line.
directory: Hierarchically structured set of associations between a name, an object and attributes of the object.
directory service: Online, directory based, lookup service that supports indexed access via hierarchies to resources; they supply details on people, network services, files etc.
Document Object Model: DOM is a specification allowing all elements of a Web page, including styles, to be manipulated and acted on by programs and scripting languages. Currently the document object model supported by Netscape and IE are slightly different, but the W3C is defining a standard DOM that will be used by both in the future.
domain name: Compound textual name for computers attached to the Internet such as adam.astro.yale.edu. It is interpreted using the domain name system.
Domain Name System: DNS is a hierarchically structured, distributed information system on the Internet whose main function is to allow domain names for Internet hosts to be resolved into the numerically based IP addresses for these hosts used by the Internet's packet routing system.
driver: Software that can control and run other software through its interface. Typical drivers simplify the task of running software through complex interactive interfaces.
Document Type Definition: DTD is a formal description of the allowed elements, attributes and entities in a particular type of document. In SGML in defines the grammar of a particular markup language.
Data Transfer Process: DTP handles communication of data between FTP peers.
Demilitarized Zone: DMZ is a less secure perimeter network containing hosts for public services that is separated from from a local, private network.
Dublin Core: 15 element metadata standard that aims to facilitate discovery of electronic resources.
e-mail: Electronic mail is computer based messaging system modelled on postal mail that sends, receives and stores messages solely within electronic media.
e-mail filter: Software that automatically processes e-mail messages in a user's mailbox on the basis of a set of filtering rules. These rules cause messages to be deleted, saved in special folders, forwarded, or automatically replied to. Filter actions are usually triggered by pattern matching on e-mail message header values.
e-mail gateway: Software that handles the exchange of e-mail messages between different e-mail systems such as Internet e-mail, X.400 or MS-Mail. E-mail gateways translate between message formats, addressing schemes and use of transfer protocols.
e-mail list: Moderatable facility whereby all subscribers receive by e-mail a copy of each article sent to address of e-mail list.
entity: Named object in an XML document. Often a character or character sequence that cannot be easily represented on all platforms, so is referred to by name using an entity reference.
entity reference: Reference to a named object (normally a sequence of characters) in an XML document. The entity reference may be replaced by the referred to object when the document is processed.
ethernet frame: Ethernet frame is an encapsulation of an IP datagram at the data link layer in accordance with the Ethernet standard.
event handler: Piece of program that executes in reaction to an event. When a user clicks on a web form element, a JavaScript program installed for that purpose may execute causing the display to change in some appropriate way.
extranet: Less secure network external to an organisation's secure organisational network that is open to access both from wide area networks and the organisation's internal network.
Fibre Distributed Data Interface: FDDI is standard for data transmission on fibre optic lines up to 200 kms range and with a 100 Mbps capacity.
File Transfer Protocol: FTP is an application level protocol defined in RFC 959 covering the passing of files across the Internet.
finger: TCP based Internet protocol specified in RFC 742 for requesting information about which users are logged into an Internet host or for requesting more detailed information about a particular user.
firewall: Network gateway that filters network traffic to limit access either way only to allowed services. It is often used to protect the security of a LAN from hostile access from a WAN connection such as the Internet.
flame: Starkly critical news article of another's news postings. Breach of netiquette is a common reason for this.
flooding: Flooding is the practice of sending copies of data such as an IP packet along all available network paths.
flow control: Flow quenching mechanism used in reliable communications protocols to regulate the flow of information that lets a process receiving the flow temporarily stop the generating process until the receiving process is able to handle more information.
fork: Act of process creation in Unix by duplication of an existing process.
forwarding: Forwarding is the practice of sending packets from one network to another in accordance with their network addresses in order to deliver them to their destination.
fragment: Fragment is a portion of something such as a TCP segment that lies within something else such as an IP packet.
gateway: Full OS computer sitting on 2 networks that connects them at the application layer level. It can translate between different network protocols on the two networks and can proxy & broker at the application level.
General Packet Radio Services: GPRS is a new nonvoice value added service that allows information to be sent and received across a mobile telephone network. It supplements today's Circuit Switched Data and Short Message Service.
Global System for Mobile Communications: GSM is the main wireless digital technology for cellular phones in the world.
Graphical User Interface: GUI supports windows, menus, icons and pointers. Examples include X Window, MacIntosh user interface and Microsoft Windows.
GUI terminal: End user computing device enabling access to personal computing applications that processes graphics operations locally but requires all other application processing to be done on remote servers.
H.323: H.323 is standard for sending audio and video data across IP networks.
helper application: Separate program invoked by a web browser to provide functionality to render web resources such as video files that the browser cannot handle itself.
hop count: Small counter added to broadcast packets to stop datagrams looping round in networks. Whenever a gateway open to broadcast traffic encounters a broadcast packet, it decrements the hop count by 1 before rebroadcasting the packet on the other side of the gateway. Broadcast packets with a 0 hop count are never passed on.
host: Networked computer offering services to other computers on a network.
hub: Hub is hardware that repeats signals in order to connect multiple network segments together in a physical way.
hyperlink: Hyperlinks link documents together. A user can navigate from one document to another by clicking on the hyperlinks, which are commonly indicated as underlined words.
hypermedia: Multimedia resources linked together in the manner of hypertext.
hypertext: Text that contains links to other documents, such that if words or phrases are selected by the reader another document is retrieved and displayed.
HyperText Markup Language: HTML is a language used to create hypertext documents for use on the World Wide Web.
HyperText Transfer Protocol: HTTP is stateless, network application protocol to handle information transfer in the distributed, collaborative, hypermedia information system called the World Wide Web.
ident: TCP based Internet protocol specified in RFC 1413 for asking a remote host the system name of the user who is behind a TCP connection established between that remote host and the local host.
Interactive Mail Access Protocol: IMAP is an ascii network application layer protocol suitable for interactive and programmed use to access e-mail dynamically from a mailbox server. It is specified in RFC 3501 Its latest version is IMAP version 4. It is more sophisticated than POP, supports concurrent access and is more suitable for use where only selective retrieval of e-mail messages is needed.
information retrieval system: IR systems store text and are geared for fast indexing of stored text by word or string matching. They are used in libraries, in online bibliographies and catalogues and in office automation systems.
Internet Control Message Protocol: ICMP is protocol defined in RFC 792 that is an integral part of IP and is used for reporting errors in the processing of IP datagrams.
Internet: World's largest world wide network of networks or internetwork based on the use of the TCP/IP protocols.
Internet Architecture Board: IAB is small group that oversees IETF and provides leadership on standards and evolution of Internet. It is chartered by RFC 2850.
Internet Corporation for Assigned Names and Numbers: ICANN is non-profit corporation responsible for IP addresses, domain names, protocol parameters and supervises control of root server system of DNS.
Internet Engineering Task Force: IETF is community of network designers, operators, vendors & researchers concerned with evolution and operation of Internet. It works in groups with a charter.
Internet Protocol: IP is network layer protocol defined in RFC 791 for passing packets of data across networks that is used on the Internet.
Internet Protocol address: IP address is 32 bit integer address of Internet host that is often represented in dot form like this 137.195.24.54 where each dot delimited sequence of up to 3 digits represents one byte (0 to 255) of 4 byte address.
Internet Relay Chat: IRC is network application level textual conferencing protocol defined by RFC 1459
Internet Assigned Numbers Authority: IANA is the precursor body to ICANN that was subsumed by it in 1998. It manages the DNS Root Zone, coordinates the global IP and AS number space with Regional Internet registries and acts as the central repository for protocol name and number registries, used in many Internet protocols.
Internet Research Task Force: IRTF promotes research important to evolution of Internet and is composed of focused, long-term, small research groups.
Internet Societal Task Force: ISTF is body that identifies ways in which Internet can be a positive force in social and economic dimensions and aims to describes steps to assure that Internet is for everyone. It does its work through discussion lists, white papers, local educational initiatives and workshops.
Internet Society: ISOC has mission to provide leadership in developing the Internet, charters various Internet bodies - IESG, IAB and IETF and licenses their setting of Internet infrastructure standards.
internetwork: Connection of different networks such as Internet.
Integrated Services Digital Network: ISDN is a set of standards for digital transmission over ordinary telephone copper wire at a variety of higher speeds than over modem connections. It requires adapters at both ends of the transmission.
intranet: Organised provision of Internet services such as the web, e-mail, news etc. on an organisation's secure internal network.
interprocess communication: IPC is communication between processes that are usually but not necessarily on different hosts.
Java DataBase Connectivity: JDBC is Java API for remotely accessing relational databases using SQL
Java Naming and Directory Interface: JNDI is a Java API for writing applications that access naming and directory services.
Java Server Pages: JSP is scripting extension of servlet technology that enables dynamic content authoring at HTML or XML level.
JavaStation: Commercially unsuccessful but historically important network computer developed by Sun Microsystems in 1997.
Java Virtual Machine: JVM is abstract machine for executing compiled version of Java. It can be realised in a variety of ways including by software emulation.
Lightweight Directory Access Protocol: LDAP is simplified version of the X.500 Directory Access Protocol defined in RFC 1777
Local Area Network: LAN is privately owned network housed within single building or campus of few kms in size that is often a broadcast network in a bus, ring or star configuration.
mailbox: File or store recording the e-mail messages sent to an e-mail recipient.
mainframe: Large, powerful and expensive computer usually with a highly reliable, proprietary operating system providing traditional computing services such as batch processing in a centralised manner
markup: Characters or other symbols inserted in a text to indicate how it should be displayed or to describe the document's logical structure. Markup indicators are sometimes called "tags."
metadata: Data describing attributes of information resources.
metalanguage: Language used to define or talk about other languages.
Metropolitan Area Network: MAN is private or public city sized LAN that supports data, voice and even video. It often lacks switching elements & may have a dual bus structure.
middleware: Software components in a distributed system that form a middle tier of processing between client applications interfacing with users and backend components such as databases or application servers.
mirror: Server replicating service provided by a server elsewhere. Mirrors can relieve congestion at a site by splitting a server's load or offer a faster fetch of information from a local replica of the service than from the remote origin site.
Multipurpose Internet Mail Extension: MIME is two part Internet classification scheme for media types of online resources such as audio, video and text files
multicasting: Sending messages from one host to multiple hosts.
multiprocessing: Process based multiprogramming.
multiprogramming: Form of program execution in which several programs are stored in main memory at same time and each program is executed as separate thread or process with execution chances on the processor being shared among them.
multithreading: Thread based multiprogramming.
name resolution: Process of using a naming service to look up what a name refers to.
Namespace: Mechanism enabling XML authors to use element names defined by others by using prefixes associated with a unique URI.
naming service: Network service supporting a naming scheme in which network applications are able to look up names and update the bindings of names.
netcasting: Term for push technology application on the Internet.
network address class: Network address class is one of 5 ranges of IPv4 network addresses labelled A, B, C, D and E that depends on whether the 4 most significant bits are less than 128, between 128 and up to 192, between 192 and up to 224, between 224 and up to 240 or 240 and above.
Network Computer: NC is end user computing vehicle supporting GUI and application processing but no persistent local storage of data.
network reference model: Layered model for understanding how a computing network functions in terms of the protocols it uses. OSI networks have a 7 layer reference model and TCP/IP networks have a 5 layer reference model.
net PC: PC without a floppy drive or with the floppy drive blocked.
network architecture: Model of a network as a set of network layers with their associated protocols.
Network News Transfer Protocol: NNTP is ascii protocol for interactive and programmed use to support distribution, inquiry, retrieval & posting of news articles. It is defined in RFC 977
network layer: Layer of TCP/IP network architecture that provides connections and routing of packets in network including handling and decoding of packet addresses and maintaining routing data for proper response to load.
network news: Forum based electronic messaging medium for asynchronous discussion whose largest realisation on the Internet is called USENET News and is mostly realised by NNTP.
newbie: Newcomer to an online discussion medium such as Internet Relay Chat or USENET News. Usually used as derogatory term for newcomers who display characteristic ignorance of conventional good practice in their contributions.
newsfeed: Major source of news articles for a news server.
newsgroup: Named forum for online discussion in online news service.
New Technology: NT is operating system designed and developed in the early 1990s originally as a file and print server for PCs and for single user workstations by Microsoft. It has evolved into a multi-user, general purpose, modern operating system for a wide range of computing platforms. Its current incarnation is called Windows2000, XP or NT5.
Network Virtual Terminal: NVT is virtual device providing standard, network-wide, intermediate representations of canonical terminals. It is a key abstraction used by Telnet.
object oriented database: Database management system that supports the modelling, storage and retrieval of data as objects in the sense of object oriented programming languages. It is suitable for handling storing complex, hierarchies of objects. See the Object-Oriented Database System Manifesto for details.
Open DataBase Connectivity: ODBC is standard API for remotely accessing relational databases based around the SQL call-level interface
Online Public Access Catalogue: OPAC is online catalogue open to public usually of a library's books. Typical systems are often based on the Z39.50 protocol.
out-of-band: Type of communication on a communications medium that is sent immediately and directly and isn't held up by any non-out-of-band messages already in the pipeline.
packet: Small amount of data with a header detailing how to handle its contents that is used by network protocols as its standard unit of communication.
packet-switched: Type of network infrastructure that mixes together packets for different destinations and routes them according to their address in the style of postal mail. Opposite of circuit-switched.
page: Fixed size block of memory used for handling data in chunks.
Personal Computer: PC is computer supporting GUI, local application processing, persistent local storage of data and a single user operating system. Examples include Windows PCs and MacIntoshes.
physical layer: Layer of TCP/IP network architecture that handles (electro)mechanical details of bit transmission.
ping: Network utility providing a low interference way to see if a remote host is alive. It can also be used to time how long communication with a remote host takes.
plug-in: Code module that can be installed in a web browser to extend its functionality in an integrated way. Popular web browsers support plug-ins for playing sound files, movies or streaming media, for presenting documents in various formats, and for supporting multimedia productions, virtual environments or interactive animations.
point to point network: Type of network in which hosts are connected by multiple connections and packets usually have to be routed via intermediate hosts to reach their destination.
port: Address used for an Internet transport protocol communication end point. It has a value between 1 and 65535 and a type of either TCP or UDP. Port numbers between 1 and 1023 are usually reserved for exclusive use by privileged users and typically for well known services.
Point to Point Protocol: PPP is a data link layer protocol often used to connect PCs via modems to remote sites.
Post Office Protocol: POP is network application protocol defined in RFC 1225 to access mail dynamically from a mailbox server
pre-emption: Interruption of execution of process or thread during time-sharing execution before its time-slice has expired in order to context switch to another process or thread which has been given execution priority over it.
prioritised scheduling: Scheme for scheduling the execution of runnable processes or threads that favours those with a higher priority.
process: Executing or executable task on a computer with its attached resources.
protocol: Rules and conventions used in interprocess communication governing the formats of data exchanged, the structuring of the dialogue and the handling of exceptional circumstances.
protocol stack: List of network protocols, one per network layer.
proxy: Proxy is a surrogate for a service provider that emulates the provision of its services. Proxies are used as intermediaries in network applications between clients and servers in order to speed up, replicate, monitor or safeguard service provision.
peer to peer model: Model of distributed computing based upon two or more distributed processes that both consume and provide services to each other and are at times active and at other times passive.
publish and subscribe model: Model of distributed computing based upon a service provider or publisher generating a stream of data along a channel and a service consumer or subscriber receiving the stream so long as it subscribes to service.
push technology: Technology based on service providers providing enduring (information) services to consumers at the initiative of the provider. It is based on the publish and subscribe model not the client server model.
quoted printable: Character encoding scheme in which encoded characters are represented by three characters - "=" followed by two hexadecimal digits representing the byte value. It is intended for encodings of text where the vast majority of the text is unencoded and only a small proportion of it such as Ascii values over 127 is encoded.
Remote Method Invocation: RMI is powerful Java API for invoking methods on remote Java objects that provides a general means for realising distributed systems of objects.
RPC is procedure P that a caller process C gets a server process S to execute as if C had executed P in C's own address space. RFC 1831 specifies an "Open Network Computing" version of RPC.
repeater: Device connecting two physical layer components on networks that aims to regenerates attenuated and distorted signals to permit signal to be sent further.
Request For Comment: RFC is authoritative series of online documents published on the Internet http://www.ietf.org/rfc/ giving details of standards, proposed standards or other information relevant to use of Internet. RFC authoring is controlled by the RFC editor who is appointed by the IESG and is primarily for IETF working groups.
Resource Description Framework: RDF is XML standard for metadata developed in 1999.
resource discovery: Term used for issues concerned with finding information resources on electronic information media such as the WWW, USENET news archives and FTP sites.
router: Device connecting two networks of same type at the network layer level that processes packet headers, picks route for packets and is an addressable node itself.
rwho: Network utility that produces and consumes status information on local hosts. It is exercised by the rwho command which shows who is logged in on local machines and the ruptime command which shows how long local machines have been up.
schema: Similar to a DTD, a schema describes the allowed elements in a document. Schemas are written in XML, and have additional functionality beyond DTDs, through the use of complex type definitions.
scripting language: Interpreted programming language which is designed for rapid programming of lightweight tasks. For convenience it is usually weakly typed.
searching: Goal driven rather than exploratory form of resource discovery where the seeker has a specific informational objective. It can be contrasted with browsing.
selector: CSS way of identifying which style declarations are associated with which elements of a document. Simple selectors apply to a named HTML element, such as <h3> or <p>.
Serial Line Internet Protocol: SLIP is a link layer encapsulation protocol for sending IP packets along serial lines such as modems
server: Hardware or software providing computing service usually as part of client server model of computing
server push: Term for push technology application on the web in which the server regularly or irregularly sends data to a waiting web client which uses it to update its display.
servlet: Java API extending functionality of servers using request reply protocols. Servlets are most often used by web servers to interface web clients to programs in a similar manner to CGI.
ShockWave: Plug-in made by Macromedia for viewing animations and multimedia.
Short Message Service: SMS is text messaging service used to send and receive text messages from mobile telephones.
Simple Mail Transfer Protocol: SMTP is Ascii protocol defined in RFC 2821 that is suitable for interactive and programmed use for sending mail messages to Internet mail message transfer agents.
Simple Network Management Protocol: SNMP is protocol for managing network elements described in RFC 1157
socket: Communication endpoint using the TCP or UDP transport protocols usually for establishing point to point communications between processes on the Internet.
spam: Unsolicited and unwanted e-mail or the action of flooding someone's mailbox.
stream socket: Socket suitable for byte stream communication in a connection-oriented manner, that is reliable, order preserving and flow controlled. It supports out of band communication and is realised by use of the TCP transport protocol.
stylesheet: Instructions concerning a document's appearance. CSS and XSL are both stylesheet languages for the World Wide Web.
Standard General Markup Language: SGML is a standard for creating markup languages. HTML is a specific markup language based on SGML.
tag: Symbols used to define HTML and XML elements. An element, such as a heading, is normally delimited by a start tag, such as <H1> and an end tag, such as </H1>.
telnet: Remote login facility of Internet described in RFC 854
thin client: End user computing vehicle enabling access to personal computing applications but having less than the full range of PC capabilities to keep its cost and size down. Examples include GUI terminals such as Winterms or X terminals and Network Computers such as Java Stations.
thread: Identifiable computation unit with state executing a task
time-sharing: Multiprogramming where threads or processes are run for a time-slice and then context switched to allow other runnable threads or processes a chance to execute.
time-slice: Quota of time allocated to a process or thread to be executed before context switching to another runnable process or thread of equal priority during time-sharing multiprogramming.
time to live: TTL is quota of time left to a cached resource during which it is deemed to be a fresh copy of its original.
traceroute: Network utility that prints route that packets take to a remote network host.
transport layer: Level of network reference model concerned with handling low level access to network and transfer of messages among nodes including partitioning messages, keeping packet order, flow control & address generation
Transmission Control Protocol: TCP is a reliable, connection-oriented transport protocol defined in RFC 793 for IP networks that supports flow control and out-of-band communication.
TCP/IP Network Reference Model: Network reference model for TCP/IP networks that views it as having 5 layers - application, transport, network, data link and physical.
Uniform Resource Characteristics: Metadata specification for a URI.
Uniform Resource Identifier: URI is an identifier for an online or offline abstract/physical resource composed of a compact sequence of characters (alphanumerics & a few symbols) which is either a URL or URN. It is specified in RFC 3986
Uniform Resource Locator: URL represents location and access method of Internet resource with the general form <scheme>:<scheme-specific-part>. It is defined by RFC 1738
Uniform Resource Name: URN is a designation in a extensible, scalable name space for web resources. It offers a globally unique, location independent name that continues to have meaning even after the lifetime of resource. URNs are intended to be resoluble to resources, URLs or URCs by a network accessible service that has yet to be established.
unicode: Universal character set standard that uses 16 bits to encode characters, allowing far more characters to be encoded than ASCII (which uses 8 bits).
Unix: Widely used modern network operating system suitable for computers from laptops up to mainframes and supercomputers.
USENET News: Internet based set of discussion forums organised in hierarchical structure of over 10,000 newsgroups and largely implemented using the NNTP protocol.
User Datagram Protocol: UDP is a simple transport level protocol defined in RFC 768 for nonreliably passing datagrams across the Internet.
Voice over IP: Set of facilities for arranging the delivery of voice data over IP networks. This usually means sending voice as discrete packets of digital data over the Internet rather than as analogue electrical signals in the circuit-switched manner of traditional telecommunications networks. It saves on phone bills but risks audio quality if transient network congestion delays voice data packets.
Virtual Reality Modeling Language: VRML is a high level modelling language for virtual environments defined by the Web3D consortium
Warez: Warez is pirated material such as copyrighted works traded in violation of copyright law.
Warwick Framework: Container architecture for handling metadata.
web: Short for World Wide Web.
webcasting: Term for push technology application on the web.
whiteboard: Computer based collaborative tool accessible from multiple networked computers consisting of a drawing space upon which users may mutually communicate graphics and interactive drawings.
white pages: Directory service of people's names, addresses and locations.
Wireless Application Protocol: WAP is a protocol for a mobile phone to talk to a server installed in a mobile phone network. A WAP gateway enables a mobile phone to communicate with standard network computing services.
Wide Area Network: WAN is large scale network covering a country or large geographic region. It usually consists of transmission lines and switches, has irregular topology and is often packet switched.
workstation: Powerful end user computing vehicle running sophisticated operating system such as UNIX or NT.
World Wide Web: WWW is distributed hypermedia information system running on the Internet that refers to resources using Uniform Resource Locators or URLs, moves resources using the HyperText Transfer Protocol or HTTP and uses a scripting language called HyperText Markup Language or HTML to support hyperlinking of these resources
X: Network application protocol defined by X Consortium to provide a network transparent graphical user interface primarily for the UNIX operating system.
X-500: Powerful directory service protocol defined by ISO 9594 and explained in RFC 1684
eXtensible HyperText Markup Language: XHTML is reformulation of HTML 4.0 in XML allowing improved interoperability.
eXtensible Markup Language: XML is simplified form of SGML developed by W3 consortium that provides standard syntax for grammatically validatable document markup and data exchange. It is intended to replace HTML as markup language for World Wide Web.
eXtensible Stylesheet Language: XSL is language for creating a stylesheet specifying how an XML document should be presented to the user. It also contains rich mechanisms for translating XML documents from one form to another and to HTML.
yellow pages: Network lookup service for system data based on distributed database of maps whose records are looked up by their keys.
zombie: Unix process, which has terminated, and given up all its resources, but has not yet performed its final act of notifying its parent of its demise. Zombies continue to occupy slots in the Unix process table.
zone transfer: AXFR is a DNS query request explained in RFC 1034 asking a DNS server for all resource records from a zone. The primary purpose of a zone transfer is to allow a secondary DNS server for a domain zone to refresh its knowledge of the domain from the primary DNS server. Many authoritative DNS servers refuse to honour zone transfer requests from anything other than secondary DNS servers.
Z39.50: Standard protocol for accessing information retrieval systems. It is used with online public access catalogues like library catalogues.