Glossary
As networking terminology changes, so do glossaries. This glossary doesn’t claim to define everything; nothing can. However, web glossaries (such as www.webopedia.com) offer frequently updated definitions of current computer and networking terms.
A hardware component in a computer used to support attached devices.
Identifiers placed in packets (protocol data units, or PDUs) to identify the source and destination nodes for the PDU.
American Standard Code for Information Exchange (ASCII)
A convention for using the binary numbers (0 and 1) to represent letters, numerals, and special notations, such as ESC.
application programming interface (API)
A software facility that permits a user’s application to communicate with another piece of software. Also known as function or library calls.
The end user’s software, such as email, word processors, video players, audio players, and photo editors.
ARPA (Advanced Research Projects Agency)
A U.S. Department of Defense establishment that is responsible for creating the Internet.
A network link that provides different capacity (in bits per second, or bps) in each direction (up link and down link).
Systems, such as networks, that don’t use a common clock for synchronizing their signals between network nodes.
Asynchronous Transfer Mode (ATM)
An international standard describing how to create small packets and route them through a wide area network (WAN).
A collection of Transmission Control Protocol/Internet Protocol (TCP/IP)-based networks that a company or organization administers.
A term to describe tested and proven behaviors leading to effective operating procedures.
The capacity of a network or communications channel based on how many bits per second are sent across the channel.
A wireless network standard designed to connect low capacity nodes.
An Internet route discovery protocol as well as a tool for establishing peering relationships between Internet service providers (ISPs) and Internet Exchange Points (IXPs).
(a). A local area network (LAN) device that connects network nodes. (b). A machine acting as a central relay point on a star network topology using MAC addresses.
A high-capacity network (more bits per second) available from telephone, cable TV, and satellite companies.
An arrangement in which one node in a network sends data to all other nodes.
A network topology consisting on a serial link connecting all nodes.
A string of seven or eight bits.
Used in two contexts: (1) In wireless networks, a cell is a geographical area covered by a specific radio antenna; (2) In data networks, it’s a small packet (53 bytes) that Asynchronous Transfer Mode (ATM) systems use.
The overall hardware controller of a computer.
A method for detecting corrupted data.
Data that has been encrypted.
Classless Inter-Domain Routing (CIDR)
A method of altering the IP address format to permit the use of additional addresses.
Data that has not been encrypted.
A network in which a central computer called a server performs a variety of services to the attached computers, which are called clients. The servers play a lead role in these operations.
A set of rules by which computers must communicate with each other.
A connection through a physical medium of two or more computers.
A discrete unit of data (also called a packet).
DHCP (Dynamic Host Configuration Protocol)
An Internet protocol used to dynamically assign IP addresses to network nodes.
A method using pubic key procedures for proving an identity.
A high-capacity link operated by local telephone companies.
direct sequence spread spectrum (DSSS)
A wireless technology in which sender and receiver privately communicate with an agreed-upon code to cipher and decipher the traffic.
A process in which data is placed on more than one disk.
DNS Security Protocol (DNSSEC)
An Internet protocol that guards against receiving invalid DNS information from servers.
Internet standards and procedures for (a) registering reserved Internet names and (b) correlating an IP address with the name.
A special term that describes communications lines that use digital signaling techniques and a specific convention (developed by AT&T) for encoding the signals.
Placing the contents of one frame or packet in the data field of another frame or packet.
A local area network (LAN) standard published by the Institute of Electronic and Electrical Engineers (IEEE).
A private computer network.
A hardware setup where components are duplexed. There are two of each device.
A security feature on a network that filters unwanted traffic from entering a network or a computer.
A high-speed interface published by the Institute of Electronic and Electrical Engineers.
A special type of software that is rarely (if ever) changed.
A unit of data into which packets or datagrams are encapsulated. The most common example is the Ethernet frame, which contains a packet/datagram in its user information field.
frequency hopping spread spectrum (FHSS)
A wireless technology in which the sender and receiver communicate with each other by frequently changing (hopping) frequencies.
A widely used Internet standard that defines procedures for exchanging files between computers.
A software command invoking the execution of other software. Sometimes called library calls.
On a communications link, adding, combining, separating, and dropping payloads from different users.
An application that a community of users shares.
Clustering multiple computers for backup purposes.
A general (and vague) term describing a hardware device that is attached to a network. Some vendors use the word to describe a computer; others use the word to describe a server.
Replacing disk drives while the system is up and running.
A machine acting as a central relay point on a star network topology.
A network supporting both wire-based and wireless connections.
A reference to another part of a document, a different document, or a different site on the Internet.
Text that allows users to link the text to other images or other websites.
Hypertext Markup Language (HTML)
Code that defines the content and look of web documents.
Hypertext Transfer Protocol (HTTP)
An Internet standard for sending and receiving linked hypertext files.
IMAP4 (Internet Message Access Protocol, version 4)
A widely used Internet email standard.
The communications interfaces(s) between network providers’ equipment within the same network.
The public computer network.
Internet Packet Exchange (IPX)
A proprietary protocol developed by Novell.
Connecting network nodes together so they can communicate and exchange data with each other.
A private computer network.
A set of Internet standards that define means to protect the integrity of user data in an Internet Protocol (IP) packet.
ISP (Internet service provider)
A commercial organization that provides access to the Internet, such as AOL.
An organization that controls Internet routing nodes, which form the backbone of the Internet.
The basic, key part of an operating system (OS).
A software application of such consequence that it affects the operations of an organization or a network.
Layer 2 Tunneling Protocol (L2TP)
An Internet standard to extend PPP capabilities across networks.
Those communications links that are rented from communications carriers, such as AT&T.
A communications channel, such as a copper wire. This is not to be confused with a web link, which is a form of an address.
A network that’s designed for connecting devices located close together. Usually a private network.
Network actions that permit the transfer of data between computers, usually the execution of software routines.
Conventions in software for sending and receiving traffic on the physical media.
A nickname for software and or packets that can do harm to a user’s computer system.
The links (channels) in a communications network.
Layer 2 of a local area network (LAN).
MIB (Management Information Base)
A database containing information about managed resources in a network, such as Ethernet connections. Usually accessed by the Simple Network Management Protocol (SNMP).
MIME (Multipurpose Internet Mail Extensions)
An Internet standard that defines and identifies different types of files, such as video, text, and graphics.
From modulator/demodulator, a device that converts binary, digital signals into analog signals at the sending site and performs a reverse operation at the receiving site.
The central circuit board in a computer.
The sending of traffic from one network node to three or more nodes.
Sharing a communications link with more than one user.
Multiprotocol Label Switching (MPLS)
A wide area technology using labels (instead of addresses) to identify and forward traffic.
Network Address Translation (NAT)
An Internet protocol that allows private IP addresses to be reused by translating them into fewer public IP addresses.
The logical and physical structure and behavior of a computer network.
The hardware inside a computer that’s attached to a physical port, such as a USB.
See network card.
Used in two contexts: (1) Operating a device attached to a network, or (2) Learning how to build and operate a network.
network-network interface (NNI)
The communications interface(s) between network providers’ equipment between networks.
A generic term to denote a machine, such as a computer or router, that is attached to a network.
Open Systems Interconnection model (OSI)
A widely used representation of the major functions of a computer network, and how these functions are related to each other.
The central set of software on a computer, which directs the actions of all other components.
A self-contained piece of data, including a header with destination and source addresses. Also called a datagram.
A process in which software is swapped into and out of computer memory.
The part of a packet or frame containing user data.
An arrangement between Internet ISPs and Internet Exchange Points (IXPs) to allow the transport of traffic between these parties.
A network in which all nodes play equal roles in the interactions.
One or more communications lines in a network that are linked to each through switches or other cross-connect devices. The links may be shared with many users, but each user is preallocated access to the end-to-end facility and guaranteed a certain amount of bandwidth. Thus, the service mimics a leased line.
The hardware and physical channels of a network.
The conventions for using wiring, plugs, and antenna, as well as the physical signals on these media.
plain old telephone service (POTS)
A nickname for conventional telephone service.
An Internet standard for authentication and negotiating services between two network devices.
Point-to-Point Tunneling Protocol (PPTP)
An extension to Point-to-Point Protocol (PPP), used to transmit PPP packets through networks.
POP3 (Post Office Protocol, version 3)
A widely used Internet email standard.
Used in two contexts: (1) A physical interface on a computer, and (2) An Internet identifier associated with a specific software process, such as email or domain names.
The use of parts of the IP address to provide address aggregation.
An encryption/decryption key, known only to its creator.
An agreement on how to exchange data between two or more devices; usually documented in a standard.
A computer that translates and converts protocols to allow two or more computers that use different procedures to communicate with each other.
A generic term to describe any self-contained unit of data, such as a packet, a frame, a datagram, or a cell.
An encryption/decryption key known to the public.
The measurement and provision of a certain level of service (such as response time and throughput) by a network provider to a user.
RAID (redundant arrays of inexpensive disks)
A method of providing backup for data and software.
Capturing data, modifying or replicating it, and resending it to the legitimate receiver.
A somewhat inaccurate term to describe a high-capacity link between a network provider and a residence, or an office.
The entries in a Domain Name System (DNS) database. The most common RR is the correlation of a domain name to an Internet Protocol (IP) address.
A network topology that forms a concentric link between nodes.
The operation by a router in which possible routes to a destination are chosen or not chosen.
A machine acting as a central relay point on a network.
A security login protocol found on UNIX and Linux operating systems.
Secure Socket Tunneling Protocol (SSTP)
An extension to PPP, which allows remote access data to pass through a firewall.
An Internet protocol used for authentication.
A means to establish secure communications between two parties.
A general term to describe either software or hardware that provides support services to user computers, such as email and print operations.
server operating systems (SOS)
Software that operates in a server. Also called a network operating system (NOS).
SMTP (Simple Mail Transport Protocol)
A widely used Internet email standard.
SNMP (Simple Network Management Protocol)
An Internet standard that defines the structure and use of network management messages.
Used in two contexts: (1) A physical interface inside a computer, or (2) an Internet identifier, consisting of an Internet port number, an IP address, and a protocol ID.
SONET (Synchronous Optical Network)
An advanced digital, optical transport technology, usually implemented inside core networks.
A physical network arrangement in which a central connection point, such as a hub or router, acts as a relay unit (a switch) between the attached computers.
A part of a full network, distinguished by separating the physical network into logical subnets by configuring nodes with various IP addresses.
A machine acting as a central relay point on a star network topology.
Systems, such as networks, that use a common clock for synchronizing their signals between network nodes.
A general term to describe a range of digital communications links offered by long-distance companies and local telephone companies.
TCP/IP (Transmission Control Protocol/Internet Protocol)
Used in two contexts: (1) A general term to describe a range of Internet standards and protocols, and (2) TCP: A Layer 4 protocol that provides end-to-end traffic integrity; IP: A Layer 3 protocol used to forward packets containing IP addresses.
Sharing a communications link with multiple users by taking turns using the link.
The physical shape of a network, such as a ring or star.
The configuration and tuning of hardware and software to manage (engineer) traffic.
A hidden piece of software, such as a virus, that is triggered by an event, such as a date.
A term used by telephone personnel to describe a communications link or channel.
An Internet Layer 4 protocol that’s used in place of Transmission Control Protocol (TCP) if users don’t need traffic accountability or can’t tolerate the overhead of TCP.
uniform resource locator (URL)
An identifier that correlates a hyperlink to a domain name.
A standard physical interface on computers.
The communications interface(s) between a user’s equipment and a network provider’s equipment.
Identifiers placed in Asynchronous Transfer Mode (ATM) protocol data units (PDUs) to identify the payload (user data, control data).
A public network designed in such a way (with privacy and security safeguards) that it appears to the users as a private network.
A piece of code that damages software or files.
A set of Internet standards that define procedures for transporting digital voice traffic in Internet Protocol (IP) packets.
A nickname for roaming an area and tapping into someone’s wireless network.
A network connecting devices that are not located close together. A WAN is often implemented as a public network, such as the Internet.
A wireless networking standard designed to interconnect low to high capacity nodes.
A device used to connect wireless nodes and relay traffic among these nodes.
Wireless Equivalent Privacy (WEP)
A security protocol used in wireless networks, typically those employing Wi-Fi standards.
Wireless Protected Access (WPA)
A security protocol used in wireless networks, typically those employing Wi-Fi standards.
A set of computers that share resources among themselves.