Network Glossary
10Base2 - A physical layer communications specification for 10Mbps, .........baseband data transmission over a coaxial cable (Thinnet) with a maximum cable segment length of 185 meters.
10Base5 - A physical layer communications specification for 10Mbps, .........baseband data transmission over a coaxial cable (Thicknet) with a maximum cable segment length of 500 meters.
10BaseF - A physical layer communications specification for 10Mbps, baseband data transmission over a fiber-optic cable.
10BaseT - A physical layer communications specification for 10Mbps, baseband data transmission over a twisted-pair copper wire.
100BaseT - 100BaseT Ethernet is a standard for transmitting Ethernet signals over Twisted Pair Wiring at a Speed of 100 Million Bits Per Second.
1000Base-T - A recent LAN standard for implementing 1000 Mbps Ethernet on Category 5e cable.
802.11 - The set of IEEE Working Groups and subsequent standards for the definition of wireless LAN protocols.
Asynchronous - Transmission by individual bytes, not related to specific timing on the transmitting end.
Autosensing - Network adapters that support both traditional and Fast Ethernet -- so-called 10/100 adapters -- choose the speed at which they run through a procedure called autosensing. Autosensing involves probing the capability of the network using low-level signalling techniques to select compatible Ethernet speeds.
Bandwidth - The amount of information or data that can be sent through a given communications circuit.
Backbone cable - Cable used to connect your communication closets or buildings.
Birds nest - Bundle of tangled cable, often accompanied by a frustrated data communications engineer.
BNC - Bayonet Nut Connector. A connector used on coaxial cables such as 10Base2 Ethernet.
Broadband - A transmission medium capable of supporting a wide range of frequencies. It can carry multiple signals by dividing the total capacity of the medium into multiple, independent bandwidth channels, where each channel operates only on a specific range of frequencies.
Broadcast - A special type of multicast packet which all nodes on the network are always willing to receive.
Broadcast storm - An incorrect packet broadcast onto a network that causes multiple hosts to respond all at once, typically with equally incorrect packets which causes the storm to grow exponentially in severity.
Category 5e cable - Most common type of cable used today. Can support up to Gigabit Ethernet.
Category 6 cables - A high quality twisted-pair copper cable specified to a frequency of 250 MHz. The only cables to provide a better signal quality are Category 7 (not yet widely available) and fibre optics. Category 6 has larger copper conductors than Category 5e, but uses the same connectors.
Collision - When more than one computer or other device try to send data over the network at the same time, the Packets may collide and interfere with each other. Ethernet standards are designed to detect such collisions. When they happen, each computer waits a random number of milliseconds and then tries again. The random element avoids strings of successive collisions. Collisions rarely become a problem unless a network is overloaded with traffic.
Communication closet - Central point for cabling and network hardware.
Connection-oriented - The data communication method in which communication proceeds through three well-defined phases: connection establishment, data transfer, connection release. TCP is a connection-oriented protocol.
Connectionless - The data communication method in which communication occurs between hosts with no previous set-up. Packets between two hosts may take different routes, as each is independent of the other.
Cross-over Cable - A cable that crosses the transmit and receive pins so that two devices can communicate directly.
EMI - Electro Magnetic Interference. Outside interference that can disrupt transmission in a copper cable.
Ethernet - A 10-Mb/s standard for LANs, initially developed by Xerox, and later refined by Digital, Intel and Xerox (DIX). All hosts are connected to a coaxial cable where they contend for network access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD) paradigm.
Fast Ethernet - 100-Mb/s standard for LANs.
Fibre Distributed Data Interface (FDDI) - A 100Mb/s LAN standard. The underlying medium is fibre optics, and the topology is a dual-attached, counter- rotating token ring.
Fibre Optic Cable. This is the solution to the Backbone, and it is also, quite literally, a tunnel of light. Fibre Optic Cable is formed of a very fine strand of very pure glass. Signals are transmitted as pulses of light rather than as electrical current. There has to be a device at the end of the cable that translates these signals into the electrical current used by computers. However, the higher level structure of digital data is identical. It is still Bits (now represented by light pulses) strung together to form bytes, characters, data Packets, headers, etc. Fibre provides higher quality data transmission over longer distances with less chance of interference than copper wire.
FTP - Foil Twisted Pair. Recommended for Category 5e and Category 6 cable in a noisy (EMI) environment.
Full-Duplex - A physical medium in which data can .........travel in both directions at the same time.
Gbit/s - Gigabits (thousand million - or strictly 2 to the power 30 - bits) per second.
Gigabit Ethernet - supports a maximum data rate of 1000 Mbps. At one time, it was believed that these speeds required fibre optic or copper cabling, but Gigabit Ethernet has now successfully been implemented on CAT5e and 6 cable.
The migration from 100 Mbps Fast Ethernet to Gigabit will likely not be as smooth or rapid as was the migration from traditional Ethernet to Fast. Much more legacy Ethernet technology (both 10 and 100 Mbps varieties) exists now than it did even five years ago. Today, Gigabit can only be found mainly in research institutions. A decrease in cost, increase in demand, and improvements in other aspects of LAN technology will be required to drive the adoption of Gigabit Ethernet.
Half-Duplex - A physical medium in which data .........travels in one direction.
Hub - A wiring connection device which retransmits signals received from one device to all other devices connected to the hub.
Horizontal Cable - The portion of a cable system that extends from the wall jack to the device.
IEEE - Institute of Electrical and Electronics Engineers
International Organisation for Standardisation (ISO) - A voluntary, non-treaty organisation founded in 1946 which is responsible for creating international standards in many areas, including computers and communications. Its members are the national standards organisations of the 89 member countries, including ANSI for the U.S.
LAN Local Area Network - A data network intended to serve an area of only a few square kilometres or less. Because the network is known to cover only a small area, optimisations can be made in the network signal protocols that permit data rates up to 1000Mb/s.
MAC address - The hardware address of a device connected to a shared media.
Mbit/s - Megabits - million (or strictly 2 to the power 20) bits per second. Transmission speed of network devices.
MT-RJ - A small form factor, dual fibre connector.
Multi-Mode Fibre - Most common type of fibre cable used in LANs up to 2,000m.
Network - A computer network is a data communications system, which interconnects computer systems at various different sites. A network may be composed of any combination of LANs or WANs.
Packet - The unit of data sent across a network. "Packet" a generic term used to describe unit of data at all levels of the protocol stack, but it is most correctly used to describe application data units.
Patch Cable - A short length of network cable used to connect two devices together.
Patch Panel - A device where data cables are terminated.
Physical Layer - The OSI layer that provides the means to activate and use physical connections for bit transmission. In plain terms, the Physical Layer provides the procedures for transferring a single bit across a Physical Media.
Physical Media - Any means in the physical world for transferring signals between systems.
Point Of Presence (POP) - A site where there exists a collection of telecommunications equipment, usually digital leased lines and multi-protocol routers.
Power sum - A mathematical addition of noise from multiple disturbers. Applied to NEXT and ELFEXT requirements.
Propagation delay - The amount of time it takes a signal to travel through a cable or system.
Propagation delay skew - The difference in propagation delay between the slowest and fastest pairs in a cable or system.
Protocol - A formal description of message formats and the rules two computers must follow to exchange those messages. Protocols can describe low-level details of machine-to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level exchanges between allocation programs (e.g., the way in which two programs transfer a file across the Internet).
RJ-11 - The most common type of telephone jack.
RJ-45 - The most common type of computer jack.
Return loss - A measure of the signal reflected back toward the transmitter as a result of impedance variations in the cabling system.
Riser - A vertical shaft or conduit used to route cables between floors.
Router - A device, which forwards traffic between networks. The forwarding decision is based on network layer information and routing tables, often constructed by routing protocols.
Route - The path that network traffic takes from its source to its destination. Also, a possible path from a given host to another host or destination.
SC connector - A duplex optical fibre connector. The standard connector for optical fiber per the 568-cabling standard.
Single-Mode fibre - Normally used for running Gigabit Ethernet over long distances.
ST connector - A bayonet style optical fibre connector.
Subnet - A portion of a network, which may be a physically independent network segment, which shares a network address with other portions of the network and is distinguished by a subnet number. A subnet is to a network what a network is to an Internet.
Switch - A small device that joins multiple computers together at a low-level network protocol layer. Technically, switches operate at layer two (Data Link Layer) of the OSI model.
Switches look nearly identical to hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub. Unlike hubs, switches are capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately. By delivering messages only to the connected device that it was intended for, switches conserve network bandwidth and offer generally better performance than hubs.
Synchronous - Data communications in which transmissions are sent at a fixed rate, with the sending and receiving devices synchronised.
TCP/IP Protocol Suite - Transmission Control Protocol over Internet Protocol. This is a common shorthand which refers to the suite of transport and application protocols which runs over IP.
Thick-wire Ethernet - Thick-wire Ethernet is a standard for transmitting Ethernet signals over Coaxial Cable at 10 Mega-Bits per Second. Although Thick-wire was once used as the primary network connection for small numbers of computers, it's primary use through the late 1980's and early 1990's has been as a backbone medium. This function has largely been taken over by Fibre Optic Cable. The basic difference between Thick-wire and Thin wire is the thickness of the conductor in the wire.
Thin-wire Ethernet - Thin-wire Ethernet is a standard for transmitting Ethernet signals over Coaxial Cable at 10 Mega-Bits per Second. In the 1980's Thin-wire was probably the predominant networking medium for businesses or campuses. Twisted Pair Wiring became dominant in the 1990's.
T568A and B - The two standard wiring patterns for 8-position modular jacks.
Token ring - A token ring is a type of LAN with nodes wired into a ring. Each node constantly passes a control message (token) on to the next; whichever node has the token can send a message. Often, "Token Ring" is used to refer to the IEEE 802.5 token ring standard, which is the most common type of token ring.
Topology - A network topology shows the computers and the links between them. A network layer must stay abreast of the current network topology to be able to route packets to their final destination.
Transceiver - Transmitter-receiver. The physical device that connects a host interface to a local area network, such as Ethernet. Ethernet transceivers contain electronics that apply signals to the cable and sense collisions.
Transmission Control Protocol (TCP) - An Internet Standard transport layer protocol. It is connection-oriented and stream-oriented.
Tunnel Rat - Smallest data communications engineer in an organisation. Often volunteered for work in lofts and ducts.
Urban legend - A story, which may have started with a grain of truth, which has been embroidered and retold until it has passed into the realm of myth. It is an interesting phenomenon that these stories get spread so far, so fast and so often. Urban legends never die; they just end up in the engineer's mess room!
UTP - Unshielded twisted pair. Most common type of Category 5e and Category 6 cable.
WAN - Spans a large geographic area, such as a county, region or country. WANs often connect multiple smaller networks, such as LANs. The most popular WAN in the world today is the Internet.
Wireless Application Protocol (WAP) - A stack of protocols, akin to the OSI model or the TCP/IP stack, to implement the layers needed for communication with wireless devices, security, applications, etc, promoted as an open standard by the WAP Forum.
Wireless Local Area Network (WLAN) - A data network intended to serve an area of only a few hundred square metres or less, using radio communications between mobile computers and (typically) a fixed access point which provides onward connections to fixed networks such as the Internet.
