Glossary of Terms


µm Micrometre or Micron – a measurement denoting one millionth of a metre.


10/100Mb – Denotes that this device can support both Ethernet (at a data transfer rate of 10Mpbs) and Fast Ethernet (at 100Mpbs).

10/100/1000T – Denotes that this device can support both Ethernet (at a data transfer rate of 10Mpbs) and Fast Ethernet (at 100Mpbs) and Gigabit Ethernet (at 1000Mpbs).

10/100TX – Denotes that this device can support both Ethernet (at a data transfer rate of 10Mpbs) and Fast Ethernet (at 100Mpbs).

1000Base-BX10 – A standard of Gigabit Ethernet which is over a single strange of Single Mode fibre is capable of a distance of up to 10km.

1000Base-LH – Also known as 1000BaseLX10, a Gigabit Ethernet standard which due to higher quality fibre optics can achieve a longer distance (up to 10km) over Single Mode fibres than the 1000Base-LX Gigabit Ethernet standard.

1000Base-LX – A Gigabit Ethernet standard over fibre optic with a maximum length of 50km for Single Mode fibre and 550m for Multi Mode fibre.

100Base-FX – A version of Fast Ethernet over multi-mode optical fibre with a maximum length of 400 metres for half-duplex connections and 20km for full duplex connections.

1000Base-T A Gigabit Ethernet standard over copper wiring using Category 5 or better cable with a maximum length of 100 metres.

1000Base-TX – A Gigabit Ethernet standard over copper wiring using Category 6 or better cable with a maximum length of 100 metres.

1000Base-SX – A version of Fast Ethernet over optical fibre using two strands of Multi Mode optical fibre to receive and transmit operating up to a distance of 550m.

10GbE 10 Gigabit Ethernet – a version of Ethernet with a data of 10Gbit/s, 10 times faster than Gigabit Ethernet.

1Gb 1 Gigabit.

1RU One Rack Unit – measurement denoting the height of equipment for mounting in a 19″ rack, 1 Rack Unit or 1U = 1.75″ or 44.45mm in height. More commonly referred to as 1U.

1U One Rack Unit – measurement denoting the height of equipment for mounting in a 19″ rack, 1 Rack Unit or 1U = 1.75″ or 44.45mm in height.


Alien Crosstalk or AXT Electromagnetic noise that occurs from different cables in either a group or bundle. Alien Crosstalk reduces the signal-to-noise ratio culminating in a degradation of network performance.

Aramid Yarn A heat resistant and strong synthetic yarn found in Ruggedised fibre optic cables.

Armoured Cable reinforced with a metallic sheath that provides improved protection to the cable core.

Attenuation When signals are being transmitted, they by nature become weaker or “attenuated” the further they travel.

Auto-MDIX Automatic Medium-Dependent Interface Crossover – a technology that automatically detects whether a straight through or crossed cable is required, and configures the connection accordingly. This eliminates the need to consider whether crossed or straight cables are required for the connection.

Autonegotiation A procedure which adjusts parameters such as speed, duplex mode, and flow control between two connected devices to the highest performance transmission mode they both support.

AWG American Wire Gauge – a standard of wire gauge for the diameters of round conductor wire where the smaller the unit the larger the diameter.


Backbone Part of a network infrastructure that connects LAN’s or subnetworks. These can be within a building or campus wide and usually have a higher data carrying capacity than the networks connected to it.

Balun A transformer for levelling out impedance differences so that a signal generated onto a coaxial cable can transfer onto a twisted pair if necessary, the use of baluns usually results in some level of signal degradation.


Campus Backbone See Backbone

Checksum Offloading – A feature of some Allied Telesis fibre LAN adapters with the purpose of detecting accidental errors. Checksum offloading is performed with hardware assistance with the aim of automatically computing the checksum in the network adapter prior to transmission over the network.

CSTA Corrugated Steel Tape Armoured – A type of cable providing crush resistance and rodent protection.

Coupler – See Fibre Adapter


DHCP Dynamic Host Configuration Protocol – protocol that enables a server to assign an IP address automatically to a computer.

DiffServ or Differentiated Service – Computer architecture that specifies a simple and scalable mechanism for classifying and managing network traffic in a way that it provides Quality of Service. For example, priority can be given to critical network traffic such as VoIP and lower priority given to non-critical traffic.

DIN Rail – A metal rail used for mounting industrial control equipment such as power supplies.

DoS Attack Denial of Service Attack – an attempt to make a computer resource unavailable to its potential users.

Duplex Cable – A technique allowing bi-directional, simultaneous transmission along a channel as opposed to only in one direction at a time. Often referred to as Full Duplex.


EMI – Electromagnetic Interference, a disturbance affecting a networking circuit. This disturbance can be electromagnetic induction or radiation but is always emitted from an external source.

Ethernet – Available since the 1980s, it is a type of networking for LANs running over twisted pair and fibre optic cables. Ethernet can run up to a speed of 10Mbit/s.

EPSR Ethernet Protection Switching Ring. From Allied Telesis, this provides fast failover between nodes in a ring of switches. This is a feature of certain Allied Telesis switches such as the AT-x900-12XT/S.


Failover – The capability to switch to a redundant or standby server or network upon server/network failure. This process occurs without human intervention.

Fast Ethernet – An Ethernet standard that carries traffic at a rate of 100Mbit/s.

Fibre Adapter Fibre optic adaptors are used either within fibre patch panels and other termination units, or externally to interconnect pre terminated fibre optic cables. The adapter or uniter precisely aligns the ferules for both cables to maintain communication path. The alignment sleeve in a Single-Mode adapter is ceramic and is the most precise; this can be used for both Single and Multi-Mode applications. The bronze alignment sleeve in a Multi-Mode adapter is only suitable for Multi-Mode cables. Also known as a Uniter or Coupler.

Flow Control – This is a mechanism for temporarily stopping the transmission of data on an Ethernet network.

FRNC – Flame Retardant Non-Corrosive.

Full Duplex – Transmission and reception of signals or communications occurs simultaneously, compared to Half Duplex.

Fusion Splicing – The joining of two optical fibres end-to-end using heat, this means that light passing through is not scattered nor reflected back by the splice.


GBIC – Gigabit Interface Connector.

Gigabit Ethernet – A standard of Ethernet which supports a data transfer rate of 1 Gigabit (1000 Megabits per second).

Gland – A device used to attach and secure the end of a cable to networking equipment.

GUI – Graphical User Interface such as a computer which allows users to interact with images rather than text commands.


Half Duplex A sequential two-way transmission of data in which information can be transmitted in both direction but only in one direction at a time. See also Full Duplex.

Hermaphroditic – Also known as Genderless Connectors, which have simultaneous male and female aspects.

Hot Swappable – The replacing, inserting or removing of system components occurs without the need to shut down the system.

HSSDC – High Speed Serial Data Connector, a connector type that allows a higher level of bandwidth transmittal.


IEC International Electrotechnical Commission – an international standards committee responsible for putting in place standards for electrical and electronic technologies.

IGMP Internet Group Management Protocol – used by routers and hosts on IP networks to establish multicast group memberships.

IGMP Snooping – A protocol of IPv4 which allows a switch to listen in to Internet Group Management Protocol network traffic to ensure that hosts and routers have IP multicast streams if they require them.

Infiniband – A form of input/output architecture used in higher-end clusters and networks to extend connections via external networks at a speed of 2.5Gbps in each direction.

Insertion Loss – Loss of signal power following the insertion of any device.

IP Internet Protocol.

IPv4 – Internet Protocol Version 4. Read More on IPv4 at Wikipedia.

IPv6 – Internet Protocol Version 6. Read More on IPv6 at Wikipedia.

Jumbo Frames – An Ethernet data packet (or Ethernet frame) that is more that 1500 bytes.

Jumbo Packets – See Jumbo Frames.


Knockout A weaker piece of metal built into Wall Boxes and Patch Panels that can be knocked out to allow for cable entry.

KVM – Keyboard, Video/Visual Display Unit and Mouse. This allows a user to control multiple computers from a single Keyboard, Video/Visual Display Unit or Mouse.


LACP Link Aggregation Control Protocol – A control protocol that allows a switch to aggregate links to and between ports dynamically meaning thus allowing higher bandwidth throughput.

Link Aggregation – Is the process where two or more ports in an Ethernet switch are combined together to operate as a single virtual port to both increase the available bandwidth between devices and also provides continuity of connectivity if one link is broken.

Link Loss Forwarding – This feature enables networking equipment to shut down data transmission if a link connection has failed.

LLDP Link Layer Discovery Protocol – Used by network devices for advertising their identity, capabilities and neighbours.

Loose Tube A protective tube loosely surrounding a fibre optic cable.

Low Smoke/LOSH/LSZH – Low Smoke Zero Halogen. A Low Smoke cable sheath made of compounds that produce little smoke and zero halogen in the event of a fire or other exposure to high heat therefore a harmful, toxic smoke is not emitted.


MAN Metropolitan Area Network – Describes a network spanning a geographical area greater than a LAN (local area network) but less than a WAN (wide area network) e.g. the span of a city or a large campus.

Managed Switch These types of switches contain one or more methods to modify the operation of the switch by users such as a GUI or web-based management systems.

MDI Medium Dependent Interface see Auto-MDIX.

MDIX Medium Dependent Interface Crossover see Auto-MDIX.

Media Converter – A networking device that allows the connection of fibre optic cable systems to copper cabling installations or other dissimilar media types.

MHz MegaHertz – Denotes a transmission rate of one million cycles per second.

Micron See µ

Mini-Zip Refers to cable that has been manufactured with a sheath measuring 1.8mm in diameter (Simplex Cable). This is opposed to a standard Zip cable whereby the diameter is 2.8mm for a Simplex Cable.

Mil Tac A type of fibre optic cable that is suitable for Military Tactical applications and other environments where deployment and retrieval for reuse is required.

MissingLink – A feature of some Allied Telesis Media Converters which allows accurate reporting to network management systems as well as allowing devices with redundant link capabilities to be inter-connected with these Media Converters, as a failure in one fibre link will be signalled to the network switch allowing the second link to be activated.

MLD Snooping Multicast Listener Discovery Snooping – A protocol of IPv6, similar to IGMP Snooping which reduces the amount of multicast traffic on a network by sending streams only to interested recipients not all recipients. This results in a more efficient use of bandwidth.

MMF – See Multi Mode Fibre.

Mode Conditioning Patch Cord/Cable Used with a 1000Base-LX transceiver to extend the range of Gigabit over OM1 (62.5/125 cable) from 250m to 550m.

MPO Multi-Fibre Push On Connector.

MTP©MPO Multi-Fibre Termination Push On Connector. A high performance MPO connector manufactured by Us Conec. These can contain either 12 fibres or 6 duplex fibres in a connector which is smaller than most duplex connectors that are common today providing savings in rack space.

Multi Mode Fibre Or MM fibre is a type of fibre used for networking over small distances with a data range of between 10 Mbit/s up to 10 Gbit/s up to 600m.


NEBS Network Equipment Building Systems – A series of safety and conformance standards applied to telecommunications equipment in the USA. A feature of some Allied Telesis© products.

NIC Network Interface Card – Also known as a Network or LAN adapter is a piece of computer hardware that allows a computer to connect to a network.

Nm Nanometre – A unit of length denoting one billionth of a metre.


OSPF Open Shortest Path First – A routing protocol that allows routers to negotiate fast convergence of paths through a network. It allows load balancing across links, path configuration across multiple technologies and high performance routing across large infrastructures.


Packets – A formatted unit of data carried over a network which contains both control information (such as error checking and destination address) and user data.

PDU Power Distribution Unit – A device which distributes electrical power, these can be floor mounted on rack based. Both take high voltage electricity currents and reduce it into lower levels of voltage which have more usages.

PE Sheathed A Polyethylene outer sheath for copper cables meaning that the cables can be used outside as the sheath provides extra protection against outdoor elements as well as moisture and oil protection.

Pigtail – A short fibre optical cable that has an optical connector on one end and exposed fibre on the other. These are commonly used to splice onto a single fibre in another multi fibre cable to breakout the cable into its fibre components for connection to end equipment.

Plug and Play – A computing term describing a device which facilitates the discovery of a hardware component without the need for physical configuration or user intervention.

PoE Power over Ethernet – a system whereby electrical power is passed safely over Ethernet cabling along with data. PoE provides 15.4w of DC power to each device.

PoE+ – Like PoE but PoE+ provides 25.5w of power to each device.

Port The exit and entrance point for information going our of and into a computer or other data communications device.

Port Mirroring – Used on a network switch, Port Mirroring sends a copy of the network packets in use on one port to a network monitoring connection on another switch port.

Port Trunking See Link Aggregation

Priority Queues Data packets have differing priorities, in a Priority Queue there are four queues with different priorities levels assigned. Higher priority queues are served first and lower priority queues are only served if or when the high priority queues are empty.

PSU – Power Supply Unit, the unit by which power is supplied to components.


Q in Q – An Ethernet networking standard which allows multiple VLAN headers to be inserted into a single frame, a must for metropolitan area networking.

QoS Quality of Service – A range of resource control mechanisms that aim to guarantee a certain level of network performance or to provide different priorities to applications or users.


RADIUS Server Remote Authentication Dial in User Service – a networking protocol that centralises authentication, authorisation and accounting management for PCs to connect and use a network service.

Rate Limiting – This is a mechanism that controls the rate of traffic sent or received on a network, traffic that exceeds the set rate is then dropped or limited.

Return Loss – Also known as reflection loss, meaning a loss of signal power due to a reflection caused by a discontinuity in an optical fibre – the discontinuity may arise from improper termination for example.

RFI Radio Frequency Interference. See EMI

RIP Routing Information Protocol – A protocol that automatically creates and maintains network routes, giving protection against failure.

RIPng Routing Information Protocol Next Generation – RIP that supports IPv6.

RPS Redundant Power Supply – In the event of main power supply failure to a network device, a redundant power supply is able to power the device thus improving network reliability by decreasing downtime.

RSTP Rapid Spanning Tree Protocol – A supersession to Spanning Tree Protocol providing faster spanning tree convergences. RSTP has the ability to respond to failures in a few milliseconds or changes in around 6 seconds.

Ruggedised Or Ruggedized – A standard duplex patch cable that with an additional Low Smoke Zero Halogen sheath providing extra durability and stiffness to avoid kinking.


sFlow – A technology present in some HP switches for monitoring network devices traffic levels.

SFP Small Form Factor Pluggable – A hot-swappable input/output device that plugs into a SFP slot on a switch and provides copper or fibre connectivity.

SFP+ – As SFP but capable of data rate of 10Gbit/s compared to the SFPs 4.25Gbit/s.

Single Mode Fibre Or SM fibre – An optical fibre that carries only one ray of light (a mode) through it.

SNMP – A protocol for managing devices on an IP network for conditions that require administrative attention.

Spanning Tree Protocol – Sometimes referred to as STP, this is a data link layer protocol that ensures a loop free layout for an Ethernet LAN with the aim of preventing broadcast radiation.

Shielded Twisted Pair STP – A type of cable that includes one or more sets of cable pair moulded together by insulating materials and covered with a braided shielding conductor offering better noise protection than Unshielded Twisted Pair.

SWA Steel Wire Armour – A cable that is armoured providing the highest level of crush resistance and rodent protection meaning that it is suitable for rugged external installations. Compared to CSTA the cable is more flexible but heavier.


Tactical Fibre – Extremely strong and lightweight fibre cable that offers exceptional cut, abrasion and chemical resistance.

Tight Buffered Fibre – A type of fibre cable with includes a polymer coating component used to tightly encapsulate the optical fibres to provide increased protection suitable for both internal and external use.

Twisted Pair A cable with two insulated copper wires twisted together with the twists varied in length to reduce potential signal interference between the pairs.


Uniter – Another name for an adapter.

Unmanaged Switch – A plug and play switch which is desktop or rack mounted, these types of switches have no configuration interfaces or options.

UPS Uninterruptible Power Supply – An electrical apparatus that provides emergency power when the primary power source fails, this switchover is instantaneous and provides protection against business disruption and data loss.

Unshielded Twisted Pair UTP – A cable with insulated copper twisted pairs but without a shield.


VCSTACK Virtual Chassis Stacking – A feature of some Allied Telesis switches where through configuration, two or more switches act as a single switch.

VLAN Virtual Local Area Network or Virtual LAN – Configured through software, a party of hosts who have similar sets of requirements communicate as if they belonged to the same broadcast domain, despite the location of the group of hosts.

VRRP Virtual Router Redundancy Protocol – A router based application that allows a group of routers to act as one.


Wirespeed – The rate of data transfer/bandwidth that a networking device can achieve at the physical wire level.


XFP 10 Gigabit Small Form Factor Pluggable.

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