Industrial Ethernet Lexicon

	1:1 wire cable	1:1 wire cables or straight through cables are required for connecting ETHERNET components over copper cable. In general 1:1 wire cables are required for connections between terminal devices such as SPS, HMI, etc. and network components such as hubs, switches, etc.
	10Base2	Standard for data transmission of 10 Mbit/s ETHERNET on thin coaxial cables (thin wire, cheapernet). Segment length max. 185 m.
	10Base5	Standard for data transmission of 10 Mbit/s ETHERNET on coaxial cables (thick wire, yellow cable). Segment length max. 500 m.
	10Base-FL	Standard for data transmission of 10 Mbit/s ETHERNET on fiber optic cables. Each connection is created with 2 fibers, in each case, one fiber for "Transmit Data" and another one for "Receive Data".
	10Base-T	Standard for data transmission of 10 Mbit/s ETHERNET on unshielded twisted pair cables (category 3, 4 or 5). Each connection is created with 2 wire pairs, in each case with one wire pair for "Transmit Data" and another one for "Receive Data".
	100Base-FX	Standard for data transmission of 100 Mbit/s ETHERNET on fiber optic cables. Each connection is created with 2 fibers, in each case, one fiber for "Transmit Data" and another one for "Receive Data".
	100Base-TX	Standard for data transmission of 100 Mbit/s ETHERNET on twisted pair cables (category 5). Each connection is created with 2 wire pairs, in each case with one wire pair for "Transmit Data" and another one for "Receive Data".
	1000Base-LX	Standard for data transmission of 1000 Mbit/s ETHERNET on fiber optic cables for a wavelength of 1300 nm. Each connection is created with 2 fibers, in each case, one fiber for "Transmit Data" and another one for "Receive Data".
	1000Base-SX	Standard for data transmission of 1000 Mbit/s ETHERNET on fiber optic cables for a wavelength of 850 nm. Each onnection is created with 2 fibers, in each case, one fiber for "Transmit Data" and another one for "Receive Data".
	1000Base-TX	Standard for data transmission of 1000 Mbit/s ETHERNET on twisted pair cables (category 5e). Each connection is created with 4 wire pairs, in each case with all 4 pairs being used for "Transmit Data" and "Receive Data" simultaneously.

A

	Aging	Process for the updating of data, especially of address tables. An address is marked as "old" after the expiry of the certain period of time and then it is deleted at the time of the next pass if it is not detected at a port once again.
	ARP	A ddress R esolution P rotocol A protocol that asks for the relevant MAC address on the basis of an IP address. Each device manages its own dynamic ARP table. If the MAC address of a participant to whom a message is to be sent is not present in the table, the device first sends an ARP request. This message is read by all stations. The device whose IP address is contained in the request sends an ARP reply with its MAC address. The participant making the request completes his ARP table with this MAC address and is then able to transmit the message.
	AUI	A ttachment U nit I nterface Designation of an ETHERNET interface with a 15-pole Sub-D plug connector.
	Autocrossing	A function that enables automatic crossing of transmission and reception lines on twisted pair interfaces. Switches that support this function can be connected to each other over a 1:1 wire cable instead of a crossover cable.
	Autonegotiation	A protocol in Fast ETHERNET with which the participant devices agree a common transmission mode before the actual data transmission (100 Mbit/s or 10 Mbit/s, full duplex or half duplex).
	Autopolarity	A function of devices with 10Base-T or 100Base TX interface for automatic correction of wiring errors in twisted pair cables that lead to a polarity reversal of the data signals.
	Autosensing	A function that enables a device to automatically detect the data rate (10 Mbit/s or 100 Mbit/s) and to transmit and receive at this data rate.
	Auto-MDI/MDI-X	See autocrossing.

B

	Backpressure	A function that simulates a collision in half duplex operation by generating a jam signal.
	Bandwidth	A characteristic size for fiber optic ables.
	Bandwith Length Product	The bandwidth length product is a factor that decides the maximum length of multimode fibers.
	BFOC	B ayonet F iber O ptic C onnector A widely used plug connector for fiber optic cables with bayonet locking. It is also called ST plug. The only plug connector that is standardized in ETHERNET with a transmission speed of 10 Mbit/s. (ST is a registered trademark of AT&T.)
	BNC	B ayonet N eill C oncelman A widely used plug connector for connecting coaxial cables and transceivers as per 10Base2; named after the developers.
	BootP	B ootstrap P rotocol A protocol that delivers a statically allocated IP address to a device connected to the ETHERNET on the basis of its MAC address.
	Bridge	A device that works on Layer 2 of the OSI reference model and connects 2 similar networks to each other. In this connection, data packets are transferred from one subnetwork to another subnetwork through the analysis of the MAC address.
	Broadcast	Term for transmitting a message to a group of unspecified receivers.
	Browser	Term for software that enables the viewing and processing of data in the Internet. The most well-known browsers are Microsoft Internet Explorer and Netscape.
	Burst	Term for a short-term increase in load that occurs suddenly.

C

	CSA<	www.csa.ca C anadian S tandard A ssociation
	CSA	Canadian standard for the security of C22.2 No. 950 IT devices, including electrical office machines based on the IEC 950.
	CSA	Canadian standard for the safety of C22.2 No. 142 industrial control equipment, based on UL 508.
	CSA	Canadian standard for electrical operating C22.2 No. 213 equipment for explosion-endangered rooms of the Class I and II, Department 2, and Class III; based on UL 1604.
	Cheapernet	See 10Base2.
	Collision	The CSMA/CD access process limits the Domain runtime of a data package from one participant to another. Depending on the data rate, what results is a spatially limited network, the so-termed collision domain. The maximum diameter of collision domain is 5120 m at 10 Mbit/s (ETHERNET) and 512 m at 100 Mbit/s (Fast ETHERNET). The full duplex operation of a connection enables expansion over this limit value since it precludes collisions. The precondition for this is the use of bridges or switches.
	Concentrator	See Hub.
	CoS	C lass o f S ervice
	Connection	A function that enables the copying of data
	Crossover Cable	For connecting ETHERNET components over copper cable, what are required are either 1:1 wire cables, or crossover cables. Crossover cables are required for direct cabling of terminal devices such as SPS, HMI, etc. or network components such as hubs, switches, etc. to each other. If the devices support autocrossing, one can also use 1:1 wire cables.
	CRC	C yclic R edundancy C heck Term for algorithms that are used for error detection and correction of bit-oriented protocols.
	CSMA/CD	C arrier S ense M ultiple A ccess/ C ollision D etection Access process in ETHERNET as per IEEE 802.3. A station ready to transmit checks whether the transmission medium is free (carrier sense). It then starts transmitting while simultaneously checking whether other stations (multiple access) have also started to transmit data. If 2 or more stations transmit simultaneously, there is a collision. The stations stop transmission accordingly (collision detection) and attempt transmission later on. In the CSMA/CD process, the network expansion is determined by a maximum permissible runtime of data signals on the network that depend on the data rate.
	cUL 508	US standard for the security of industrial control equipment.
	cUL 1604	US standard for electrical operating equipment for explosion-endangered rooms of the Class I and II, Department 2, and Class III; based on UL 1604.
	cUL 60950	US standard for the safety of IT equipments including electrical office machines; based on IEC 950.
	Cut Through	Method of working of switches in which a data packet is immediately relayed further after detecting the target address. The delay time (latency time) is thereby small, but wrong packets are also transmitted onward. In this process, it is not possible to adjust the speed between the individual segments. The phenomenon is also called "On-the- Fly-Switching".

D

	DA	D estination A ddress Target address within a data telegram.
	DCE	D ata C ircuit-terminating E quipment Term for devices that are used for network termination and to which terminal equipments such as computers, control systems and printers are connected.
	DHCP	D ynamic H ost C onfiguration P rotocol A protocol that temporarily allocates an IP address to ETHERNET participants from an established range of IP addresses.
	Dispersion	Runtime differences in a LWL (fiber-optic cable). Through dispersion, a pulse transmitted in a fiber optic cable is extended. A distinction is made between mode, material and wave dispersion. Mode dispersion arises due to runtime difference between the individual modes. For this reason, this type of dispersion occurs only in multimode fiber optic cables. The material dispersion arises due to the wave length dependency of the refractive index. The fiber optic cable dispersion arises due to differing extension speeds in the energy transmitted in the core and in the jacket. This type of dispersion is of practical importance only for single mode fiber optic cables.The chromatic dispersion is a characteristic quantity for single mode fiber optic cables. It is the total of material and wave dispersion.
	DSC	D uplex S traight C onnector A widely used plug connector for fiber optic cables. Also see SC.
	DNS	D omain N ame S ystem Term for a system which maps host names in plain text to IP addresses. The data source for the conversion are for example DNS servers or files with the designation "Hosts ".
	DTE	D ata T erminal E quipment Term for terminal equipment such as computers, control systems and printers that are connected to a network. In German, they are also referred to as Datenendeinrichtung (DEE).
	Dual Homing	A term that was coined in connection with FDDI networks. Dual homing is a technology in which a device is connected to a network through 2 independent connecting points. One connecting point is for the primary connection, the other is a standby connection. If the primary connection fails, the standby connection is automatically activated. With this technology, it is also possible to connect network segments redundantly.

E

	EGP	E xterior G ateway P rotocol Classification of routing protocols for exchanging information between routers of independent networks.
	EIA	www.eia.org E lectronic I ndustries A ssociation American industrial association of electrical industry active in the field of standardization. Standards of the EIA are designated with RS (related EIA standard). The wellknown standards include the serial interfaces RS 232 C, RS 422 and RS 485.
	EMV	Electromagnetic compatibility. In EMV, both the aspects of interference immunity as well as interference emission must be kept in mind. Electrical devices, installations and systems must have a specific immunity against normal interference effects that normally occur in the planned environment. In addition, devices should not emit any interference variables that may possibly disturb other devices in their environment.
	EN	E uropean N orm European standards relate to standards developed by CENELEC and CEN.
	EN 61000-4-2	EMV Part 4: Measurement and Testing Processes, Main chapter 2: Testing interference immunity to the discharge of static electricity. Details in the catalog: x kV Contact discharge x kV Air discharge
	EN 61000-4-3	EMV Part 4: Measurement and Testing Processes, Main chapter 3: Testing interference immunity to high-frequency electromagnetic fields.
	EN 61000-4-4	EMV Part 4: Measurement and Testing Processes, Main chapter 4: Testing the Interference immunity to fast, short disturbance variables (Burst). Details in the catalog: x kV DC Power lines x kV Data lines
	EN 61000-4-5	EMV Part 4: Measurement and Testing Processes, Main chapter 5: Testing interference immunity to surges. Details in the catalog: x kV Power supply asymmetrical (power supply) x kV Data lines
	EN 61000-6-2	Generic standard Part 6-2: Interference immunity in industry.
	EN 50081-1	Generic Standard Interference Emission, Part 1: Residential, business and trade sectors as well as small businesses.
	EN 50081-2	Generic Standard Interference Emission, Part 2: Industry.
	EN 50082-1	Generic Standard Interference Immunity, Part 1: Residential, business and trade sectors as well as small businesses.
	EN 50082-2	Generic Standard Interference Immunity, Part 2: Industry no longer valid since the 01.04.2002.
	EN 55022	Product Group Standard Interference Emission for IT installations.
	EN 55024	Product Group Standard Interference Immunity for IT installations.
	EN 60950	Safety of IT installations including electrical office machines. European standard, based on the IEC 950.
	EN 60825-1	Safety Of Laser Devices,Part 1: Classification of Installations, Requirements and User Guidelines.
	EN 61131-2	Product Group Standard Stored-Program Control Systems, Part 2: Requirements and Tests for Operating Materials.
	Encapsulation	See Tunneling.
	ETHERNET	Term for a data network that has been standardized since 1985 by the IEEE 802.3. The standard specifies the functions and the construction of the Levels 1 and 2 in accordance with the OSI reference model. ETHERNET is based on the access process CSMA/CD with a variable packet length of between 64 and 1518 bytes and transmission speeds of 10 Mbit/s ( 4 bytes TAG field optional). The concept of ETHERNET is often used as a general designation without making any distinction between the different variations (ETHERNET, Fast ETHERNET, etc.). In addition, the protocols of the Levels 3 and 4 are often included.
	EtherNet/IP	www.ab.com/networks ETHERNET /Industrial P rotocol. A standard for Industrial ETHERNET applications, based on TCP and UDP.
	ETHERNET Packet	Term for an ETHERNET data packet. The packet size varies between 64 and 1522 bytes. It contains the destination and source address field (DA or SA) apart from the actual payload data, the TAG field as well as the length/type field.
	ESD	E lectro S tatic D ischarge Term for electrostatic discharges. Electrostatic discharges can cause short and irregular disturbances in electronic devices or they may destroy electronic components.
	Ex	Independent designation of devices under DIN EN 50020 that can be used in accordance with the specifications even inside explosion-endangered areas.

F

	Fast ETHERNET	Term for a fast data network that was standardized in 1995 by the IEEE 802.3. Based on a transmission speed of 100 Mbit/s with a variable packet length ranging from 64 to 1518 bytes (4 bytes TAG field optional).
	FCC	www.fcc.gov F ederal C ommunications C ommission A US authority established in 1934, responsible for telecommunications. It administers the frequency spectrum and allocates it over local, regional and national levels.
	FCC CFR47 Part 15	F ederal C ommunications C ommission C ode of F ederal R egulations Standard for interference emission for IT installations. t - min. 64, max. 1518 Octets - Preamble Field - Data Field - Start Frame Delimiter Field - Destination Address Field Source Address Field - Length/Type Field - Data Field - Pad Field - Frame Check - Sequence Field
	FCS	F rame C heck S equence Term for a bit field for data security of payload data in bit-oriented protocols. The sender of a message determines a checksum according to an established algorithm, and this checksum is affixed to the end of the packet. In the receiver a checksum is also created according to the same algorithm, and this checksum is compared to the checksum received. With this process, errors in the data transmission can be detected.
	FDX	See Full Duplex.
	FDDI	F iber D istributed D ata I nterface A standard for data networks, that covers the Layers 1 and 2 of the OSI reference model. FDDI is originally based on a double ring topology with fiber optic cables as the transmission medium.
	Fiber optic	In contrast to electrical transmission cable technology in which twisted pair cables are used for data transmission, glass or plastic is used as a transmission medium for optical transmission technology. Fiber optic cables come in the form of multimode and single- mode fibers (monomode fibers).
	Firewall	Term for protective measures that partitions off a LAN from another network, for example the Internet.
	Flow Control	A function that in case of overload at an output port, dumps packets at the input port or signals connected devices to stop transmission. The signal to stop transmission is sent in half duplex operation by simulating a collision or, in full duplex, by sending special "Pause" packets.
	Flow Controls	See Flow Control.
	FM 3611	US standard for electrical operating equipment for explosion-endangered rooms of the Classes I and II, Department 2, and Class III.
	FM 3810	US standard for the Safety of Process Control Equipment
	FTP	F ile T ransfer P rotocol A protocol on Layer 5 of the OSI reference model for the transportation of files.
	Full Duplex	A mode of operation in which a device can simultaneously transmit and receive data. If a transmission path is operated in full duplex in ETHERNET, the CSMA/CD bus access process does not apply and network diameter then depends solely on the performance limits of the transmission and reception components used.
	F/O	F iber O ptics See Fiber Optic Cable.

G

	GARP	G eneric A ttribute R egistration P rotocol Term for a protocol family that is used for exchanging parameters between switches and Layer 2 of the OSI reference model. At present there are the protocols GMRP and GVRP.
	Gateway	A device that operates above the Layer 2 of the OSI reference model and converts protocols. At Layer 3, these devices are generally designated as routers.
	Gbps	G iga b it p er s econd.
	Gigabit ETHERNET	Term for an extremely fast data network that has been standardized by the IEEE 802.3 in 1999. Based on a transmission speed of 1000 Mbit/s with a variable packet length of 64 to 1518 bytes (4 bytes TAG field optional). LAN 1 LAN 2 RS2-FX/FX RS2-FX/FX F/O cable 2 x 10 Mbit/s = 20 Mbit/s
	GL	G ermanischer L loyd A company for the classification of seagoing ships, established 1867 in Hamburg.
	GMRP	G ARP M ulticast R egistration P rotocol A protocol standardized as per IEEE 802.1p that enables participants to log-on and logoff to/from multicast groups dynamically. Switches that support GMRP only switch multicasts to those ports at which participants of the respective multicast groups are registered.
	GVRP	G ARP V LAN R egistration P rotocol A protocol that can use switches to exchange information on VLANs. If a VLAN is installed on a switch, the switch sends this information to all the other switches in the network. In addition, the port at which the information was received can also be made a participant of this VLAN.

H

	Half Duplex	A mode of operation in which a device can either send or receive data at any given point in time. In half duplex, collision detection is active in ETHERNET. Network expansion is limited by the runtime delay of the devices and transmission media.
	HCS	A name for a fiber optic cable, the optical core of which is made of silica glass and whose optical jacket is made of a special patented plastic layer (HCS is a registered trademark of Spectran Specialty Optics).
	HDX	See Half Duplex.
	Header	Term for that part of a data packet that is located before the payload data and contains data such as addresses, packet numbers, etc.
	HIPER-Ring	Term for a redundancy process based on the construction of ring-shaped network structures. In rings of these types, network components that support the HIPER-Ring are connected to each other over their backbone or ring ports. A redundancy manager carries out monitoring of the ring and prevents circulating telegrams.
	HMI	H uman M achine I nterface Devices for operating and observing machines and equipment.
	Hops	Term for the routers that a data packet may pass through on its way through a network. The number of hops within a connection does not indicate anything about the quality of the connection. Thus for example a connection with eight hops may be faster than a connection with five or six hops.
	HSRP	H ot S tandby R outing P rotocol A protocol for controlling redundant routers.
	HTML	H yper T ext M arkup L anguage A format for displaying websites.
	HTTP	H yper T ext T ransfer P rotocol A protocol used by browsers and webservers for transmitting websites.
	Hub	A device that works on Layer 1 of the OSI reference model and that regenerates incoming signals before distributing the same to all the other ports. Synonym: star coupler or repeater.

I

	IAONA-EU	www.iaona-eu.com I ndustrial A utomation O pen N etworking A lliance EU rope An independent umbrella organization set up in 1999 in Europe, the objective of which is to standardize and harmonize Industrial ETHERNET technologies.
	ICMP	I nternet C ontrol M essage P rotocol A protocol that is used to signal failures and errors during transmission of IP packets. An extremely well-known command of this protocol is the "ping" command.
	ID	ID entifier
	IDA	www.ida-group.org I nterface for D istributed A utomation A standard in the field of Industrial ETHERNET developed by a group of companies using TCP and UDP.
	IE	I ndustrial E THERNET Term for ETHERNET in automation technology. The enhanced requirements concern the accessibility and the security of the network and the environmental conditions to which ETHERNET components are exposed.
	IEC	I nternational E lectrotechnical C ommission A commission set up in 1906 for the standardization of electrical components and modules.
	IEC 60068-2-6	Environmental tests Part 2: Fc test, sine-shaped vibrations.
	IEC 60068-2-27	Environmental tests Part 2: Ea test, shock.
	IEC 60068-2-32	Environmental tests Part 2: Ed test, free fall.
	IEEE	www.ieee.org I nstitute of E lectrical and E lectronics E ngineers An association of technicians and engineers having their headquarters in the USA that develops de facto standards, particularly in the field of data communication.
	IEEE 802.3	A committee of the Institute of Electrical and Electronics Engineers, that lays down standards for LANs.
	IETF	www.ietf.org I nternet E ngineering T ask F orce A group that consists of several technical persons interested in the Internet, responsible for technical questions.
	IFG	I nter F rame G ap A measure for the minimum distance between 2 data packets.
	IGMP	I nternet G roup M anagement P rotocol Term for a Layer 3 protocol that communicates the association of participants and routers to multicast groups to the adjacent routers.
	IGMP Snooping	I nternet G roup M anagement P rotocol Snooping A function in which switches investigate IGMP packets and allocate membership of a participant to a multicast group to the respective port. Thereby muliticasts can also be switched specifically to those segments in which the participants of a group are located.
	IGP	I nterior G ateway P rotocol Classification of routing protocols for exchanging information between routers within an independent network. The protocols used include IGRP, RIP and OSPF.
	IGRP	I nterior G ateway R outing P rotocol Routing protocol developed by Cisco.
	IP	I nternet P rotocol A protocol on Layer 3 of the OSI reference model. It is used for the connectionless transportation of data over several networks. Each telegram is allocated a clear IP address. The telegrams may arrive at the receiving end in a sequence different to the one in which they were sent. TCP is responsible for assembly in the correct sequence.
	IP Address	The address of a participant on Layer 3 of the OSI reference model. In Version 4, an IP address consists of 4 bytes separated from each other by decimal points. These 4 bytes indicate the address for the network (Net ID) and the address area of the terminal devices (Host ID). The entire address range is classified into classes from A to E in accordance with the number of network addresses and host addresses, the number of host addresses becoming increasingly smaller from A to E. Since IP addresses must be unique on the Internet, the network addresses are managed by a central organization. The allocation of host addresses is done by the administrator of the respective local network. In order to split-up local networks into smaller subnetworks that are easier to manage, part of the host addresses is used. The network address is thereby increased with a subnetwork component. This extension is done using a subnetwork mask. The subnetwork mask marks all the bits of an IP address that identify the network and subnetwork. A device that wants to transmit, compares its IP address with the IP address of the receiver. If the addresses do not match within the framework of the network mask, it means that the receiver is in a different network. In such case the message is sent to a gateway or a router.
	IPv4	I nternet P rotocol v ersion 4 The IPv4 has an address length of 4 bytes. Also see IP.
	IPv6	I nternet P rotocol v ersion 6 The IPv6 has an address length of 16 bytes. In addition, it is also differentiated by the structure of the header and the division of the networks into address types rather than classes.
	IPX	I nternetwork P acket E xchange Term for a protocol by Novell that creates connections to Internet protocols.
	ISO	www.iso.org I nternational S tandards O rganization An umbrella organization of national standardization committees that is also a member of the Deutsches Institut für Normung (DIN) (German Standards Institute). More than 200 technical committees (TC) make up the various bodies of the ISO. The TCs may be subdivided if so required into subcommittees (SC). The SCs in turn may be split up into working groups (WG) and special task groups.
	IT	I nformation T echnology
	ITU-T	www.itu.int I nternational T elecommunications U nion- T elecommunication Standardization committee with its head office in Geneva.

J

	Jabber	Term for an ETHERNET packet with more than 1522 bytes.
	Jitter	Term for the oscillation of signal edge in time.

K

Kbps

K ilo b it p er s econd (kbit/s)

L

	LAN	L ocal A rea N etwork Term for local network which is typically no bigger than 10 km in diameter.
	Latency Time	Term for the time difference between the receipt and the relaying of data. As a rule, the latency time is measured between the last bit received and first bit sent out.
	LED	L ight E mitting D iode An electronic component that emits light.
	Link Aggregation	Term for a function that combines up to 4 ports with the same transmission speed to one virtual port. The result is redundancy in the case of failure of a connection. Also called trunking.
	Long Haul	Term for optical transceivers with a very high link budget that is used in connection with single-mode fibers.
	LSB	L east S ignificant B it Low-value bit within a bit sequence.
	LWL	See Fiber Optic Cable.

M

	MAC	M edia A ccess C ontrol Term for a sublayer of Layer 2 of the OSI reference model. It controls access to the transmission medium. In this sublayer, processes may be used in which either several equally authorized participants are competing for access (for example CSMA/CA or CSMA/CD) or in which no collisions occurs, for example such as token ring.
	MAC-Address	The address of a participant on Layer 2 of the OSI reference model.
	MAN	M etropolitan A rea N etwork Term for a network within a city that connects various LANs to each other.
	MAP	M anufacturing A utomotion P rotocol A protocol developed in the early 1980s on the initiative of General Motors. However in view of its complexity, it was hardly used commercially.
	MAU	M edium A ttachment U nit A coupling module between an ETHERNET terminal device and the transmission medium. As a rule the terminal device is connected to an AUI interface. Also see Transceiver.
	Mbps	M ega b it p er s econd (Mbit/s)
	MDI	M edium D ependent I nterface Term for the physical (electrical, optical) and mechanical interface of a device for connection to the transmission medium.
	MDI-X	MDI-Crossover Term for a MDI interface with crossed connected signal lines.
	MDI/MDI-X	See Autocrossing.
	MIB	M anagement I nformation B ase A database for objects and functions which help network management systems manage individual objects using Simple Network Management Protocol (SNMP).
	MII	M edia I ndependent I nterface Term for an interface as per the OSI reference model between the Physical Layer (1) and the Data Link Layer (2).
	Media Converter	A device that operates on Layer 1 of the OSI reference model and converts signals between various media. For example optical signals into electrical signals.
	Mirroring	Transmission between 2 ports of a switch to other ports, in order to have the data analyzed by an analyzer.
	Monomode Fiber	See Single-mode Fiber and Fiber Optic Cable.
	MSB	M ost S ignificant B it The most significant bit within a bit sequence.
	MTBF	M ean T ime B etween F ailures Probability factor that indicates after how much time an error may be expected.
	MTRJ	A widely used small sized plug connector for fiber optic cables.
	Multicast	Term for transmission of a message to a group of specific receivers. It is possible to contact this group using only one address.
	Multicast Filtering	Term for processes that enable a switch to relay multicasts in a targeted manner.
	Multimode Fiber	Multimode fibers are fiber optic cables that are distinguished through core diameters of comparable size. The typical core diameter for step-index fiber optic cables is 100 µm for glass fibers, 200 µm for PCS/HCS fibers and 980 m for POF fibers. The graded index fibers on the other hand have a typical core diameter 50 or 62.5 µm. Because of this relatively large core diameter, the light in multimode fibers spreads over several paths and modes. The distance that can be covered by a multimode fiber depends on several factors: the characteristics of the fiber, the link budgets and the attenuation due to plug connectors, splices and other components. For example: A 62.5/125 µm fiber with an attenuation of 1 dB/km and a bandwidth of 500 MHz * km should transmit data packets over Fast ETHERNET using light with a wavelength of 1300 nm. The link budget is 11 dB. A reserve of 3 dB should be taken into account. The attenuation of the plug connectors should be ignored. Attenuation: Lmax = (Link Budget Reserve)/ fiber attenuation Lmax = (11 dB-3 dB)/1 dB/km Lmax = 8 km Bandwidth length product Lmax = Bandwidth/Signal bandwidth Lmax = (500 km* MHz)/125 MHz Lmax = 4 km In this example, the maximum distance to be covered is 4 km. Signal bandwidths: ETHERNET = 10 MHz, Fast ETHERNET = 125 MHz and Gigabit ETHERNET = 1.25 GHz
	Multiplexer	Term for devices or function units that combine several channels of low capacity into one channel of high capacity.
	Multiport Bridge	A bridge that connects not only 2 but several LANs together. In ETHERNET LANs, multiport bridges are also designated as switches.

N

	NAT	N etwork A ddress T ranslation Term for a protocol that is defined in RFC 1631 and RFC 1918.
	NEXT	N ear- E nd Xr oss T alk A form of crosstalk in which signals of participants that are located on the same side of a twisted pair cable get superimposed.
	NIC	N etwork I nterface C ard Term for PC insertion cards that enable connection to an ETHERNET network.
	Network Nodes	Term for network elements such as hubs, switches and routers on which different data transmission paths run together.
	Network Management	A general concept for the management, configuration and monitoring of network nodes and the devices connected the same. The tasks of a network management system may be subdivided into error management, configuration management, safety management and performance management. To do this, the network management agent communicates with the network management station using the network management protocol SNMP.
	Network Mask	The network mask marks all bits in an IP address for identifying the network and the subnetwork. Also see IP address.
	NMS	N etwork M anagement S tation See Network Management.
	Node	Term for a participant in a network.
	NRZ	N on- R eturn to Z ero Term for a coding process in which the electrical signals do not go back to zero even when there is a sequence of several logical ones.
	NRZI	N on- R eturn-to- Z ero, I nvert on ones Term for a coding process with inverted NRZ signals.

O

	OID	O bject ID entification
	OLE	O bject L ink and E mbedding Term for a central architecture principle in Windows.
	On-the-Fly Switching	Working method of switches see Cut Through. Binary notation IP address 10010101.11011010.00010011.01011010 Network mask 11111111.11111111.11111111.00000000 ->Subnetwork 10010101.11011010.00010011.00000000 Decimal notation IP address 149.218.19.90 Network mask 255.255.255.0 - >Subnetwork 149.218.19.0 Available address range Host addresses 149.218.19.1 to 149.218.19.254 Broadcast address 149.218.19.255
	OPC	www.opcfoundation.org O LE for P rocess C ontrol Standard interface for Windows applications for data exchange concerning process data and status information.
	OSI	O pen S ystems I nterconnection An international standardization program that has been instituted by the ISO and theITU. The objective is to lay down standards for data networks that ensure the compatibility of devices made by various manufacturers.
	OSI Reference Model	Also termed ISO/OSI reference model. This model is divided into 7 Layers that describe the communication of open, distributed systems. The individual layers form a group, that are independent of each other, but each describes an area that is relevant for data transmission and processing.The layers are termed the Physical Layer (1) the Data Link Layer (2) Network Layer (3) the Transport Layer (4) the Session Layer (5) the Presentation Layer (6) and the Application Layer (7).
	OSPF	O pen S hortest P ath F irst Term for a routing protocol. OSPF uses information given by the routers over the topology of the network in order to find the shortest path between the routers. The precondition for this is that each router creates a routing table in which the current topology of the network is fully displayed. Since each router immediately communicates changes in the topology to the adjacent routers, the routing tables in the routers get constantly updated. The advantage of OSPF over RIP consists in the speed and the better distribution of load.
	OUI	O rganizationally U nique I dentifier Term for the first 3 bytes of the MAC address.

P

	Packet Size	See ETHERNET Packet.
	Patch Cable	Term for cables that are used for connecting ETHERNET component within a room (19" rack, control cabinet, etc.). Patch cables are mostly used in connection with patch panels.
	Patch Field	Term for a patching distribution frame.
	PCF	Term for a fiber optic cable, the optical core of which is made of silicon glass with an optical jacket consisting of a polymer layer.
	PDU	P rotocol D ata U nit Term for a data packet assembled on a layer of the OSI reference model that is relayed to the layer below it over a Service Access Point (SAP).
	Ping	P acket In ternet G roper A program for testing connections between 2 IP addresses.
	PLC	P rogrammable L ogic C ontrol Stored-program control systems.
	POF	P lastic O ptical F iber Term for a fiber optic cable, the optical core and jacket of which is made of plastic. POF fibers have a typical core diameter of 0.98 mm.
	Port	General term for an interface to devices for transmission of data and control information in the transmission and reception direction. Port Mirroring A function that enables the copying of incoming and outgoing data at one port of a switch to another port, in order to be analyzed there with an analyzer for example.
	Port Security	A function that offers protection against unauthorized access to the network. Switches that support this function offer the possibility of setting, for each port, the terminal device from which data can be transmitted or received. The checks are carried out on the basis of the MAC addresses of the devices connected. If the device is connected to a port, the MAC address of which is not registered, this port can be automatically switched off.
	Port Trunking	See Link Aggregation.
	PPP	P oint-to- P oint- P rotocol A protocol of the TCP/IP family for serial data transfer over dial-up connections such as the telephone. This is used for connecting computers that are not permanently connected over LANs to the Internet.
	pps	P ackets p er S econd Measurement unit for the switching speed.
	Prioritization	In a prioritized data transmission, data packets are switched on the basis of the defined criteria. The tagging of such packets is done at Layer 2 of the OSI reference models in the TAG field and at Layer 3 in the TOS field.
	PROFInet	www.profibus.org A concept that defines the communication from the field level to the conducting level with the integration of profibus and ETHERNET as well as a model for companywide engineering.

Q

QoS

Q uality o f S ervice
Term for a range of factors that have an effect on the quality of a network. These factors include network breakdown times, delay times, stability of connections and many more. For QoS, there is a series of different definitions.

R

	RAM	R andom A ccess M emory Term for a volatile memory.
	RARP	R everse A ddress R esolution P rotocol A protocol that delivers statically allocated IP addresses to a MAC address.
	Redundancy Manager	Term for a switch or hub in a HIPER-Ring that monitors the ring and in case of an interruption in the ring structure, activates the connection that has been switched off upto that point. After the interruption has been removed, the redundancy manager again switches this connection off. The ring is thereby physically switched off, but from the point of view of communication, it is interrupted.
	RFC xxx	R equest F or C omments An abbreviation that was coined within the context of the Internet. It is closely linked to the publication of Internet standard.
	RIP	R outing I nformation P rotocol A protocol for the cyclic exchange of routing tables between routers within independent networks per broadcast. RIP is one of the oldest, easiest and most widely used routing protocols. The successor of RIP is the more complex OSPF.
	RJ45	A widely used plug connector in telephone technology and in LANs. It is also known as the Western plug with 8 poles.
	RMON	R emote network MON itoring A protocol for network management. RMON defines new classes of data that relate to and can be recorded on the lower layers of the OSI reference model. The data are then transmitted to a network management station using Simple Network Management Protocol (SNMP).
	RMON 2	R emote network MON itoring A protocol for network management. RMON 2 is an extension of RMON and extends to higher layers of the OSI reference model.
	Router	A device that works at Layer 3 of the OSI reference model and connects different segments of the network to each other, or splits-up networks into subnetworks. A router transmits only data packets to other segments that are sent to its own MAC addresses. The router then sends the data packets onward on the basis of routing tables. In other words, the transmitting participant must know that the receiver is not located in the same network segment. The transmitting station obtains this information from the IP address of the recipient. Routing tables are either given as fixed tables or are given by the router itself using routing protocols.
	Routing	A function of Layer 3 of the OSI reference model. A distinction is made between dynamic and static routing. In dynamic routing, routers calculate rules and parameters for path selection through the network. This information is written to routing tables and exchanged using routing protocols between routers. This ensures that the path selection is adapted to the current topology and load distribution of network. In dynamic routing, each telegram is individually routed. As a result, telegrams may arrive at the receiving end in a sequence different to the one in which they were sent. In static routing, the paths for data transmission between the transmitters and receivers is fixed and a specific bandwidth is reserved for each connection. As a result, data packets take the same path between two terminal devices. It is therefore not possible to respond automatically to changes in the topology or in the case of overloads of connections. Since all changes in the network structure are entered into the routers by hand, routers do not have to support any routing protocols in this process. While dynamic routing supports the transmission of data in an optimized manner, in static routing, the transmission of data, speech and video are equally supported.
	Routing Protocol	Term for protocols that routers use during dynamic routing in order to exchange information over connected networks amongst each other. This information is stored in routing tables in the routers.
	RS 232 C	R ecommended S tandard 232 C A widely used serial interface for data transmission with data rates of up to 20 kbit/s and over distances up to 15 m. This interface was standardized by the EIA in 1969 as standard no. 232 in Version C. It is also often referred to as RS 232.
	RS 422	R ecommended S tandard 422 A serial interface for data transmission in full duplex operation. This interface was standardized in the 70s by the EIA as standard no. 422.
	RS 485	R ecommended S tandard 485 A serial interface for data transmission that enables a bus structure with several participants. This interface was standardized by the EIA in the 70s as standard no. 485.
	RSVP	R esource Re S er V ation Setup P rotocol A protocol that reserves resources for applications over the Internet. After a path has been established from the sender to the receiver, all the routers participating in this path are notified via RSVP that they should reserve specific resources for this connection.
	RTP	R eal- T ime P rotocol A protocol that supports real-time applications such as video conferencing on the Internet. In this protocol, additional information such as the nature of the payload data transmitted (speech, video, etc.) or the time of generation of the payload data is transmitted.
	Rx	Abbreviation for Receiver. Term for the connection to a port at which data is received.

S

	SA	S ource A ddress Source address within a data telegram.
	SAP	S ervice A ccess P oint Term for the interface between two layers of the OSI reference model where a layer that is placed at a higher level makes use of services in the layer below.
	SC	S traight C onnector A widely used plug connector for fiber optic cables. Also see DSC.
	SCADA	S upervisory C ontrol A nd D ata A cquisition Term for systems for control and visualization of processes. SCADA systems are based on Windows operating systems as a rule.
	SDH	S ynchronous D igital H ierarchy A European standard that defines several standards of transmission rates and transmission forms for optical fibers (fiber optic cable).
	SFD	S tart of F rame D elimiter Part of an ETHERNET telegram.
	Shared Network	Term for an ETHERNET network in which participants share the available bandwidth. In these networks, the CSMA/CD process controls the access of the participants to the transmission medium.
	Single-mode	A single-mode fiber is a fiber optic cable fiber that is characterized by its extremely small core diameter (max. 10 µm). As a result, in this fiber, the light after the cutoff waveline can only get extended along one path one mode. The distance that is to be covered by a single-mode fiber depends on several factors: the characteristic data of the fiber, the link budget as well as the attenuation to plug connectors, splices and other components. Example: A 9/125 µm fiber with an attenuation (A) of 0.3 dB/km should transmit a wavelength of 1550 nm of Fast ETHERNET data packets. The link budget is 29 dB. A reserve of 3 dB is taken into account. The attenuation of the plug connector is to be ignored. Attenuation: Lmax = (Link Budget-Reserve)/Fiber attenuation Lmax = (29 dB-3 dB) /0.3 dB/km Lmax = 86.6 km In this example, the maximum distance to be covered is 86.6 km. Signal bandwidths: ETHERNET = 10 MHz, Fast ETHERNET = 125 MHz and Gigabit ETHERNET = 1.25 GHz
	SLIP	S erial L ine I nternet P rotocol A protocol for serial data transfer over dialup connections such as the telephone. It is used for connecting computers that are not networked permanently over LANs to the Internet. In comparison to the more recent PPP, SLIP has the disadvantage that erroneous data is not recognized.
	SMTP	S imple M ail T ransfer P rotocol Term for a protocol for sending e-mail messages.
	SNMP	S imple N etwork M anagement P rotocol A protocol for network management. SNMP defines commands for the reading and writing of information, status and error messages as well as providing a structured model. This model consists of agents with their respective Management Information Base (MIB) and a Manager. The Manager is a program that runs on a network management station. Agents are mostly located within devices such as switches, routers and terminal devices that support the SNMP. The task of the agents consists in collecting and preparing data in the MIB. These data is requested at regular intervals by the Manager and displayed on the network management station. The devices are configured, for example, with the data that the Manager writes to the MIBs in question. In urgent cases, the agent can also send messages (traps) directly to the Manager.
	SOHO	S mall O ffice H ome O ffice Network solutions and access technologies to the Internet for small offices and offices at home that are not directly connected to large company networks.
	Spanning Tree	Term for a protocol that is used in ETHERNET networks for path determination. It is specified as standard IEEE 802.1 D. The spanning tree algorithm prevents the circulation of data packets in a LAN with several possible paths by switching-off individual connections or ports. In addition it determines the optimum path if there are several alternatives. If a path fails due to the fault or interruption, an alternative connection is searched for using the spanning tree protocol. The reconfiguration of a network of this type may takes 30-90 seconds.
	SPS	Stored memory controlled system.
	Star Coupler	See Hub.
	ST	A widely used plug connector for fiber optic cable with bayonet locking. It is also known as BFOC plug. It is standardized as the only plug connector for ETHERNET (10 Mbit/s). (ST is a registered trademark of AT&T).
	Store-and-Forward	A method of working for switches in which a data packets is first read-in completely and checked for errors before the switch relays the same. This process enables the connection of segments with differing transmission rates.
	STP	S hielded T wisted P air See Twisted Pair Cable.
	Subnetwork Mask	Network mask or subnet mask. The network mask marks all the bits of an IP address for the identification of the network and the subnetwork. Also see IP address.
	Switch	A device that works on Layer 2 of the OSI reference model. In contrast to hubs, switches analyze the incoming data packets and only relay them to ports at which the receiver is registered. Exceptions from such targeted switching are multicasts and broadcasts that are sent to all ports. The transmission of data packages can be done at several ports simultaneously and in full duplex operation. Thus switches optimize the available bandwidth of the LAN. Recently, Layer 3- and Layer 4-switches have been brought out, that have additionally implemented the partial function of these layers.
	Switched Network	Term for an ETHERNET network that is made up of switches.
	Switching Hub	See Switch.

T

	TAG Field	An optional field in the ETHERNET telegram that contains information about the priority and associated VLAN of the payload data.
	TCP	T ransmission C ontrol P rotocol A connection-oriented protocol at Layer 4 of the OSI reference model. It enables a full duplex point-to-point connection and extends the Internet protocol below it by functions for data security and connection control.
	Telnet	An emulation program based on TCP/IP that executes processes or uses programs on a different device. The system resources of the other device are used. This distinguishes Telnet from FTP for example, which only searches for file systems.
	TFTP	T rivial F ile T ransfer P rotocol A protocol based on Layer 5 of the OSI reference model and uses UDP for fast and uncomplicated transmission of files. TFTP is considerably quicker than FTP.
	Thick Wire	See 10Base5.
	Thin Wire	See 10Base2.
	Transceiver	1. General term for a transmission/reception component. 2. Term for media converter within the Rail family. In addition there are plug-on transceivers for fiber optic cables, twisted pair and coax cables. These transceivers are provided with power supply over the 15-pole AUI interface by the terminal device connected.
	Topology	A description of the type of line routing. The essential basic forms are line topology, tree topology, ring topology and star topology.
	TOS	T ype O f S ervice A field in the Internet protocol for prioritizing data.
	TP	T wisted P air See Twisted Pair Cables.
	Trap	Term for the signaling of error signals to a network management station.
	Trunking	See Link Aggregation.
	TTL	T ime T o L ive A field in the header of the Internet protocol that indicates for how long the packet is valid.
	Tunnelling	Term for the packaging of data in data packets of another protocol that operates on the same Layer of the OSI reference model. This process is also termed encapsulation.
	Twisted Pair Cable	Term for 2 wires that are isolated from each other but are twisted together. A distinction is made in this connection between Unscreened (UTP) and Screened Twisted Pair cables (STP).
	Tx	Abbreviation for transmitter. Term for the connection to a port to which data is sent.
	Transmission Rate	Term for the speed at which data is transmitted. For ETHERNET: 10, 100, 1000 and 10000 Mbit/s.

U

	UDP	U ser D atagram P rotocol A connectionless protocol at Layer 4 of the OSI reference model. In contrast to the Transport Control Protocol (TCP), UDP does not have any functions for data security and connection control. As a result it is considerably faster and more suitable for real-time applications such as speech and video transmissions as well as for the transmission of short messages that can be repeated in case of error.
	UL	www.ul.com U nderwriters L aboratories Independent institution in the USA that lays down and executes safety tests for products.
	Unicast	Term for sending a message to a specific receiver.
	UPS	U ninterruptible P ower S upply
	URL	U niform R esource L ocator A standardized scheme for access to hypertext documents and other services through a browser.
	USB	U niversal S erial B us Term for a serial bus for connection of modems, mice, keyboards, printers and other peripheral devices. A maximum of 127 devices can be connected to the bus. The cable length between two devices must not exceed 5 m.
	UTP	U nshielded T wisted P air See Twisted Pair Cable.

V

	VLAN	V irtual LAN Term for LANs that are logically configured independently of their real physical topology. A distinction is made between static and dynamic VLANs. In static VLANs, the ports of a switch are permanently allocated to one or more VLANs. A subnetwork is therefore made up of a list of port numbers. In the case of dynamic VLANs, the subnetworks are made up of MAC or IP addresses that are maintained in a database. The ports of the switches are automatically configured on the basis of this database. VLANs are intended for making groups of participants who can only communicate with each other in accordance with predefined rules. A further application of VLANs is the delimitation of broadcasts.
	VPN	V irtual P rivate N etwork Virtual private networks are used in connection with public networks for secure data transmission, consequently the entire data traffic is transmitted in encoded form.
	VRRP	V irtual R edundant R outer P rotocol A protocol for the control of redundant routers.

W

	WAN	W ide A rea N etwork Term for private or public networks that frequently connect several LANs or MANs together.
	Web Interface	Term for the interface of a device that enables access to device data over browsers.
	WFQ	W eighted F air Q ueuing A process with which queues in a switch are processed when the data is prioritized. This process ensures that all the queues are serviced on the basis of the bandwidths that are allocated to the queues.
	Wire Speed	Term for the relaying of data with line speed.
	WLAN	W ireless LAN Wireless data transmission in local networks.
	WWW	W orld W ide W eb Term for an application in the Internet that enables access to database information through hyperlinks. There are software programs called browsers to view and further process data.

XYZ

Yellow Cable

See 10Base5.