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10Base2

10-Mbps base-band Ethernet specification using 50-ohm thin coaxial cable. 10Base2, which is part of the IEEE802.3 specification, has a distance limit of 606.8 feet (185meters) per segment. See also Cheapernet, EtherChannel, IEEE 802.3, and Thinnet.

10Base-5
The implementation of the 802.3 standard also known as standard Ethernet or thicknet. 10Base-5 networks run on thick coaxial cable at 10 Megabits per second base-band.

10BaseFL
10-Mbps base-band Ethernet specification using fiber-optic cabling. 10BaseFL is part of the IEEE 10BaseF specification and, although able to interoperate with FOIRL, is designed to replace the FOIRL specification. 10BaseFL segments can be up to 3280 feet (1000meters) long if used with FOIRL, and up to 1.24 miles (2000meters) if 10BaseFL is used exclusively. See also 10BaseF , EtherChannel, and FOIRL.

10Base-T
An IEEE standard for Ethernet networking over unshielded twisted pair (UTP) cable.

100BaseFX
A 100-Mbps base-band Fast Ethernet specification using two strands of multimode fiber-optic cable per link. To guarantee proper signal timing, a 100BaseFX link cannot exceed 1312 feet (400 meters) in length. Based on the IEEE802.3 standard. See also 100BaseX, Fast Ethernet, and IEEE 802.3.

100Base-TX
IEEE 802.3u standard for 100Mbps Fast Ethernet over unshielded twisted pair cable. 100Base-TX runs over 2-pair Category 5 cable.

1000Base-F
A 1-Gbps IEEE standard for Ethernet LANs.

10BASE-T–compliant
Conforms to the IEEE 802.3 10BASE-T standard.

802.x
A set of IEEE standards for the definition of LAN protocols.

802.3
The numerical designation for the IEEE standard governing the use of the CSMA/CD media-access method.

802.3u
Supplement to the IEEE 802.3 standard which defines 100 Mbps Fast Ethernet.

802.3x
A draft to 802.3 for Full-Duplex Ethernet (FDX).

802.3y
A draft supplement to the IEEE 802.3 standard for the operation of 100 Mbps Fast Ethernet over two pairs of category 3 UTP/STP.

802.3z
A draft to 802.3 for gigabit Ethernet.

822
The short form of RFC 822. Refers to the format of Internet-style e-mail as defined in RFC 822.

AC
Alternating current.

Address
A unique numeric identifier of a node on a local area network.

Alignment error
In IEEE 802.3 networks, an error that occurs when the total number of bits of a received frame is not divisible by eight. Alignment errors usually are caused by frame damage due to collisions.

ARP
Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. Defined in RFC 826. Compare with RARP. See also proxy ARP.

AUI
Attachment unit interface. IEEE 802.3 interface between an MAU and a NIC. The term AUI also can refer to the rear panel port to which an AUI cable might attach. Also called transceiver cable . See also IEEE 802.3, MAU, and NIC.

Auto-negotiation
Feature that allows Fast Ethernet cards hubs and switches to automatically determine the maximum speed of a connection between devices. Auto-negotiation will select the fastest speed (10Mb half-duplex, 10Mb full-duplex, 100Mb half-duplex, 100Mb full duplex) common to both devices on each end of a connection.

Backbone
A network topology consisting of a length of cable with multiple network connection points.

Bandwidth
Based on the transmission speed of the network. It defines the raw data throughput theoretically possible over the network to be shared with other users within the same collision domain. For example, 10Base-T Ethernet provides 10Mbps of bandwidth.

Bandwidth reservation
The process of assigning bandwidth to users and applications served by a network. Involves assigning priority to different flows of traffic based on how critical and delay-sensitive they are. This makes the best use of available bandwidth, and if the network becomes congested, lower-priority traffic can be dropped. Sometimes called bandwidth allocation .

BNC connector
The standard connector used to connect IEEE 802.3 10Base2 coaxial cable to an MAU.

Bridge
A device that links two or more similar networks forms a single, larger network. Bridges isolate network traffic by monitoring the destination network address within an individual data packet to determine if that packet should be passed onto the other side of the network. Bridges are not protocol dependent; therefore they do not care what type of data is actually inside the packet.

broadcast
Data packet that are sent to all nodes on a network. Broadcasts are identified by a broadcast address. Compare with multicast and unicast. See also broadcast.

broadcast domain
Set of all devices that receive broadcast frames originating from any device within the set. Broadcast domains typically are bounded by routers because routers do not forward broadcast frames.

broadcast storm
An undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs.

buffer
A storage area used for handling data in transit. Buffers are used in internetworking to compensate for differences in processing speed between network devices. Bursts of data can be stored in buffers until they can be handled by slower processing devices. Sometimes referred to as a packet buffer .

Cascading
The term used to describe the connection of twisted pair hubs by running twisted pair cable from one hub to another.

Category 3 & 5 Cabling
Category 3 is a type of UTP/STP cable that can handle signaling up to 16Mhz (16 Mbps). Category 5 can handle signaling up to 100 MHz (100 Mbps). Both Category 3 and Category 5 have been standardized by the EIA/TIA. N.B. If Category 5 is in use, all components (i.e. patch panels, wall boxes, patch cables, etc.) must be Category 5 certified.

Cheapernet
Industry term used to refer to the IEEE 802.3 10Base2 standard or the cable specified in that standard. Compare with Thinnet. See also 10Base2 , EtherChannel, and IEEE 802.3.

Coaxial
One of the types of cabling used in Ethernet networks. Inside its outer insulator, a coaxial cable has two concentric conductors separated by a layer of insulation.

codec
coder-decoder. Integrated circuit device that typically uses pulse code modulation to transform analog signals into a digital bit stream and digital signals back into analog signals.

Collapsed backbone
When a single hub or switch is used to connect multiple hubs and switches together via unshielded twisted pair cabling.

Collision
A situation that occurs when two devices on a network try to transmit at the same time and their transmissions bump into each other. When a collision occurs, both sets of data must be retransmitted. Retransmission is handled automatically by the Ethernet devices.

Collision domain
A single collision domain consists of one or more Ethernet hubs and nodes connected together. Each device within the collision domain shares the available network bandwidth with the other devices in the same domain. Switches and bridges are used to separate collision domains that are too large in order to improve performance and network reliability.

community
In SNMP, a logical group of managed devices and NMSs in the same administrative domain.

CoS
class of service. An indication of how an upper-layer protocol requires a lower-layer protocol to treat its messages. In SNA subarea routing, CoS definitions are used by subarea nodes to determine the optimal route to establish a given session. A CoS definition comprises a virtual route number and a transmission priority field. Also called ToS .

CPE
customer premises equipment. Terminating equipment, such as terminals, telephones, and modems, supplied by the telephone company, installed at customer sites, and connected to the telephone company network. Can also refer to any telephone equipment residing on the customer site.

CSMA/CD
An acronym that stands for Carrier Sense Multiple Access/Collision Detection. It defines how an Ethernet network works by detecting collisions after they have occurred and automatically correcting for them.

dB
decibels. Unit for measuring relative power ratios in terms of gain or loss. Units are expressed in terms of the logarithm to base 10 of a ratio and typically are expressed in watts. dB is not an absolute value, rather it is the measure of power lost or gained between two devices. For example, a -3dB loss indicates a 50% loss in power; a +3dB reading is a doubling of power. The rule of thumb to remember is that 10 dB indicates an increase (or a loss) by a factor of 10; 20 dB indicates an increase (or a loss) of a factor of 100; 30 dB indicates an increase (or a loss) by a factor of 1000.

Because antennas and other RF devices/systems commonly have power gains or losses on the orders of magnitude or even orders of four orders of magnitude, dB is a more easily used expression.

dBm
decibels per milliwatt. 0 dBm is defined as 1 mw at 1 kHz of frequency at 600 ohms of impedance.

dedicated LAN
Network segment allocated to a single device. Used in LAN switched network topologies.
Device Electronic equipment used on a network, such as a hub, router, workstation, or printer.

DHCP
Dynamic Host Configuration Protocol. Provides a mechanism for allocating IP addresses dynamically so that addresses can be reused when hosts no longer need them.

DWDM
dense wavelength division multiplexing. Optical transmission of multiple signals over closely spaced wavelengths in the 1550 nm region. (Wavelength spacings are usually 100 GHz or 200 GHz, which corresponds to 0.8 nm or 1.6 nm.)

EIA/TIA
Electronic Industry Association/Telecommunications Industry Association. A body involved in the setting of various industry standards including those applicable to cabling.

EMI
electromagnetic interference. Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels.

enterprise network
Large and diverse network connecting most major points in a company or other organization. Differs from a WAN in that it is privately owned and maintained.

Ethernet

A 10 megabit per second (Mbps) baseband-type network that uses the contention-based CSMA/CD media access method. Invented by Robert Metcalfe at Xerox's Palo Alto Research Center in the mid-1970s.

Ethernet II Frame
An Ethernet frame format defined by the IEEE. Ethernet II frames are usually associated with the TCP/IP protocol.

Ethernet adapter
A component installed in a device that enables the device to connect to, and communicate on, an Ethernet network; usually an Ethernet interface card with Ethernet driver software.

Fast Ethernet
IEEE 802.3u standard defining a type of local area network characterized by a 100-megabit per second (Mbps) data rate. Fast Ethernet networks can run over different types of cabling. The most popular is 100Base-TX Fast Ethernet which uses category 5 unshielded twisted-pair cabling.

FDX
Full-Duplex Ethernet. Ethernet (both 10 Mbps and 100 Mbps), without collisions. Since no collisions take place the bit budget of Ethernet is not applicable. Extended distances (when using Single-Mode fiber) can be achieved if Full-Duplex Ethernet is used.

FDX
Full-Duplex Ethernet. Ethernet (both 10 Mbps and 100 Mbps), without collisions. Since no collisions take place the bit budget of Ethernet is not applicable. Extended distances (when using Single-Mode fiber) can be achieved if Full-Duplex Ethernet is used.

Fiber Optic cable
Special cable that uses light, instead of electrical signals, to transmit network data at high speeds and over longer distances.

Filtering
The process that a switch or bridge uses to examine an Ethernet packet and either pass it to the other side of the network or isolate it from the rest of the network. (See the definition for a Bridge.)

firmware
Software instructions set permanently or semipermanently in ROM.

flooding
Traffic passing technique used by switches and bridges in which traffic received on an interface is sent out all the interfaces of that device except the interface on which the information was received originally.

flow control
Technique for ensuring that a transmitting entity, such as a modem, does not overwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed. In IBM networks, this technique is called pacing .

FOIRL
fiber-optic inter-repeater link. Fiber-optic signaling methodology based on the IEEE802.3 fiber-optic specification. FOIRL is a precursor of the 10BaseFL specification, which is designed to replace it. See also 10BaseFL .

Frame
A term applied to an Ethernet packet. Full Duplex When two network devices, such as a card and a switch, can simultaneously send and receive data, effectively doubling the bandwidth of a connection.

Gateway
An historically INCORRECT term used by the Internet. In reality, a gateway is really a router or bridge which allows connection onto the Internet.

Gigabit Ethernet
A new standard for transmitting Ethernet packets at 1000Mbps.

GUI

graphical user interface. A user environment that uses pictorial as well as textual representations of the input and the output of applications and the hierarchical or other data structure in which information is stored. Such conventions as buttons, icons, and windows are typical, and many actions are performed using a pointing device (such as a mouse). Microsoft Windows and the Apple Macintosh are prominent examples of platforms using a GUI.

half duplex
Capability for data transmission in only one direction at a time between a sending station and a receiving station.BSC is an example of a half-duplex protocol. See also BSC. Compare with full duplex and simplex.

Hop count
From the IEEE 802.3 Ethernet standard, the hop count for an Ethernet network is defined by the number of hubs an Ethernet signal must pass through to get to its final destination. 10Base-T rules limit the maximum number of hops to four hubs, while Fast Ethernet limits the number of hops to two.

host
Computer system on a network. Similar to node, except that host usually implies a computer system, whereas node generally applies to any networked system, including access servers and routers.

Hot-swapping
The ability to remove and replace a network device interface without taking the network out of service or powering down the network device.

Hub
A multi-port repeater; the center of an active star network. IEEE ( Institute of Electrical and Electronic Engineers) an international professional society that issues its own standards related to electrical and electronic devices.

Hybrid network
Internet work made up of more than one type of network technology, including LANs and WANs.

IAB
Internet Architecture Board - The "top" committee of the Internet. Responsible for overseeing the IETF and IESG.

IANA
Internet Assigned Numbers Authority - A committee responsible for assigning "numbers" for the Internet suit of protocol (IP addresses, enterprise specific MIBs, etc).

ICMP
Internet Control Message Protocol - A reporting protocol for the IP component of TCP/IP. ICMP relays messages as to the status of an IP connection.

IEA

Electronic Industries Association - A professional organization that formulates computer and communications standards in the U.S.

IEEE

Institute of Electrical and Electronics Engineers. Professional organization whose activities include the development of communications and network standards. IEEE LAN standards are the predominant LAN standards today.

IEEE 802

A committee responsible for setting standards for LANs. LAN (Local Area Network) Workstations and shared devices connected in a limited area, usually a single building.

IEEE 802.1

IEEE specification that describes an algorithm that prevents bridging loops by creating a spanning tree. The algorithm was invented by Digital Equipment Corporation. The Digital algorithm and the IEEE 802.1 algorithm are not exactly the same, nor are they compatible. See also spanning tree, spanning-tree algorithm, and Spanning-Tree Protocol.

IEEE 802.2

IEEE LAN protocol that specifies an implementation of the LLC sublayer of the data link layer. IEEE 802.2 handles errors, framing, flow control, and the network layer (Layer 3) service interface. Used in IEEE 802.3 and IEEE 802.5 LANs. See also IEEE 802.3 and IEEE 802.5 .

IEEE 802.3

IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sub-layer of the data link layer. IEEE 802.3 uses CSMA/CD access at a variety of speeds over a variety of physical media. Extensions to the IEEE 802.3 standard specify implementations for Fast Ethernet. Physical variations of the original IEEE 802.3 specification include 10Base2 , 10Base5 , 10BaseF , 10BaseT , and 10Broad36 . Physical variations for Fast Ethernet< include 100BaseT , 100BaseT4 , and 100BaseX .

IEEE 802.3 Repeater MIB
The IEEE MIB for repeaters and hubs.

IESG
Internet Engineering Steering Group - The coordinators of IETF and standard setters for the Internet.

IETF
Internet Engineering Task Force - A task force under supervision of the IAB responsible for answering the "short term" needs of the Internet.

IGMP
Internet Group Management Protocol. Used by IP hosts to report their multicast group memberships to an adjacent multicast router.

Interference
Unwanted communication channel noise.

Internet
A collection of computer networks all running the Internet suite of protocols. The Internet is the basic foundation for the "information super-highway".

internet (with a small "I")

A term applied to a group of interconnected networks.

Interoperability

Capability of computing equipment manufactured by different vendors to communicate with one another successfully over a network.

IP

Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internet work service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security. Defined in RFC 791.

IP address
32-bit address assigned to hosts using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as 4 octets separated by periods (dotted decimal format). Each address consists of a network number, an optional sub-network number, and a host number. The network and sub-network numbers together are used for routing, and the host number is used to address an individual host within the network or sub-network. A subnet mask is used to extract network and sub-network information from the IP address. CIDR provides a new way of representing IP addresses and subnet masks. Also called an Internet address.

IP multicast
Routing technique that allows IP traffic to be propagated from one source to a number of destinations or from many sources to many destinations. Rather than sending one packet to each destination, one packet is sent to a multicast group identified by a single IP destination group address.

ISO

International Organization for Standardization. International organization that is responsible for a wide range of standards, including those relevant to networking. ISO developed the OSI reference model, a popular networking reference model.

ISO 9000
Set of international quality-management standards defined by ISO. The standards, which are not specific to any country, industry, or product, allow companies to demonstrate that they have specific processes in place to maintain an efficient quality system.

LAN

Local-area network. High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies.

laser
light amplification by stimulated emission of radiation. Analog transmission device in which a suitable active material is excited by an external stimulus to produce a narrow beam of coherent light that can be modulated into pulses to carry data. Networks based on laser technology are sometimes run over SONET.

LED
light emitting diode. Semiconductor device that emits light produced by converting electrical energy. Status lights on hardware devices are typically LEDs.

Loop

Route where packets never reach their destination, but simply cycle repeatedly through a constant series of network nodes.

MAC

Media Access Control. Lower of the two sub-layers of the data link layer defined by the IEEE. The MAC sub-layer handles access to shared media, such as whether token passing or contention will be used.

MAC address
Standardized data link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. MAC addresses are 6 bytes long and are controlled by the IEEE. Also known as a hardware address , MAC layer address , and physical address .

MAN
metropolitan-area network. Network that spans a metropolitan area. Generally, a MAN spans a larger geographic area than a LAN, but a smaller geographic area than a WAN.

MIB

Short for Management Information Base, a database of objects that can be monitored by a network management system. Both SNMP and RMON use standardized MIB formats that allows any SNMP and RMON tools to monitor any device defined by a MIB.

Network administrator
A person who coordinates the design, installation and management of a network. A network administrator is also responsible for adding new users to the network and troubleshooting.

Network topology

A physical arrangement of devices and cable in a network.

NIC
Network Interface Card - An adapter card providing the physical connection between a computer and the network medium.

NMS
Network Management Software - A term applied to ANY SNMP compliant management software. Not to be confused with NetWare Management Services from Novell.

Node
A single, addressable device on a network. Computers, networked printers, and routers are nodes.

Non-volatile RAM
Memory which holds its information even when main power is turned off. Usually, non-volatile RAM is backed up via a battery.

Octet
Eight bytes make an octet. Many MIBs have a managed object for counting the number of octets received by the MAC, the port or the index.

Packet
A group of digital information (known as bits) that has been formatted together to be transmitted across a network.

POP

1. point of presence. In OSS, a physical location where an inter-exchange carrier installed equipment to interconnect with a local exchange carrier (LEC) .

2. Post Office Protocol. Protocol that client e-mail applications use to retrieve mail from a mail server.

Port
An access point for data to enter, exit, or be repeated across a network; a hardware receptacle on a network device, such as a socket or jack, into which you can plug a connector.

Promiscuous Mode
The MAC interface on the device that will record/capture ALL packets on the collision domain, regardless to the fact that the packet may NOT be destined to this MAC. Protocol A language or set of rules used for network communication. Popular protocols used in most networks include TCP/IP, IPX and AppleTalk.

Protocol Stack
Several protocols that are stacked on top of each other to form a layered structure in which each protocol utilizes the services provided by the layer below and provides services to the layer above.

RARP

Reverse Address Resolution Protocol. Protocol in the TCP/IP stack that provides a method for finding IP addresses based on MAC addresses.

Repeater

A device that rebroadcasts a network signal, allowing it to travel for longer distances. Repeaters have no effect on the speed of a network signal. Hubs are multi-port repeaters.

RFC
Request For Comment - A document describing an Internet protocol (e.g.: RFC1155 is the "core" document for SNMP).

RFC1155 SMI
Structure and identification of Management Information. The core RFC for SNMP compliant devices.

RFC1157 SNMP
Definition of the SNMP command set and PDU.

RFC1212 Concise MIB definition
The RFC outlining how MIBs should be structured.

RFC1213 Management Information Base II
The Internet Standard MIB. The minimum MIB requirement in order to be called SNMP compatible.

RFC1271 RMON MIB
Remote MONitor MIB. A MIB designed for monitoring and diagnosing traffic on a collision domain.

RFC1398
MIB for "Ether-like" interfaces.

RFI
Radio Frequency Interference - Unwanted "noise" created by current-producing devices such as electric motors and fluorescent lights. RFI effects the quality of the signal passing through some data transmission medium.

Ring topology
Network topology that consists of a series of repeaters connected to one another by unidirectional transmission links to form a single closed loop. Each station on the network connects to the network at a repeater. Although logically a ring, ring topologies most often are organized in a closed-loop star

RJ -45
A telephone-industry connector type usually containing eight pins.

RMON
remote monitoring. MIB agent specification described in RFC 1271 that defines functions for the remote monitoring of networked devices. The RMON specification provides numerous monitoring, problem detection, and reporting capabilities.

Router
A device that connects two or more networks; a router receives data from other network devices and retransmits the data to its proper destination over the most efficient path from one network to another.

Routing protocol
Protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include IGRP, OSPF, and RIP.

Routing table
Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes.

RS-232

Popular physical layer interface. Now known as EIA/TIA-232. See also EIA/TIA-232.

RS232-C

An IEA standard definition for the 25-pin interface linking DTEs and DCEs. RS232-C is suitable for both synchronous and asynchronous communications.

RS422
An IEA recommended standard definition for extending an RS 232C interface beyond the 50 foot limit.

RS485
Similar to RS422 but is used in multi-point application where up to 64 network devices may be interconnected.

Segment
An electronically continuous portion of a network, usually consisting of the same coaxial cable with multiple devices attached.

Single-Mode Fiber
A type of fiber that uses a single path for light transmission (i.e. the light is not reflected within the core). Single-Mode supports greater distances than multi-mode. Typically, Single-Mode fiber may support distances from between 2Km up to 20Km. The distance supported is a factor of the loss budget of the cable vs. the power budget of the Single-Mode transmitter.

SGMP
Simple Gateway Monitoring Protocol - The forerunner of SNMP. SGMP was developed by the Internet community to manage the gateways which provide access to the Internet.

SNMP

Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security.

SNMPv2

Version 2 of the SNMP Protocol. The next release of SNMPv2 adds extra security, commands and statistics.

Socket
A unique number defined by the TCP/IP protocol indicating what type of services or packet the frame is composed of. (e.g.: socket 161 is a UDP/SNMP socket)

spanning tree
Loop-free subset of a network topology. See also spanning-tree algorithm and Spanning-Tree Protocol .

spanning-tree algorithm
Algorithm used by the Spanning-Tree Protocol to create a spanning tree. Sometimes abbreviated as STA. See also spanning tree and Spanning-Tree Protocol .

Star topology
A network design where several network branches are connected at one central location.

Store and forward

Function whereby a message is transmitted to some intermediate relay point and temporarily stored before forwarding to the next relay point.

STP
Shielded Twisted Pair - Cabling with metal-backed mylar, plastic or PVC covering to protect it from EMI and RFI. STP cable offers better noise protection than UTP (Unshielded Twisted Pair) cabling.

Subnet
A physically distinct network identified by its IP address.

Subnet-mask
A 32-bit number used by IP to identify subnets.

Subnet-number
The part of the IP address which identifies a certain subnet.

Switch
An advanced type of Ethernet, Fast Ethernet or Gigabit Ethernet hub that uses the destination address of a data packet to intelligently direct network traffic to specific devices on the network, thus optimizing overall network performance.

TCP/IP

Transmission Control Protocol/Internet Protocol. Common name for the suite of protocols developed by the U.S. DoD in the 1970s to support the construction of worldwide internetworks. TCP and IP are the two best-known protocols in the suite.

Telnet

Standard terminal emulation protocol in the TCP/IP protocol stack. Telnet is used for remote terminal connection, enabling users to log in to remote systems and use resources as if they were connected to a local system. Telnet is defined in RFC 854.

Terminal server
Communications processor that connects asynchronous devices, such as terminals, printers, hosts, and modems, to any LAN or WAN that uses TCP/IP, X.25, or LAT protocols. Terminal servers provide the internet work intelligence that is not available in the connected devices.

Throughput
The actual speed in which data is transmitted over the network. In some cases, this may be significantly lower than the bandwidth available.

Transceiver
Hardware that transmits and receives network signals. Every device on an Ethernet network needs a transceiver. Some Ethernet transceivers are integrated, such as the transceiver circuitry built into the Ethernet cards; others are external.

tree topology
LAN topology similar to a bus topology, except that tree networks can contain branches with multiple nodes. Transmissions from a station propagate the length of the medium and are received by all other stations.

Twisted-pair
Cable type as specified by 10BASE-T in IEEE 802.3; 8-wire telephone cable using RJ-45 connectors.

Uplink
The auxiliary port of an Ethernet hub or switch which can be used for connecting to a larger Ethernet network.

UTP
Unshielded Twisted Pair - Cabling with insulation material like that commonly used with telephone cabling but without a covering to protect it from EMI and RFI. The cable consists of at least two conductors twisted together six twists per inch to minimize the effects of electromagnetic radiation.

Virtualization
Process of implementing a network based on virtual network segments. Devices are connected to virtual segments independent of their physical location and their physical connection to the network.

Virus
Hidden, self-replicating section of computer software, usually malicious logic, that propagates by infecting—that is, inserting a copy of itself into and becoming part of—another program. A virus cannot run by itself; it requires that its host program be run to make the virus active.

VLAN

Virtual LAN. Group of devices on one or more LANs that are configured (using management software) so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible.

WAN (Wide Area Network)
Two or more LANs in separate geographic locations that are connected using long distance communications methods, such as telephone lines and satellites.

wavelength
The length of one complete wave of an alternating or vibrating phenomenon, generally measured from crest to crest or from trough to trough of successive waves.

WDM

Wavelength division multiplexing. Multiple optical wavelengths can share the same transmission fiber. The spectrum occupied by each channel must be adequately separated from the others.

Wiring closet
A central location where a building’s telephone and network wiring is connected. Telephone lines in a wiring closet branch out to individual extensions. Multi-story buildings with ten floors have a main wiring closet in the basement and satellite wiring closets on each

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