Net+ Chapter 5

Front 1

10GBase-LW

Back 1

A variation of the 10GBase-LR standard that is specially encoded to operate over SONET links

Front 2

10GBase-SR

Back 2

A Physical layer standard for achieving 10-Gbps data transmission over multimode fiber using wavelengths of 850 nanometers. The maximum segment length for 10GBase-SR can reach up to 300 meters, depending on the fiber core diameter and modal bandwidth used.

Front 3

10GBase-SW

Back 3

A variation of the 10GBase-SR standard that is specially encoded to operate over SONET links.

Front 4

10GBase-T

Back 4

A Physical layer standard for achieving 10-Gbps data transmission over twisted pair cable. Described in its 2006 standard 802.3an, IEEE specifies Cat 6 or Cat 7 cable as the appropriate medium for 10GBase-T. The maximum segment length for 10GBase-T is 100 meters.

Front 5

100Base-FX

Back 5

A Physical layer standard for networks that specifies baseband transmission,

multimode fiber cabling, and 100-Mbps throughput. 100Base-FX networks have a

maximum segment length of 2000 meters. 100Base-FX may also be called Fast Ethernet.

Front 6

100Base-T

Back 6

A Physical layer standard for networks that specifies baseband transmission, twisted pair cabling, and 100-Mbps throughput. 100Base-T networks have a maximum segment length of 100 meters and use the star topology. 100Base-T is also known as Fast Ethernet

Front 7

100Base-TX

Back 7

A type of 100Base-T network that uses two wire pairs in a twisted pair cable, but uses faster signaling to achieve 100-Mbps throughput. It is capable of full-duplex transmission and requires Cat 5 or better twisted pair media.

Front 8

1000Base-LX

Back 8

A Physical layer standard for networks that specifies 1-Gbps transmission over fiber-optic cable using baseband transmission. 1000Base-LX can run on either single-mode or multimode fiber. The LX represents its reliance on long wavelengths of 1300 nanometers. 1000Base-LX can extend to 5000-meter segment lengths using single-mode, fiber-optic cable. 1000Base-LX networks can use one repeater between segments.

Front 9

1000Base-SX

Back 9

A Physical layer standard for networks that specifies 1-Gbps transmission

over fiber-optic cable using baseband transmission. 1000Base-SX runs on multimode fiber.

Its maximum segment length is 550 meters. The SX represents its reliance on short

wavelengths of 850 nanometers. 1000Base-SX can use one repeater.

Front 10

1000Base-T

Back 10

A Physical layer standard for achieving 1 Gbps over UTP. 1000Base-T achieves its higher throughput by using all four pairs of wires in a Cat 5 or better twisted pair cable to both transmit and receive signals. 1000Base-T also uses a different data encoding scheme than that used by other UTP Physical layer specifications

Front 11

5-4-3 rule

Back 11

A guideline for 10-Mbps Ethernet networks stating that between two communicating nodes, the network cannot contain more than five network segments connected by four repeating devices, and no more than three of the segments may be populated.

Front 12

802.3ab

Back 12

The IEEE standard that describes 1000Base-T, a 1-gigabit Ethernet technology that runs over four pairs of Cat 5 or better cable.

Front 13

802.3ae

Back 13

The IEEE standard that describes 10-gigabit Ethernet technologies, including 10GBase-SR, 10GBase-SW, 10GBase-LR, 10GBase-LW, 10GBase-ER, and 10GBase-EW.

Front 14

802.3af

Back 14

The IEEE standard that specifies a way of supplying electrical Power over Ethernet

(PoE). 802.3af requires Cat 5 or better UTP or STP cabling and uses power sourcing

equipment to supply current over a wire pair to powered devices. PoE is compatible with

existing 10Base-T, 100Base-TX, 1000Base-T, and 10GBase-T implementations.

Front 15

802.3an

Back 15

The IEEE standard that describes 10GBase-T, a 10-Gbps Ethernet technology that runs on Cat 6 or Cat 7 twisted pair cable.

Front 16

802.3u

Back 16

The IEEE standard that describes Fast Ethernet technologies, including

100Base-TX.

Front 17

802.3z

Back 17

The IEEE standard that describes 1000Base (or 1-gigabit) Ethernet technologies, including 1000Base-LX and 1000Base-SX

Front 18

access method

Back 18

A network’s method of controlling how nodes access the communications channel. For example, CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is the access method specified in the IEEE 802.3 (Ethernet) standard.

Front 19

active topology

Back 19

A topology in which each workstation participates in transmitting data over the network. A ring topology is considered an active topology

Front 20

broadcast domain

Back 20

Logically grouped network nodes that can communicate directly via broadcast transmissions. By default, switches and repeating devices such as hubs extend broadcast domains. Routers and other Layer 3 devices separate broadcast domains.

Front 21

bus

Back 21

The single cable connecting all devices in a bus topology.

Front 22

bus topology

Back 22

A topology in which a single cable connects all nodes on a network without

intervening connectivity devices.

Front 23

Carrier Ethernet

Back 23

A level of Ethernet service that is characterized by very high throughput and reliability and is used between carriers, such as NSPs.

Front 24

circuit switching

Back 24

A type of switching in which a connection is established between two network nodes before they begin transmitting data. Bandwidth is dedicated to this connection and remains available until users terminate the communication between the two nodes.

Front 25

collapsed backbone

Back 25

A type of backbone that uses a router or switch as the single central connection point for multiple subnetworks.

Front 26

collision

Back 26

In Ethernet networks, the interference of one node’s data transmission with the

data transmission of another node sharing the same segment.

Front 27

collision domain

Back 27

The portion of an Ethernet network in which collisions could occur if two nodes transmit data at the same time. Switches and routers separate collision domains.

Front 28

CSMA/CD (Carrier Sense Multiple Access with Collision Detection)

Back 28

A network access method specified for use by IEEE 802.3 (Ethernet) networks. In CSMA/CD, each node waits its turn before transmitting data to avoid interfering with other nodes’ transmissions. If a node’s NIC determines that its data have been involved in a collision, it immediately stops transmitting. Next, in a process called jamming, the NIC issues a special 32-bit sequence that indicates to the rest of the network nodes that its previous transmission was faulty and that those data frames are invalid. After waiting, the NIC determines if the line is again available; if it is available, the NIC retransmits its data.

Front 29

daisy chain

Back 29

A group of connectivity devices linked together in a serial fashion.

Front 30

data propagation delay

Back 30

The length of time data take to travel from one point on the segment to another point. On Ethernet networks, CSMA/CD’s collision detection routine cannot operate accurately if the data propagation delay is too long.

Front 31

distributed backbone

Back 31

A type of backbone in which a number of intermediate connectivity devices are connected to one or more central connectivity devices, such switches or routers, in a hierarchy.

Front 32

enterprise

Back 32

An entire organization, including local and remote offices, a mixture of computer systems, and a number of departments. Enterprise-wide computing takes into account the breadth and diversity of a large organization’s computer needs.

Front 33

Ethernet II

Back 33

The original Ethernet frame type developed by Digital Equipment Corporation, Intel, and Xerox, before the IEEE began to standardize Ethernet. Ethernet II is distinguished from other Ethernet frame types in that it contains a 2-byte type field to identify the upper layer protocol contained in the frame. It supports TCP/IP and other higher-layer protocols.

Front 34

Fast Ethernet

Back 34

A type of Ethernet network that is capable of 100-Mbps throughput. 100Base-T and 100Base-FX are both examples of Fast Ethernet.

Front 35

fault tolerance

Back 35

The capability for a component or system to continue functioning despite damage or malfunction.

Front 36

Gigabit Ethernet

Back 36

A type of Ethernet network that is capable of 1000-Mbps, or 1-Gbps, throughput.

Front 37

hybrid topology

Back 37

A physical topology that combines characteristics of more than one simple physical topology.

Front 38

jamming

Back 38

A part of CSMA/CD in which, upon detecting a collision, a station issues a special 32-bit sequence to indicate to all nodes on an Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty.

Front 39

logical topology

Back 39

A characteristic of network transmission that reflects the way in which data are transmitted between nodes. A network’s logical topology may differ from its physical topology. The most common logical topologies are bus and ring.

Front 40

MPLS (multiprotocol label switching)

Back 40

A type of switching that enables any one of several Layer 2 protocols to carry multiple types of Layer 3 protocols. One of its benefits is the

ability to use packet-switched technologies over traditionally circuit-switched networks. MPLS can also create end-to-end paths that act like circuit-switched connections.

Front 41

modal bandwidth

Back 41

A measure of the highest frequency of signal a multimode fiber-optic cable can support over a specific distance. Modal bandwidth is measured in MHz-km.

Front 42

packet switching

Back 42

A type of switching in which data are broken into packets before being transported. In packet switching, packets can travel any path on the network to their destination because each packet contains a destination address and sequencing information.

Front 43

padding

Back 43

The bytes added to the data (or information) portion of an Ethernet frame to ensure this field is at least 46 bytes in size. Padding has no effect on the data carried by the frame.

Front 44

parallel backbone

Back 44

A type of backbone that consists of more than one connection from the central router or switch to each network segment.

Front 45

passive topology

Back 45

A network topology in which each node passively listens for, then accepts, data directed to it. A bus topology is considered a passive topology.

Front 46

PD (powered device)

Back 46

On a network using Power over Ethernet, a node that receives power from power sourcing equipment.

Front 47

physical topology

Back 47

The physical layout of the media, nodes, and devices on a network. A physical topology does not specify device types, connectivity methods, or addressing schemes. Physical topologies are categorized into three fundamental shapes: bus, ring, and star. These shapes can be mixed to create hybrid topologies.

Front 48

PoE (Power over Ethernet)

Back 48

A method of delivering current to devices using Ethernet connection cables.

Front 49

preamble

Back 49

The field in an Ethernet frame that signals to the receiving node that data are incoming and indicates when the data flow is about to begin.

Front 50

PSE (power sourcing equipment)

Back 50

On a network using Power over Ethernet, the device that supplies power to end nodes.

Front 51

QoS (quality of service)

Back 51

The result of specifications for guaranteeing data delivery within a certain period of time after their transmission.

Front 52

ring topology

Back 52

A network layout in which each node is connected to the two nearest nodes so that the entire network forms a circle. Data are transmitted in one direction around the ring. Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation in the ring.

Front 53

serial backbone

Back 53

A type of backbone that consists of two or more internetworking devices connected to each other by a single cable in a daisy chain.

Front 54

SFD (start-of-frame delimiter)

Back 54

A 1-byte field that indicates where the data field begins in an Ethernet frame.

Front 55

signal bounce

Back 55

A phenomenon, caused by improper termination on a bus-topology network, in which signals travel endlessly between the two ends of the network, preventing new signals from getting through.

Front 56

star topology

Back 56

A physical topology in which every node on the network is connected through a central connectivity device. Any single physical wire on a star network connects only two devices, so a cabling problem will affect only two nodes. Nodes transmit data to the device, which then retransmits the data to the rest of the network segment where the destination node can pick it up.

Front 57

star-wired bus topology

Back 57

A hybrid topology in which groups of workstations are connected in a star fashion to connectivity devices that are networked via a single bus.

Front 58

star-wired ring topology

Back 58

A hybrid topology that uses the physical layout of a star and the token-passing data transmission method.

Front 59

switching

Back 59

A component of a network’s logical topology that manages how packets are filtered and forwarded between nodes on the network.

Front 60

terminator

Back 60

A resistor that is attached to each end of a bus topology network and that causes the signal to stop rather than reflect back toward its source.