CCNA 1 and 2 Companion Guide, Revised (Cisco Networking Academy Program) part 104 potx

protocol stack A set of related communications protocols that operate together and, as a group, address communication at some or all of the seven layers of the OSI reference model.. Not

plenum An open ceiling that acts as an air-return duct for heating, ventilation, and

air-conditioning systems

plug-in Software or a program that can easily be installed and used as part of a web

browser

PM (phase modulation) Modulates the polarity (phase) of the wave

poison reverse updates Updates that are necessary to defeat larger routing loops

Generally speaking, increases in routing metrics indicate routing loops Poison reverse

updates are then sent to remove the route and place it in holddown

port In IP terminology, an upper-layer process that receives information from lower

layers Ports are numbered, and many are associated with a specific process For example,

SMTP is associated with port 25 A port number of this type is called a well-known

port or address

power cord Connects an electrical device to an electrical outlet to provide power to

the device

power supply Supplies power to a computer

power-on self-test (POST) Set of hardware diagnostics that runs on a hardware device

when that device is powered up

presentation layer Layer 6 of the OSI reference model This layer ensures that

infor-mation sent by the application layer of one system can be read by the application layer

of another

printed circuit board (PCB) A thin plate on which chips (integrated circuits) and other

electronic components are placed

privileged mode Used for copying and managing entire configuration files

propagation delay A simple measurement of how long it takes for a signal to travel

along the cable being tested

protocol stack A set of related communications protocols that operate together and,

as a group, address communication at some or all of the seven layers of the OSI reference

model Not every protocol stack covers each layer of the model, and often a single

pro-tocol in the stack addresses a number of layers at once TCP/IP is a typical propro-tocol

stack

protocol suite A set of related communications protocols that operate together and,

as a group, address communication at some or all of the seven layers of the OSI

refer-ence model Not every protocol stack covers each layer of the model, and often a single

protocol in the suite addresses a number of layers at once TCP/IP is a typical protocol

suite

protocol A formal description of a set of rules and conventions that govern how devices on a network exchange information

effect of ELFEXT from all wire pairs

from all wire pairs in the cable

pulse Pulses determine the value of the data being transmitted If a disturbance is deliberately caused and involves a fixed, predictable duration, it is called a pulse

queuing A process by which ACLs can designate certain packets to be processed by

a router before other traffic, on the basis of some configurable parameter such as spec-ifying a protocol

raceway Channels that contain cables in an installation Raceways include common electrical conduit, specialized cable trays or ladder racks, in-floor duct systems, and plastic or metal surface-mounted raceways

RAM (random-access memory) Volatile memory that can be read and written by a microprocessor

data written to it as well as stored data read from it

range error A frame that had a legal-size value in the Length field but that did not match the actual number of octets counted in the Data field of the received frame

RARP (Reverse Address Resolution Protocol) Protocol in the TCP/IP stack that provides

a method for finding IP addresses based on MAC addresses

RCP (remote copy protocol) Protocol that allows users to copy files to and from a file system residing on a remote host or server on the network

prerecorded

reflection Reflection is the photons of light striking a surface and leaving that surface

in an equal but opposite direction

refraction Refraction is the change in direction of a beam of light when it enters another medium

repeater A networking device that exists at Layer 1, the physical layer, of the OSI reference model The purpose of a repeater is to regenerate and retime network signals

at the bit level, allowing them to travel a longer distance on the medium

resistance The property of a material that resists electron movement.

RFI (radio frequency interference) Noise from other signals being transmitted

nearby

ring topology A topology in which hosts are connected in the form of a ring or circle

Unlike the physical bus topology, the ring topology has no beginning or end that needs

to be terminated

most common IGP in the Internet RIP uses hop count as a routing metric

RJ-45 A connector commonly used for finishing a twisted-pair cable

routed protocol A protocol that can be routed by a router A router must be capable

of interpreting the logical internetwork as specified by that routed protocol Examples

of routed protocols are AppleTalk, IPX, and IP

router A network layer device that uses one or more metrics to determine the optimal

path along which network traffic should be forwarded Routers forward packets from

one network to another based on network-layer information contained in routing updates

Occasionally called a gateway (although this definition of gateway is becoming

increasingly outdated)

routing The process of finding a path to a destination host Routing is very complex

in large networks because of the many potential intermediate destinations that a

packet might traverse before reaching its destination host

Routing Information Protocol (RIP) An IGP supplied with UNIX BSD systems The

most common IGP in the Internet RIP uses hop count as a routing metric

routing metric A method by which a routing algorithm determines that one route is

better than another This information is stored in routing tables and is sent in routing

updates Metrics include bandwidth, communication cost, delay, hop count, load,

MTU, path cost, and reliability Sometimes simply called a metric.

routing protocol A protocol that accomplishes routing through the implementation

of a specific routing algorithm Examples of routing protocols are IGRP, OSPF, and RIP

routing table A 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

routing update A message sent from a router to indicate network reachability and

associated cost information Routing updates are typically sent at regular intervals

and after a change in network topology Compare with flash update

SCS (structured cabling system) Integrated cable plans that include the connectors, wiring, distribution centers, and installation techniques developed by specific companies

segment A section of a network that is bounded by bridges, routers, or switches

segment In the TCP specification, a logical information group at transport layers of the OSI reference model

serial port Can be used for serial communication in which only 1 bit is transmitted at

a time

session layer Layer 5 of the OSI reference model This layer establishes, manages, and terminates sessions between applications and manages data exchange between presentation layer entities

shortest path first (SPF) algorithm A calculation performed on the database resulting

in the SPF tree

simplex The capability for transmission in only one direction between a sending station and a receiving station Broadcast television is an example of a simplex technology

sine waves Graphs of mathematical functions of many natural occurrences that change regularly over time, such as the distance from the earth to the sun, the distance from the ground while riding a Ferris wheel, and the time of day that the sun rises

single-mode Single-mode is an optical fiber that has only one mode of light transmis-sion Contrast with multimode

SNAP (Subnetwork Access Protocol) Internet protocol that operates between a net-work entity in the subnetnet-work and a netnet-work entity in the end system SNAP specifies

a standard method of encapsulating IP datagrams and ARP messages on IEEE networks The SNAP entity in the end system makes use of the services of the subnetwork and performs three key functions: data transfer, connection management, and QoS selection

used almost exclusively in TCP/IP networks SNMP provides a means of monitoring and controlling network devices and managing configurations, statistics collection, performance, and security

SNR (signal-to-noise ratio) The ratio of useable signal being transmitted to the undesired signal (noise) It is a measure of transmission quality The ratio of good data (signal) to bad (noise) on a line, expressed in decibels (dB)

sound card An expansion board that handles all sound functions

spectrum analyzer An electronic device that creates graphs for frequency-domain

analysis Engineers also use frequency-domain analysis to study signals

split horizon A routing technique in which information about routes is prevented

from exiting the router interface through which that information was received

Split-horizon updates are useful in preventing routing loops

square waves Graphs that do not continuously vary with time The values remain the

same for some time, then suddenly change, then remain the same, and then suddenly

return to the initial value

SS (spread spectrum) A modulation technique developed in the 1940s that spreads a

transmission signal over a broad band of radio frequencies The term spread spectrum

describes a modulation technique that sacrifices bandwidth to gain signal-to-noise

performance

standard A set of rules or procedures that are either widely used or officially specified

standard ACL ACL that compares source IP addresses to the rules defining a

stan-dard ACL.

star topology The most commonly used physical topology in Ethernet LANs The

star topology is made up of a central connection point that is a device such as a hub,

switch, or router, where all the cabling segments meet

static routing The process of manually defining and configuring the routes

storage-area network (SAN) A dedicated, high-performance network that moves

data between servers and storage resources

store-and-forward switching A packet-switching technique in which frames are

pro-cessed completely before being forwarded out the appropriate port This processing

includes calculating the CRC and checking the destination address In addition, frames

must be stored temporarily until network resources (such as an unused link) are

avail-able to forward the message

STP (shielded twisted-pair) STP is a two-pair wiring medium used in a variety of

network implementations STP cabling has a layer of shielded insulation to reduce EMI

STP (Spanning Tree Protocol) Bridge protocol that uses the spanning tree algorithm,

enabling a learning bridge dynamically to work around loops in a network topology

by creating a spanning tree Bridge exchange BPDU messages with other bridges to

detect loops and then remove the loops by shutting down selected bridge interfaces

straight-through cable A cable that maintains the pin connection all the way through

the cable Thus, the wire connected to pin 1 is the same on both ends of the cable

structured cabling A uniform cabling system with standards that define the actual cable, cabling distances, type of cable, and type of terminating devices

stub network An OSPF area that carries a default route, intra-area routes, and inter-area routes, but that does not carry external routes

subnet address A portion of an IP address that is specified as the subnetwork by the subnet mask

subnet mask A 32-bit address mask used in IP to indicate the bits of an IP address

that are used for the subnet address Sometimes simply called a mask.

subnetting The method of dividing full network address classes into smaller pieces This has prevented complete IP address exhaustion

subnetwork mask A 32-bit address mask used in IP to indicate the bits of an IP address that are being used for the subnet address

subnetwork 1 In IP networks, a network sharing a particular subnet address Sub-networks are Sub-networks arbitrarily segmented by a network administrator to provide

a multilevel, hierarchical routing structure while shielding the subnetwork from the

addressing complexity of attached networks Sometimes called a subnet 2 In OSI

net-works, a collection of ESs and ISs under the control of a single administrative domain and using a single network access protocol

switch A device that connects LAN segments, uses a table of MAC addresses to determine the segment on which a frame needs to be transmitted, and reduces traffic Switches operate at much higher speeds than bridges

switch Network device that filters, forwards, and floods frames based on the destina-tion address of each frame The switch operates at the data link layer of the OSI model

system routes Routes to networks within an autonomous system Cisco IOS Software derives system routes from directly connected network interfaces and system route information provided by other IGRP-speaking routers or access servers System routes

do not include subnet information

TB (terabyte) Approximately 1 trillion bytes Hard drive capacity on some high-end computers is measured in TB

Tbps (terabits per second) One trillion bits per second A standard measurement of the amount of data transferred over a network connection Some high-speed core Internet routers and switches operate at more than Tbps

TCP (Transmission Control Protocol) A connection-oriented transport-layer protocol

that provides reliable full-duplex data transmission TCP is part of the TCP/IP

proto-col stack

TCP (Transmission Control Protocol) Connection-oriented transport layer protocol

that provides reliable full-duplex data transmission TCP is part of the TCP/IP

proto-col stack

TCP/IP (Transmission Control Protocol/Internet Protocol) Common name for the

suite of protocols developed by the U.S Department of Defense in the 1970s to

sup-port the construction of worldwide internetworks TCP and IP are the two best-known

protocols in the suite

TDR (time domain reflectometer) A device that can measure the lengths of cables

that are installed and locate faults It does these tasks by sending a signal down a cable

and then measuring the amount of time that it takes for that signal to return

Telnet A 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

TFTP (Trivial File Transfer Protocol) Simplified version of FTP that allows files to be

transferred from one computer to another over a network, usually without the use of

client authentication (for example, username and password)

thicknet Thicknet is an early form of coaxial cable using 10BASE5 for networking

Thicknet was once desirable because it could carry signals up to 500 meters

Thinnet Thinnet is a simple, thin, coaxial network cable for the 10BASE2 system

Thinnet can carry a signal only 185 meters, but was much easier to work with than

thicknet

net-work devices to ensure transmission synchronization before sending user data

throughput The rate of information arriving at or passing through a particular point

in a network system

TIA (Telecommunications Industry Association) TIA is a standards association that

publishes standards for telecommunications

TIA/EIA-568-B standard Specifies ten tests that a copper cable must pass if it is used

for modern, high-speed Ethernet LANs

TLVs (Type Length Values) Blocks of information embedded in CDP advertisements

token passing An access method by which network devices access the physical medium in an orderly fashion based on possession of a small frame called a token

runs at 4 or 16 Mbps over a ring topology

topological database A collection of information gathered from LSAs

TR (telecommunications room) The area within a building that houses the telecom-munications cabling system equipment

traceroute Program available on many systems that traces the path a packet takes to

a destination It is used mostly to debug routing problems between hosts

trailer Control information appended to data when encapsulating the data for net-work transmission

Transmission Control Protocol/Internet Protocol (TCP/IP) A 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

transport layer Layer 4 of the OSI reference model This layer is responsible for reli-able network communication between end nodes The transport layer provides mecha-nisms to establish, maintain, and terminate virtual circuits, transport fault detection and recovery, and information flow control

triggered update A triggered update is an update that is sent without waiting for the update timer to expire

UDP (User Datagram Protocol) A connectionless transport layer protocol in the TCP/IP protocol stack UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retrans-mission be handled by other protocols UDP is defined in RFC 768

unicast Message sent to a single network destination

universal serial bus (USB) port Lets peripheral devices such as mice, modems, key-boards, scanners, and printers be plugged in and unplugged without resetting the system

update timer Specifies how frequently routing update messages are sent The IGRP default for this variable is 90 seconds

uptime The amount of time that the device is functional and in service relative to the users’ requirements for its availability

UTP (unshielded twisted-pair) UTP is a four-pair wire medium used in a variety of networks

vertical cabling Backbone cables, intermediate and main cross-connects, mechanical

terminations, and patch cords or jumpers used for backbone-to-backbone

cross-connections

video card A board that plugs into a PC to give it display capabilities

virtual private network (VPN) A private network constructed within a public network

infrastructure such as the global Internet

geo-graphic area, such as a state, province or country WANs often use transmission

facili-ties provided by common carriers, for example, telephone companies

wave Energy traveling from one place to another

wavelength The length of a wave measured from any point on one wave to the

corre-sponding point on the next wave The wavelength of light is usually measured in

nanometers (nm)

WDM (wavelength-division multiplexing) Multiple optical wavelength can share

the same transmission fiber The spectrum occupied by each channel must be separated

adequately from the other

web browser A graphical user interface (GUI)-based hypertext client application, such

as Internet Explorer or Netscape Navigator, used to access hypertext documents and

other services located on remote servers throughout the WWW and the Internet

well-known ports These ports are defined in RFC 1700 and are reserved in both TCP

and UDP These well-known ports can identify applications that run above the

trans-port layer protocols

WEP (wired equivalent privacy) A security mechanism, defined within the 802.11

standard, that is designed to protect the over-the-air transmission between wireless

LAN access points and NICs

white noise Noise that affects all transmission frequencies equally

wide-area network (WAN) A data communications network that serves users across

a broad geographic area and often uses transmission devices provided by common

carriers

windowing A flow-control mechanism requiring that the source device receive an

acknowledgment from the destination after transmitting a certain amount of data

work area A space where computers, telephones, and other network equipment is used