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Data Communications and Computer Networks
Plymouth State University CS3240
1141
Computer Science
Undergraduate 3
10/10/2011

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Term
1000Base-CX
Definition
A two-wire STP implementation of Gigabit Ethernet.
Term
1000Base-LX
Definition
A two-wire fiber implementation of Gigabit Ethernet using long-wave laser.
Term
1000Base-SX
Definition
A two-wire fiber implementation of Gigabit Ethernet using short-wave laser signals.
Term
1000Base-T
Definition
A four-wire UTP implementation of Gigabit Ethernet.
Term
100Base-FX
Definition
A two-wire fiber implementation of Fast Ethernet.
Term
100Base-T4
Definition
A four-wire UTP implementation of Fast Ethernet.
Term
100Base-TX
Definition
A two-wire UTP implementation of Fast Ethernet.
Term
10Base2
Definition
The thin coaxial cable implementation of Standard Ethernet.
Term
10Base5
Definition
The thick coaxial cable implementation of Standard Ethernet.
Term
10Base-E
Definition
The extended implementation of Ten-Gigabit Ethernet.
Term
10Base-F
Definition
The fiber implementation of Standard Ethernet.
Term
10Base-L
Definition
A fiber implementation of Ten-Gigabit Ethernet using long-wave laser.
Term
10Base-S
Definition
A fiber implementation of Ten-Gigabit Ethernet using short-wave laser.
Term
10Base-T
Definition
The twisted-pair implementation of Standard Ethernet.
Term
1-persistent strategy
Definition
A CSMA persistence strategy in which a station sends a frame immediately if the line is idle.
Term
2B1Q encoding
Definition
A line encoding technique in which each pulse represents 2 bits.
Term
4B/5B encoding
Definition
A block coding technique in which 4 bits are encoded into a 5-bit code.
Term
4-dimensional, 5-level pulse amplitude modulation (4D-PAM5)
Definition
An encoding scheme used by 1000Base-T.
Term
56K modem
Definition
A modem technology using two different data rates: one for uploading and one for downloading from the Internet.
Term
800 service
Definition
A telephone service free to the caller.
Term
8B/10B encoding
Definition
A block coding technique in which 8 bits are encoded into a 10-bit code.
Term
8B/6T encoding
Definition
A block coding technique in which 8 bits are encoded into a 6-bit code.
Term
900 service
Definition
A telephone service paid by the caller.
Term
Abstract Syntax Notation 1 (ASN.1)
Definition
A standard for representing simple and structured data.
Term
access control
Definition
The determination of link control through a data link protocol.
Term
access point
Definition
A central base station in a BSS.
Term
access rate
Definition
In Frame Relay, the data rate that can never be exceeded.
Term
acknowledgment (ACK)
Definition
A response sent by the receiver to indicate the successful receipt and acceptance of data.
Term
active close
Definition
In the client-server model, the closing of a communication by the client.
Term
active document
Definition
In the World Wide Web, a document executed at the local site using Java.
Term
active open
Definition
In the client-server model, the opening of a communication by the client.
Term
adaptive delta modulation
Definition
A delta modulation technique in which the value of delta changes according to the amplitude of the analog signal.
Term
add/drop multiplexer
Definition
A SONET device that multiplexes signals from different sources or demultiplexes a signal to multiple destinations.
Term
additive increase
Definition
With slow start, a congestion avoidance strategy in which the window size is increased by just one segment instead of exponentially.
Term
address aggregation
Definition
A mechanism in which the blocks of addresses for several organizations are aggregated into one larger block.
Term
Address Resolution Protocol (ARP)
Definition
In TCP/IP, a protocol for obtaining the physical address of a node when the Internet address is known.
Term
address space
Definition
The total number of addresses used by a protocol.
Term
address-mask request and reply ICMP
Definition
Messages that find the network mask.
Term
ADSL Lite
Definition
A splitterless ADSL. This technology allows an ASDL Lite modem to be plugged directly into a telephone jack and connected to the computer. The splitting is done at the telephone company.
Term
Advanced Encryption Standard (AES)
Definition
A secret-key cryptosystem adapted by NIST to replace DES.
Term
Advanced Mobile Phone System (AMPS)
Definition
A North American analog cellular phone system using FDMA.
Term
Advanced Research Projects Agency (ARPA)
Definition
The government agency that funded ARPANET.
Term
Advanced Research Projects Agency Network (ARPANET)
Definition
The packet-switching network that was funded by ARPA.
Term
ALOHA
Definition
The original random multiple access method in which a station can send a frame any time it has one to send.
Term
alternate mark inversion (AMI)
Definition
A digital-to-digital bipolar encoding method in which the amplitude representing 1 alternates between positive and negative voltages.
Term
American National Standards Institute (ANSI)
Definition
A national standards organization that defines standards in the United States.
Term
American Standard Code for Information Interchange (ASCII)
Definition
A character code developed by ANSI and used extensively for data communication.
Term
amplitude
Definition
The strength of a signal, usually measured in volts, amperes, or watts.
Term
amplitude modulation (AM)
Definition
An analog-to-analog conversion method in which the carrier signal's amplitude varies with the amplitude of the modulating signal.
Term
amplitude shift keying (ASK)
Definition
A modulation method in which the amplitude of the carrier signal is varied to represent binary 0 or 1.
Term
analog
Definition
A continuously varying entity.
Term
analog data
Definition
Data that are continuous and smooth and not limited to a specific number of values.
Term
analog hierarchy
Definition
A telephone company system in which multiplexed signals are combined into successively larger groups for more efficient transmission.
Term
analog leased service
Definition
A service featuring a dedicated line between two users.
Term
analog signal
Definition
A continuous waveform that changes smoothly over time.
Term
analog switched service
Definition
A temporary analog connection between two users.
Term
analog-to-analog modulation
Definition
The representation of analog information by an analog signal.
Term
analog-to-digital conversion
Definition
The representation of analog information by a digital signal.
Term
angle of incidence
Definition
In optics, the angle formed by a light ray approaching the interface between two media and the line perpendicular to the interface.
Term
anonymous FTP
Definition
A protocol in which a remote user can access another machine without an account or password.
Term
anycast address
Definition
An address that defines a group of computers with addresses that have the same beginning.
Term
aperiodic signal
Definition
A signal that does not exhibit a pattern or repeating cycle.
Term
applet
Definition
A computer program for creating an active Web document. It is usually written in Java.
Term
application adaptation layer (AAL)
Definition
A layer in ATM protocol that breaks user data into 48-byte payloads.
Term
application layer
Definition
The fifth layer in the Internet model; provides access to network resources.
Term
application programming interface (API)
Definition
A set of declarations, definitions, and procedures followed by programmers to write client-server programs.
Term
area
Definition
A collection of networks, hosts, and routers all contained within an autonomous system.
Term
area border router
Definition
A router inside an area that summarizes the information about the area and sends it to other areas.
Term
area identification
Definition
A 32-bit field that defines the area within which the routing takes place.
Term
association
Definition
A connection in SCTP
Term
asymmetric digital subscriber line (ADSL)
Definition
A communication technology in which the downstream data rate is higher than the upstream rate.
Term
asynchronous balanced mode (ABM)
Definition
In HDLC, a communication mode in which all stations are equal.
Term
asynchronous connectionless link (ACL)
Definition
A link between a Bluetooth master and slave in which a corrupted payload is retransmitted.
Term
Asynchronous Transfer Mode (ATM)
Definition
A wide area protocol featuring high data rates and equal-sized packets (cells); ATM is suitable for transferring text, audio, and video data.
Term
asynchronous transmission
Definition
Transfer of data with start and stop bit(s) and a variable time interval between data units.
Term
ATM LAN
Definition
A LAN using ATM technology.
Term
ATM layer
Definition
A layer in ATM that provides routing, traffic management, switching, and multiplexing services.
Term
ATM switch
Definition
An ATM device providing both switching and multiplexing functions.
Term
attachment unit interface (AUI)
Definition
A 10Base5 cable that performs the physical interface functions between the station and the transceiver.
Term
attenuation
Definition
The loss of a signal's energy due to the resistance of the medium.
Term
audio
Definition
Recording or transmitting of sound or music.
Term
authenticating state
Definition
In PPP, an optional state that verifies the identity of the receiver.
Term
authentication
Definition
Verification of the sender of a message.
Term
Authentication Header (AH) Protocol
Definition
A protocol defined by IPSec at the network layer that provides integrity to a message through the creation of a digital signature by a hashing function.
Term
authentication server (AS)
Definition
The KDC in the Kerberos protocol.
Term
automatic repeat request (ARQ)
Definition
An error-control method in which correction is made by retransmission of data.
Term
automatic tunneling
Definition
Tunneling in which the receiving host has an IPv6 compatible address; no reconfiguration is necessary.
Term
autonegotiation
Definition
A Fast Ethernet feature that allows two devices to negotiate the mode or data rate.
Term
autonomous system (AS)
Definition
A group of networks and routers under the authority of a single administration.
Term
autonomous system boundary router
Definition
Routers responsible for dissipating information about other autonomous systems into the current system.
Term
available bit rate (ABR)
Definition
The minimum data rate in ATM at which cells can be delivered.
Term
back off
Definition
In multiple access, waiting before re-sending after a collision.
Term
backbone
Definition
A network that connects smaller networks in an organization.
Term
backbone router
Definition
A router inside the backbone.
Term
backward explicit congestion notification (BECN)
Definition
A bit in the Frame Relay packet that notifies the sender of congestion.
Term
band-pass channel
Definition
A channel that can pass a range of frequencies.
Term
bandwidth
Definition
The difference between the highest and the lowest frequencies of a composite signal. It also measures the information-carrying capacity of a line or a network.
Term
bandwidth on demand
Definition
A digital service that allows subscribers higher speeds through the use of multiple lines.
Term
bandwidth-delay product
Definition
A measure of the number of bits that can be sent while waiting for news from the receiver.
Term
banyan switch
Definition
A multistage switch with microswitches at each stage that route the packets based on the output port represented as a binary string.
Term
Barker sequence
Definition
A sequence of 11 bits used for spreading.
Term
base header
Definition
In IPv6, the main header of the datagram.
Term
baseband transmission
Definition
Transmission of digital or analog signal without modulation using a low-pass channel.
Term
baseline wandering
Definition
In decoding a digital signal, the receiver calculates a running average of the received signal power. This average is called the baseline. A long string of 0s and 1s can cause a drift in the baseline (baseline wandering) and make it difficult for the receiver to decode correctly.
Term
Basic Encoding Rule (BER)
Definition
A standard that encodes data to be transferred through a network.
Term
Basic Latin
Definition
ASCII character set.
Term
basic service set (BSS)
Definition
The building block of a wireless LAN as defined by the IEEE 802.11 standard.
Term
baud rate
Definition
The number of signal elements transmitted per second. A signal element consists of one or more bits.
Term
Bayone-Neill-Concelman (BNC) connector
Definition
A common coacxial cable connector.
Term
best-effort delivery
Definition
The unreliable transmission mechanism by IP that does not guarantee message delivery.
Term
bidirectional authentication
Definition
An authentication method involving a challenge and a response from sender to receiver and vice versa.
Term
bidirectional frame (B-frame)
Definition
An MPEG frame that is related to the preceding and following I-frame or P-frame.
Term
binary exponential backup
Definition
In contention access methods, a retransmission delay strategy used by a system to delay access.
Term
binary notation
Definition
Representation of IP addresses in binary.
Term
biphase
Definition
A type of polar encoding where the signal changes at the middle of the bit interval. Manchester and differential Manchester are examples of biphase encoding.
Term
bipolar encoding
Definition
A digital-to-digital encoding method in which 0 amplitude represents binary 0 and positive and negative amplitudes represent alternate 1s.
Term
bipolar n-zero substitution (BnZS)
Definition
An encoding method to provide synchronization for long strings of 0s.
Term
bipolar with 8-zero substitution (B8ZS)
Definition
A scrambling technique in which a stream of 8 zeros are replaced by a predefined pattern to improve bit synchronization.
Term
bit
Definition
binary digit; the smallest unit of data(0 or 1)
Term
bit interval
Definition
The time required to send one bit.
Term
bit padding
Definition
In TDM, the addition of extra bits to a device's source stream to force speed relationships.
Term
bit rate
Definition
The number of bits transmitted per second.
Term
bit stuffing
Definition
In a bit-oriented protocol, the process of adding an extra bit in the data section of a frame to prevent a sequence of bits from looking like a flag.
Term
bit-oriented protocol
Definition
A protocol in which the data frame is interpreted as a sequence of bits.
Term
bits per second (bps)
Definition
A measurement of data speed; bits transmitted per second.
Term
block cipher
Definition
An encryption/decryption algorithm that has a block of bits as its basic unit.
Term
block code
Definition
An error detection/correction code in which data are divided into units called datawords. Redundant bits are added to each dataword to create a codeword.
Term
block coding
Definition
A coding method to ensure synchronization and detection of errors.
Term
blocking
Definition
An event that occurs when a switching network is working at its full capacity and cannot accept more input.
Term
blocking port
Definition
A port on a bridge that does not forward a frame.
Term
Bluetooth
Definition
A wireless LAN technology designed to connect devices of different functions such as telephones and notebooks in a small area such as a room.
Term
BNC connector
Definition
A common coaxial cable connector.
Term
Bootstrap Protocol (BOOTP)
Definition
The protocol that provides configuration information from a table (file).
Term
Border Gateway Protocol (BGP)
Definition
An interautonomous system routing protocol based on path vector routing.
Term
bridge
Definition
A network device operating at the first two layers of the Internet model with filtering and forwarding capabilities.
Term
broadband transmission
Definition
Transmission of signals using modulation of a higher frequency signal. The term implies a wide-bandwidth data combined from different sources.
Term
broadcast address
Definition
An address that allows transmission of a message to all nodes of a network.
Term
broadcast/unknown server (BUS)
Definition
A server connected to an ATM switch that can multicast and broadcast frames.
Term
broadcasting
Definition
Transmission of a message to all nodes in a network.
Term
browser
Definition
An application program that displays a WWW document. A browser usually uses other Internet services to access the document.
Term
BSS-transition mobility
Definition
In a wireless LAN, a station that can move from one BSS to another but is confined inside one ESS.
Term
bucket brigade attack
Definition
See man-in-the middle attack
Term
burst error
Definition
Error in a data unit in which two or more bits have been altered.
Term
bursty data
Definition
Data with varying instantaneous transmission rates.
Term
bus topology
Definition
A network topology in which all computers are attached to a shared medium.
Term
byte
Definition
A group of eight bits.
Term
byte stuffing
Definition
In a byte-oriented protocol, the process of adding an extra byte in the data section of a frame to prevent a byte from looking like a flag.
Term
byte-oriented protocol
Definition
A protocol in which the data section of the frame is interpreted as a sequence of bytes (characters).
Term
cable modem
Definition
A technology in which the TV cable provides Internet access.
Term
cable modem transmission system (CMTS)
Definition
A device installed inside the distribution hub that receives data from the Internet and passes them to the combiner.
Term
cable TV network
Definition
A system using coaxial or fiber optic cable that brings multiple channels of video programs into homes.
Term
caching
Definition
The storing of information in a small, fast memory.
Term
Caesar cipher
Definition
A shift cipher used by Julius Caesar with the key value of 3.
Term
carrier extension
Definition
A technique in Gigabit Ethernet that increases the minimum length of the frame to achieve a higher maximum cable length.
Term
carrier sense multiple access (CSMA)
Definition
A contention access method in which each station listens to the line before transmitting data.
Term
carrier sense multiple access with collision avoidance (CSMA/CA)
Definition
An access method in which collision is avoided.
Term
carrier sense multiple access with collision detection (CSMA/CD)
Definition
An access method in which stations transmit whenever the transmission medium is available and retransmit when collision occurs.
Term
carrier signal
Definition
A high frequency signal used for digital-to-analog or analog-to-analog modulation. One of the characteristics of the carrier signal (amplitude, frequency, or phase) is changed according to the modulating data.
Term
cell
Definition
A small, fixed-size data unit; also, in cellular telephony, a geographical area served by a cell office.
Term
cell network
Definition
A network using the cell as its basic data unit.
Term
cellular telephony
Definition
A wireless communication technique in which an area is divided into cells. A cell is served by a transmitter.
Term
Certification Authority (CA)
Definition
An agency such as a federal or state organization that binds a public key to an entity and issues a certificate.
Term
Challenge Handshake Authentication Protocol (CHAP)
Definition
In PPP, a three-way handshaking protocol used for authentication.
Term
channel
Definition
A communications pathway.
Term
channelization
Definition
A multiple access method in which the available bandwidth of a link is shared in time.
Term
character-oriented protocol
Definition
See byte-oriented protocol
Term
checksum
Definition
A field used for error detection. It is formed by adding bit streams using one's complement arithmetic and then complementing the result.
Term
chip
Definition
In CDMA, a number in a code that is assigned to a station.
Term
choke point
Definition
A packet sent by a router to the source to inform it of congestion.
Term
chunk
Definition
A unit of transmission in SCTP.
Term
cipher
Definition
An encryption/decryption algorithm.
Term
cipher block chaining (CBC) mode
Definition
A DES and triple DES operation mode in which the encryption (or decryption) of a block depends on all previous blocks.
Term
cipher feedback mode (CFM)
Definition
A DES and triple DES operation mode in which data is sent and received 1 bit at a time, with each bit independent of the previous bits.
Term
cipher stream mode (CSM)
Definition
A DES and triple DES operation mode in which data is sent and received 1 byte at a time.
Term
cipher suite
Definition
AA list of possible ciphers.
Term
ciphertext
Definition
The encrypted data.
Term
circuit switching
Definition
A switching technology that establishes an electrical connection between stations using a dedicated path.
Term
cladding
Definition
Glass or plastic surrounding the core of an optical fiber; the optical density of the cladding must be less than that of the core.
Term
class A address
Definition
An IPv4 address with the first octet between 0 and 127.
Term
class B address
Definition
An IPv4 address with the first octet between 128 and 191.
Term
class C address
Definition
An IPv4 address with the first octet between 192 and 223.
Term
class D address
Definition
An IPv4 multicast address.
Term
class E address
Definition
An IPv4 address reserved for special purposes.
Term
classful addressing
Definition
An IPv4 addressing mechanism in which the IP address space is divided into 5 classes: A, B, C, D, and E. Each class occupies some part of the whole address space.
Term
classless addressing
Definition
An addressing mechanism in which the IP address space is not divided into classes.
Term
Classless InterDomain Routing (CIDR)
Definition
A technique to reduce the number of routing table entries when supernetting is used.
Term
client process
Definition
A running application program on a local site that requests service from a running application program on a remote site.
Term
client-server model
Definition
The model of interaction between two application programs in which a program at one end (client) requests a service from a program at the other end (server).
Term
closed-loop congestion control
Definition
A method to alleviate congestion after it happens.
Term
coaxial cable
Definition
A transmission medium consisting of a conducting core, insulating material, and a second conducting sheath.
Term
code division multiple access (CDMA)
Definition
A multiple access method in which one channel carries all transmissions simultaneously.
Term
codeword
Definition
The encoded dataword.
Term
ColdFusion
Definition
A dynamic web technology that allows the fusion of data items coming from a conventional database.
Term
collision
Definition
The event that occurs when two transmitters send at the same time on a channel designed for only one transmission at a time; data will be destroyed.
Term
collision domain
Definition
The length of the medium subject to collision.
Term
committed burst size
Definition
The maximum number of bits in a specific time period that a Frame Relay network must transfer without discarding any frames.
Term
committed information rate (CIR)
Definition
The committed burst size divided by time.
Term
common carrier
Definition
A transmission facility available to the public and subject to public utility regulation.
Term
Common Gateway Interface (CGI)
Definition
A standard for communication between HTTP servers and executable programs. CGI is used in creating dynamic documents.
Term
community antenna TV (CATV)
Definition
A cable network service that broadcasts video signals to locations with poor or no reception.
Term
compatible address
Definition
An IPv6 address consisting of 96 bits of zero followed by 32 bits of IPv4.
Term
competitive local exchange carrier (CLEC)
Definition
A telephone company that cannot provide main telephone services; instead, other services such as mobile telephone service and toll calls inside a LATA are provided.
Term
complementary code keying (CCK)
Definition
An HR-DSSS encoding method that encodes four or eight bits into one symbol.
Term
composite signal
Definition
A signal composed of more than one sine wave.
Term
concurrent client
Definition
A client running the same time as another client of the same process.
Term
concurrent server
Definition
A server that can process many requests at the same time and share its time between many requests.
Term
congestion
Definition
Excessive network or internetwork traffic causing a general degradation of service.
Term
congestion avoidance
Definition
In Frame Relay, a method using two bits that explicitly notify the source and destination of congestion.
Term
congestion control
Definition
A method to manage network and internetwork traffic to improve throughput.
Term
connecting device
Definition
A tool that connects computers or networks.
Term
connection control
Definition
The technique used by the transport layer to deliver segments.
Term
connection establishment
Definition
The preliminary setup necessary for a logical connection prior to actual data transfer.
Term
connection termination
Definition
A message sent to end a connection.
Term
connectionless iterative server
Definition
A connectionless server that processes one request at a time.
Term
connectionless service
Definition
A service for data transfer without connection establishment or termination.
Term
connection-oriented concurrent server
Definition
A connection-oriented server that can serve many clients at the same time.
Term
connection-oriented service
Definition
A service for data transfer involving establishment and termination of a connection.
Term
constant bit rate (CBR)
Definition
The data rate of an ATM service class that is designed for customers requiring real-time audio or video services.
Term
constellation diagram
Definition
A graphical representation of the phase and amplitude of different bit combinations in digital-to-analog modulation.
Term
Consultative Committee for International Telegraphy and Telephony (CCITT)
Definition
An international standards group now known as the ITU-T.
Term
contention
Definition
An access method in which two or more devices try to transmit at the same time on the same channel.
Term
control connection
Definition
The FTP connection used for control information (commands and responses).
Term
controlled access
Definition
A multiple access method in which the stations consult one another to determine who has the right to send.
Term
convergence sublayer (CS)
Definition
In ATM protocol, the upper AAL sublayer that adds a header or a trailer to the user data.
Term
cookie
Definition
A string of characters that holds some information about the client and must be returned to the server untouched.
Term
core
Definition
The glass or plastic center of an optical fiber.
Term
Core-Based Tree (CBT)
Definition
In multicasting, a group-shared protocol that uses a center router as the root of the tree.
Term
country domain
Definition
A subdomain in the Domain Name System that uses two characters as the last suffix.
Term
CRC checker
Definition
The process that validates the CRC remainder.
Term
CRC generator
Definition
The process that creates the CRC remainder.
Term
critical angle
Definition
In refraction, the value of the angle of incidence that produces a 90-degree angle of refraction.
Term
crossbar switch
Definition
A switch consisting of a lattice of horizontal and vertical paths. At the intersection of each horizontal and vertical path, there is a crosspoint that can connect the input to the output.
Term
crosspoint
Definition
The junction of an input and an output on a crossbar switch.
Term
crosstalk
Definition
The noise on a line caused by signals traveling along another line.
Term
cryptography
Definition
The science and art of transforming messages to make them secure and immune to attacks.
Term
CSNET
Definition
A network sponsored by the National Science Foundation originally intended for universities.
Term
cycle
Definition
The repetitive unit of a periodic signal.
Term
cyclic code
Definition
A linear cod in which the cyclic shifting (rotation) of each codeword creates another code word.
Term
cyclic redundancy check (CRC)
Definition
A highly accurate error-detection method based on interpreting a pattern of bits as a polynomial.
Term
data connection
Definition
The FTP connection used for data transfer.
Term
data element
Definition
The smallest entity that can represent a piece of information. A bit.
Term
data encryption standard (DES)
Definition
The U.S. government standard encryption method for nonmilitary and nonclassified use.
Term
data exchange protocol
Definition
A protocol that uses the secret key to encrypt the data for secrecy and to encrypt the message digest for integrity.
Term
data level
Definition
The number of different symbols used to represent a digital signal.
Term
data link connection identifier (DLCI)
Definition
A number that identifies the virtual circuit in Frame Relay.
Term
data link control
Definition
The responsibilities of the data link layer: flow control and error control.
Term
data link layer
Definition
The second layer in the Internet model. It is responsible for node-to-node delivery.
Term
Data Over Cable System Interface Specifications (DOCSIS)
Definition
A standard for data transmission over an HFC network.
Term
data rate
Definition
The number of data elements sent in one second.
Term
data transfer phase
Definition
The intermediate phase in circuit-switched or virtual-circuit network in which data transfer takes place.
Term
data transparency
Definition
See transparency.
Term
datagram
Definition
In packet switching, an independent data unit.
Term
datagram approach (to packet switching)
Definition
A data transmission method in which each data unit is independent of others.
Term
datagram network
Definition
A packet-switched network in which packets are independent from each other.
Term
datagram socket
Definition
A structure designed to be used with a connectionless protocol such as UDP.
Term
dataword
Definition
The smallest block of data in block coding.
Term
DC component
Definition
See direct current.
Term
de facto standard
Definition
A protocol that has not been approved by an organized body but adopted as a standard through widespread use.
Term
de jure standard
Definition
A protocol that has been legislated by an officially recognized body.
Term
deadlock
Definition
A situation in which a task cannot proceed because it is waiting for an even that will never occur.
Term
decibel (dB)
Definition
A measure of the relative strength of two signal points.
Term
decryption
Definition
Recovery of the original message from the encrypted data.
Term
default mask
Definition
The mask for a network that is not subnetted.
Term
default routing
Definition
A routing method in which a router is assigned to receive all packets with no match in the routing table.
Term
Defense Advanced Research Projects Agency (DARPA)
Definition
A government organization, which, under the name of ARPA funded ARPANET and the Internet.
Term
delayed response strategy
Definition
A technique used by IGMP to prevent unnecessary traffic on a LAN.
Term
delta modulation
Definition
An analog-to-digital conversion technique in which the value of the digital signal is based on the difference between the current and the previous sample values.
Term
demodulation
Definition
The process of separating the carrier signal from the information-bearing signal.
Term
demodulator
Definition
A device that performs demodulation.
Term
demultiplexer (DEMUX)
Definition
A device that separates a multiplexed signal into its original components.
Term
denial of service attack
Definition
A form of attack in which the site is flooded with so many phony requests that is eventually forced to deny service.
Term
dense wave-division multiplexing (DWDM)
Definition
A WDM method that can multiplex a very large number of channels by spacing channels closer together.
Term
destination-unreachable message
Definition
An ICMP error-reporting message sent to a source when a router cannot route a datagram or a host cannot deliver a datagram.
Term
dibit
Definition
A unit of data consisting of two bits.
Term
differential Manchester encoding
Definition
A digital-to-digital polar encoding method that features a transition at the middle of the bit interval as well as an inversion at the beginning of each 1 bit.
Term
Differentiated Services (DS or Diffserv)
Definition
A class-based QoS model designed for IP.
Term
Diffie-Hellman protocol
Definition
A key management protocol that provides a one-time session key for 2 parties.
Term
digest
Definition
A condensed version of a document.
Term
digital AMPS (D-AMPS)
Definition
A second-generation cellular phone system that is a digital version of AMPS.
Term
digital data
Definition
Data represented by discrete values or conditions.
Term
digital data service (DDS)
Definition
A digital version of an analog leased line with a rate of 64 Kbps.
Term
digital service unit (DSU)
Definition
A device that allows the connection of a user's device to a digital line.
Term
digital signal
Definition
A discrete signal with a limited number of values.
Term
digital signal (DS) service
Definition
A telephone company service featuring a hierarchy of digital signals.
Term
digital signature
Definition
A method to authenticate the sender of a message.
Term
digital subscriber line (DSL)
Definition
A technology using existing telecommunication networks to accomplish high-speed delivery of data, voice, video, and multimedia.
Term
digital subscriber line access multiplexer (DSLAM)
Definition
A telephone company site device that functions like an ADSL modem.
Term
digital-to-analog conversion
Definition
The representation of digital information by an analog signal.
Term
digital-to-analog modulation
Definition
The representation of digital information by an analog signal.
Term
digital-to-digital conversion
Definition
The representation of digital information by a digital signal.
Term
digital-to-digital encoding
Definition
The representation of digital information by a digital signal.
Term
digitization
Definition
Conversion of analog information to digital information.
Term
Dijkstra's algorithm
Definition
In link state routing, an algorithm that finds the shortest path to other routers.
Term
direct current (DC)
Definition
A zero-frequency signal with a constant amplitude.
Term
direct delivery
Definition
A delivery in which the final destination of the packet is a host connected to the same physical network as the sender.
Term
direct sequence spread spectrum (DSSS)
Definition
A wireless transmission method in which each bit to be sent by the sender is replaced by a sequence of bits called a chip code.
Term
discard eligibility (DE)
Definition
A bit that defines that a packet can be discarded if there is congestion in the network.
Term
discrete cosine transform (DCT)
Definition
A JPEG phase in which a transformation changes the 64 values so that the relative relationships between pixels are kept but the redundancies are revealed.
Term
discrete multitone technique (DMT)
Definition
A modulation method combining elements of QAM and FDM.
Term
Distance Vector Multicast Routing Protocol (DVMRP)
Definition
A protocol based on distance vector routing that handles multicast routing in conjunction with IGMP.
Term
distance vector routing
Definition
A routing method in which each router sends its neighbors a list of networks it can reach and the distance to that network.
Term
distortion
Definition
Any change in a signal due to noise, attenuation, or other influences.
Term
distributed coordination fucntion (DCF)
Definition
The basic access method in wireless LANs; stations contend with each other to get access to the channel.
Term
distributed database
Definition
Information stored in many locations.
Term
distributed interframe space (DIFS)
Definition
In wireless LANs, a period of time that a station waits before sending a control frame.
Term
distributed processing
Definition
A strategy in which services provided for the network reside at multiple sites.
Term
distribution hub
Definition
In an HFC network, a site that modulates and distributes signals.
Term
DNS server
Definition
A computer that holds information about the name space.
Term
domain
Definition
A subtree of the domain name space.
Term
domain name
Definition
In the DNS, a sequence of labels separated by dots.
Term
domain name space
Definition
A structure for organizing the name space in which the names are defined in an inverted-tree structure with the root at the top.
Term
Domain Name System (DNS)
Definition
A TCP/IP application service that converts user-friendly names to IP addresses.
Term
dotted-decimal notation
Definition
A notation devised to make the IP address easier to read; each byte is converted to its decimal equivalent and then set off from its neighbor by a decimal.
Term
downlink
Definition
Transmission from a satellite to an earth station.
Term
downloading
Definition
Retrieving a file or data from a remote site.
Term
downstream data band
Definition
In an HFC network, the 550 to 750 MHz band for data from the Internet to the subscriber premises.
Term
dual stack
Definition
Two protocols (IPv4 and IPv6) on a station.
Term
duplex mode
Definition
See full-duplex mode.
Term
dynamic document
Definition
A Web document created by running a CGI program at the server site.
Term
Dynamic Domain Name System (DDNS)
Definition
A method to update the DNS master file dynamically.
Term
Dynamic Host Configuration Protocol (DHCP)
Definition
An extension to BOOTP that dynamically assigns configuration information.
Term
dynamic mapping
Definition
A technique in which a protocol is used for address resolution.
Term
dynamic routing
Definition
Routing in which the routing table entries are updated automatically by the routing protocol.
Term
E lines
Definition
The European equivalent of T lines.
Term
echo-request and reply message
Definition
An ICMP query message that determines whether two systems (hosts or routers) can communicate with each other.
Term
effective bandwidth
Definition
The bandwidth that the network needs to allocate for the flow of traffic; a function of three values: average data rate, peak data rate, and maximum burst size.
Term
electromagnetic spectrum
Definition
The frequency range occupied by electromagnetic energy.
Term
electronic code block (ECB) mode
Definition
A DES and triple DES operation method in which a long message is divided into 64-bit blocks before being encrypted separately.
Term
electronic mail (email)
Definition
A method of sending messages electronically based on mailbox addresses rather than a direct host-to-host exchange.
Term
Electronics Industries Association (EIA)
Definition
An organization that promotes electronics manufacturing concerns. It has developed interface standards such as EIA-232, EIA-449, and EIA-530.
Term
email
Definition
See electronic mail.
Term
Encapsulating Security Payload (ESP)
Definition
A protocol defined by IPSec that provides privacy as well as a combination of integrity and message authentication.
Term
encapsulation
Definition
The technique in which a data unit from one protocol is placed within the data field portion of the data unit of another protocol.
Term
encryption
Definition
Converting a message into an unintelligible form that is unreadable unless decrypted.
Term
end office
Definition
A switching office that is the terminus for the local loops.
Term
end system
Definition
A sender or receiver of data.
Term
ephemeral port number
Definition
A port number used by the client.
Term
error control
Definition
The detection and handling of errors in data transmission.
Term
error correction by retransmission
Definition
The process of correcting bits by resending the data.
Term
error-reporting message
Definition
An ICMP message sent to the source to report an error.
Term
ESS-transition mobility
Definition
A station in a wireless LAN that can move from one ESS to another.
Term
establishing state
Definition
In PPP, a state in which communication begins and options are negotiated.
Term
Ethernet
Definition
A local area network using CSMA/CD access method. See IEEE Project 802.3.
Term
even parity
Definition
An error-detection method in which an extra bit is added to the data unit so that the total number of 1s becomes even.
Term
excess burst size
Definition
In Frame Relay, the maximum number of bits in excess of Bc that the user can send during a predefined period of time.
Term
Extended Service Set (ESS)
Definition
A wireless LAN service composed of two or more BSSs with APs as defined by the IEEE 802.11 standard.
Term
extension header
Definition
Extra headers in the IPv6 datagram that provide additional functionality.
Term
exterior routing
Definition
Routing between autonomous systems.
Term
external link LSA
Definition
A message that announces all the networks outside the AS.
Term
extranet
Definition
A private network that uses the TCP/IP protocol suite that allows authorized access from outside users.
Term
Fast Ethernet
Definition
Ethernet with a data rate of 100 Mbps.
Term
Fast Ethernet
Definition
See 100Base-T.
Term
fast retransmission
Definition
Retransmission of a segment in TCP protocol when three acknowledgements have been received that imply the loss or corruption of that segment.
Term
Federal Communications Commission (FCC)
Definition
A government agency that regulates radio, television, and telecommunications.
Term
fiber distributed data interface (FDDI)
Definition
A high-speed (100-Mbps) LAN, defined by ANSI, using fiber optics, dual ring topology, and the token-passing access method. Today an FDDI network is also used as a MAN.
Term
fiber link Ethernet
Definition
Ethernet using fiber optic media.
Term
fiber node
Definition
In an HFC network, the location of the optical fiber and coaxial fiber juncture.
Term
fiber-optic cable
Definition
A high-bandwidth transmission medium that carries data signals in the form of pulses of light. It consists of a thin cylinder of glass or plastic, called the core, surrounded by a concentric layer of glass or plastic called the cladding.
Term
File Transfer Protocol (FTP)
Definition
In TCP/IP, an application layer protocol that transfers files between two sites.
Term
filtering
Definition
A process in which a bridge makes forwarding decisions.
Term
finite state machine
Definition
A machine that goes through a limited number of states.
Term
firewall
Definition
A device (usually a router) installed between the internal network of an organization and the rest of the Internet to provide security.
Term
first-in, first-out (FIFO) queue
Definition
A queue in which the first item in is the first item out.
Term
flag
Definition
A bit pattern or a character added to the beginning and the end of a fame to separate the frames.
Term
flag field
Definition
In an HDLC frame, an 8-bit synchronization sequence that identifies the beginning or end of a frame.
Term
flat name space
Definition
A method to map a name to an address in which there is no hierarchical structure.
Term
flooding
Definition
Saturation of a network with a message.
Term
flow control
Definition
A technique to control the rate of flow of frames (packets or messages).
Term
flow label
Definition
An IPv6 mechanism to enable the source to request special handling of a packet.
Term
footprint
Definition
An area on Earth that is covered by a satellite at a specific time.
Term
forward error correction
Definition
Correction of errors at the receiver.
Term
forward explicit congestion notification (FECN)
Definition
A bit in the Frame Relay packet that notifies the destination of congestion.
Term
forwarding
Definition
Placing the packet in its route to its destination.
Term
forwarding port
Definition
A port on a bridge that forwards a received frame.
Term
Fourier analysis
Definition
The mathematical technique used to obtain the frequency spectrum of an aperiodic signal if the time-domain representation is given.
Term
fragmentation
Definition
The division of a packet into smaller units to accommodate a protocol's MTU.
Term
fragmentation offset
Definition
A field in the IP header used in fragmentation to show the relative position of the fragment with respect to the whole datagram.
Term
frame
Definition
A group of bits representing a block of data.
Term
frame bursting
Definition
A technique in CSMA/CD Gigabit Ethernet in which multiple frames are logically connected to each other to resemble a longer frame.
Term
frame check sequence (FCS)
Definition
The HDLC error-detection field containing either a 2- or 4-byte CRC.
Term
Frame Relay
Definition
A packet-switching specification defined for the first two layers of the Internet model. There is no network layer. Error checking is done on end-to-end basis instead of on each link.
Term
Frame Relay assembler/disassembler (FRAD)
Definition
A device used in Frame Relay to handle frames coming from other protocols.
Term
framing bit
Definition
A bit used for synchronization purposes in TDM.
Term
frequency
Definition
The number of cycles per second of a periodic signal.
Term
frequency
Definition
The number of cycles per second of a periodic signal.
Term
frequency division multiple access (FDMA)
Definition
A multiple access method in which the bandwidth is divided into channels.
Term
frequency hopping spread spectrum (FHSS)
Definition
A wireless transmission method in which the sender transmits at one carrier frequency for a short period of time, then hops to another carrier frequency for the same amount of time, hops again for the same amount of time, and so on. After N hops, the cycle is repeated.
Term
frequency modulation (FM)
Definition
An analog-to-analog modulation method in which the carrier signal's frequency varies with the amplitude of the modulating signal.
Term
frequency shift keying (FSK)
Definition
A digital-to-analog encoding method in which the frequency of the carrier signal is varied to represent binary 0 or 1.
Term
frequency-division multiple access (FDMA)
Definition
An access method technique in which multiple sources use assigned bandwidth in a data communication band.
Term
frequency-division multiplexing (FDM)
Definition
The combining of analog signals into a single signal.
Term
frequency-domain plot
Definition
A graphical representation of a signal's frequency components.
Term
full-duplex mode
Definition
A transmission mode in which communication can be two way simultaneously.
Term
full-duplex switched Ethernet
Definition
Ethernet in which each station, in its own separate collision domain, can both send and receive.
Term
fully qualified domain name (FQDN)
Definition
A domain name consisting of labels beginning with the host and going back through each level to the root node.
Term
fundamental frequency
Definition
The frequency of the dominant sine wave of a composite signal.
Term
gatekeeper
Definition
In the H.323 standard, a server on the LAN that plays the role of the registrar server.
Term
gateway
Definition
A device used to connect two separate networks that use different communication protocols.
Term
general header
Definition
A part of an HTTP request or response message that gives general information about the message.
Term
generic domain
Definition
A subdomain in the domain name system that uses generic suffixes.
Term
geographical routing
Definition
A routing technique in which the entire address space is divided into blocks based on physical landmasses.
Term
geosynchronous Earth orbit
Definition
An orbit that allows a satellite to remain fixed above a certain spot on earth.
Term
Gigabit Ethernet
Definition
Ethernet with a 1000 Mbps data rate.
Term
gigabit medium independent interface (GMII)
Definition
In Gigabit Ethernet, a specification that defines how the reconciliation sublayer is to be connected to the transceiver.
Term
global Internet
Definition
The Internet.
Term
Global Positioning System (GPS)
Definition
An MEO public satellite system consisting of 24 satellites and used for land and sea navigation. GPS is not used for communications.
Term
Global System for Mobile Communication (GSM)
Definition
A second-generation cellular phone system used in Europe.
Term
Globalstar
Definition
An LEO satellite system with 48 satellites in six polar orbits with each orbit hosting eight satellites.
Term
Go-Back-N ARQ
Definition
An error-control method in which the frame in error and all following frames must be retransmitted.
Term
grafting
Definition
Resumption of multicast messages.
Term
ground propagation
Definition
Propagation of radio waves through the lowest portion of the atmosphere (hugging the earth).
Term
group
Definition
An analog signal created by 12 voice channels multiplexed together.
Term
group membership
Definition
Belonging to a group.
Term
group-shared tree
Definition
A multicast routing feature in which each group in the system shares the same tree.
Term
guard band
Definition
A bandwidth separating two signals.
Term
guided media
Definition
Transmission media with a physical boundary.
Term
H.323
Definition
A standard designed by ITU to allow telephones on the public telephone network to talk to computers (called terminals in H.323) connected to the Internet.
Term
half-duplex mode
Definition
A transmission mode in which communication can be two-way but not at the same time.
Term
Hamming code
Definition
A method that adds redundant bits to a data unit to detect and correct bit errors.
Term
Hamming distance
Definition
The number of differences between the corresponding bits in two datawords.
Term
handoff
Definition
Changing to a new channel as a mobile device moves from one cell to another.
Term
handshake protocol
Definition
A protocol to establish or terminate a connection.
Term
harmonics
Definition
Components of a digital signal, each having a different amplitude, frequency, and phase.
Term
hash function
Definition
An algorithm that creates a fixed-size digest from a variable-length message.
Term
hashed-message authentication code (HMAC)
Definition
A MAC based on a keyless hash function such as SHA-1.
Term
head end
Definition
A cable TV office.
Term
header
Definition
Control information added to the beginning of a data packet. Also, in an email, the part of the message that defines the sender, the receiver, the subject of the message, and other information.
Term
header translation
Definition
Conversion of the IPv6 header to IPv4.
Term
hertz (Hz)
Definition
Unit of measurement for frequency.
Term
hexadecimal colon notation
Definition
In IPv6, an address notation consisting of 32 hexadecimal digits, with every four digits separated by a colon.
Term
hierarchical name space
Definition
A name space made of several parts, with each succeeding part becoming more and more specific.
Term
hierarchical routing
Definition
A routing technique in which the entire address space is divided into levels based on specific criteria.
Term
high bit rate digital subscriber line (HDSL)
Definition
A service similar to the T1-line that can operate at lengths up to 3.6 km.
Term
High Rate Direct Sequence Spread Spectrum (HR-DSSS)
Definition
A signal generation method similar to DSSS except for the encoding method (CCK).
Term
High-level Data Link Control (HDLC)
Definition
A bit-oriented data link protocol defined by the ISO. It is used in X.25 protocol. A subset, called link access procedure (LAP), is used in other protocols. It is also a base for many data link protocols used in LANs.
Term
homepage
Definition
A unit of hypertext or hypermedia available on the Web that is the main page for an organization or an individual.
Term
hop count
Definition
The number of nodes along a route. It is a measurement of distance in routing algorithms.
Term
hop limit
Definition
An IPv6 field that limits the number of routers that a packet can visit.
Term
hop-to-hop delivery
Definition
Transmission of frames from one node to the next.
Term
horn antenna
Definition
A scoop-shaped antenna used in terrestrial microwave communication.
Term
host
Definition
A station or node on a network.
Term
host file
Definition
A file, used when the Internet was small, that mapped host names to host addresses.
Term
hostid
Definition
The part of an IP address that identifies a host.
Term
host-specific routing
Definition
A routing method in which the full IP address of a host is given in the routing table.
Term
hub
Definition
A central device in a star topology that provides a common connection among the nodes.
Term
Huffman encoding
Definition
A statistical compression method using variable-length codes to encode a set of symbols.
Term
hybrid network
Definition
A network with a private internet and access to the global Internet.
Term
hybrid-fiber-coaxial (HFC) network
Definition
The second generation of cable networks; uses fiber optic and coaxial cable.
Term
hypermedia
Definition
Information containing text, pictures, graphics, and sound that are linked to other documents through pointers.
Term
hypertext
Definition
Information containing text that is linked to other documents through pointers.
Term
HyperText Markup Language (HTML)
Definition
The computer language for specifying the contents and format of a web document. It allows additional text to include codes that define fonts, layouts, embedded graphics, and hypertext links.
Term
HyperText Transfer Protocol (HTTP)
Definition
An application service for retrieving a web document.
Term
idle state
Definition
In PPP, a state in which the link is inactive.
Term
image file
Definition
In FTP, the default format for transferring binary files. The file is sent as continuous streams of bits without any interpretation or encoding.
Term
incumbent local exchange carrier (ILEC)
Definition
A telephone company that provided services before 1996 and is the owner of the cabling system.
Term
indirect delivery
Definition
A delivery in which the source and destination of a packet are in different networks.
Term
infrared wave
Definition
A wave with a frequency between 300 GHz and 400 THz; usually used for short-range communications.
Term
inner product
Definition
A number produced by multiplying two sequences, element by element, and summing the products.
Term
Institute of Electrical and Electronics Engineers (IEEE)
Definition
A group consisting of professional engineers which has specialized societies whose committees prepare standards in members' areas of specialty.
Term
Integrated Services (IntServ)
Definition
A flow-based QoS model designed for IP.
Term
integrity
Definition
A data quality of being noncorrupted.
Term
interactive audio/video
Definition
Real-time communication with sound and images.
Term
interautonomous system routing protocol
Definition
A protocol to handle transmissions between autonomous systems.
Term
interdomain routing
Definition
Routing among autonomous systems.
Term
interexchange carrier (IXC)
Definition
A long-distance company that, prior to the Act of 1996, provided communication services between two customers in different LATAs.
Term
interface
Definition
The boundary between two pieces of equipment. It also refers to mechanical, electrical, and functional characteristics of the connection.
Term
interference
Definition
Any undesired energy that interferes with the desired signals.
Term
interframe space (IFS)
Definition
In wireless LANs, a time interval between two frames to control access to the channel.
Term
Interim Standard 95 (IS-95)
Definition
One of the dominant second-generation cellular telephony standards in North America.
Term
interior routing
Definition
Routing inside an autonomous system.
Term
interleaving
Definition
Taking a specific amount of data from each device in a regular order.
Term
International Organization of Standardization (ISO)
Definition
A worldwide organization that defines and develops standards on a variety of topics.
Term
International Telecommunications Union-Telecommunication Standardization Sector (ITU-T)
Definition
A standards organization formerly known as the CCITT.
Term
internet
Definition
A collection of networks connected by internetworking devices such as routers or gateways.
Term
Internet
Definition
A global internet that uses the TCP/IP protocol suite.
Term
Internet address
Definition
A 32-bit or 128-bit network-layer address used to uniquely define a host on an internet using the TCP/IP protocol.
Term
Internet Architecture Board (IAB)
Definition
The technical adviser to the ISOC; oversees the continuing development of the TCP/IP protocol suite.
Term
Internet Assigned Numbers Authority (IANA)
Definition
A group supported by the U.S. government that was responsible for the management of Internet domain names and addresses until October 1998.
Term
Internet Control Message Protocol (ICMP)
Definition
A protocol in the TCP/IP protocol suite that handles error and control messages.
Term
Internet Control Message Protocol, version 6 (ICMPv6)
Definition
A protocol in IPv6 that handles error and control messages.
Term
Internet Corporation for Assigned Names and Numbers (ICANN)
Definition
A private, nonprofit corporation managed by an international board that assumed IANA operations.
Term
Internet draft
Definition
A working Internet document (a work in progress) with no official status and a six-month lifetime.
Term
Internet Engineering Steering Group (IESG)
Definition
An organization that oversees the activity of IETF.
Term
Internet Engineering Task Force (IETF)
Definition
A group working on the design and development of the TCP/IP protocol suite and the Internet.
Term
Internet Group Management Protocol (IGMP)
Definition
A protocol in the TCP/IP protocol suite that handles multicasting.
Term
Internet Key Exchange (IKE)
Definition
A protocol designed to create security associations in SADBs.
Term
Internet Mail Access Protocol, version 4 (IMAP4)
Definition
A complex and powerful protocol to handle the transmission of electronic mail.
Term
Internet Mobile Communication for year 2000 (ITM-2000)
Definition
An ITU issued blueprint that defines criteria for third generation cellular telephony.
Term
Internet model
Definition
A 5-layer protocol stack that dominates data communications and networking today.
Term
Internet Network Information Center (INTERNIC)
Definition
An agency responsible for collecting and distributing information about TCP/IP protocols.
Term
Internet Protocol (IP)
Definition
The network-layer protocol in the TCP/IP protocol suite governing connectionless transmission across packet switching networks.
Term
Internet Protocol next generation (IPng)
Definition
See Internet Protocol version 6 (IPv6).
Term
Internet Protocol version 4 (IPv4)
Definition
The current version of Internet Protocol.
Term
Internet Protocol, version 6 (IPv6)
Definition
The sixth version of the Internetworking Protocol; it features major IP addressing changes.
Term
Internet Research Task Force (IRTF)
Definition
A forum of working groups focusing on long-term research topics related to the Internet.
Term
Internet Security Association and Key Management Protocol (ISAKMP)
Definition
A protocol designed by the national Security Agency (NSA) that actually implements the exchanges defined in IKE.
Term
Internet service provider (ISP)
Definition
Usually, a company that provides Internet services.
Term
Internet Society (ISOC)
Definition
The nonprofit organization established to publicize the Internet.
Term
Internet standard
Definition
A thoroughly tested specification that is useful to and adhered to by those who work with the Internet. It is a formalized regulation that must be followed.
Term
internetwork (internet)
Definition
A network of networks.
Term
Internetwork Protocol Control Protocol (IPCP)
Definition
In PPP, the set of protocols that establish and terminate a network layer connection for IP packets.
Term
internetworking
Definition
Connecting several networks together using internetworking devices such as routers and gateways.
Term
intracoded frame (I-frame)
Definition
An independent frame that is not related to any other frame and appearing at regular intervals.
Term
intranet
Definition
A private network that uses the TCP/IP protocol suite.
Term
inverse domain
Definition
A subdomain in the DNS that finds the domain name given the IP address.
Term
inverse multiplexing
Definition
Taking data from one source and breaking it into portions that can be sent across lower-speed lines.
Term
IP datagram
Definition
The Internetworking Protocol data unit.
Term
IP Security (IPSec)
Definition
A collection of protocols designed by the IETF (Internet Engineering Task Force) to provide security for a packet carried on the Internet.
Term
IrDA port
Definition
A port that allows a wireless keyboard to communicate with a PC.
Term
Iridium
Definition
A 66-satellite network that provides communication from any Earth site to another.
Term
ISDN user port (ISUP)
Definition
A protocol at the upper layer of SS7 that provides services similar to those of an ISDN network.
Term
isochronous transmission
Definition
A type of transmission in which the entire stream of bits is synchronized under the control of a common clock.
Term
iterative resolution
Definition
Resolution of the IP address in which the client may send its request to multiple servers before getting an answer.
Term
iterative server
Definition
In the client-server model, a server that can serve only one client at a time.
Term
jamming signal
Definition
In CSMA/CD, a signal sent by the first station that detects collision to alert every other station of the situation.
Term
Java
Definition
A programming language used to create active Web documents.
Term
jitter
Definition
A phenomenon in real-time traffic caused by gaps between consecutive packets at the receiver.
Term
Joint Photographic Experts Group (JPEG)
Definition
A standard for compressing continuous-tone picture.
Term
jumbo group
Definition
An analog signal created by six multiplexed master groups.
Term
Karn's Algorithm
Definition
An algorithm that does not include the retransmitted segments in calculation of round-trip time.
Term
keepalive message
Definition
A message that establishes a relationship between the two routers.
Term
keepalive timer
Definition
A timer that prevents a long idle connection between two TCPs.
Term
Kerberos
Definition
An authentication protocol used by Windows 2000.
Term
key
Definition
A number that a cipher operates on.
Term
key distribution center (KDC)
Definition
In secret key encryption, a trusted third party that shares a key with each user.
Term
LAN emulation (LANE)
Definition
Local area network emulation using ATM switches.
Term
LAN emulation client (LEC)
Definition
In ATM LANs, client software that receives services from a LES.
Term
LAN emulation server (LES)
Definition
In ATM LANs, server software that creates a virtual circuit between the source and destination.
Term
layered architecture
Definition
A model based on ordered tiers.
Term
leaky bucket algorithm
Definition
An algorithm to shape bursty traffic.
Term
least-cost tree
Definition
An MOSPF feature in which the tree is based on a chosen metric instead of shortest path.
Term
leave report
Definition
An IGMP message sent by a host when no process is interested in a specific group.
Term
legacy ATM LAN
Definition
LAN in which ATM technology is used as a backbone to connect traditional LANs.
Term
line coding
Definition
Converting binary data into signals.
Term
linear block code
Definition
A block code in which adding two codewords creates another codeword.
Term
line-of-sight propagation
Definition
The transmission of very high frequency signals in straight lines directly from antenna to antenna.
Term
link
Definition
The physical communication pathway that transfers data from one device to another.
Term
Link Control Protocol (LCP)
Definition
A PPP protocol responsible for establishing, maintaining, configuring, and terminating links.
Term
link local address
Definition
An OPv6 address used by a private LAN.
Term
link state advertisement (LSA)
Definition
In OSPF, a method that disperses information.
Term
link state database
Definition
In link state routing, a database common to all routers and made from LSP information.
Term
link state packet (LSP)
Definition
In link state routing, a small packet containing routing information sent by a router to all other routers.
Term
link state routing
Definition
A routing method in which each router shares its knowledge of changes in its neighborhood with all other routers.
Term
link state update packet
Definition
A packet that provides information about a specific route or routes.
Term
load
Definition
The number of packets sent to a network.
Term
local access
Definition
Using a terminal directly connected to the computer.
Term
local access and transport area (LATA)
Definition
An area covered by one or more telephone companies.
Term
local address
Definition
The part of an email address that defines the name of a special file, called the user mailbox, where all of the mail received for a user is stored for retrieval by the user agent.
Term
local area network (LAN)
Definition
A network connecting devices inside a single building or inside buildings close to each other.
Term
local area network emulation (LANE)
Definition
Software that enables an ATM switch to behave like a LAN switch.
Term
local call service
Definition
A telephone service handling local calls, usually charging a flat monthly fee.
Term
local exchange carrier (LEC)
Definition
A telephone company that handles services inside a LATA.
Term
local Internet service provider
Definition
The same as an Internet service provider.
Term
local ISP
Definition
The same as an Internet service provider.
Term
local loop
Definition
The link that connects a subscriber to the telephone central office.
Term
local management information (LMI)
Definition
A protocol used in Frame Relay to provide. management features.
Term
logical address
Definition
An address defined in the network layer.
Term
logical link control (LLC)
Definition
The upper sublayer of the data link layer as defined by IEEE Project 802.2.
Term
Logical Link Control and Adaptation Protocol (L2CAP)
Definition
A Bluetooth layer used for data exchange on an ACL link.
Term
logical tunnel
Definition
The encapsulation of a multicast packet inside a unicast packet to enable multicast routing by non-multicast routers.
Term
longest mask matching
Definition
The technique in CIDR in which the longest prefix is handled first when searching a routing table.
Term
low Earth orbit (LEO)
Definition
A polar satellite orbit with an altitude between 500 and 2000 km. A satellite with this orbit has a rotation period of 90 to 120 minutes.
Term
low-pass channel
Definition
A channel that passes frequencies between 0 and f.
Term
mail transfer agent (MTA)
Definition
An SMTP component that transfers the mail across the Internet.
Term
management Information Base (MIB)
Definition
The database used by SNMP that holds the information necessary for management of a network.
Term
Manchester encoding
Definition
A digital-to-digital polar encoding method in which a transition occurs at the middle of each bit interval for the purpose of synchronization.
Term
man-in-the-middle attack
Definition
A key management problem in which an intruder intercepts and sends messages between the intended sender and receiver.
Term
mapped address
Definition
An IPv6 address used when a computer that has migrated to Ipv6 wants to send a packet to a computer still using IPv4.
Term
mask
Definition
For IPv4, a 32-bit binary number that gives the first address in the block (the network address) when ANDed with an address in the block.
Term
master
Definition
The one Bluetooth station in a piconet that controls all the others.
Term
master group
Definition
An analog signal created by 10 multiplexed supergroups.
Term
maximum burst size
Definition
The maximum length of time traffic is generated at the peak rate.
Term
maximum transfer unit (MTU)
Definition
The largest size data unit a specific network can handle.
Term
media player
Definition
A help application that plays an audio/video file; used by a browser.
Term
media server
Definition
A server accessed by a media player to download an audio/video file.
Term
medium access control (MAC) sublayer
Definition
The lower sublayer in the data link layer defined by the IEEE 802 project. It defines the access method and access control in different local area network protocols.
Term
medium attachment unit (MAU)
Definition
See transceiver.
Term
medium bandwidth
Definition
The difference between the highest and lowest frequencies a medium can support.
Term
medium dependent interface (MDI)
Definition
In Fast Ethernet, implementation-specific hardware that connects the transceiver to the medium.
Term
medium Earth orbit (MEO)
Definition
A satellite orbit positioned between the two Van Allen belts. A satellite at this orbit takes six hours to circle the earth.
Term
medium independent interface (MII)
Definition
In Fast Ethernet hardware that connects an external transceiver to the reconciliation layer.
Term
membership report
Definition
An IGMP message sent by a host or router interested in joining a specific group.
Term
mesh topology
Definition
A network configuration in which each device has a dedicated point-to-point link to every other device.
Term
message access agent (MAA)
Definition
A client-server program that pulls the stored email messages.
Term
message authentication
Definition
A security measure in which the sender of the message is verified for every message sent.
Term
message authentication code
Definition
A keyed hash function.
Term
message transfer agent (MTA)
Definition
An SMTP component that transfers the message across the Internet.
Term
metric
Definition
A cost assigned for passing through a network.
Term
metropolitan area network (MAN)
Definition
A network that can span a geographical area the size of a city.
Term
microwave
Definition
Electromagnetic waves ranging from 2 GHz to 40 GHz.
Term
minimum Hamming distance
Definition
In a set of words, the smallest Hamming distance between all possible pairs.
Term
minislot
Definition
In an HFC network, a time slot for timesharing of the upstream channels.
Term
mixer
Definition
A device that combines real-time signals from different sources into one signal.
Term
mobile host
Definition
A host that can move from one network to another.
Term
mobile switching center (MSC)
Definition
In cellular telephony, a switching office that coordinates communication between all base stations and the telephone central office.
Term
mobile telephone switching office (MTSO)
Definition
An office that controls and coordinates communication between all of the cell offices and the telephone control office.
Term
modem
Definition
A device consisting of a modulator and a demodulator. It converts a digital signal into an analog signal (modulation) and vice versa (demodulation).
Term
modification detection code (MDC)
Definition
The digest created by a hash function.
Term
modular arithmetic
Definition
Arithmetic that uses a limited range of integers (O to n-1).
Term
modulation
Definition
Modification of one or more characteristics of a carrier wave by an information-bearing signal.
Term
modulator
Definition
A device that converts a digital signal to an analog signal suitable for transmission across a telephone line.
Term
modulus
Definition
The upper limit in modular arithmetic (n).
Term
monoalphabetic substitution
Definition
An encryption method in which each occurrence of a character is replaced by another character in the set.
Term
motion picture experts group (MPEG)
Definition
A method to compress videos.
Term
MT-RJ
Definition
A fiber-optic cable connector.
Term
multicast address
Definition
An address used for multicasting.
Term
multicast backbone (MBONE)
Definition
A set of internet routers supporting multicasting through the use of tunneling.
Term
Multicast Open Shortest Path First (MOSPF)
Definition
A multicast protocol that uses multicast link state routing to create a source-based least cost tree.
Term
multicast router
Definition
A router with a list of loyal members related to each router interface that distributes the multicast packets.
Term
multicasting
Definition
A transmission method that allows copies of a single packet to be sent to a selected group of receivers.
Term
multihoming service
Definition
A service provided by SCTP that allows a computer to be connected to different networks.
Term
multiline transmission, 3-level (MLT-3) encoding
Definition
A line coding scheme featuring 3 levels of signals and transitions at the beginning of the 1 bit.
Term
multimode graded-index fiber
Definition
An optical fiber with a core having a graded index of refraction.
Term
multimode step-index fiber
Definition
An optical fiber with a core having a uniform index of refraction. The index of refraction changes suddenly at the core/cladding boundary.
Term
multiple access (MA)
Definition
A line access method in which every station can access the line freely.
Term
multiple unicasting
Definition
Sending multiple copies of a message, each with a different unicast address.
Term
multiplexer (MUX)
Definition
A device used for multiplexing.
Term
multiplexing
Definition
The process of combining signals from multiple sources for transmission across a single data link.
Term
multiplicative decrease
Definition
A congestion avoidance technique in which the threshold is set to half of the last congestion window size, and the congestion window size starts from one again.
Term
Multipurpose Internet Mail Extension (MIME)
Definition
A supplement to SMTP that allows non-ASCII data to be sent through SMTP.
Term
multistage switch
Definition
An array of switches designed to reduce the number of crosspoints.
Term
multistream service
Definition
A service provided by SCTP that allows data transfer to be carried using different streams.
Term
n2 problem
Definition
A problem due to the large number of keys needed in symmetric key distribution.
Term
Nagle's algorithm
Definition
An algorithm that attempts to prevent silly window syndrome at the sender's site; both the rate of data production and the network speed are taken into account.
Term
name space
Definition
All the names assigned to machines on an internet.
Term
name-address resolution
Definition
Mapping a name to an address or an address to a name.
Term
national service provider (NSP)
Definition
A backbone network created and maintained by a specialized company.
Term
Needham-Schroeder protocol
Definition
A key management protocol using multiple challenge-response interactions between 2 entities.
Term
negative acknowledgment (NAK)
Definition
A message sent to indicate the rejection of received data.
Term
netid
Definition
The part of an IP address that identifies the network.
Term
network
Definition
A system consisting of connected nodes made to share data, hardware, and software.
Term
network access point (NAP)
Definition
A complex switching station that connects backbone networks.
Term
network address
Definition
An address that identifies a network to the rest of the Internet; it is the first address in a block.
Term
network address translation (NAT)
Definition
A technology that allows a private network to use a set of private addresses for internal communication and a set of global Internet addresses for external communication.
Term
network allocation vector (NAV)
Definition
In CSMA/CA, the amount of time that must pass before a station can check the line for idleness.
Term
Network Control Protocol (NCP)
Definition
In PPP, a set of control protocols that allows the encapsulation of data coming from network layer protocols.
Term
network interface card (NIC)
Definition
An electronic device, internal or external to a station, that contains circuitry to enable the station to be connected to the network.
Term
network layer
Definition
The third layer in the Internet model, responsible for the delivery of a packet to the final destination.
Term
network link LSA
Definition
An LSA packet that announces the existence of all of the routers connected to the network.
Term
Network Virtual Terminal (NVT)
Definition
A TCP/IP application protocol that allows remote login.
Term
networking state
Definition
A PPP state in which packets of user data and packets for control are transmitted.
Term
network-specific routing
Definition
Routing in which all hosts on a network share one entry in the routing table.
Term
network-to-network interface (NNI)
Definition
In ATM, the interface between two networks.
Term
next header
Definition
In IPv6, an 8-bit field defining the header that follows the base header in the datagram.
Term
next-hop routing
Definition
A routing method in which only the address of the next hop is listed in the routing table instead of a complete list of the stops the packet must make.
Term
node
Definition
An addressable communication device (e.g., a computer or router) on a network.
Term
node-to-node delivery
Definition
Transfer of a data unit from one node to the next.
Term
noise
Definition
Random electrical signals that can be picked by the transmission medium and result in degradation or distortion of the data.
Term
noiseless channel
Definition
An error-free channel.
Term
noisy channel
Definition
A channel that can produce error in data transmission.
Term
nonce
Definition
A large random number that is used once to distinguish a fresh authentication request from a used one.
Term
nonpersistent connection
Definition
A connection in which one TCP connection is made for each request/response.
Term
nonpersistent strategy
Definition
A random multiple access method in which a station waits a random period of time after a collision is sensed.
Term
nonrepudiation
Definition
A security aspect in which a receiver must be able to prove that a received message came from a specific sender.
Term
nonreturn to zero (NRZ)
Definition
A digital-to-digital polar encoding method in which the signal level is always either positive or negative.
Term
nonreturn to zero, invert (NRZ-I)
Definition
An NRZ encoding method in which the signal level is inverted each time a 1 is encountered.
Term
nonreturn to zero, level (NRZ-L)
Definition
An NRZ encoding method in which the signal level is directly related to the bit value.
Term
normal response mode (NRM)
Definition
In HDLC, a communication mode in which the secondary station must have permission from the primary station before transmission can proceed.
Term
notification message
Definition
A BGP message sent by a router whenever an error condition is detected or a router wants to close the connection.
Term
no-transition mobility
Definition
In wireless LANs, mobility confined inside a BSS or non-mobility.
Term
Nyquist bit rate
Definition
The data rate based on the Nyquist theorem.
Term
Nyquist theorem
Definition
A theorem that states that the number of samples needed to adequately represent an analog signal is equal to twice the highest frequency of the original signal.
Term
Oakley
Definition
A key creating protocol, developed by Hilarie Orman, which is one of the three components of IKE protocol.
Term
odd parity
Definition
An error-detection method in which an extra bit is added to the data unit such that the sum of all 1-bits becomes odd.
Term
omnidirectional antenna
Definition
An antenna that sends out or receives signals in all directions.
Term
on-demand audio/video
Definition
Another name for streaming stored audio/video.
Term
one's complement
Definition
A representation of binary numbers in which the complement of a number is found by complementing all bits.
Term
open message
Definition
A BGP message sent by a router to create a neighborhood relationship.
Term
open shortest path first (OSPF)
Definition
An interior routing protocol based on link state routing.
Term
open system
Definition
A model that allows two different systems to communicate regardless of their underlying architecture.
Term
Open Systems Interconnection (OSI) model
Definition
A seven-layer model for data communication defined by ISO.
Term
open-loop congestion control
Definition
Policies applied to prevent congestion.
Term
optical carrier (OC)
Definition
The hierarchy of fiber-optic carriers defined in SONET. The hierarchy defines up to 10 different carriers (OC-1, OC-3, OC-12, . . . , OC-192), each with a different data rate.
Term
optical fiber
Definition
A thin thread of glass or other transparent material to carry light beams.
Term
optional attribute
Definition
A BGP path attribute that need not be recognized by every router.
Term
orbit
Definition
The path a satellite travels around the earth.
Term
Orthogonal Frequency Division Multiplexing (OFDM)
Definition
A multiplexing method similar to FDM, with all the subbands used by one source at a given time.
Term
orthogonal sequence
Definition
A sequence with special properties between elements.
Term
Otway-Rees protocol
Definition
A key management protocol with less steps than the Needham-Schroeder method.
Term
out-of-band signaling
Definition
Using two separate channels for data and control.
Term
output feedback (OFB) mode
Definition
A mode similar to the CFB mode with one difference. Each bit in the ciphertext s independent of the previous bit or bits.
Term
overhead
Definition
Extra bits added to the data unit for control purposes.
Term
packet
Definition
Synonym for data unit, mostly used in the network layer.
Term
packet switching
Definition
Data transmission using a packet-switched network.
Term
packet-filter firewall
Definition
A firewall that forwards or blocks packets based on the information in the network-layer and transport-layer headers.
Term
packet-switched network
Definition
A network in which data are transmitted in independent units called packets.
Term
page
Definition
A unit of hypertext or hypermedia available on the Web.
Term
parabolic dish antenna
Definition
An antenna shaped like a parabola used for terrestrial microwave communication.
Term
parallel transmission
Definition
Transmission in which bits in a group are sent simultaneously, each using a separate link.
Term
parameter-problem message
Definition
An ICMP message that notifies a host that there is an ambiguous or missing value in any field of the datagram.
Term
parity bit
Definition
A redundant bit added to a data unit (usually a character) for error checking.
Term
parity check
Definition
An error-detection method using a parity bit.
Term
partially qualified domain name (PQDN)
Definition
A domain name that does not include all the levels between the host and the root node.
Term
passive open
Definition
The state of a server as it waits for incoming requests from a client.
Term
Password Authentication Protocol (PAP)
Definition
A simple two-step authentication protocol used in PPP.
Term
path
Definition
The channel through which a signal travels.
Term
path layer
Definition
A SONET layer responsible for the movement of a signal from its optical source to its optical destination.
Term
path overhead
Definition
Control information used by the SONET path layer.
Term
path vector routing
Definition
A routing method on which BGP is based; in this method, the ASs through which a packet must pass are explicitly listed.
Term
P-box
Definition
A hardware circuit used in encryption that connects input to output.
Term
peak amplitude
Definition
The maximum signal value of a sine wave.
Term
peak data rate
Definition
The maximum data rate of the traffic.
Term
peer-to-peer process
Definition
A process on a sending and a receiving machine that communicate at a given layer.
Term
per hop behavior (PHB)
Definition
In the Diffserv model, a 6-bit field that defines the packet-handling mechanism for the packet.
Term
period
Definition
The amount of time required to complete one full cycle.
Term
periodic signal
Definition
A signal that exhibits a repeating pattern.
Term
permanent virtual circuit (PVC)
Definition
A virtual circuit transmission method in which the same virtual circuit is used between source and destination on a continual basis.
Term
persistence timer
Definition
A technique to handle the zero window-size advertisement.
Term
persistent connection
Definition
A connection in which the server leaves the connection open for more requests after sending a response.
Term
persistent strategy
Definition
In CSMA, a strategy in which the station sends a frame after sensing the line.
Term
Personal Communication System (PCS)
Definition
A generic term for a commercial cellular system that offers several kinds of communication services.
Term
phase
Definition
The relative position of a signal in time.
Term
phase modulation (PM)
Definition
An analog-to-analog modulation method in which the carrier signal's phase varies with the amplitude of the modulating signal.
Term
phase shift keying (PSK)
Definition
A digital-to-analog modulation method in which the phase of the carrier signal is varied to represent a specific bit pattern.
Term
PHY sublayer
Definition
The transceiver in Fast Ethernet.
Term
physical address
Definition
The address of a device used at the data link layer (MAC address).
Term
physical layer
Definition
The first layer of the Internet model, responsible for the mechanical and electrical specifications of the medium.
Term
physical layer signaling (PLS) sublayer
Definition
An Ethernet sublayer that encodes and decodes data.
Term
physical topology
Definition
The manner in which devices are connected in a network.
Term
piconet
Definition
A Bluetooth network.
Term
piggybacking
Definition
The inclusion of acknowledgment on a data frame.
Term
pipelining
Definition
In Go-Back-n ARQ, sending several frames before news is received concerning previous frames.
Term
pixel
Definition
A picture element of an image.
Term
plain old telephone system (POTS)
Definition
The conventional telephone network used for voice communication.
Term
plaintext
Definition
In encryption/decryption, the original message.
Term
playback buffer
Definition
A buffer that stores the data until they are ready to be played.
Term
point coordination function (PCF)
Definition
In wireless LANs, an optional and complex access method implemented in an infrastructure network.
Term
point of presence (POP)
Definition
A switching office where carriers can interact with each other.
Term
point-to-point access
Definition
See point-to-point connection.
Term
point-to-point connection
Definition
A dedicated transmission link between two devices.
Term
point-to-point link
Definition
A dedicated transmission link between two devices.
Term
Point-to-Point Protocol (PPP)
Definition
A protocol for data transfer across a serial line.
Term
poison reverse
Definition
A feature added to split horizon in which a table entry that has come through on interface is set to infinity in the update packet.
Term
polar encoding
Definition
A digital-to-analog encoding method that uses two levels (positive and negative) of amplitude.
Term
policy routing
Definition
A path vector routing feature in which the routing tables are based on rules set by the network administrator rather than a metric.
Term
poll
Definition
In the primary/secondary access method, a procedure in which the primary station asks a secondary station if it has any data to transmit.
Term
poll/final (P/F) bit
Definition
A bit in the control field of HDLC; if the primary is sending, it can be a poll bit; if the secondary is sending, it can be a final bit.
Term
poll/select
Definition
An access method protocol using poll and select procedures. See poll. See select.
Term
polling
Definition
An access method in which one device is designated as a primary station and the others as the secondary stations. The access is controlled by the primary station.
Term
polyalphabetic substitution
Definition
An encryption method in which each occurrence of a character can have a different substitute.
Term
polynomial
Definition
An algebraic term that can represent a CRC divisor.
Term
port
Definition
In a URL, the port number of the server.
Term
port address
Definition
In TCP/IP protocol an integer identifying a process.
Term
port number
Definition
An integer that defines a process running on a host.
Term
Post Office Protocol, version 3 (POP3)
Definition
A popular but simple SMTP mail access protocol.
Term
p-persistent
Definition
A CSMA persistence strategy in which a station sends with probablity p if it finds the line idle.
Term
p-persistent strategy
Definition
A CSMA persistence strategy in which a station sends with probability p if it finds the line idle.
Term
preamble
Definition
The 7-byte field of an IEEE 802.3 frame consisting of alternating 1s and 0s that alert and synchronize the receiver.
Term
predicted frame (P-frame)
Definition
An MPEG frame which contains only the changes from the preceding frame.
Term
predictive encoding
Definition
In audio compression, encoding only the differences between the samples.
Term
prefix
Definition
The common part of an address range.
Term
presentation layer
Definition
The sixth layer of the OSI model responsible for translation, encryption, authentication, and data compression.
Term
Pretty Good Privacy (PGP)
Definition
A protocol that provides all four aspects of security in the sending of email.
Term
primary server
Definition
A server that stores a file about the zone for which it is an authority.
Term
primary station
Definition
In primary/secondary access method, a station that issues commands to the secondary stations.
Term
priority queueing
Definition
A queuing technique in which packets are assigned to a priority class, each with its own queue.
Term
privacy
Definition
A security aspect in which the message makes sense only to the intended receiver.
Term
private key
Definition
In conventional encryption, a key shared by only one pair of devices, a sender and a receiver. In public-key encryption, the private key is known only to the receiver.
Term
private network
Definition
A network that is isolated from the Internet.
Term
process
Definition
A running application program.
Term
process-to-process delivery
Definition
Delivery of a packet from the sending process to the destination process.
Term
product block
Definition
A combination of P-boxes and S-boxes to get a more complex cipher block.
Term
Project 802
Definition
The project undertaken by the IEEE in an attempt to solve LAN incompatibility. See also IEEE Project 802.
Term
propagation speed
Definition
The rate at which a signal or bit travels; measured by distance/second.
Term
propagation time
Definition
The time required for a signal to travel from one point to another.
Term
protocol
Definition
Rules for communication.
Term
Protocol Independent Multicast (PIM)
Definition
A multicasting protocol family with two members, PIM-DM and PIM-SM; both protocols are unicast-protocol dependent.
Term
Protocol Independent Multicast, Dense Mode (PIM-DM)
Definition
A source-based routing protocol that uses RPF and pruning/grafting strategies to handle multicasting.
Term
Protocol Independent Multicast, Sparse Mode (PIM-SM)
Definition
A group-shared routing protocol that is similar to CBT and uses a rendezvous point as the source of the tree.
Term
protocol suite
Definition
A stack or family of protocols defined for a complex communication system.
Term
proxy ARP
Definition
A technique that creates a subnetting effect; on server answers ARP requests for multiple hosts.
Term
proxy firewall
Definition
A firewall that filters a message based on the information available in the message itself (at the application layer).
Term
proxy server
Definition
A computer that keeps copies of responses to recent requests.
Term
pruning
Definition
Stopping the sending of multicast messages from an interface.
Term
pseudoheader
Definition
Information from the IP header used only for checksum calculation in UDP and TCP packet.
Term
pseudorandom noise (PN)
Definition
A pseudorandom code generator used in FHSS.
Term
public key
Definition
In public-key encryption, a key known to everyone.
Term
public key infrastructure (PKI)
Definition
A hierarchical structure of CA servers.
Term
public-key cryptography
Definition
A method of encryption based on a nonreversible encryption algorithm. The method uses two types of keys: The public key is known to the public; the private key (secret key) is known only to the receiver.
Term
pulse amplitude modulation (PAM)
Definition
A technique in which an analog signal is sampled; the result is a series of pulses based on the sampled data.
Term
pulse code modulation (PCM)
Definition
A technique that modifies PAM pulses to create a digital signal.
Term
pulse rate
Definition
The number of symbols per second.
Term
pulse stuffing
Definition
In TDM, a technique that adds dummy bits to the input lines with lower rates.
Term
pure ALOHA
Definition
The original ALOHA.
Term
quadbit
Definition
A unit of data consisting of four bits.
Term
quadrature amplitude modulation (QAM)
Definition
A digital-to-analog modulation method in which the phase and amplitude of the carrier signal vary with the modulating signal.
Term
quality of service (QoS)
Definition
A set of attributes related to the performance of the connection.
Term
quantization
Definition
The assignment of a specific range of values to signal amplitudes.
Term
query message
Definition
An ICMP message that helps a host or a network manager get specific information from a router or another host. Or, an IGMP message that requests group information from a router or a host. Or, a DNS message that requests information.
Term
queue
Definition
A waiting list.
Term
radio wave
Definition
Electromagnetic energy in the 3-KHz to 300-GHz range.
Term
random access
Definition
A medium access category in which each station can access the medium without being controlled by any other station.
Term
ranging
Definition
In an HFC network, a process that determines the distance between the CM and the CMTS.
Term
rate adaptive asymmetrical digital subscriber line (RADSL)
Definition
A DSL-based technology that features different data rates depending on the type of communication.
Term
raw socket
Definition
A structure designed for protocols that directly use the services of IP and use neither stream sockets nor datagram sockets.
Term
read-only memory (ROM)
Definition
Permanent memory with contents that cannot be changed.
Term
Real-Time Streaming Protocol (RTSP)
Definition
An out-of-band control protocol designed to add more functionality to the streaming audio/video process.
Term
Real-time Transport Control Protocol (RTCP)
Definition
A companion protocol to RTP with messages that control the flow and quality of data and allow the recipient to send feedback to the source or sources.
Term
Real-time Transport Protocol (RTP)
Definition
A protocol for real-time traffic; used in conjunction with UDP.
Term
receiver window
Definition
In the TCP sliding window protocol, the window at the receiver site.
Term
reconciliation sublayer
Definition
A Fast Ethernet sublayer which passes data in 4-bit format to the MII.
Term
recursive resolution
Definition
Resolution of the IP address in which the client sends its request to a server that eventually returns a response.
Term
redirection
Definition
An ICMP message type that informs the sender of a preferred route.
Term
redundancy
Definition
The addition of bits to a message for error control.
Term
Reed-Solomon
Definition
A complex, but efficient, cyclic code.
Term
reflection
Definition
The phenomenon related to the bouncing back of light at the boundary of two media.
Term
refraction
Definition
The phenomenon related to the bending of light when it passes from one medium to another.
Term
regenerator
Definition
A device that regenerates the original signal from a corrupted signal. See also repeater.
Term
regional cable head (RCH)
Definition
In an HFC network, the main distribution site.
Term
regional ISP
Definition
A small ISP that is connected to one or more NSPs.
Term
registrar
Definition
An authority to register new domain names.
Term
registrar server
Definition
In SIP, a server that knows the IP address of the callee.
Term
reliability
Definition
A QoS flow characteristic; dependability of the transmission.
Term
remote access
Definition
Using a terminal that is not directly connected to a computer.
Term
remote bridge
Definition
A device that connects LANs and point-to-point networks; often used in a backbone network.
Term
remote host
Definition
The computer that a user wishes to access while seated physically at another computer.
Term
remote server
Definition
A program run at a site physically removed from the user.
Term
rendezvous router
Definition
A router that is the core or center for each multicast group; it becomes the root of the tree.
Term
rendezvous-point tree
Definition
A group-shared tree method in which there is one tree for each group.
Term
repeater
Definition
A device that extends the distance a signal can travel by regenerating the signal.
Term
replay attack
Definition
The resending of a message that has been intercepted by an intruder.
Term
Request for Comment (RFC)
Definition
A formal Internet document concerning an Internet issue.
Term
request header
Definition
A part of the HTTP request message that specifies the client's configuration and the client's preferred document format.
Term
resolver
Definition
The DNS client that is used by a host that needs to map an address to a name or a name to an address.
Term
Resource Reservation Protocol (RSVP)
Definition
A signaling protocol to help IP create a flow and make a resource reservation to improve QoS.
Term
response header
Definition
A part of the HTTP response message that specifies the server's configuration and special information about the request.
Term
response message
Definition
A DNS message type that returns information.
Term
retransmission time-out
Definition
The expiration of a timer that controls the retransmission of packets.
Term
retransmission timer
Definition
A timer that controls the waiting time for an acknowledgment of a segment.
Term
return to zero (RZ)
Definition
A digital-to-digital encoding technique in which the voltage of the signal is zero for the second half of the bit interval.
Term
reuse factor
Definition
In cellular telephony, the number of cells with a different set of frequencies.
Term
Reverse Address Resolution Protocol (RARP)
Definition
A TCP/IP protocol that allows a host to find its Internet address given its physical address.
Term
reverse path broadcasting (RPB)
Definition
A technique in which the router forwards only the packets that have traveled the shortest path from the source to the router.
Term
reverse path forwarding (RPF)
Definition
A technique in which the router forwards only the packets that have traveled the shortest path from the source to the router.
Term
reverse path multicasting (RPM)
Definition
A technique that adds pruning and grafting to RPB to create a multicast shortest path tree that supports dynamic membership changes.
Term
Rijndael algorithm
Definition
An algorithm named after its two Belgian inventors, Vincent Rijmen and Joan Daemen that is the basis of AES.
Term
ring topology
Definition
A topology in which the devices are connected in a ring. Each device on the ring receives the data unit from the previous device, regenerates it, and forwards it to the next device.
Term
Rivest, Shamir, Adleman (RSA) encryption
Definition
See RSA encryption.
Term
RJ45
Definition
A coaxial cable connector.
Term
roaming
Definition
In cellular telephony, the ability of a user to communicate outside of his own service provider's area.
Term
root server
Definition
In DNS, a server whose zone consists of the whole tree. A root server usually does not store any information about domains but delegates its authority to other servers, keeping references to those servers.
Term
rotary dialing
Definition
Accessing the switching station through a phone that sends a digital signal to the end office.
Term
rotation cipher
Definition
A keyed or keyless cipher in which the input bits are rotated to the left or right to create output bits.
Term
round-trip time (RTT)
Definition
The time required for a datagram to go from a source to a destination and then back again.
Term
route
Definition
A path traveled by a packet.
Term
router
Definition
An internetworking device operating at the first three OSI layers. A router is attached to two or more networks and forwards packets from one network to another.
Term
router link LSA
Definition
An LSA packet that advertises all of the links of a router.
Term
router-solicitation and advertisement message
Definition
An ICMP message sent to obtain and disperse router information.
Term
routing
Definition
The process performed by a router; finding the next hop for a datagram.
Term
Routing Information Protocol (RIP)
Definition
A routing protocol based on the distance vector routing algorithm.
Term
routing table
Definition
A table containing information a router needs to route packets. The information may include the network address, the cost, the address of the next hop, and so on.
Term
RSA encryption
Definition
A popular public-key encryption method developed by Rivest, Shamir, and Adleman.
Term
sampling
Definition
The process of obtaining amplitudes of a signal at regular intervals.
Term
sampling rate
Definition
The number of samples obtained per second in the sampling process.
Term
satellite network
Definition
A combination of nodes that provides communication form one point on the earth to another.
Term
S-box
Definition
An encryption device made of decoders, P-boxes, and encoders.
Term
scatternet
Definition
A combination of piconets.
Term
scrambling
Definition
In digital-to-digital conversion, modifying part of the rules in line coding scheme to create bit synchronization.
Term
search algorithm
Definition
A rule for finding the next hop.
Term
secondary server
Definition
In DNS, a server that transfers the complete information about a zone from another server (primary or secondary) and stores the file on its local disk.
Term
secondary station
Definition
In poll/select access method, a station that sends a response in answer to a command from a primary station.
Term
secret-key encryption
Definition
A security method in which the key for encryption is the same as the key for decryption; both sender and receiver have the same key.
Term
Secure Hash Algorithm 1 (SHA-1)
Definition
A hash algorithm designed by the National Institute of Standards and Technology (NIST). It was published as a Federal Information Processing Standard (FIPS).
Term
Secure Socket Layer (SSL)
Definition
A protocol designed to provide security and compression services to data generated from the application layer.
Term
security
Definition
The protection of a network from unauthorized access, viruses, and catastrophe.
Term
Security Association (SA)
Definition
An IPSec signaling protocol that creates a logical connection between 2 hosts.
Term
Security association database (SADB)
Definition
A database defining a set of single security associations.
Term
security parameter index (SPI)
Definition
A parameter that uniquely distinguish on security association from the others.
Term
segment
Definition
The packet at the TCP layer. Also, the length of transmission medium shared by devices.
Term
segmentation
Definition
The splitting of a message into multiple packets; usually performed at the transport layer.
Term
segmentation and reassembly (SAR)
Definition
The lower AAL sublayer in the ATM protocol in which a header and/or trailer may be added to produce a 48-byte element.
Term
select
Definition
In poll/select access method, a procedure in which the primary station asks a secondary station if it is ready to receive data.
Term
selective-repeat ARQ
Definition
An error-control method in which only the frame in error is resent.
Term
self-synchronization
Definition
Synchronization of long strings of 1s or 0s through the coding method.
Term
semantics
Definition
The meaning of each section of bits.
Term
sender window
Definition
In the TCP sliding window protocol, the window at the sender site.
Term
sequence number
Definition
The number that denotes the location of a frame or packet in a message.
Term
serial transmission
Definition
Transmission of data one bit at a time using only one single link.
Term
server
Definition
A program that can provide services to other programs, called clients.
Term
server control point (SCP)
Definition
In SS7 terminology, the node that controls the whole operation of the network.
Term
service-point address
Definition
See port address.
Term
Session Initiation Protocol (SIP)
Definition
In voice over IP, an application protocol that establishes, manages, and terminates a multimedia session.
Term
session layer
Definition
The fifth layer of the OSI model, responsible for the establishment, management, and termination of logical connections between two end users.
Term
setup phase
Definition
In virtual circuit switching, a phase in which the source and destination use their global addresses to help switches make table entries for the connection.
Term
S-frame
Definition
An HDLC frame used for supervisory functions such as acknowledgment, flow control, and error control; it contains no user data.
Term
Shannon capacity
Definition
The theoretical highest data rate for a channel.
Term
shielded twisted-pair (STP)
Definition
Twisted-pair cable enclosed in a foil or mesh shield that protects against electromagnetic interference.
Term
shift cipher
Definition
The simplest monoalphabetic cipher in which the plaintext and ciphertext consist of letters. In the encryption algorithm, the characters are shifted down the character list; in the decryption algorithm, the characters are shifted up the character list.
Term
shift register
Definition
A register in which each memory location, at a time click, accepts the bit at its input port, stores the new bit, and displays it on the output port.
Term
short interframe space (SIFS)
Definition
In CSMA/CA, a period of time that the destination waits after receiving the RTS.
Term
shortest path tree
Definition
A routing table formed by using the Dijkstra algorithm.
Term
signal
Definition
Electromagnetic waves propagated along a transmission medium.
Term
signal element
Definition
The shortest section of a signal (time-wise) that represents a data element.
Term
signal level
Definition
The number of values allowed in a particular signal.
Term
signal point (SP)
Definition
In SS7 terminology, the user telephone or computer is connected to the signal points.
Term
signal rate
Definition
The number of signal elements sent in one second.
Term
Signal transport port (STP)
Definition
In SS7 terminology, the node used by the signaling network.
Term
signaling connection control point (SCCP)
Definition
In SS7, the control points used for special services such as 800 calls.
Term
Signaling System Seven (SS7)
Definition
The protocol that is used in the signaling network.
Term
signal-to-noise ratio (SNR)
Definition
The signal strength divided by the noise, both in decibels.
Term
silly window syndrome
Definition
A situation in which a small window size is advertised by the receiver and a small segment sent by the sender.
Term
simple and efficient adaptation layer (SEAL)
Definition
An AAL layer designed for the Internet (AAL5).
Term
simple bridge
Definition
A networking device that links two segments; requires manual maintenance and updating.
Term
Simple Mail Transfer Protocol (SMTP)
Definition
The TCP/IP protocol defining electronic mail service on the Internet.
Term
Simple Network Management Protocol (SNMP)
Definition
The TCP/IP protocol that specifies the process of management in the Internet.
Term
Simple Protocol
Definition
The simple protocol we used to show an access method without flow and error control.
Term
simplex mode
Definition
A transmission mode in which communication is one way.
Term
sine wave
Definition
An amplitude-versus-time representation of a rotating vector.
Term
single-bit error
Definition
Error in a data unit in which only one single bit has been altered.
Term
single-mode fiber
Definition
An optical fiber with an extremely small diameter that limits beams to a few angles, resulting in an almost horizontal beam.
Term
site local address
Definition
An IPv6 address for a site having several networks, but not connected to the Internet.
Term
SKEME
Definition
A protocol for key exchange designed by Hugo Krawcyzk. It is one of the three protocols that form the basis of IKE.
Term
sky propagation
Definition
Propagation of radio waves into the ionosphere and then back to earth.
Term
slash notation
Definition
A shorthand method to indicate the number of 1s in the mask.
Term
slave
Definition
In a piconet, a station under control of a master.
Term
sliding window
Definition
A protocol that allows several data units to be in transition before receiving an acknowledgment.
Term
sliding window ARQ
Definition
An error-control protocol using sliding window concept.
Term
slotted ALOHA
Definition
The modified ALOHA access method in which time is divided into slots and each station is forced to start sending data only at the beginning of the slot.
Term
slow convergence
Definition
A RIP shortcoming apparent when a change somewhere in the internet propagates very slowly through the rest of the internet.
Term
slow start
Definition
A congestion-control method in which the congestion window size increases exponentially at first.
Term
socket
Definition
An end point for a process; two sockets are needed for communication.
Term
socket address
Definition
A structure holding an IP address and a port number.
Term
socket interface
Definition
An API based on UNIX that defines a set of system calls (procedures) that are an extension of system calls used in UNIX to access files.
Term
solicited response
Definition
A RIP response sent only in answer to a request.
Term
source address (SA)
Definition
The address of the sender of the message.
Term
source quench
Definition
A method, used in ICMP for flow control, in which the source is advised to slow down or stop the sending of datagrams because of congestion.
Term
source quench message
Definition
An ICMP message sent to slow down or stop the sending of datagrams.
Term
source routing
Definition
Explicitly defining the route of a packet by the sender of the packet.
Term
source routing bridge
Definition
A source or destination station that performs some of the duties of a transparent bridge as a method to prevent loops.
Term
source-based tree
Definition
A tree used for multicasting by multicasting protocols in which a single tree is made for each combination of source and group.
Term
source-to-destination delivery
Definition
The transmission of a message from the original sender to the intended recipient.
Term
space propagation
Definition
A type of propagation that can penetrate the ionosphere.
Term
space-division switching
Definition
Switching in which the paths are separated from each other spatially.
Term
spanning tree
Definition
A tree with the source as the root and group members as leaves; a tree that connects all of the nodes.
Term
spanning tree algorithm
Definition
An algorithm that prevents looping when two LANs are connected by more than one bridge.
Term
spatial compression
Definition
Compressing an image by removing redundancies.
Term
special-query message
Definition
An IGMP query message sent by a router to ensure that no host or router is interested in continuing membership in a group.
Term
specific host on this network
Definition
A special address in which the netid is all 0s and the hostid is explicit.
Term
spectrum
Definition
The range of frequencies of a signal.
Term
split horizon
Definition
A method to improve RIP stability in which the router selectively chooses the interface from which updating information is sent.
Term
spread spectrum
Definition
A wireless transmission technique that requires a bandwidth several times the original bandwidth.
Term
Standard Ethernet
Definition
The conventional Ethernet operating at 10 mbps.
Term
star backbone
Definition
A backbone in which the logical topology is a star.
Term
star topology
Definition
A topology in which all stations are attached to a central device (hub).
Term
start bit
Definition
In asynchronous transmission, a bit to indicate the beginning of transmission.
Term
start frame delimiter (SFD)
Definition
A 1-byte field in the IEEE 802.3 frame that signals the beginning of the readable (nonpreamble) bit stream.
Term
state transition diagram
Definition
A diagram to illustrate the states of a finite state machine.
Term
static document
Definition
On the World Wide Web, a fixed-content document that is created and stored in a server.
Term
static mapping
Definition
A technique in which a list of logical and physical address correspondences is used for address resolution.
Term
static routing
Definition
A type of routing in which the routing table remains unchanged.
Term
stationary host
Definition
A host that remains attached to one network.
Term
statistical TDM
Definition
A TDM technique in which slots are dynamically allocated to improve efficiency.
Term
status line
Definition
In the HTTP response message a line that consists of the HTTP version, a space, a status code, a space, a status phrase.
Term
stop bit
Definition
In asynchronous transmission, one or more bits to indicate the end of transmission.
Term
stop-and-wait ARQ
Definition
An error-control protocol using stop-and-wait flow control.
Term
Stop-and-Wait Protocol
Definition
A protocol in which the sender sends on frame, stops until it receives confirmation from the receiver, and then sends the next frame.
Term
store-and-forward switch
Definition
A switch that stores the frame in an input buffer until the whole packet has arrived.
Term
straight tip connector
Definition
A type of fiber-optic cable connector using a bayonet locking system.
Term
Stream Control Transmission Protocol (SCTP)
Definition
The transport layer protocol designed for Internet telephony and related applications.
Term
stream socket
Definition
A structure designed to be used with a connection-oriented protocol such as TCP.
Term
streaming live audio/video
Definition
Broadcast data from the Internet that a user can listen to or watch.
Term
streaming stored audio/video
Definition
Data downloaded as files from the Internet that a user can listen to or watch.
Term
strong collision
Definition
Creating two message with the same digest.
Term
Structure of Management Information (SMI)
Definition
In SNMP, a component used in network management.
Term
STS multiplexer/demultiplexer
Definition
A SONET device that multiplexes and demultiplexes signals.
Term
stub link
Definition
A network that is connected to only one router.
Term
subnet
Definition
subnetwork.
Term
subnet address
Definition
The network address of a subnet.
Term
subnet mask
Definition
The mask for a subnet.
Term
subnetwork
Definition
A part of a network.
Term
subscriber channel connector
Definition
A fiber-optic cable connector using a push/pull locking mechanism.
Term
substitution cipher
Definition
A bit-level encryption method in which n bits substitute for another n bits as defined by P-boxes, encoders, and decoders.
Term
suffix
Definition
For a network, the varying part (similar to the hostid) of the address. In DNS, a string used by an organization to define its host or resources.
Term
summary link to AS boundary router LSA
Definition
An LSA packet that lets a router inside an area know the route to an autonomous boundary router.
Term
summary link to network LSA
Definition
An LSA packet that finds the cost of reaching networks outside of the area.
Term
supergroup
Definition
A signal composed of five multiplexed groups.
Term
supernet
Definition
A network formed from two or more smaller networks.
Term
supernet mask
Definition
The mask for a supernet.
Term
supervisory frame
Definition
See S-frame.
Term
switch
Definition
A device connecting multiple communication lines together.
Term
switched Ethernet
Definition
An Ethernet in which a switch, replacing the hub, can direct a transmission to its destination.
Term
switched virtual circuit (SVC)
Definition
A virtual circuit transmission method in which a virtual circuit is created and in existence only for the duration of the exchange.
Term
switched/56
Definition
A temporary 56-Kbps digital connection between two users.
Term
switching office
Definition
The place where telephone switches are located.
Term
symmetric digital subscriber line (SDSL)
Definition
A DSL-based technology similar to HDSL, but using only one single twisted-pair cable.
Term
symmetric key
Definition
The key used for both encryption and decryption.
Term
symmetric-key cryptography
Definition
A cipher in which the same key is used for encryption and decryption.
Term
synchronization points
Definition
Reference points introduced into the data by the session layer for the purpose of flow and error control.
Term
synchronous connection oriented (SCO) link
Definition
In a Bluetooth network, a physical link created between a master and a slave that reserves specific slots at regular intervals.
Term
Synchronous Digital Hierarchy (SDH)
Definition
The ITU-T equivalent of SONET.
Term
Synchronous Optical Network (SONET)
Definition
A standard developed by ANSI for fiber optic technology that can transmit high-speed data. It can be used to deliver text, audio, and video.
Term
synchronous payload envelope (SPE)
Definition
The part of the SONET frame containing user data and transmission overhead.
Term
synchronous TDM
Definition
A TDM technique in which each input has an allotment in the output even when it is not sending data.
Term
synchronous transmission
Definition
A transmission method that requires a constant timing relationship between the sender and the receiver.
Term
synchronous transport module (STM)
Definition
A signal in the SDH hierarchy.
Term
synchronous transport signal (STS)
Definition
A signal in the SONET hierarchy.
Term
syndrome
Definition
A sequence of bit generated by applying the error checking function to a codeword.
Term
syntax
Definition
The structure or format of data, meaning the order in which they are presented.
Term
T lines
Definition
A hierarchy of digital lines designed to carry speech and other signals in digital forms. The hierarchy defined T-1, T-2, T-3, and T-4 lines.
Term
tag
Definition
A formatting instruction embedded in an HTML document.
Term
tandem office
Definition
The toll office in a telephone network.
Term
TCP timer
Definition
The timers used by TCP to handle retransmission, zero window-size advertisements, long idle connections, and connection termination.
Term
TCP/IP protocol suite
Definition
A group of hierarchical protocols used in an internet.
Term
TDM bus
Definition
A time-division switch in which the input and output lines are connected to a high-speed bus through microswitches.
Term
teardown phase
Definition
In virtual circuit switching, the phase in which the source and destination inform the switch to erase their entry.
Term
telecommunications
Definition
Exchange of information over distance using electronic equipment.
Term
teleconferencing
Definition
Audio and visual communication between remote users.
Term
Teledesic
Definition
A system of satellites that provides fiber-optic communication (broadband channels, low error rate, and low delay)
Term
telephone user port (UTP)
Definition
A protocol at the upper layer of SS7 that is responsible for setting up voice calls.
Term
TELNET
Definition
See Terminal Network.
Term
temporal compression
Definition
An MPEG compression method in which redundant frames are removed.
Term
Ten-Gigabit Ethernet
Definition
The new implementation of Ethernet operating at 10 Gbps.
Term
Terminal Network (TELNET)
Definition
A general purpose client-server program that allows remote login.
Term
terminating state
Definition
A PPP state in which several packets are exchanged between the two ends for house cleaning and closing the link.
Term
terminator
Definition
An electronic device that prevents signal reflections at the end of a cable.
Term
thick Ethernet
Definition
See 10Base5.
Term
thin Ethernet
Definition
See 10Base2.
Term
three-layer switch
Definition
A switch at the network layer; a router.
Term
three-way handshake
Definition
A sequence of events for connection establishment or termination consisting of the request, then the acknowledgment of the request, and then confirmation of the acknowledgment.
Term
three-way handshaking
Definition
A sequence of events for connection establishment or termination consisting of the request, then the acknowledgment of the request, and then confirmation of the acknowledgment.
Term
throughput
Definition
The number of bits that can pass through a point in one second.
Term
ticket
Definition
An encrypted message containing a session key.
Term
ticket-granting server (TGS)
Definition
A Kerberos server that issues tickets.
Term
time division duplexing TDMA (TDD-TDMA)
Definition
In a Bluetooth network, a kind of half-duplex communication in which the slave and receiver send and receive data, but not at the same time (half-duplex).
Term
time division multiple access (TDMA)
Definition
A multiple access method in which the bandwidth is just one time-shared channel.
Term
time to live (TTL)
Definition
The lifetime of a packet.
Term
time-division multiplexing (TDM)
Definition
The technique of combining signals coming from low-speed channels to share time on a high-speed path.
Term
time-division switching
Definition
A circuit-switching technique in which time-division multiplexing is used to achieve switching.
Term
time-domain plot
Definition
A graphical representation of a signal's amplitude versus time.
Term
time-exceeded message
Definition
An ICMP message sent to inform a source that (1) its datagram has a time-to-live value of zero, or (2) the fragments of a message have not been received within a set time limit.
Term
time-slot interchange (TSI)
Definition
A time-division switch consisting of RAM and a control unit.
Term
timestamp
Definition
An IP header option used to record the time of datagram processing by a router. Also, a method to handle jitter in interactive real-time audio/video.
Term
timestamp-request and reply message
Definition
An ICMP message sent to determine the round-trip time or to synchronize clocks.
Term
time-waited timer
Definition
A TCP timer used in connection termination that allows late segments to arrive.
Term
T-lines
Definition
A hierarchy of digital lines designed to carry speech and other signals in digital forms. The hierarchy defines T-1, T-2, T-3, and T-4 lines.
Term
token
Definition
A small packet used in token-passing access method.
Term
token bucket
Definition
An algorithm that allows idle hosts to accumulate credit for the future in the form of tokens.
Term
token passing
Definition
An access method in which a token is circulated in the network. The station that captures the token can send data.
Term
Token Ring
Definition
A LAN using a ring topology and token-passing access method.
Term
toll call service
Definition
An inter-LATA or intra-LATA telephone service charged to the caller.
Term
topology
Definition
The structure of a network including physical arrangement of devices.
Term
touch-tone dialing
Definition
A telephone dialing method in which each key is represented by two small bursts of analog signals.
Term
traffic
Definition
Messages on a network.
Term
traffic control
Definition
A method for shaping and controlling traffic in a wide area network.
Term
traffic shaping
Definition
A mechanism to control the amount and the rate of the traffic sent to the network to improve QoS.
Term
trailer
Definition
Control information appended to a data unit.
Term
transaction capablities application port (TCAP)
Definition
A protocol at the upper layer of SS7 that provides remote procedure calls that let an application program on a computer invoke a procedure on another computer.
Term
transceiver
Definition
A device that both transmits and receives.
Term
transceiver cable
Definition
In Ethernet, the cable that connects the station to the transceiver. Also called the attachment unit interface.
Term
transient link
Definition
A network with several routers attached to it.
Term
transition state
Definition
The different phases through which a PPP connection goes.
Term
translation
Definition
Changing from one code or protocol to another.
Term
Transmission Control Protocol (TCP)
Definition
A transport protocol in the TCP/IP protocol suite.
Term
Transmission Control Protocol/Internetworking Protocol (TCP/IP)
Definition
A five-layer protocol suite that defines the exchange of transmissions across the Internet.
Term
transmission medium
Definition
The physical path linking two communication devices.
Term
transmission path (TP)
Definition
In ATM, the physical connection between two switches.
Term
transmission rate
Definition
The number of bits sent per second.
Term
transparency
Definition
The ability to send any bit pattern as data without it being mistaken for control bits.
Term
transparent bridge
Definition
Another name for a learning bridge.
Term
transparent data
Definition
Data that can contain control bit patterns without being interpreted as control.
Term
transport layer
Definition
The fourth layer in the Internet and OSI model; responsible for reliable end-to-end delivery and error recovery.
Term
Transport Layer Security (TLS)
Definition
A security protocol at the transport level designed to provide security on the WWW.
Term
transpositional cipher
Definition
A character-level encryption method in which the position of the character changes.
Term
trellis-coded modulation
Definition
A modulation technique that includes error correction.
Term
triangulation
Definition
A two-dimensional method of finding a location given the distances from 3 different points.
Term
tribit
Definition
A unit of data consisting of three bits.
Term
trilateration
Definition
A two-dimensional method of finding a location given the distances from 3 different points.
Term
triple DES
Definition
An algorithm compatible with DES that uses three DES blocks and two 56-bit keys.
Term
Trivial File Transfer Protocol (TFTP)
Definition
An unreliable TCP/IP protocol for file transfer that does not require complex interaction between client and server.
Term
trunk
Definition
Transmission media that handle communications between offices.
Term
tunneling
Definition
In multicasting, a process in which the multicast packet is encapsulated in a unicast packet and then sent through the network. In VPN, the encapsulation of an encrypted IP datagram in a second outer datagram. For IPv6, a strategy used when two computers using IPv6 want to communicate with each other when the packet must pass through a region that uses IPv4.
Term
twisted-pair cable
Definition
A transmission medium consisting of two insulated conductors in a twisted configuration.
Term
twisted-pair Ethernet
Definition
An Ethernet using twisted-pair cable; 10Base-T.
Term
two-dimensional parity check
Definition
An error detection method in two dimensions.
Term
two-layer switch
Definition
A bridge with many ports and a design that allows better (faster) performance.
Term
type of service (TOS)
Definition
A criteria or value that specifies the handling of the datagram.
Term
U-frame
Definition
An HDLC unnumbered frame carrying link management information.
Term
unbalanced configuration
Definition
An HDLC configuration in which one device is primary and the others secondary.
Term
unguided medium
Definition
A transmission medium with no physical boundaries.
Term
unicast address
Definition
An address belonging to one destination.
Term
unicast message
Definition
A message sent to just one destination.
Term
unicast routing
Definition
The sending of a packet to just one destination.
Term
unicasting
Definition
The sending of a packet to just one destination.
Term
Unicode
Definition
The international character set used to define valid characters in computer science.
Term
unidirectional antenna
Definition
An antenna that sends or receives signals in one direction.
Term
Uniform Resource Locator (URL)
Definition
A string of characters (address) that identifies a page on the World Wide Web.
Term
unipolar encoding
Definition
A digital-to-digital encoding method in which one nonzero value represents either 1 or 0; the other bit is represented by a zero value.
Term
unnumbered frame
Definition
See U-frame.
Term
unshielded twisted-pair (UTP)
Definition
A cable with wires that are twisted together to reduce noise and crosstalk. See also twisted-pair cable and shielded twisted-pair.
Term
unspecified bit rate (UBR)
Definition
The data rate of an ATM service class specifying only best-effort delivery.
Term
update message
Definition
A BGP message used by a router to withdraw destinations that have been advertised previously or to announce a route to a new destination.
Term
uplink
Definition
Transmission from an earth station to a satellite.
Term
uploading
Definition
Sending a local file or data to a remote site.
Term
upstream data band
Definition
In an HFC network, the 5 to 42 MHz band for data from the subscriber premises to the Internet.
Term
user agent (UA)
Definition
An SMTP component that prepares the message, creates the envelope, and puts the message in the envelope.
Term
user authentication
Definition
A security measure in which the sender identity is verified before the start of a communication.
Term
user datagram
Definition
The name of the packet in the UDP protocol.
Term
User Datagram Protocol (UDP)
Definition
A connectionless TCP/IP transport layer protocol.
Term
user network interface (UNI)
Definition
The interface between a user and the ATM network.
Term
user support layers
Definition
The session, presentation, and application layers.
Term
user-to-network interface (UNI)
Definition
In ATM, the interface between an end point (user) and an ATM switch.
Term
V series
Definition
ITU-T standards that define data transmission over telephone lines. Some common standards are V.32, V32bis, V.90, and V92.
Term
variable bit rate (VBR)
Definition
The data rate of an ATM service class for users needing a varying bit rate.
Term
very high bit rate digital subscriber line (VDSL)
Definition
A DSL-based technology for short distances.
Term
video
Definition
Recording or transmitting of a picture or a movie.
Term
video band
Definition
In an HFC network, the band from 54 to 550 MHz for downstream video.
Term
Vigenere cipher
Definition
A polyalphabetic substitution scheme that uses the position of a character in the plaintext and the character's position in the alphabet.
Term
virtual channel identifier (VCI)
Definition
A field in an ATM cell header that defines a channel.
Term
virtual circuit (VC)
Definition
A logical circuit made between the sending and receiving computer. The connection is made after both computers do handshaking. After the connection, all packets follow the same route and arrive in sequence.
Term
virtual circuit approach to packet switching
Definition
A packet switching method in which all packets of a message or session follow the exact same route.
Term
virtual circuit identifier (VCI)
Definition
A field in an ATM cell header that defines a channel.
Term
virtual circuit switching
Definition
A switching technique used in switched WANs.
Term
virtual connection identifier
Definition
A VCI or VPI.
Term
virtual link
Definition
An OSPF connection between two routers that is created when the physical link is broken. The link between them uses a longer path that probably goes through several routers.
Term
virtual local area network (VLAN)
Definition
A technology that divides a physical LAN into virtual workgroups through software methods.
Term
virtual path (VP)
Definition
In ATM, a connection or set of connections between two switches.
Term
virtual path identifier (VPI)
Definition
A field in an ATM cell header that identifies a path.
Term
virtual path identifier/virtual channel identifier (VPI/VCI)
Definition
Two fields used together to route an ATM cell.
Term
virtual private network (VPN)
Definition
A technology that creates a network that is physically public, but virtually private.
Term
virtual tributary (VT)
Definition
A partial payload that can be inserted into a SONET frame and combined with other partial payloads to fill out the frame.
Term
Voice Over Frame Relay (VOFR)
Definition
A Frame Relay option that can handle voice data.
Term
voice over IP
Definition
A technology in which the Internet is used as a telephone network.
Term
Walsh table
Definition
In CDMA, a two-dimensional table used to generate orthogonal sequences.
Term
wave-division multiplexing (WDM)
Definition
The combining of modulated light signals into one signal.
Term
wavelength
Definition
The distance a simple signal can travel in one period.
Term
weak collision
Definition
Given a digest, creating a second message with the same digest.
Term
Web