Glossary- Q
A Data Communication Historical Series
By Bob Pollard

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Q:

See Queu

QAM: See Quadrature Amplitude Modulation

QBIT:

See Qualifier Bit

QLLC:

Qualified Logical Link Control: Data link layer protocol defined by IBM that allows SNA data to be transported across X.25 networks

See Qualified Logical Link Control

Q.921/931:

ITU-TS Q Series Recommendations describing Lap- D, the Layer Two protocol for an ISDN D-channel.

1) Q.2931: ITU-T specification, based on Q.931, for establishing, maintaining, and clearing network connections at the B-ISDN user-network interface. The UNI 3.1 specification is based on Q.2931.

2) Q.920/Q.921: ITU-T specifications for the ISDN UNI data link layer.

3) Q.922A: ITU-T specification for Frame Relay encapsulation

4) Q.931: ITU-T specification for signaling to establish, maintain, and clear ISDN network connections.

5) Q.93B: ITU-T specification for signaling to establish, maintain, and clear BISDN network connections; an evolution of ITU-T recommendation Q.931.

QoS:

Quality of Service: Measure of performance for a transmission system that reflects its transmission quality and service availability.

QoS PARAMETERS:

Quality of Service Parameters: Parameters that control the amount of traffic the source in an ATM network sends over a SVC. If any switch along the path cannot accommodate the requested QoS parameters, the request is rejected and a rejection message is forwarded back to the originator of the request.

QPPB:

QoS Policy Propagation on BGP: Feature that classifies packets by IP precedence based on BGP community lists, BGP autonomous system paths, and access lists. After a packet is classified, other quality of service features such as Committed Access Rate (CAT) and Weighted Random Early Detection (WRED) can specify and enforce policies to fit a business model.

QPM:

QoS Policy Manager: Cisco policy server application for dynamically managing network traffic flows

QPSK:

Quaternary Phase Shift Keying: Digital frequency modulation technique used for sending data over coaxial cable networks. Because it’s easy to implement and fairly resistant to noise, QPSK is used primarily for sending data upstream to the Internet

QRS:

See Quasi-Random Signal

QRSS:

Quasi-Random Signal Sequence: A test pattern widely used to simulate voice signals

See Quasi-random Signal Source

QSIG:

Q Signaling: Signaling standard. Common channel signaling protocol based on ISDN Q.931 standards and used by many digital PBX(s).

QTA:

A communications term indicating that a message has been interrupted, and it will be repeated in its entirety with out any action on the part of the receiving station (terminal) receiving the QTA notice.

QTB:

A communications term sent to the receiving terminal, indicating a message has been interrupted while being automatically relayed and cannot be retransmitted in a complete form. It normally is the responsibility of the receiving terminal to request a retransmission of the message in question from the originating terminal.

OUAD:

A cable containing two twisted pairs of conductors

QUADRATURE AMPLITUDE MODULATION: (QAM):

A combination of phase and amplitude modulation: For a high-speed, synchronous MODEM.

QUADRATURE DISTORTION:

The distortion of an analog signal often occurring in phase modulation

QUALIFIED LOGICAL LINK CONTROL (QLLC):

1) Routines that provide Synchronous Data Link Control (SDLC) functions

2) Data link layer protocol defined by IBM that allows SNA data to be transported across X.25 networks

QUALIFIER BIT (Qbit):

Refers to the X.25 networks, bit 8 in an octet of the packet header. It is used to indicate if a packet contains control information.

QUANTIZING NOISE / QUANTIZING DISTORTION:

Transmission anomalies of a dynamic nature during the analog/digital conversion process of codec in digital transmission systems; the dynamic nature is that these extraneous artifacts appear only when an input signal is present; they cannot be measured or observed on an idle, quiet channel.

QUANTIZATION NOISE:

Signal errors or noise that occurs from digitizing a continuously variable signal.

QUARTET SIGNALING:

Part of the 100BaseVG-AnyLAN standard involving transmission over all four wires (2-pairs) simultaneously in voice-grade Unshielded Twisted Pair (UTP) cable, expanding the transmission capacity to 100Mbps.

QUASI-RANDOM SIGNAL (QRS):

A digital test signal consisting of a bit sequence that approximates a random signal

QUASI RANDOM SIGNAL SOURCE (QRSS):

A form of Pseudo-Random Binary Pulse Sequence

QUERY:

The process where a master-station (computer) queries a station (terminal) for identification and operational status: This process could be accomplished through the use of control characters or a message.

Message used to inquire about the value of some variable or set of variables

QUEUE / QUEUING:

In communication computers it is the storage of messages awaiting delivery and controlling the sequence of message delivery. Other queue theories:

1) Input Process: The statistical pattern by which the data arrives at the service facility also called ‘random arrivals’.

2) Queue Structure: The actual ‘waiting line’, which may consist of one queue or several queues. The line(s) may be conceptual rather than physical, such as remote terminals (stations) waiting to be polled by a computer.

3) Service Facility: One or more service channels in parallel, attached to one or more servers in series.

4) Service Process: The time required to completely service a unit waiting in a queue. The time is determined by probability formulas.

5) Service Discipline: The rules by which units are selected and serviced. Service may be FIFO (first in, first out), random, or according to a priority procedure.

6) A backlog of packets waiting to be forwarded over a router interface.

QUEUING DELAY:

Amount of time that data must wait before it can be transmitted.

QUEUING THEORY:

Scientific principles governing congestion on a network or interface media

QUICK LAUNCH:

A customizable toolbar that lets a user display the Windows desktop or start a program with a single click. A person can add buttons to start favorite programs from the Quick Launch location on the taskbar.

QUICK TEST:

Automatic test procedures for testing DS1 or DDS circuits in REACT 2000

QUIPU:

Pioneering software package developed to study the OSI Directory and to provide extensive pilot capabilities.

QWP:

Query with Permission

QWK:

A type of mail packet