Internetworking Terms

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. See also Q.931 and UNI.

ITU-T specifications for the ISDN UNI data link layer. See also UNI.

ITU-T specification for Frame Relay encapsulation.

ITU-T specification for signaling to establish, maintain, and clear ISDN network connections. See also Q.93B.

ITU-T specification for signaling to establish, maintain, and clear BISDN network connections. An evolution of ITU-T recommendation Q.931. See also Q.931.

quadrature amplitude modulation. Method for encoding digital data in a n analog signal in which each combination of phase and amplitude represents one of sixteen four-bit patterns. This is required for fax transmission at 9600 bits per second.

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

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

quality of service parameters. Parameters that control the amount of traffic the source in an ATM network sends over an 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.

See QPPB.

QoS Policy Propagation on BGP. Feature that classified 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.

See QPM in the "Cisco Systems Terms and Acronyms" section.

quaternary phase shift keying. Digital frequency modulation technique used for sending data over coaxial cable networks. Because it's both easy to implement and fairly resistant to noise, QPSK is used primarily for sending data from the cable subscriber upstream to the Internet.

quasi-random signal sequence. A test pattern widely used to simulate voice signals.

Q (point of the ISDN model) Signaling. Signaling standard. Common channel signaling protocol based on ISDN Q.931 standards and used by many digital PBXs.

See QLLC.

See QoS.

Signaling technique used in 100VG-AnyLAN networks that allows data transmission at 100 Mbps over four pairs of UTP cable at the same frequencies used in 10BaseT networks. See also 100VG-AnyLAN.

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

1. Generally, an ordered list of elements waiting to be processed.

2. In routing, a backlog of packets waiting to be forwarded over a router interface.

Amount of time that data must wait before it can be transmitted onto a statistically multiplexed physical circuit.

Scientific principles governing the formation or lack of formation of congestion on a network or at an interface.

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

query with permission.