Q

Q-series protocols

Also called Series Q protocols, a set of protocols developed by the International Telecommunication Union (ITU) that includes the following:

• Q.920/921:

Specifies the User-Network Interface (UNI) data-link layer for Integrated Services Digital Network (ISDN), including the ISDN D channel’s Link Access Procedure D (LAP-D) data-link protocol.

• Q.922A:

Specifies the ITU encapsulation method for frame relay networks.

• Q.931:

Specifies mechanisms for establishing, maintaining, and tearing down ISDN connections. This includes working with connections in the LAP-D data-link protocol, which runs on the ISDN D channel.

• Q.93B:

The Asynchronous Transfer Mode (ATM) signaling protocol, which specifies mechanisms for establishing, maintaining, and tearing down broadband ISDN (B-ISDN) connections.

Quality of service (QoS)

Generally, any networking technology that has predictable latency and data loss. More specifically, any mechanism that allows either absolute or relative performance requirements to be defined for different traffic streams carried over a network. In other words, a quality of service (QoS) network can guarantee a certain level of throughput for a specific path, connection, or type of traffic. This makes it possible to ensure that critical network applications receive priority handling.

Quartet signaling

A signaling method used in 100VG-AnyLan (100BaseVG) networks. Signals are transmitted over all four pairs of wire in voice-grade unshielded twisted-pair (UTP) cabling. Quartet signaling makes possible the transmission of data at a speed of 100 Mbps while using the same transmission frequencies that are used on standard 10BaseT networks. Quartet signaling also enables 100VG-AnyLan to leverage existing installations of category 3, 4, and 5 UTP cabling for 100-Mbps transmission

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