Q.2931 - Derived from Q.93B, the narrowband ISDN signaling protocol, an ITU standard describing the signaling protocol to be used by switched virtual circuits on ATM LANs.

QA (Quality Assurance) - A planned and systematic pattern of all steps necessary to ensure that a product conforms to established technical requirements.

QD (Queuing Delay) - Queuing delay refers to the delay imposed on a cell by its having to be buffered because of unavailability of resources to pass the cell onto the next network function or element. This buffering could be a result of oversubscription of a physical link, or due to a connection of higher priority or tighter service constraints getting the resource of the physical link.

QoS (Quality of Service) - Quality of Service is defined on an end-to-end basis in terms of the following attributes of the end-to-end ATM connection:
Cell Loss Ratio
Cell Transfer Delay
Cell Delay Variation

QoSExp (QoS Expansion) - Refers to specific forward and backward CDV, CLR, and forward CTD values that may be assigned to a new signaling channel or SPVC PNNI connection.

QoSExt (QoS Extension) - Refers to maximum CTD, CDV, and CLR values that may be assigned to individual QoS Service types.

Queuing - Defines how to organize buffered cells.