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Glossary E-15
Q
Q.921/Q.931
ITU-T specifications for the ISDN use network interface (UNI) data link layer.
QSIG
A common-channel message-oriented signalling protocol, defined by the European
Telecommunications Standard Institute (ETSI), commonly used by private branch exchanges
(PBXes). The INS Dynamic Network Switching application supports QSIG signalling to the
Cisco WAN switching network.
queue
A buffer that is used to temporarily hold data while it waits to be transmitted to the network or to
the user.
R
RIF (Rate increase factor)
Controls the amount by which the cell transmission rate may increase upon receipt of an RM cell.
RDF (Rate decrease factor)
Controls the amount by which the cell transmission rate may decrease upon receipt of an RM cell.
red alarm
Another name for local alarm as the local alarm lamp on most digital transmission equipment is
red in color.
remote alarm
An IPX alarm indicating that the associated T1 line is down due to a receive line failure on
another node. (See also yellow alarm.)
RPS (repetitive pattern suppression)
Also called data frame multiplexing (DFM). An option for data circuits where repeating strings
of data are replaced on the packet line by a single occurrence of the data string and a code that
indicates to the far end how may repetitions of the string was being transmitted. Used to conserve
network bandwidth.
robbed bit signaling
A type of signaling used on T1 lines where the signaling bits for each channel are substituted for
the least significant voice bit in each channel word during frames 6 and 12.
RS-232
A physical and electrical interface standard for a low-speed, unbalanced, serial, data interface
adopted by the EIA committee on data communications. Generally used for data circuits
operating at data rates below 56 Kbps.
RS-422/423
Another EIA standard electrical interface for serial data circuits operating at higher data rates
than RS232. RS422 is a balanced interface; RS423 is unbalanced. Uses RS-449 for the physical
interface (connector).