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Glossary
15
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.10, Part Number 78-11603-01 Rev. D0, July 2001
Soft PVC
A PVC in the INS Dial-Up Frame Relay application that is dormant in the networks database until it
is activated by a call into the network by a user.
spanning tree
An network topology in which there is only one path available between any two sources in a frame
relay multicast group. Spanning trees are required to prevent frames broadcast from a single source to
multiple receptors from circulating endlessly around the network a result of frame relay circuits not
having properly closed loops.
speech detection
Determining the presence or absence of speech for Digital Speech Interpolation. Performed in either
the CDP card.
split clock
A data clocking configuration where the timing for the transmit data is obtained from one source (such
as a user device) and the timing for the receive data is obtained from another source (such as a switch).
Status Enquiry
A message transmitted by a FR NNI port requesting an updated status from the attached foreign
network. This message is used as a heartbeat to detect when a port has failed.
StrataBus
On the BPX switch, contains crosspoint wiring used to carry ATM trunk data between both the
network interface and service interface modules and the crosspoint switch as well as providing
control, clock, and communications.
subrate data
Multiple low-speed data circuits carried in a single DS0 timeslot.
superrate data
Single high-speed data circuit carried in multiple DS0 timeslots.
SCR (Sustained Cell
Rate)
Long term limit on the rate a connection can sustain.
SVC (switched
virtual circuit)
A virtual circuit that is dynamically established on demand and torn down when transmission is
complete.SVSdonotneedtoreserveanynetworkresourceswhentheyarenotinuse.Calleda
switched virtual connection in ATM terminology. Compare with PVC.
T
T1
The standard US. multiplexed 24-channel voice/data digital span line. Operates at a data rate of
1.544 Mbps.
T3
Transmission service at DS3 rate of 44.736 Mbps.
TBE (Transient
Buffer Exposure)
The negotiated number of cells that the network would prefer to limit the source to send during the
start-up period.
TDM (time division
multiplexing)
The process of combining several communication channels by dividing a channel into time increments
and assigning each channel to a timeslot.
timestamp
A field in certain FastPacket formats that indicates the amount of time the packet has spent waiting in
queues during the transmission between its source and destination nodes. Used to control the delay
experienced by the packet.
Trm
An upper bound on the time between RM cells for an active source, i.e., RM cell must be sent at least
once every Trm msec.
S