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List of terms
Nortel Multiservice Switch 7400/15000/20000
Terminology
NN10600-005 7.2S1 Standard
PCR7.2 and up March 2006
Copyright © 2006, Nortel Nortel Confidential
cell
A small, fixed-length data unit, with associated control header (cell header),
that is transmitted across the network. Many cells can be required to carry a
complete message for a customer. The ATM cell is 53 bytes long.
cell delay variation (CDV)
The allowable variation in time that a cell can take to travel over a virtual
connection. Also, the measurable variation in the interval between ATM cells
arriving at a network element. The accumulation of this variation results in cell
clumping. Also known as cell delay variance.
cell delay variation tolerance (CDVT)
One of a set of ATM traffic characterization values. CDVT defines the
tolerance to cell clumping that results from the accumulating amount of cell
delay variation or “jitter” in the network or customer premises equipment
(CPE). CDVT is Nortel Multiservice Switch node-specific and is not part of the
ATM Forum specification.
cell header
Information wrapped within a cell that determines the destination of the cell
and carries sequencing and error detection information.
cell loss priority (CLP)
A bit located in the ATM cell header that identifies the priority of the cell as
eligible for discard at a point of congestion.
cell loss ratio (CLR)
The allowable percentage of cells that can be lost for a given traffic type. CLR
is the ratio between ATM cells transmitted by the source over a link and the
number of cells discarded by the destination due to congestion. CLR is a QOS
class parameter that defines the loss ratio that the service provider agrees to
over the lifetime of a connection.
cell queue controller (CQC)
The hardware chip that supports traffic shaping and usage parameter control
on ATM interfaces and connections, and that permits per-VC queuing. The
CQC ASIC defines the series of CQC ATM function processors as distinct
from other series of ATM function processors.
cell queue memory (CQM)
The RAM memory used by the cell queue controller (CQC). This memory is
used as buffer space for the link transmit queues, reserved space, and
connection space.