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Parameter
VCI
ATM QoS
PCR
SCR
Description
VCI is the label given to an ATM VC to identify it and
determine its destination. The VCI is a 16-bit number that
is included in the header of an ATM cell. The valid range
for the VCI is 32 to 65535. Enter the VCI assigned by the
ISP.
CBR (Constant Bit Rate) – This class is used for
emulating circuit switching. The cell rate is constant with
time. Select CBR to specify fixed (always on) bandwidth
for voice or data traffic.
UBR (Unspecified Bit Rate) – Select UBR for applications
that are non-time sensitive, such as e-mail.
rtVBR (real time Variable Bit Rate) – This class is similar
to nrtVBR but is designed for applications that are
sensitive to cell-delay variation. Examples for real-time
VBR are voice with speech activity detection (SAD) and
interactive compressed video.
nrtVBR (non-real time Variable Bit Rate) – This class
allows users to send traffic at a rate that varies with time
depending on the availability of user information.
Statistical multiplexing is provided to make optimum use
of network resources. Multimedia e-mail is an example of
nrtVBR.
Divide the DSL line rate (bps) by 424 (the size of an ATM
cell) to find the PCR (Peak Cell Rate). This is the
maximum rate at which the sender can send cells.
SCR (Sustain Cell Rate) is the average rate, as
measured over a long interval, in the order of the
connection lifetime.
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