What Do The Parameters (Pcr, Scr, And Mbs) Mean; What Do The Atm Qos Types (Cbr, Ubr, Vbr, Rtvbr, Nrtvbr) Mean?10 - ZyXEL Communications P-660RU-Tx Series Support Notes

6. What do the parameters (PCR, SCR, and MBS) mean?

Traffic shaping parameters (PCR, SCR, MBS) can be set in Web Configurator,
Interface Setup, Interface Setup -> Internet -> QoS:
Peak Cell Rate (PCR):
The VC connection throughput is limited by PCR.
Sustainable Cell Rate (SCR):
When there are multi-VCs on the same line, the VC throughput is guaranteed by
SCR.
Maximum Burst Size(MBS):
at the Peak Cell Rate before yielding to other VCs. Total bandwidth of the line is
dedicated to single VC if there is only one VC on the line. However, as the other
VC asking the bandwidth, the MBS defines the maximum number of cells
transmitted via this VC with Peak Cell rate before yielding to other VCs.
The P-660RU-Tx holds the parameters for shaping the traffic among its virtual
channels. If you do not need traffic shaping, please set SCR = 0, MBS =
0 and PCR as the maximum value according to the line rate (for examp le, 2.3
Mbps line rate will result PCR as 5424 cell/sec.)
7. What do the ATM QoS Types (CBR, UBR, VBR, rtVBR, nrtVBR) mean?
Constant bit rate (CBR): An ATM bandwidth-allocation service that requires
the user to determine a fixed bandwidth requirement at the time the connection
is set up so that the data can be sent in a steady stream. CBR service is often
used when transmitting fixed-rate uncompressed video.
Unspecified bit rate (UBR): An ATM bandwidth-allocation service that
does not guarantee any throughput levels and uses only available
bandwidth. UBR is often used when transmitting data that can tolerate
delays, such as e-mail.
Variable bit rate (VBR): An ATM bandwidth-allocation service that allows users to
specify a throughput capacity (i.e., a peak rate) and a sustained rate but data is
not sent evenly. You can select VBR for burst traffic and bandwidth sharing with
other applications. It contains two subclasses:
Non-real time variable bit rate (nrtVBR) and Real time variable bit rate
(rtVBR).
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P-660RU-Tx Series Support Note s
The maximum bandwidth allocated to this connection.
The least guaranteed bandwidth of a VC.
The amount of cells transmitted through this VC
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