P-660RU-Tx v 3 Series Support Note s
6. What do the parameters (PCR, SCR, and MBS) mea n?
Traffic shaping parameters (
PCR, SCR, MBS
) can be set in Web Configurator,
Interface Se tup,
Interface Setup -> Inter net -> QoS
:
Peak Cell Rate (PCR):
The m aximum bandwidth allocated to this connection.
The VC connection throughput is limited by PCR.
Sustainable Ce ll Rate (SCR):
The least guaranteed bandwidth of a VC.
When there are m ulti-VCs on the sam e line, the VC throughput is guaranteed by
SCR.
Maxim um Burst Size(MBS):
The am ount of cells transmitted through this VC
at the Peak Cell Rate before yielding to other VCs. Total bandwidth o f the line is
dedicated to single VC if there is only one VC on the line. Howe ve r, as the other
VC asking the bandwidth, the MBS defines the m aximum num ber of cells
transm itted via this VC with Peak Cell rate before yielding to other VCs.
The P-660R U-Tx v3 holds the param eters for shaping the traffic am ong its
virtual channels. If you do not need traffic shaping, please set SCR = 0, MBS =
0 and PCR as the m aximum value according to the line ra te (for e xam p 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 fi xed bandwidth requirem ent at the tim e the connection
is set up so that the da ta can be sent in a steady stream . CBR service is often
used when transmitting fi xed -rate uncom pressed video.
Unspec ifie d bit rate (UBR)
: An ATM bandwidth-allocation service that
does not guarantee an y throughput le vels and uses only a vailable
bandwidth. UBR is often used when transm itting 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 ra te) 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 tim e varia ble bit rate (nrtVBR)
and
Real tim e variable bit rate
(rtVBR).
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All contents copyright © 2008 Zy XEL Communications Corporation.
Summary of Contents for P-660RU-Tx v3 SERIES
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