User guide

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ATM VPI/VCI pair, upon saving and restarting, autodetection is disabled and only the
new VPI/VCI pair configuration will be enabled.
VPI/VCI Autodetection consists of eight static VPI/VCI pair configurations. These are 0/
35, 8/35, 0/32, 8/32, 1/35, 1/1, 1/32, 2/32. These eight VPI/VCI pairs will be cre-
ated if the Gateway is configured for autodetection. the Gateway does not establish a
circuit using any of these preconfigured VPI/VCI pairs, then you can manually enter a
VPI/VCI pair in the ATM Circuits page.
ATM Traffic Shaping: You can prioritize delay-sensitive data by configuring the Quality
of Service (QoS) characteristics of the virtual circuit. Click the ATM Traffic Shaping
link.
You can choose UBR (Unspecified Bit Rate), CBR (Constant Bit Rate), or VBR (Variable
Bit Rate) from the pull-down menu and set the Peak Cell Rate (PCR) in the editable field.
UBR (Unspecified Bit Rate) guarantees no minimum transmission rate. Cells are
transmitted on a “best effort” basis. However, there is a cap on the maximum transmis-
sion rate for UBR VCs. In a practical situation:
• UBR VCs should be transmitted at a priority lower than CBR.
• Bandwidth should be shared equally among UBR VCs.
UBR applications are non-real-time traffic such as IP data traffic.
CBR (Constant Bit Rate) guarantees a certain transmission rate (although the appli-
cation may underutilize this bandwidth). A Peak Cell Rate (PCR) characterizes CBR. CBR
is most suited for real time applications such as real time voice / video, although it can
be used for other applications.
VBR (Variable Bit Rate) This class is characterized by:
• a Peak Cell Rate (PCR), which is a temporary burst, not a sustained rate, and
• a Sustained Cell Rate (SCR),
• a Burst Tolerance (BT), specified in terms of Maximum Burst Size (MBS). The MBS
is the maximum number of cells that can be transmitted at the peak cell rate and
should be less than, or equal to the Peak Cell Rate, which should be less than, or equal
to the line rate.