PLANET ADE-3100 - Manual (Page 17)

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VCI: A Virtual Channel Identifier is a virtual channel that is identified by a unique
numerical tag that is defined by a 16-bit field in the ATM cell header. The purpose of the
virtual channel is to identify where the cell should travel. The VCI field specifies this 16 bit
numerical tag that determines the destination.
Range: 0-65535 Default: 35
Service Category: This field allows you to select from the following service categories.
l UBR (default): When configured as UBR (Unspecified Bit Rate), traffic is
delivered with best efforts but with no guarantee. This allows for fluctuation in
times of temporary increase of available bandwidth. For example, if a PVC with
CBR is temporarily inactive, the PVC(s) with UBR will utilize that bandwidth while it
is available. UBR is intended for applications that do not require any maximum
bound on the transfer delay.
l CBR: When a PVC is specified as a CBR (Constant Bit Rate), that PVC is
guaranteed a certain bandwidth, characterized by the Peak Cell Rate (PCR). The
CBR does not have to transmit with a peak cell rate, and when it does, it is only
when the bandwidth specified by the PCR is guaranteed.
l VBR-nrt: An PVC enabled with VBR-nrt (Variable Bit Rate - non real time) can
transmit a cell only if the PVC has a token available. The PVC accumulates tokens
at the rate of the Sustainable Cell Rate, and the PVC can only accumulate a
maximum of the value specified by Maximum Burst Size tokens.
When a PVC has a token available, it can transmit cells at the rate of PCR. After a cell is
transmitted, the PVC loses the token it has accumulated.
In the case of multiple PVCs, CBR specified PVCs will have higher priority than
PVCs with UBR. For example, the CBR PVCs will take their bandwidth and the
remaining bandwidth will be split among the UBR PVCs. In the case of total PVC CBR
bandwidth exceeding ADSL upstream, the total upstream bandwidth will be shared
proportionally to the bandwidth allocated for each CBR PVC.
Peak Cell Rate: This value specifies the maximum, and in some cases guaranteed, cell
rate for CBR and VBR-nrt. Peak Cell Rates are typically measured in Cells/Second,
however, the user entered value is in kbps and is then converted by the firmware.
Range: 0-32767 Default: 0
Sustainable Cell Rate: It is the sustained rate at which a PVC enabled with VBR-nrt can
transmit ATM cells. Sustainable Cell Rate (SCR) can be considered as the true reserved
bandwidth for a PVC.
Range: 0-32767 Default: 0
Max Burst Size: It is the number of cells a PVC enabled with VBR-nrt can transmit
continuously at peak cell rate (PCR).
Range: 0-32767 Default: 0