Beta Draft Confidential
10-281/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Configuring ATM PVCs
About the PVC Tabs
FCP Discard
(Forward/Reverse)
Displays only if you selected a QoS class that supports FCP
Discard. Select one of the following options:
CLP1 – (default) You can provision selective CLP1 discard for
UBR, ABR, and VBR-NRT PVCs. If the current cell causes the
queue for a PVC to exceed the discard thresholds, and the cell has
CLP set to 1, the cell is discarded. Note that EPD is not performed
in this case.
EPD – Early Packet Discard. The ATM FCP can perform EPD for
UBR, ABR, and VBR-NRT PVCs. If you select this option, when
a cell causes the queue for a PVC to exceed the discard thresholds,
the VC enters the EPD state. The cells in the current packet of the
VC are admitted to the queue. However, when the end of the
current packet is detected, all of the cells in the next packet are
discarded for that PVC.
See “ATM FCP Discard Mechanisms” on page 5-18 for more
information.
Although the frame discard attribute is only applicable to a CBX
500 with an FCP, this attribute is offered as a selection on
non-CBX endpoints. This is because even though one or both
endpoints may not be on a CBX with FCP, the PVC might traverse
a CBX 500 FCP trunk. In this case, the provisioned attribute is
used.
Note: On ATM CE endpoint(s), the FCP Discard (Fwd/Rev) option
is not available.
Bandwidth Priority
(0-15)
Specify a value from zero (0) through 15, where zero (0) is the
default and indicates the highest priority.
See Appendix E, “Priority Routing,” for more information.
CDV Tolerance
(1-65535) (microsec)
(PVCs with CBX/GX
endpoints only)
Configure the cell delay variation tolerance (CDVT). The usage
parameter control (UPC) uses this value to police the requested
TD. Valid values are between 1 - 65535 µsec. The default is
600 µsec.
Note: If you are using the CBX 500 3-Port Channelized DS3/1 IMA
IOM or the CBX 3500 3-Port Channelized DS3/1 Enhanced IMA
module, the recommended minimum CDV Tolerance value is
1000 µsec.
The recommended minimum for the 1-Port Channelized STM-1/E1
IMA IOM or the CBX 3500 1-Port Channelized STM-1/E1
Enhanced IMA module is 1200 µsecs.
Table 10-5. Add PVC: User Preference Tab Fields (Continued)
Field Action/Description
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