Beta Draft Confidential
Configuring ATM PVCs
Configuring Frame Relay-to-ATM Interworking Circuits
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/0510-61
Table 10-13. Add PVC: User Preference Tab Fields
Field Action/Description
Graceful Discard 
(Forward/Reverse)
(PVCs with frame 
relay UNI endpoints 
only)
Select or clear the check box to define how this circuit handles 
“red” packets. Red packets are designated as those bits received 
during the current time interval that exceed the Bc and Be 
thresholds, including the current frame. The DE bit for a red packet 
is set to 1, meaning the network cannot discard this packet unless 
the check box in the Graceful Discard field is selected.
Check box selected – (default) Forwards some red packets if there 
is no congestion. 
Check box cleared – Immediately discards red packets.
Note: For the ATM UNI DS3/E3, if you set this value for shaping 
purposes, the switch software ignores the PCR, SCR, and MBS 
values calculated from the Add PVC: Traffic Type tab 
(Figure 10-12 on page 10-54); the switch instead picks the highest 
PCR queue available and sets the SCR to that PCR.
Red Frame Percent 
(Forward/Reverse)
(PVCs with frame 
relay UNI endpoints 
only)
Set this value only if Graceful Discard is set to On. See “Graceful 
Discard” on page 10-46 for more information. The Red Frame 
Percent limits the number of red frames the network is responsible 
to deliver. 
PVC Loopback 
Status (Fwd/Rev)
Displays the current loopback state. If None is not displayed in the 
PVC Loopback Status field, do not attempt to modify or delete the 
selected circuit. See the Switch Diagnostics User’s Guide for 
CBX 3500, CBX 500, GX 550, and B-STDX 9000 for more 
information about loopback testing and the options for this field.