Respecifying Existing Frame Relay To Atm Interworking Soft Pvcs; Configuring Overflow Queuing - Cisco Catalyst 8540 MSR Configuration Manual

Chapter 20 Configuring Frame Relay to ATM Interworking Port Adapter Interfaces
Respecifying Existing Frame Relay to ATM Interworking Soft
PVCs
For existing Frame Relay to ATM interworking soft permanent virtual channels (soft PVCs), a
connection is disabled to prevent an explicit path from being used for routing while it is reconfigured.
The
bringing down connections. Existing connections remain unaffected unless a reroute takes place.
If rerouting occurs, the new explicit path configuration takes effect.
To enable or disable soft PVC and respecify explicit-path configuration, use the following interface
command:
Command
frame-relay soft-vc dlci_a [enable | disable]
[redo-explicit [explicit-path precedence
{name path-name | identifier path-id} [upto
partial-entry-index]] [only-explicit]]

Configuring Overflow Queuing

Traffic shaping in the ingress direction (Frame Relay to ATM) is enabled by default for all VBR-nrt VCs
on the Frame Relay ATM interface module. If you want to configure an individual VC to make use of
the bandwidth available when the other VCs configured on the same interface are not using all the
allocated bandwidth, you should configure overflow queuing on that VC.
For example, the policing functionality accepts frames until the PIR rate is reached, while the allowable
burst and shaping functionality tries to send the cells to the switch fabric at SCR (CIR equivalent on the
ATM side). If the CIR is very low compared to the PIR it could cause buffers to be held for a long time,
allowing frame discards on that particular VC and other VCs on the same interface.
Enabling overflow queuing allows you to schedule the frames at a rate above SCR. This means when the
bandwidth is available and when overflow queuing is enabled, the frames are sent at a higher rate.
Overflow queuing is optional and can be configured at the VC level or the interface level using the
enable, disable, or inherit keywords.
Note Overflow queuing configured at VC level overrides the option configured at the interface level. But, only
when the traffic exceeds the (CIR, Bc) bucket and Overflow-Queuing is configured for that VC will the
Overflow-Queuing feature start.
If overflow queuing is not configured at the VC level, then it inherits the configuration parameters of the
interface, which is "disabled" by default.
Also, VC level overflow queuing changes in synchronization with interface level overflow queuing. For
example, if you enable or disable overflow queuing at the interface level, overflow queuing is enabled
or disabled on those VBR-nrt VCs of that interface (if VC level overflow queuing is not already
configured).
OL-7396-01
keyword is used to allow respecifying of the explicit path configuration without
redo_explicit

Respecifying Existing Frame Relay to ATM Interworking Soft PVCs

Purpose
Respecifies the explicit path on a Frame Relay
to ATM interworking soft PVC.
ATM Switch Router Software Configuration Guide
20-43