The Frame Relay PVC Interface Priority Queueing feature provides an interface-level priority queueing scheme in which prioritization is based on destination permanent virtual circuit (PVC) rather than packet contents.
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Prerequisites for Frame Relay PVC Interface Priority Queueing
PVCs should be configured to carry a single type of traffic.
The network should be configured with adequate call admission control to prevent starvation of any of the priority queues.
Restrictions for Frame Relay PVC Interface Priority Queueing
FR PIPQ is not supported on loopback or tunnel interfaces, or interfaces that explicitly disallow priority queueing.
FR PIPQ is not supported with hardware compression.
FR PIPQ cannot be enabled on an interface that is already configured with queueing other than FIFO queueing. FR PIPQ can be enabled if WFQ is configured, as long as WFQ is the default interface queueing method.
Information About Frame Relay PVC Interface Priority Queueing
The Cisco Frame Relay MIB describes managed objects that enable users to remotely monitor Frame Relay operations using Simple Network Management Protocol (SNMP). The Frame Relay MIB Enhancements feature extends the Cisco Frame Relay MIB by adding MIB objects to monitor the following Frame Relay functionality:
Frame Relay fragmentation
Frame Relay-ATM Network Interworking (FRF.5)
Frame Relay-ATM Service Interworking (FRF.8)
Frame Relay switching
Input and output rates of individual virtual circuits (VCs)
The table below describes the MIB tables and objects that are introduced by the Frame Relay MIB enhancements. For a complete description of the MIB, see the Cisco Frame Relay MIB file CISCO-FRAME-RELAY-MIB.my, available through Cisco.com at the following URL:
Table 1 MIB Tables and Objects Introduced by the Frame Relay MIB Enhancements
Table or Object
Table of Frame Relay fragmentation information.
Table of Frame Relay-ATM Network Interworking connection information.
Table of Frame Relay-ATM Service Interworking connection information.
Table of Frame Relay switching entries.
Average rate, in bytes per second, at which data is transmitted on a circuit.
Average number of packets sent per second on a circuit.
Average rate, in bytes per second, at which data is received on a circuit.
Average number of packets received per second on a circuit.
The Frame Relay MIB Enhancements feature also modifies the
load-interval command to enable you to configure the load interval per permanent virtual circuit (PVC). The load interval is the length of time for which data is used to compute load statistics, including input rate in bits and packets per second, output rate in bits and packets per second, load, and reliability. Before the introduction of this feature, the load interval could be configured only for the interface.
FR PIPQ provides four levels of PVC priority: high, medium, normal, and low. This method of queueing ensures that time/delay-sensitive traffic such as voice has absolute priority over signalling traffic, and that signalling traffic has absolute priority over data traffic, providing different PVCs are used for the different types of traffic.
How to Configure Frame Relay PVC Interface Priority Queueing
This example shows the configuration of four PVCs on serial interface 0. DLCI 100 is assigned high priority, DLCI 200 is assigned medium priority, DLCI 300 is assigned normal priority, and DLCI 400 is assigned low priority.
The following commands configure Frame Relay map classes with PVC priority levels:
Router(config)# map-class frame-relay HI
Router(config-map-class)# frame-relay interface-queue priority high
Router(config)# map-class frame-relay MED
Router(config-map-class)# frame-relay interface-queue priority medium
Router(config)# map-class frame-relay NORM
Router(config-map-class)# frame-relay interface-queue priority normal
Router(config)# map-class frame-relay LOW
Router(config-map-class)# frame-relay interface-queue priority low
The following commands enable Frame Relay encapsulation and FR PIPQ on serial interface 0. The sizes of the priority queues are set at a maximum of 20 packets for the high priority queue, 40 for the medium priority queue, 60 for the normal priority queue, and 80 for the low priority queue.
No new or modified RFCs are supported by this functionality.
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Feature Information for Frame Relay PVC Interface Priority Queueing
The following table
provides release information about the feature or features described in this
module. This table lists only the software release that introduced support for
a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
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support and Cisco software image support. To access Cisco Feature Navigator, go
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Table 2 Feature Information for Frame Relay PVC Interface Priority Queueing
Frame Relay PVC Interface Priority Queueing
Cisco IOS XE Release 2.1
The FR PIPQ feature provides an interface-level priority queueing scheme in which prioritization is based on destination permanent virtual circuit (PVC) rather than packet contents. For example, FR PIPQ allows you to configure a PVC transporting voice traffic to have absolute priority over a PVC transporting signalling traffic, and a PVC transporting signalling traffic to have absolute priority over a PVC transporting data.
DLCI--data-link connection identifier. Value that specifies a permanent virtual circuit (PVC) or switched virtual circuit (SVC) in a Frame Relay network.
FIFOqueueing-- First-in, first-out queueing. FIFO involves buffering and forwarding of packets in the order of arrival. FIFO embodies no concept of priority or classes of traffic. There is only one queue, and all packets are treated equally. Packets are sent out an interface in the order in which they arrive.
FRF.12--The FRF.12 Implementation Agreement was developed to allow long data frames to be fragmented into smaller pieces and interleaved with real-time frames. In this way, real-time voice and nonreal-time data frames can be carried together on lower-speed links without causing excessive delay to the real-time traffic.
FRTS--Frame Relay traffic shaping. FRTS uses queues on a Frame Relay network to limit surges that can cause congestion. Data is buffered and then sent into the network in regulated amounts to ensure that the traffic will fit within the promised traffic envelope for the particular connection.
PIPQ--Permanent virtual circuit (PVC) interface priority queueing. An interface-level priority queueing scheme in which prioritization is based on destination PVC rather than packet contents.
qualityofservice--Measure of performance for a transmission system that reflects its transmission quality and service availability.
WFQ--weighted fair queueing. Congestion management algorithm that identifies conversations (in the form of traffic streams), separates packets that belong to each conversation, and ensures that capacity is shared fairly among these individual conversations. WFQ is an automatic way of stabilizing network behavior during congestion and results in increased performance and reduced retransmission.
WRED--Weighted Random Early Detection. Combines IP Precedence and standard Random Early Detection (RED) to allow for preferential handling of voice traffic under congestion conditions without exacerbating the congestion. WRED uses and interprets IP Precedence to give priority to voice traffic over data traffic, dropping only data packets.