Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring Frame RelayConfiguring Frame Relay SwitchingTo configure congestion management on switched PVCs, perform the tasks in the following sections:• Configuring Frame Relay Congestion Management on the Interface• Configuring Frame Relay Congestion Management on Traffic-Shaping QueuesConfiguring Frame Relay Congestion Management on the InterfaceTo configure Frame Relay congestion management on all switched PVCs on an interface, use thefollowing commands beginning in interface configuration mode:CommandConfiguring Frame Relay Congestion Management on Traffic-Shaping QueuesPurposeStep 1 Router(config-if)# frame-relay congestion management Enables Frame Relay congestion management onall switched PVCs on an interface and entersFrame Relay congestion managementconfiguration mode.Step 2 Router(config-fr-congest)# threshold de percentage Configures the threshold at which DE-markedpackets will be discarded from switched PVCs onthe output interface.Step 3Router(config-fr-congest)# threshold ecn {bc | be}percentageConfigures the threshold at which ECN bits willbe set on packets in switched PVCs on the outputinterface.To configure Frame Relay congestion management on the traffic-shaping queues of switched PVCs, useone or more of the following commands in map-class configuration mode:CommandRouter(config-map-class)# frame-relay congestion threshold depercentageRouter(config-map-class)# frame-relay congestion threshold ecnpercentageRouter(config-map-class)# frame-relay holdq queue-sizePurposeConfigures the threshold at which DE-markedpackets will be discarded from the traffic-shapingqueue of a switched PVC.Configures the threshold at which ECN bits willbe set on packets in the traffic-shaping queue of aswitched PVC.Configures the maximum size of a traffic-shapingqueue on a switched PVC.Configuring FRF.12 Fragmentation on Switched PVCsThe FRF.12 Implementation Agreement allows long data frames to be fragmented into smaller pieces.This process allows real-time traffic and non-real-time traffic to be carried together on lower-speed linkswithout causing excessive delay to the real-time traffic. For further information about FRF.12fragmentation, see the section “End-to-End FRF.12 Fragmentation” later in this chapter.Some Frame Relay access devices do not support the FRF.12 standard for end-to-end fragmentation.Large packets sourced from these devices can cause significant serialization delay across low-speedtrunks in switched networks. Using FRF.12 fragmentation can help prevent this delay. An edge routerthat receives large packets from a Frame Relay access device will fragment those packets beforetransmitting them across the switched network. The edge router that receives the fragmented packets will25