Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring Frame Relay SVCsConfiguring Frame RelayCommandRouter(config-if)# frame-relay lmi-n392dcethresholdRouter(config-if)# frame-relay lmi-n393dce eventsRouter(config-if)# frame-relay lmi-t392dce secondsRouter(config-if)# frame-relay lmi-n391dtekeep-exchangesRouter(config-if)# frame-relay lmi-n392dtethresholdRouter(config-if)# frame-relay lmi-n393dte eventsPurposeSets the DCE and Network-to-Network Interface (NNI) errorthreshold.Sets the DCE and NNI monitored events count.Sets the polling verification timer on a DCE or NNI interface.Sets a full status polling interval on a DTE or NNI interface.Sets the DTE or NNI error threshold.Sets the DTE and NNI monitored events count.See the chapter “Frame Relay Commands” in the Cisco IOS Wide-Area Networking Command Referencefor polling and timing interval commands.Configuring Frame Relay SVCsAccess to Frame Relay networks is made through private leased lines at speeds ranging from 56 kbps to45 Mbps. Frame Relay is a connection-oriented packet-transfer mechanism that establishes VCs betweenendpoints.Switched virtual circuits (SVCs) allow access through a Frame Relay network by setting up a path to thedestination endpoints only when the need arises and tearing down the path when it is no longer needed.SVCs can coexist with PVCs in the same sites and routers. For example, routers at remote branch officesmight set up PVCs to the central headquarters for frequent communication, but set up SVCs with eachother as needed for intermittent communication. As a result, any-to-any communication can be set upwithout any-to-any PVCs.On SVCs, quality of service (QoS) elements can be specified on a call-by-call basis to request networkresources.SVC support is offered in the Enterprise image on Cisco platforms that include a serial or HSSI interface.You must have the following services before Frame Relay SVCs can operate:• Frame Relay SVC support by the service provider—The service provider’s switch must be capableof supporting SVC operation.• Physical loop connection—A leased line or dedicated line must exist between the router (DTE) andthe local Frame Relay switch.For examples of configuring Frame Relay SVCs, see the section “SVC Configuration Examples” laterin this chapter.Operating SVCsSVC operation requires that the Data Link layer (Layer 2) be set up, running ITU-T Q.922 Link AccessProcedures to Frame mode bearer services (LAPF), prior to signalling for an SVC. Layer 2 sets itself upas soon as SVC support is enabled on the interface, if both the line and the line protocol are up. Whenthe SVCs are configured and demand for a path occurs, the Q.933 signalling sequence is initiated. Oncethe SVC is set up, data transfer begins.8