Chabot College. Frame Relay Part 1. Frame Relay Overview. Frame Relay Operation. Many other WAN technologies (PPP, ATM) can be used inside the FR cloud. Frame Relay Uses PVCs. PVCs have ID numbers called DLCIs. DLCI - Data Link Control Identifier. DLCIs Identify Connections.
Many other WAN technologies (PPP, ATM) can be used inside the FR cloud.
PVCs have ID numbers called DLCIs.
DLCI - Data Link Control Identifier
Frame Relay provides a means for statistically multiplexing many logical data conversations (referred to as virtual circuits) by assigning each pair of DTEs connection identifiers.
A number that identifies the logical circuit between the source and destination device. The FR switch maps the DLCIs between each pair of routers to create a PVC.
The clock speed (port speed) of the connection (local loop) to the Frame Relay cloud. It is the rate at which data travels into or out of the network.
A signaling standard between the CPE device and the FR switch that is responsible for managing the connection and maintaining status between the devices.
Different flavors have different features. Currently, ansi is the most common:
Remember to configure your router’s interface to use the same LMI type that the FR provider’s equipment is using.
(config-if)#frame-relay lmi-type cisco
(config-if)#frame-relay lmi-type ansi
(config-if)#frame-relay lmi-type q933a
The rate, in bits per second, that the Frame Relay switch agrees to transfer data.
Excess Burst—The maximum number of uncommitted bits that the Frame Relay switch will attempt to transfer beyond the CIR.
When the router detects network congestion, the FR switch will drop packets with the DE bit set first. The DE bit is set on the oversubscribed traffic; that is, the traffic that was received after the CIR was met.
Forward explicit congestion notification:
When a Frame Relay switch recognizes congestion in the network, it sends an FECN packet to the destination device indicating that congestion has occurred.
Backward explicit congestion notification:
When a Frame Relay switch recognizes congestion in the network, it sends a BECN packet to the source router instructing the router to reduce the rate at which it is sending packets.
The Inverse ARP mechanism allows the router to automatically build the Frame Relay map. The router learns the DLCIs that are in use from the switch during the initial LMI exchange. The router then sends an Inverse ARP request to each DLCI for each protocol configured on the interface if the protocol is supported.