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Chabot College

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.

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Chabot College

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  1. Chabot College Frame Relay Part 1

  2. Frame Relay Overview

  3. Frame Relay Operation Many other WAN technologies (PPP, ATM) can be used inside the FR cloud.

  4. Frame Relay Uses PVCs PVCs have ID numbers called DLCIs. DLCI - Data Link Control Identifier

  5. DLCIs Identify Connections 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.

  6. DLCI 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.

  7. DLCIs • Can have “local only” significance.

  8. Local Access Rate 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.

  9. Local Management Interface A signaling standard between the CPE device and the FR switch that is responsible for managing the connection and maintaining status between the devices.

  10. Possible LMI Functions • keepalive mechanism, which verifies that data is flowing • a multicast mechanism which can provide the network server with its local DLCI • multicast addressing • the ability to give DLCIs global (whole Frame Relay network) significance • a status mechanism

  11. Flavors of LMI Different flavors have different features. Currently, ansi is the most common: • cisco—LMI type defined jointly by Cisco, StrataCom, Northern Telecom, and DEC • ansi—Annex D defined by ANSI standard T1.617 • q933a—ITU-T Q.933 Annex A

  12. LMI Configuration 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

  13. CIR - Committed Info Rate 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.

  14. DE - Discard Eligibility 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.

  15. FECN and BECN 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.

  16. FECN and BECN 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.

  17. FECN and BECN

  18. DLCIs • Can be a number between 16-1007. illegal

  19. LMI - Types

  20. Frame Relay Encapsulation • The router must be configured to choose which Frame Relay encapsulation will be used. • IETF Encapsulation Type (Most common) • Cisco Encapsulation Type

  21. IETF Frame Relay Frame variable

  22. Inverse ARP

  23. Inverse ARP 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.

  24. The Frame Relay Map

  25. Frame Relay Operation

  26. Frame Relay Operation

  27. B.S. - Before Subinterfaces Network 7777 Network 8888

  28. Subinterfaces

  29. Subinterfaces

  30. Multipoint Subinterfaces

  31. Point-to-Point Subinterfaces

  32. 11.2 + Autodetects LMI type

  33. FR Verification

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