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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
Chabot College

Frame Relay

Part 1



Frame relay operation
Frame Relay Operation

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


Frame relay uses pvcs
Frame Relay Uses PVCs

PVCs have ID numbers called DLCIs.

DLCI - Data Link Control Identifier


Dlcis identify connections
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.


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.


Dlcis
DLCIs

  • Can have “local only” significance.


Local access rate
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.


Local management interface
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.


Possible lmi functions
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


Flavors of lmi
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


Lmi configuration
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


Cir committed info rate
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.


De discard eligibility
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.


Fecn and becn
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.


Fecn and becn1
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.



Dlcis1
DLCIs

  • Can be a number between 16-1007.

illegal



Frame relay encapsulation
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




Inverse arp1
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.





B s before subinterfaces
B.S. - Before Subinterfaces

Network 7777

Network 8888








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