LMI and Encapsulation Types

LMI (Local Management Interface) is a signaling standard used to communicate between the Frame Relay switch and the customer’s router. LMI defines a set of messages that are exchanged periodically between the switch and the router to ensure that the connection is up and running and to provide some basic information about the status of the connection. LMI messages are sent using the same virtual circuit that is used for user data.

Encapsulation types define how data is encapsulated and framed for transmission over the Frame Relay network. There are three types of encapsulation that are commonly used with Frame Relay:

Cisco HDLC: This is the default encapsulation used by Cisco routers. It is a proprietary protocol that is similar to HDLC but includes additional fields for Frame Relay.

Frame Relay Encapsulation (FRE): This is a standard encapsulation method that is used by most non-Cisco routers. It uses a four-byte header that includes the DLCI and other information.

Frame Relay Transport (FRT): This is a variation of FRE that is used in some networks. It uses a two-byte header and includes only the DLCI. Each virtual circuit can use a different encapsulation type, depending on the requirements of the network.