Frame relay is packet switching technology. Frame relay is a high performance WAN protocol that operate at the physical and Data Link Layers of the OSI Models. Two Types of Circuits are there:
(i) PVCs - Permanent Virtual Circuits
(ii) SVCs - Switched Virtual Circuits
Permanent Virtual Circuits (PVCs) are similar to Leased Line. PVCs is setup for a dedicated Point – to – Point connections.
Switched Virtual Circuits (SVCs) are similar to Telephone line switched connection. SVCs is setup on a Call – by – Call basis
Three states for PVCs
Active - It means everything is UP.
Inactive - It means there is problem with the far end.
Deleted - It means problem with Router and Frame Relay provider Equipment.
LMI – Local Management Interface
The main function of Local Management Interface (LMI) is to allow the frame relay DTE and DCE to exchange the status information about the Virtual Circuits (VCs)
LMI Standard Types:
CCNA Overview Page