Frame Relay

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Committed Information Rate (CIR)
The guaranteed average bandwidth a Frame Relay provider commits to deliver on a Permanent Virtual Circuit (PVC). It’s a key QoS parameter.

Extended Information Rate (EIR)
The burstable bandwidth above CIR that a user may transmit if extra capacity exists. Frames sent above CIR but within EIR are marked as discard eligible.

Discard Eligible (DE)
A bit in the Frame Relay frame header that marks traffic exceeding CIR as lower priority, making it the first to be dropped during network congestion.

Local Management Interface (LMI)
A signaling standard between the DTE (customer device) and DCE (network provider equipment) that manages PVC status, keepalives, and global addressing.

Data Link Connection Identifier (DLCI)
A numerical identifier in the Frame Relay frame header that uniquely identifies each virtual circuit within the provider’s network.