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Frame Relay

Short answer

Frame Relay is a connection-oriented WAN technology using DLCI-identified virtual circuits with no error/flow control inside the network. It discards errored frames for higher-layer recovery, offering speeds up to 45 Mbps and guaranteed CIR.

Define Frame Relay in detail.

Frame Relay is a high-speed, connection-oriented packet-switching WAN technology that works at the physical and data link layers. It was designed as a faster, simpler successor of X.25 for reliable digital (fibre) lines, and it is standardised by ITU-T and ANSI.

Key features

  • Virtual circuits: data moves over Permanent (PVC) or Switched (SVC) virtual circuits identified by a DLCI (Data Link Connection Identifier) in the frame header.
  • Low overhead: no error correction or flow control inside the network. Frames with errors are simply discarded and higher layers (TCP) recover them. This makes it much faster than X.25.
  • Speeds: typically 56 kbps up to 45 Mbps (T3/E3).
  • Variable frame length (up to about 4096 bytes), good for LAN traffic.
  • Statistical multiplexing of several virtual circuits on one link.
  • Committed Information Rate (CIR): the guaranteed bandwidth of a circuit; bursts above it may be dropped.
  • Congestion notification by FECN and BECN bits and the DE (discard eligibility) bit.

Frame format

| Flag | Address(DLCI,C/R,FECN,BECN,DE) | Data | FCS | Flag |

Use

It connects LANs of branch offices to the head office through a service provider, replacing costly leased lines. It was widely used before MPLS and the Internet-based VPNs.

✓ Answer checked by Claude Opus 5.5 (high effort)

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