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Short note: Frame relay

Short answer

Frame relay is a connection-oriented WAN technology operating at the data link layer, using virtual circuits identified by a 10-bit DLCI. It discards errored frames without hop-by-hop error recovery, relying on higher layers. Speeds up to 45 Mbps; uses CIR, FECN/BECN for congestion management.

Write a short note on frame relay.

Frame relay is a fast, connection-oriented packet-switching WAN technology (ITU-T Q.922 / ANSI T1.618) that works at the physical and data link layers only. It was designed as a simplified successor of X.25 for reliable digital links, with speeds of 56 kbps to 44.7 Mbps (T1/T3).

Features

  • Uses virtual circuits, mostly permanent (PVC), identified by a 10-bit DLCI (data link connection identifier).
  • No hop-by-hop error correction or flow control: a frame with errors is just discarded and higher layers (TCP) recover. This makes it much faster than X.25.
  • Variable-size frames up to about 1600 bytes (up to 8 kB in some cases).
  • Bursty traffic is handled with CIR (committed information rate); bits above CIR are marked DE (discard eligible).
  • Congestion indicated by FECN and BECN bits.

Frame format

 | Flag | Address (DLCI,C/R,EA,FECN,BECN,DE) | Info | FCS | Flag |
 |  1   |             2 bytes                | var  |  2  |  1   |

Uses

Connecting LANs of branch offices (LAN-to-LAN) over WAN, voice over frame relay, and Internet access. It has been largely replaced by MPLS and Ethernet WAN.

✓ Answer checked by Claude Sonnet 5.5

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