---
title: "Frame relay vs X.25"
subject: "Data Communication"
chapter: 7
key: "semester_5/data_communication:frame-relay-vs-x25"
source: https://www.bctengineer.com/q/semester_5/data_communication/frame-relay-vs-x25
site: BCT Engineering
---

# Frame relay vs X.25

Data Communication · Chapter 7: Switching

- Asked in: 2069 Asar, 5 marks
- Video: [Introduction to Connection Oriented Network | X.25 | Frame relay | ATM | Computer Network ](https://www.youtube.com/watch?v=DbzcFeH_wnQ) — Fly high 
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/frame-relay-vs-x25
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-7

## Question

Distinguish between frame relay and X.25.

## Short answer

X.25 provides hop-by-hop error/flow control at layers 2 and 3, suitable for noisy lines, with slower speeds (up to 64 kbps). Frame relay removes network error correction, relying on upper layers; operates at layer 2 only, using DLCI, and reaches 45 Mbps. Frame relay is faster and designed for reliable digital links.

## Answer

Frame relay was developed from X.25 to exploit reliable digital links, removing most of X.25's processing.

| Point | X.25 | Frame relay |
|---|---|---|
| Layers | Physical, data link (LAPB), network (packet) | Physical and data link only |
| Switching unit | Packets | Frames |
| Error control | At every hop (ACK, retransmission) | None in the network; bad frames dropped, end systems recover |
| Flow control | Hop by hop at layers 2 and 3 | None (only congestion bits FECN, BECN) |
| Speed | Up to 64 kbps (to 2 Mbps) | 56 kbps to 45 Mbps |
| Processing / delay | High, since layer-3 processing | Low |
| Circuit multiplexing | At layer 3 (LCN) | At layer 2 (DLCI) |
| Address field | LCN (12 bits) | DLCI (10 bits) |
| Link quality | Designed for noisy analog lines | Designed for reliable digital / fibre lines |
| Traffic | Low-speed terminals | Bursty LAN-to-LAN data, CIR |

Frame relay is faster because it drops error and flow control in the network and routes by DLCI at layer 2.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which uses fewer layers?
   A. X.25
   B. Frame relay (physical and data link only)
   C. Same
   D. Neither
   Answer: B. X.25 has a network layer; frame relay does not. (Key point: Layers)

2. How does error control differ?
   A. X.25 at every hop; frame relay none in network
   B. Both at every hop
   C. Frame relay at every hop
   D. Both none
   Answer: A. Frame relay drops bad frames and end systems recover. (Key point: Error control)

3. Where are circuits multiplexed?
   A. X.25 at layer 2; FR at layer 3
   B. X.25 at layer 3 (LCN); FR at layer 2 (DLCI)
   C. Both layer 3
   D. Both layer 1
   Answer: B. X.25 uses LCN at layer 3; FR uses DLCI at layer 2. (Key point: Multiplexing)

4. Why is frame relay faster?
   A. Longer cables
   B. It drops network error and flow control and routes by DLCI at layer 2
   C. More hops
   D. Bigger headers
   Answer: B. Less processing means lower delay and higher speeds. (Key point: Speed)

## Related in Data Communication

- [ATM vs frame relay](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aatm-vs-frame-relay) — Data Communication, chapter 7
- [Short note: Frame relay](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aframe-relay-short-note) — Data Communication, chapter 7
- [Switching, circuit vs packet, X.25 layers](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Aswitching-define-compare-x25-layers) — Data Communication, chapter 7

## Related in other subjects

- [Frame Relay](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Aframe-relay) — Computer Networks and Security, chapter 2
- [Design: 25 kVA transformer frame, regulation, tubes](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Adesign-25kva-cooling-tubes) — Electric Machine Design, chapter 3, asked 2×
- [Frame AFD, SFD, BMD (12 kN, 25 kNm, hinge)](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aframe-afd-sfd-bmd-12kn-25knm) — Strength of Materials, chapter 1
- [Frame AFD, SFD, BMD (100 kN, 25 kN/m, hinge)](https://www.bctengineer.com/question.md?key=semester_3%2Fstrength_of_materials%3Aframe-afd-sfd-bmd-100kn-25knm) — Strength of Materials, chapter 1