Asynchronous Transfer Mode (ATM) is also known as-
Cell relay
Understanding Asynchronous Transfer Mode (ATM)
Asynchronous Transfer Mode (ATM) is a switching technique used by telecommunication networks that uses asynchronous time-division multiplexing. It encodes data into small, fixed-sized cells instead of using variable-sized packets like Frame Relay or traditional packet switching.
Why ATM is Known as Cell Relay
The defining characteristic of ATM is its use of fixed-size data units called "cells". Each ATM cell is 53 bytes long, consisting of a 5-byte header and a 48-byte payload. This fixed size allows for very fast, hardware-based switching.
Because ATM relies on the relaying of these fixed-size cells across the network, it is frequently referred to as Cell Relay. This term highlights the fundamental operational principle of ATM networks – moving data in small, standardized chunks.
- Cell: A fixed-size data unit used in ATM.
- Relay: The process of transmitting or passing data through a network.
Therefore, the term "Cell Relay" is synonymous with Asynchronous Transfer Mode, emphasizing its core technology of switching fixed-size cells.
Analysis of Other Options
Let's briefly look at the other options provided:
- SMDS (Switched Multimegabit Data Service): SMDS was a connectionless, packet-switched service that operated at high speeds. While it shared some characteristics with ATM in terms of high speed, it was a different technology based on DQDB (Distributed Queue Dual Bus) and typically used variable-length packets or fixed-size cells that were different from ATM.
- X.25: X.25 is a standard protocol suite for packet-switched Wide Area Networks (WANs). It is an older, connection-oriented protocol that uses variable-length packets and provides error correction and flow control at each node, which introduces more overhead and delay compared to ATM.
- Frame Relay: Frame Relay is another packet-switching technology, but unlike ATM's fixed-size cells, Frame Relay uses variable-length frames. It is also typically faster than X.25 because it performs fewer error checks and relies on higher-layer protocols or the end devices to handle most error correction.
Comparing ATM (Cell Relay) with Frame Relay and X.25:
| Feature | ATM (Cell Relay) | Frame Relay | X.25 |
|---|---|---|---|
| Data Unit | Fixed-size cells (53 bytes) | Variable-size frames | Variable-size packets |
| Switching | Hardware-based, fast | Software-based, faster than X.25 | Software-based, slower |
| Error Handling | Minimal at network layer, relies on end-points | Minimal at network layer, relies on end-points | Extensive at network layer |
| Overhead | Low per cell | Higher per frame than ATM per byte | Highest due to error checking |
This comparison shows that ATM's use of fixed-size cells is its distinctive feature, leading to the alternative name Cell Relay.
Revision Table: Key Concepts
| Term | Definition/Association |
|---|---|
| Asynchronous Transfer Mode (ATM) | High-speed networking technology using fixed-size cells. |
| Cell Relay | Another name for ATM, highlighting its use of fixed-size data units (cells). |
| Cell | A 53-byte data unit (5-byte header + 48-byte payload) in ATM. |
| Frame Relay | Packet-switching technology using variable-size frames. |
| X.25 | Older packet-switching protocol using variable-size packets with extensive error checking. |
Additional Information on ATM and Cell Relay
ATM was designed to handle both voice, video, and data traffic efficiently, especially for broadband integrated services digital network (B-ISDN). The fixed size of the cells makes it easier to predict transmission delays, which is crucial for real-time traffic like voice and video.
The fixed cell size also simplifies the hardware required for switching, allowing for very high switching speeds. While ATM saw significant use in backbone networks and early broadband implementations (like ATM to the home), it has largely been superseded by IP-based technologies like Ethernet and MPLS in many areas, although it still exists in some legacy systems.
The term "Cell Relay" is often used interchangeably with ATM and emphasizes the core mechanism of data transfer within this technology.
Important Questions from Network Layer
Which of the following delays are present in packet switching?
What is the use of the 'Ping' command?
Which of the following types of firewall operates at the Network layer to examine incoming and outgoing packets?
What is the name of the protocol that allows a client to send a broadcast message with its MAC address and receive an IP address in reply?
The full form of ICANN is
