ATM Cell Fixed Length Explained | Generated by AI
Question: What is the fixed length of an ATM cell?
Answer:
The correct answer is C. 53 bytes.
Detailed explanation:
In ATM (Asynchronous Transfer Mode) networks, the basic unit of data transmission is called a cell (信元). This cell has a fixed length of exactly 53 bytes, which consists of:
- Header: 5 bytes
- Payload (information field / 用户信息域): 48 bytes
Total: 5 + 48 = 53 bytes
This fixed and relatively small cell size was deliberately chosen in the design of ATM to:
- Minimize queuing delay (especially important for real-time voice and video traffic)
- Allow efficient statistical multiplexing
- Simplify hardware switching implementation
Common incorrect options and why they are wrong:
- A. 8 bytes: Far too small — not used in ATM
- B. 16 bytes: Sometimes confused with header size in other protocols, but incorrect for ATM cells
- D. 64 bytes: Close to the 53-byte size, but not accurate (some people remember it incorrectly as “about 64 bytes”)
So the only correct answer is C. 53 bytes.
References:
- None (standard ATM protocol definition, widely documented in networking textbooks and ITU-T I.150 / I.361 recommendations)