Token Ring Frame Size Answer | Generated by AI
Question: In IEEE 802.5 Token Ring, the MAC frame has two basic formats: the token frame and the data frame. The token frame is only how many bytes long?
A. 2 bytes
B. 3 bytes
C. 4 bytes
D. 5 bytes
Answer:
The correct answer is B. 3 bytes.
Detailed explanation:
In the IEEE 802.5 Token Ring standard, there are indeed two fundamental MAC frame formats:
- Token frame (pure token)
- Consists of exactly 3 bytes:
- Starting Delimiter (SD) → 1 byte
- Access Control (AC) → 1 byte
- Ending Delimiter (ED) → 1 byte
- Total length = 3 bytes
- Consists of exactly 3 bytes:
- Data frame (also called LLC frame or information frame when it carries data)
- Much longer and variable length
- Basic structure: SD (1) + AC (1) + FC (1) + Destination Address (6) + Source Address (6) + [Information field, variable] + FCS (4) + ED (1) + Frame Status (1)
- Minimum length is typically around 19–21 bytes (without data), but can be much longer.
The key difference emphasized in the standard and most textbooks is that the token itself is only 3 bytes long.
The Starting Delimiter (SD) and Ending Delimiter (ED) each use a special violation of normal Manchester coding (J and K symbols, which are represented as “high-high” and “low-low” level pairs) to clearly mark frame boundaries and ensure data transparency.
Therefore, the correct choice is B. 3 bytes.
Your previous answer (A. 2 bytes) is incorrect. No mainstream version of the IEEE 802.5 Token Ring standard defines a 2-byte token.
References:
- IEEE 802.5-1998 standard (Token Ring access method and physical layer specifications)
- Most classic computer networking textbooks (e.g., Tanenbaum, Kurose & Ross, Peterson & Davie) describe the Token Ring token as 3 bytes