ITPEC FE Subject A April 2024 Question 14

Buffer overflow prevention — calculate minimum buffer size between a fast sender and slow receiver.

Over T seconds, data accumulates in the buffer at rate S − R:

• •Sent: S × T
• •Received: R × T
• •Accumulated: (S − R) × T

To prevent overflow, the buffer must hold all accumulated data:

L ≧ (S − R) × T

Why not others:
- (a) L < (R − S) × T — R − S is negative (sender is faster), and < gives no useful constraint
- (b) L < (S − R) × T — correct difference but wrong direction (< guarantees overflow)
- (c) L ≧ (R − S) × T — R − S is negative, so this is trivially true and meaningless

Key rule: Buffer size ≧ (send rate − receive rate) × transfer duration.

AI-generated — may contain errors