Computer Networking Basics
Roughly how long does it take to send a 100 MB file over a 100 Mbps link? Ignore overhead such as headers and latency, and take 1 MB = 10^6 bytes.
- AAbout 1 s
- BAbout 8 s
- CAbout 80 s
Show answer and explanation
Answer: B. About 8 s
Link speeds are usually given in bits per second (bps) and file sizes in bytes (B), so first align the units. One byte is 8 bits, so 100 MB = 100 × 8 = 800 megabits. Sending this at 100 Mbps takes 800 ÷ 100 = 8 seconds. In practice it takes longer because of overhead such as headers and the waiting introduced by TCP's control mechanisms.
- A. This confuses bytes with bits, treating 100 MB as 100 megabits.
- B. Correct. 800 megabits ÷ 100 Mbps = 8 seconds.
- C. This is the value for a 10 Mbps link.