Three Acks One Segment

RFC 5681 increments the congestion window during slow start with

cwnd += min(N, SMSS)

where N is the number of previously unacknowledged bytes that this ACK covers.

SMSS is 1460. The sender transmits one full 1460-byte segment. A receiver that wants to speed the sender up responds with three separate ACKs covering bytes 1..487, 488..974 and 975..1460 of that one segment.

By how much does cwnd grow?

A

0 bytes, because none of the three ACKs covers a full segment

B

About 1460 bytes, roughly one segment

C

4380 bytes, three segments

D

487 bytes