<P> The receiver also knows that the transmitter's n cannot be higher than the highest acknowledgment ever sent, which is n . So the highest sequence number we could possibly see is n + w ≤ n + w . </P> <P> Thus, there are 2w different sequence numbers that the receiver can receive at any one time . It might therefore seem that we must have N ≥ 2w . However, the actual limit is lower . </P> <P> The additional insight is that the receiver does not need to distinguish between sequence numbers that are too low (less than n) or that are too high (greater than or equal to n + w). In either case, the receiver ignores the packet except to retransmit an acknowledgment . Thus, it is only necessary that N ≥ w + w . As it is common to have w <w (e.g. see Go - Back - N below), this can permit larger w within a fixed N . </P> <P> Although commonly distinguished from the sliding - window protocol, the stop - and - wait ARQ protocol is actually the simplest possible implementation of it . The transmit window is 1 packet, and the receive window is 1 packet . Thus, N = 1 + 1 = 2 possible sequence numbers (conveniently represented by a single bit) are required . </P>

Where is tcp data stored when it is received