How "good" are checksums? Suppose a sender computes a checksum (Internet
checksum or some other checksum, which is essentially a sum of the bytes in a
segment), puts the checksum in the segment header, and sends the segment to the
receiver. The receiver receives the segment (with the checksum in the header). The
receiver computes the checksum itself (i.e., performs the same calculation as the
sender, but over the received data) and compares the checksum it has computed to
the checksum it received in the header. It finds that its computed checksum and
received checksum in the header are identical. Which of the following statements is
true?
The receiver can be absolutely certain that no errors (bit flips) have occurred in
the received data in the segment.
The receiver can be absolutely certain that an error (bit flips) have occurred in
the received data in the segment.
The receiver can't tell for certain whether errors (bit flips) have occurred in the
received data in the segment, but can be relatively confident that no errors have
occurred.
