18 Reliable Networks

In chapter 16, we saw how the transmission of data could be protected by error-correcting codes, so that information could be received accurately in spite of occasional noise. Such codes are an important ingredient in getting reliable communication, but not the whole story. Although such codes can correct or detect a small number of bits lost or garbled, often there's a bigger failure to be overcome. In a typical packet network, a whole packet (of many bits) can be lost all at once. What can we do to ensure that communication still succeeds despite that kind of loss?