indicates that the sending side of rdt is being called. The first step in developing any
protocol is to choose a good name!) On the receiving side, rdt_rcv() will be called
when a packet arrives from the receiving side of the channel. When the rdt protocol
wants to deliver data to the upper layer, it will do so by calling deliver_data(). In
the following we use the terminology “packet” rather than transport-layer “segment.”
Because the theory developed in this section applies to computer networks in general
and not just to the Internet transport layer, the generic term “packet” is perhaps more
appropriate here.