Error control
is responsible for checking each transmission and verifying that all of the PDUs
are contiguous and not erroneous. If there are missing or damaged PDUs, the destination will
not send an ACK packet for the previous transmission. (Refer to Figure 36.6.)
Once all of the data is transferred without errors, the originating system sends a termination
request, which tells the destination system that no more data needs to be transmitted. The destination
system then responds with a termination acknowledgment.
As you can see, both systems do a lot of communicating, aside from the exchange of data.
From the connection request to the termination acknowledgment, every exchange is accompanied
with control information that keeps the data transfer reliable and error free. Table 36.1
gives examples of several connection-oriented protocols. 1102