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CHAPTER 2 / COMMUNICATION FUNDAMENTALS II
2.3 PROTOCOL
The protocol specifies how to write a destination address and how to transmit a
message over the network. A message is sent to the destination node via the neigh-
boring nodes (see Figure 2.4). There are one or more processes at each node. The
message is sent to the destination process. To transmit information to the destina-
tion process, the following action is required: First, information is transmitted to
the neighboring node. This is performed under a data-link-level protocol. Second,
information is transmitted to the destination node. This can be done under a network-
level protocol. Third, information is sent to the destination process. It is done
through a transport-level protocol. To transmit the information to the destination,
it is necessary to establish the connection between the source process and its des-
tination process and to disconnect when communication is over. Furthermore, it is
necessary to specify the transmission method, such as duplex transmission (i.e.,
FIGURE 2.4 OSI protocol and TCP/IP protocol.
