What are the design issue with layers in computer network?

Some of the key design issues that occur in computer networks are present in several layers.

Every layer needs a mechanism for identifying senders and receivers. Since a network normally has many computers, some of which have multiple processes, a means is needed for a process on one machine to specify with whom it wants to talk.

Another set of design decisions concerns the rules for data transfer. In some systems, data only travel in one direction; in others, data can go both ways. The protocol must also determine how many logical channels the connection corresponds to and what their priorities are.

Error control is an important issue because physical communication circuits are not perfect.

Another problem that must be solved at several levels is the inability of all processes to accept arbitrarily long messages. This property leads to mechanisms for disassembling, transmitting, and then reassembling messages.

An issue that occurs at every level is how to keep a fast sender from swamping a slow receiver with data.