Lecture 4

briefly describe five main issues that must be addressed when designing computer network.

briefly explain why networks are modeled as a stack of layers.

briefly describe the role of an interface when modeling a network as a stack layers.

explain the role played by a session in a network connection.

state the seven layers of the OSI reference model in the correct order and briefly state the purpose of each layer.



the five main issues that must be addressed when designing computer network are addressing , error control, flow control, multiplexing and routing. addressing is to send the message to the specific address. error control is to make sure that the message is received. flow control is to match the speed of the sender with the receiver. mutiplexing is dividing the message into several part to make sure that every receiver receive the message at the same time. routing is selecting the best part to send the message to the receiver.


the process must be done in order of the hierarchy. the process must be done each step and each step cannot be skipped.

the purpose of interface when modeling a network as a stack layers is the application and the user interact directly with the application software. tis layer interact with software applications that implement a communicating component.


session  is controls the dialogues (connections) between computers. it establishes, manages and terminates the connections between the local and remote applications.

application leyer
presentation layer
session layer
transport layer
network layer
data link layer
physical layer