Answer to Question #316101 in Computer Networks for skyler

Question

The Open Systems Interconnection model is a conceptual model that characterises and standardises the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. 2.1 Describe the five principles that were followed/applied to arrive at the seven layers. (10) 2.2 Discuss the functions of each layer of the OSI model and protocols used. (15) 2.3 Describe the design issues associated with the Network layer of the OSI model

Answer 1

principles that were followed/applied to arrive at the seven layers.

1.Each layer should perform a well-defined function.

2.A layer should be created where a different abstraction is needed.

3.The function of each layer should be chosen with an eye toward defining internationally standardized protocols.

4.The number of layers should be large enough that distinct functions need not be thrown together in the same layer out of necessity and small enough that architecture does not become unwieldy

5.The layer boundaries should be chosen to minimize the information flow across the interfaces.

functions of each layer of the OSI model and protocols used.

1.The application layer

It provides protocols that allow software to send and receive information and present meaningful data to users.

2. Presentation Layer

The presentation layer prepares data for the application layer. It defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end.

3. Session Layer

The session layer creates communication channels, called sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends.

4. Transport Layer

It is responsible for reassembling the segments on the receiving end, turning it back into data that can be used by the session layer.

5. Network Layer

The network layer is responsible for breaking up segments into network packets, and reassembling the packets on the receiving end. Also responsible for routing packets by discovering the best path across a physical network.

6. Data Link Layer

The data link layer establishes and terminates a connection between two physically-connected nodes on a network. It breaks up packets into frames and sends them from source to destination.

7. Physical Layer

The physical layer is responsible for the physical cable or wireless connection between network nodes. It defines the connector, the electrical cable or wireless technology connecting the devices, and is responsible for transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control.

design issues associated with the Network layer of the OSI model

1. Reliability: It is a design issue of making a network that operates correctly even when it is made up of unreliable components.
2. Addressing: Every layer needs a mechanism to identify senders and receivers.
3. Error Control: It is an important issue because physical communication circuits are not perfect.
4. Flow Control:there must be flow control mechanism to control the loss of data by slow receivers.
5. Scalability: When network gets large, new problem arises. Thus scalability is important for network to continue working well when it gets large.
6. Routing: When there are multiple paths between source and destination, only one route is necessary.