group13_Avani:description of protocol stack

Brief description of layers of the OSI model

7. Application layer:

• it is the top layer of the OSI model.
• it is responsible for providing services to the user.
• provides a set of interfaces for sending and receiving applications to gain access to and use network services.

6. Presentation layer

• it converts the data into a generic format for network transmission for outgoing messages and for incoming messages, it converts the data from the generic network format to a format that the receiving application can understand.
• it is also responsible for certain protocol conversions, data encryption/decryption or data compression and decompression.

5. Session layer

• it manages user sessions and dialogues.
• controls establishment and termination of logic links between users.
• reports upper layer errors.
• it is also responsible for security and access control to session information(via session participant identification).

4. Transport layer

• it is responsible for the delivery of a message from one procees to another.
• manages the data flow between parties by segmenting long data streams into smaller data chunks.
• reaasembles chunks into their original sequence at the receiving end.
• provides acknowledgements for successful transmissions and requests resends for packets which arrive with errors.

3. Network layer

• it determines how data is transferred between network devices.
• routes packets according to unique network device addresses.
• provides flow and congestion control to prevent network resource depletion.

2. Data link layer

• handles special data frames(packets) between the network layer and physical layer.
• at the receiving end, it packs the raw data from the physical layer into data frames for delivery to the network layer.
• at the sending end this layer handles conversion of data into raw formats that can be handled by the physical layer.

1. Physical layer

• it is the bottom layer of the OSI model.
• converts bits into electronic signals for outgoing messages and converts electronic signals into bits for incoming messages.
• it manages the interface between the network medium(coax, twisted pair etc) and computer.