OSI Models Explaination
September 18, 2016
Categorised in: Computer Forensic & Cyber Applications
- Physical layer is the bottom(layer 1) of OSI model.
- It is responsible for the actual physical connection between the devices.
- The physical layer is responsible for movements of individual bits from one node to next.
Functions of Physical Layer
- Convert bits to signals
- Bit synchronization
- Manage physical connection
- Bit rate control
- Line configuration
- Physical topology
- Transmission mode
Data Link Layer
- Framing:- divides the data from N/W layer into frames.
- Physical Addressing:- Add a header to the frame to define the physical address of the source and the destination machines.
- Flow Control:- It is the traffic regulatory mechanism implemented by Data Link layer that prevents the fast sender from drowning the slow receiver.
- Error Control:- It provides the mechanism of error control in which it detects and retransmits damaged or lost frames.
- Feedback:- after transmitting the frames, the system waits for the feedback.
- It is responsible for the source to destination delivery of a packets across multiple networks.
- Routing:- Provide mechanism to transmit data over independent networks that are linked together.
- Logical addressing:- Adds Logical addresses of sender and Receiver.
- It is responsible for source process to destination process delivery of entire message.
- Transport layer provides two types of services:
- Connection Oriented Transmission: In this type of transmission the receiving device sends an acknowledgment back to the source after a packet or group of packet is received.
- Connectionless Transmission: In this type of transmission the receiver does not acknowledge receipt of a packet.
Functions of Transport Layer:
- Segmentation and Reassembly: Divide the message received from Session layer into Segments and number them to make a sequence for reassembly at the receiving side.
- Service point addressing: Transport layer makes sure that the message is delivered to the correct process on destination machine.
- Error Control: Make sure that the entire message arrives without errors else retransmit.
- Flow Control: Transport layer makes sure that the sender and the receiver communicate at a rate they both can handle.
- It is responsible for beginning, maintaining & ending the communication between two devices, which is called session.
- Establishment, maintaining and ending a session:
Sends SYN packet – establish request
- Receives ACK & SYN- established
- To end – Sender sends ACK
- Dialog Control: The session layer allows two systems to enter into a dialog.
- Synchronization: Allows a process to add checkpoints to a stream of data.
- This layer is concerned with the syntax and semantics of the information exchanged between two systems.
- Data Translation: Encoding and Decoding
- Sender to Common format on Sending side
- Common to Receiving format on Receiver side
- Data Encryption: For security and privacy purpose.
- Data Compression: Data compression reduces the number of bits contained in the information.
- Provides User interfaces and support for Services, like e-mail, file transfer.
- Network Virtual terminal: It allows a user to log on to a remote host.
- File Transfer Access, and Management: This application allows a user to access files in a remote host.
- Mail Services: This application provides various e-mail services.
- Directory Services: This application provides the distributed database sources and access for global information about various objects and services.
Pratik Kataria is currently learning Springboot and Hibernate.
Softwares known and worked on: Adobe Photoshop, Adobe Illustrator and Adobe After Effects.