Computer Networks - Layers in OSI Model
- 1. LAYERS IN THE OSI MODEL Open System Interconnection Layers- An Interactive Study
- 2. •The application layer enables the user (human or software) to access the network by user interfaces and support for services.Application •The presentation layer is responsible for translation, compression and encryption.Presentation •The session layer is responsible for dialog control and synchronizationSession •The transport layer is responsible for the delivery for a message for one process to another.Transport •The network layer is responsible for the delivery of individual packets from the source host to the destination host.Network •The data link layer is responsible for moving frames one hop (node) to the next.Data Link •The physical layer is responsible for movements of individual bits from one hop(node) to the next.Physical A BRIEF OVERVIEW -
- 3. A SIMPLER METHOD- •ADVICEApplication •PERSON’SPresentation •SALESSession •TRUSTTransport •NOTNetwork •DOData Link •PLEASEPhysical SUPPORT LAYERS FOR HARDWARE SUPPORT LAYERS FOR SOFTWARE
- 4. LET’S SEE WHAT HAPPENS WHEN RAJ SENDS HIS MESSAGE Let his message be DATA-MESSAGE DATA-MESSAGE
- 5. The application layer provides services to the user such as – ■ Network Virtual Terminal – via SSH/ Telnet +Putty/ CygWIN ■ File transfer, access and management –via FTP/SAMBA/AFP/DLNA ■ Mail Services via SMTP, IMAP, POP3 ■ Directory Services for accessing global information about objects and services via HTTP/HTTPS H7 DATA-MESSAGE
- 6. The presentation layer handles the semantics and syntax of the information exchanged between systems. ■ Translation– Encodes/Decodes machine-dependent format of encoded bit- streams to/from a common format. ■ Encryption & Decryption of sensitive information. ■ Compression H7 DATA-MESSAGE H6 DATA
- 7. The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interaction among communicating systems. It’s responsibilities include ■ Dialog Control by allowing communication between two processes to take place in either half-duplex mode or full-duplex mode. ■ Synchronization by utilization of synchronization checkpoints. H6 H5 DATA H7 DATA-MESSAGE
- 8. The transport layer is responsible for process- to-process delivery of the entire message. ■ Service- point addressing ( i.e. port addressing services to ports e.g. FTP to ) ■ Segmentation and reassembly of the divided message, in form of transmittable segments, each with a unique sequence number. ■ Connection Control – Connectionless or Connection-Oriented ■ Flow Control performed end-to-end. ■ Error Control performed process-to- process. Error Correction is usually performed by re-transmission of segments. H6 H4 DATA H7 DATA-MESSAGEH5
- 9. The network layer is responsible for the source-to-destination delivery of a packet, possible across multiple links. It ensures that the packet gets delivered from it’s point of origin to it’s final destination. It is not essential when two systems are connected end-to-end, i.e. to the same link. ■ Logical Addressing – for packets that are sent outside the network boundary, to distinguish source and destination systems. It adds a header that include logical address of sender and receiver. ■ Routing – to route/switch the packets to their final destination from a sender. H6H4 DATA H7H5 DATA-MESSAGE H3
- 10. The data link layer transforms the physical layer into a reliable link. It makes the physical layer appear error-free to the upper layers ( network layer ). It’s responsibilities include - ■ Framing- Dividing the stream of bits from network layer into frames. ■ Physical Addressing –Adding headers to a frame to define sender and/or receiver. ■ Flow Control – To prevent overflow of the receiving mechanism of receiver. ■ Error Control (Encapsulation)– Detecting and retransmitting lost frames by adding a tail. ■ Access Control – To determine control over link. H6H4 DATA H7H5 DATA-MESSAGEH3 H2 T
- 11. The physical layer coordinates the functions required to carry a bit stream over a physical medium. It defines the procedures and functions that physical devices and interfaces have to perform for the transmission to occur. It is characterized by – ■ Physical characteristics of the medium ■ Representation of bits, i.e. encoding ■ Data Rate/Transmission Rate ( number of bits/sec) ■ Synchronization of bits – by synchronization of sender and receiver clocks ■ Line Configuration – Connection of device to media ■ Physical Topology ■ Transmission Mode (simplex/full-duplex/half-duplex) H6H4 DATA H7H5 DATA-MESSAGEH3 H1 TH2
- 12. NOW, LET’S SEND THE MESSAGE TO THE RECEIVER Here’s what the message looks like so far - H6H4 H7H5 DATA-MESSAGEH3H1 TH2
- 13. The physical layer coordinates the functions required to carry a bit stream over a physical medium. H6H4 DATA H7H5 DATA-MESSAGEH3 H1 TH2
- 14. The data link layer transforms the physical layer into a reliable link. It makes the physical layer appear error-free to the upper layers ( network layer ). It checks and decodes now, removing the tail. ( ERROR CORRECTION IS MAINLY PERFORMED BY ASKING FOR RE- TRANSMISSION). H6H4 DATA H7H5 DATA-MESSAGEH3 H2 T
- 15. It get’s the addressing information of the receiver from from the header H3. H6H4 DATA H7H5 DATA-MESSAGE H3
- 16. The transport layer is responsible for process-to-process delivery of the entire message at the receiving end. It manages the services and is responsible for re-assembling packets according to the sequence id of packets derived from the H4 HEADER. Error Correction is usually performed by re-transmission of segments. H6 H4 DATA H7 DATA-MESSAGEH5
- 17. The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interaction by use of information checkpoints contained according to H5 Header. It also determines the mode of connection according to the header. H6 H5 DATA H7 DATA-MESSAGE
- 18. The presentation layer handles the semantics and syntax of the information exchanged between systems. Based on information from the H6 Header it performs - ■ Translation– Decodes common format encoded bit-streams to machine- dependent format. ■ Decryption of sensitive information ■ De-Compression H7 DATA-MESSAGE H6 DATA
- 19. The application layer provides services to the recieving user such according to the application used. The information about the application to be used is derived from the H7 Header. H7 DATA-MESSAGE
- 20. HERE IS THE MESSAGE TO THE RECIVER- DATA-MESSAGE
- 21. ONCE AGAIN - •ADVICEApplication •PERSON’SPresentation •SALESSession •TRUSTTransport •NOTNetwork •DOData Link •PLEASEPhysical SUPPORT LAYERS FOR HARDWARE SUPPORT LAYERS FOR SOFTWARE
- 22. THANK YOU FOR WATCHING THE PRESENTATION! BIBLIOGRAPHY • Data Communications and Networking (4TH Edition), McGraw Hill Education, Behrouz A. Foruzan OTHER SOURCES OF INFORMATION- • Dr. Mydhili K. Nair , Department of Information Science and Engineering, M.S. Ramaiah Institute of Technology, Bangalore, India Presentation made by – Shreyash Agarwal, Student, Information Science and Engineering M.S. Ramaiah Institute of Technology