OSI(Open Systems Interconnection) MODEL : is a reference model for how apps communicate over a N/W.
| Layer | Layer Namer | Data Type | Devices used | Process |
| 7 | Application Layer | – | human or software | (i) User → Application(ii) Selects suitable Protocol |
| 6 | Presentation layer | – | – | (i) Translation : ASCII – to binary or any (ii) Compressing : Reducing size to minimize the time taken to send the file (iii) Encryption/Decryption : Encrypt and decrypt the data using the SSL |
| 5 | Session Layer | Message(File) | Gateway | (i) Identify data(ii) Authenticate and Authorize the Data Transmission |
| 4 | Transport Layer | Segment : Data file part + checksum | Firewall | (i) Segmentation : Making parts of huge data And adding checksum values for integrity(getting error free data) while receiving (ii) Flow Control : Check the data flow, along with sender and receiver processing limit(iii) Error check : every segment is included with checksum value , with that missing files automatically resend takes place with ARR automatic resend request Transmission of data two types : 1) connection – oriented : receiver acknowledges(msg) receipt of a packet. Un received data resent, its reliable2) connection less : receiver does not acknowledge receipt of a packet |
| Segment : Data file part + checksum | ||||
| 3 | Network layer | Packets | Router | (i) Logical Addressing : IP Assigning (ii) Routing : Routing the path (iii) Path Detecting : Detecting a suitable for data transmission |
| Packet : Sender IP + Receivers IP + [Segment : Data file part + checksum] | ||||
| 2 | Data Link Layer | Frame | switch | Check file errors(loss of data), create frame of data ,frame(bits – divide by nic)create a way to send the data , types : 1) MAC : tracking data frames with mac2) LLC (Logical link Controller) : testing the connectivity of the network layer, whether the receiver address is alive/correct or not. |
| Frame : Senders MAC + Receivers MAC + {Sender IP + Receivers IP + [Segment : Data file part + checksum] } + Tail (Error check – binary information store) | ||||
| 1 | Hardware(physical) | Bits(binary) | NIC | Physical data conn. B.w device & N/W Card Wifi : Radio Signal < = > Digital SignalOptical Fiber : Light Signal < = > Digital Signal Copper Wire : Electrical Signal < = > Digital Signal |
Model Diagram : (Source: Wikipedia)
