Intro
| Layer | < | < | Protocol data unit (PDU) | Function |
|---|---|---|---|---|
| Host layers | 7 | Application | Data | High-level protocols such as for resource sharing or remote file access, e.g. HTTP. |
| ^ | 6 | Presentation | ^ | Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption |
| ^ | 5 | Session | ^ | Managing communication sessions, i.e., continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes |
| ^ | 4 | Transport | Segment, Datagram | Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing |
| Media layers | 3 | Network | Packet | Structuring and managing a multi-node network, including addressing, routing and traffic control |
| ^ | 2 | Data link | Frame | Transmission of data frames between two nodes connected by a physical layer |
| ^ | 1 | Physical | Bit, Symbol | Transmission and reception of raw bit streams over a physical medium |
Layers
Layer 1: Physical layer
Deals with the physical equipment involved in the network, such as cables and switches. It converts data into bits and transmits them over the network
Layer 2: Data link layer
Provides node-to-node data transfer, detecting and possibly correcting errors that may occur in the Physical layer. It packages bits into frames.
Layer 3: Network layer
Responsible for logical addressing and routing data between networks. It packages frames into packets.
Layer 4: Transport layer
Ensures complete data transfer. It segments and reassembles data into packets and provides error checking and flow control.
Layer 5: Session layer
Establishes, maintains and synchronizes communication sessions between applications. It provides checkpointing, restart and restart capabilities.
Layer 6: Presentation layer
Defines data formats, encryption, compression and conversions for application layer.
Layer 7: Application layer
Serves as the interface for network services to applications, such as email, file transfer and terminal emulation.