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This article lists protocols, categorized by the nearest layer in the Open Systems Interconnection model.This list is not exclusive to only the OSI protocol family.Many of these protocols are originally based on the Internet Protocol Suite (TCP/IP) and other models and they often do not fit neatly into OSI layers.
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium.
The PDU is passed to layer N−1, where it is known as the service data unit (SDU). At layer N−1 the SDU is concatenated with a header, a footer, or both, producing a layer N−1 PDU. It is then passed to layer N−2. The process continues until reaching the lowermost level, from which the data is transmitted to the receiving device.
Protocol data units of the OSI model are: [1] The Layer 4: transport layer PDU is the segment or the datagram. The Layer 3: network layer PDU is the packet. The Layer 2: data link layer PDU is the frame. The Layer 1: physical layer PDU is the bit or, more generally, symbol.
OSI model Layer Protocol data unit (PDU) Function [3] 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
Functions of the network layer include: Connectionless communication For example, Internet Protocol is connectionless, in that a data packet can travel from a sender to a recipient without the recipient having to send an acknowledgement. Connection-oriented protocols exist at other, higher layers of the OSI model. Host addressing
Network architects can implement aggregation at any of the lowest three layers of the OSI model.Examples of aggregation at layer 1 (physical layer) include power line (e.g. IEEE 1901) and wireless (e.g. IEEE 802.11) network devices that combine multiple frequency bands.
A network's physical topology is a particular concern of the physical layer of the OSI model. Examples of network topologies are found in local area networks , a common computer network installation. Any given node in the LAN has one or more physical links to other devices in the network; graphically mapping these links results in a geometric ...