Have you ever introduced PHY as the bottom layer of OSI? So what exactly is OSI? What other architectures are there besides PHY?
What is OSI?
The full name of the OSI model is Open System Interconnect, which is open system interconnection. Before the advent of OSI, there were numerous architectures in computer networks. Open System Interconnect is a network interconnection model studied by the ISO organization.
This architecture standard defines a seven-layer framework for network interconnection, the OSI Open Systems Interconnection Reference Model.
This framework has layers: application, presentation, session, transport, network, data link, and physical.
What is the function of each layer?
Application layer - the operating system or network system provides the interface to access communication services.
Presentation layer - transforms tangible data such as encryption, decryption, compression, and decompression.
Session layer - user-oriented, it manages data relays and handles session process communication between systems.
Transport layer - segments upper layer data and provides end-to-end, reliable transmission.
Network layer - selects appropriate routing and forwarding for packets.
Data Link Layer - combines bits into bytes and bytes into frames, sending and receiving frames using physical address addressing.
physical layer. Transmit bitstream.
The first three layers are part of the lower layers in the OSI model. They create links for network communication.
The fifth to seventh layers in the OSI model handle end-to-end data communication. The fourth layer connects the upper and lower layers.
Each layer has a specific role, provides services to the layer above, and all layers work together.
Network communication can occur in both directions, top-down (at the sending end) or bottom-up (at the receiving end). Not all communication requires all seven layers of OSI. Some only need a specific layer that both parties can use.
This means that you only need to transfer between interfaces and connect repeaters in the physical layer. The connection between routers only needs to pass through the three layers below the network layer.
Usually, the two parties communicate directly with each other and cannot communicate in a one-sided way.
