The function of layered layers of OSI in computer network

Physical Layer:

Define voltage, interface, cable standard, transmission distance, etc., it does not care about what is being transmitted, just a bit of 010011 signal

Physical Layer Media:

Coaxial Cable: Narrow range and rough range

Twisted pair: UTP, STP

Fiber: Singlemode, multimode

Wireless: Infrared, Bluetooth, WLAN technology

Function: Stream bitstream between two terminal devices

Mechanical characteristics, electrical characteristics (voltage, current range, etc.), functional characteristics (the meaning of a voltage or level representation), specifications (order of occurrence of various events, etc.)

Data Link Layer:

Responsible for transmitting data on a particular medium or link.

Framing and recognizing Frames

Data link creation, maintenance and release

Transport resource control (so that it cannot transmit data at the same time but can be used multiplexing technology to achieve simultaneous transmission general time division multiplexing to divide a period into a small segment of a small segment of the points to different users)

Flow control (prevents congestion control traffic on the network)

Error verification (transmission may occur due to some problems in the transmission of the media and physical layer regardless of this matter so the data link layer needs to detect whether there is a mistake)

Addressing (there may be many devices in a local area network that need to send frames to a particular device, so you need to identify the device for addressing)

Identify the upper layer of data (there are many protocols in the network layer so you need to identify the top to whom to handle)

Network layer:

Address addressing, routing, congestion control, various network interconnection

Addressing addresses (each destination has an IP address)

Routing (routers choose the quickest route from the source address to the destination) based on the full-screen map

Congestion control (requires control when traffic is large)

Heterogeneous network interconnection (different networks can communicate with each other)

·· IP addresses can be divided into network addresses and host address network addresses to determine whether the same network must be a full-network unique

Routable protocols: Define the format and purpose of each field within a packet, network encapsulation of data, such as IP protocol and IPX protocol to form IP packets

Routing protocol: Pass information between routers, calculate routes and form routing tables, and select paths for routable protocols. Popular is the protocol that forms the routing table RIP, OSPF, BGP

If host A to and Host B communication first host A sends a message to the application layer encapsulation, and then to the transmission into the package into segments, the incoming network layer encapsulated into a message, the incoming data link layer encapsulated into a frame, and then passed into the physical layer to parse into a bit stream,

Since host A and B are not in the same LAN, the router's port, which is the shortest path that the router finds, is passed from the physical layer to the data link layer, check if the MAC address matches, and then encapsulate the network layer if it matches, and then compare the IP address of the net layer to Destination IP address Then it means to reach the target to continue to pass up, if not to check the router's routing table to find the next router to Pass the past, the IP packet re-encapsulation, to the physical layer, and then to the next router, repeat the above steps to check that the target IP is found Then encapsulate to the application layer to accept:

Transport Layer:

Segment upper-level data (divide the big data from the upper layer into a small piece of data)

Establish an end-to-end connection

Transparent, reliable transmission (check for errors and correct errors or retransmissions)

Flow control

TCP, UDP protocol

The role of layers in the OSI layer of the computer network