Lan features and Topology

Lan features and Topology LAN is a computer network oriented to a small area. It is a computer group interconnected by multiple computers in a certain area. 1. Lan features. (1) The geographical coverage is small. (2) data networks with high speed, short communication delay, low error rate, and high reliability. (3) multiple transmission media are supported. 2. a lan is equivalent to the physical layer and data link layer of the 0SI model. It consists of network hardware (including network servers, network workstations, network printers, network adapters, and network interconnection devices) and network transmission media, and network software. 3. The three most common access control methods for LAN. (1) CSMA/CD (Multi-Channel Access Method for carrier listeners with conflict detection): After first listening, collision avoidance. When you want to send data, first listen to the network for other computers to send data, if so, wait for a while and then re-listen, if not, you can send data. If two or more computers want to send data at the same time, a signal conflict occurs, and information sending is stopped immediately. (2) ring: a ring is only applicable to LAN with a ring topology. It is a non-competing access control method and has a token that loops along the ring, only the token can be sent. If no information needs to be sent when the token is obtained, the token is passed to the next computer. If you do not receive a token when sending a message, the message cannot be sent. (3) Token Bus: Create a logical ring on the physical bus, and then control the access to the logical ring through the Token Ring access control method. 4. Common LAN topology. (1) star topology. (2) bus topology. (3) tree topology. (4) ring topology. 5. Ethernet, the most widely used LAN technology. (1) The main topology used by Ethernet is bus-type topology and star-type topology. (2) Ethernet adopts the IEEE 802.3 standard (Physical Layer connections, electrical signals, and media access layer protocols ). (3) The main physical device used: The Hub (which does not process or check the traffic on it) expands the physical media by distributing the signals received by one port to other ports only, allow all computers in the network to share the same conflict domain, broadcast and bandwidth, and work on the physical layer) and the switch (the network segment connected to each port is an independent conflict domain, working on the data link layer ). (4) Ethernet adopts the CSMA/CD mechanism with conflict detection, and nodes in the Ethernet can see all the information sent in the network. Therefore, we say that Ethernet is a broadcast network. (5) Ethernet can be divided into shared Ethernet (using a hub) and switched Ethernet (using a switch ). 6. Ethernet transmission media. It mainly includes coaxial cable, twisted pair wires, and optical fiber cables.