First, we need to analyze the functions of each device in detail:
I. Repeater
Repeater works on the first layer (Physical Layer) of OSI. repeater is the simplest network interconnection device that connects two or more network segments in the same network. It mainly implements physical layer functions, transmits information by bit on the physical layer of the two network nodes to complete signal replication, adjustment, and amplification, thereby increasing the signal transmission distance and extending the network length and coverage area, supports remote communication. Generally, the network segments at both ends of the repeater are network segments rather than subnets. The repeater only sends data from any cable segment to another cable segment, regardless of whether the data contains error data or data unsuitable for the network segment. Most people are exposed to Network Relay. Microwave Relay, laser relay, and infrared relay are involved in communication. The Mechanism is similar to that of bypass.
2. The Hub, also known as the hub, works on the first layer physical layer of the OSI Layer-7 structure and belongs to a shared-type device. It receives data broadcast and generally uses a star-connected topology in the LAN, all workstations are connected to the hub. Because of the bandwidth sharing feature of the hub, the network utilization efficiency is extremely low. Generally, the hub is not used in large and medium-sized networks. The current hubs are basically in full duplex mode, and the common hub transmission rates on the market are generally 100 Mbps. A hub is a machine that gathers Network cables together, that is, a connector for multiple hosts and devices. The main function of a hub is to connect to the received signal for Synchronous shaping and amplification to expand the transmission distance of the network. It is a form of a repeater. The difference is that a hub can provide multi-port services, it is also called a multi-port repeater. The physical layer of the hub in OSI/RM. The basic function of a hub is information distribution, which distributes all signals received by a port to all ports. Some hubs regenerate weak signals before distribution, and some hubs sort the signal timing to provide synchronous data communication between all ports.
A hub is actually a multi-port repeater. Hubs generally have 4, 8, 16, 24, 32, and other RJ45 interfaces. Through these interfaces, the hub can then complete the "relay" function for the corresponding number of computers (sort out the signals that are not completely degraded, generate a complete signal again, and then continue to transmit ). Because it is in a "center" position in the network, the hub is also called "Hub ".
The working principle of a hub is very simple. For example, a hub with eight ports is connected to eight computers. The Hub is in the "center" of the network and forwards signals through the hub. Eight computers can communicate with each other. The specific communication process is as follows: if Computer 1 needs to send a piece of information to computer 8, when computer 1's Nic sends the information to the hub through twisted pair wires, the Hub does not directly send the information to computer 8. It broadcasts the information and sends the information to the eight ports at the same time, when the computer on the eight ports receives the broadcast information, it checks the information. if it finds that the information is sent to itself, it receives the information; otherwise, it ignores it. Because the information is sent from computer 1 to computer 8, computer 8 will eventually receive the information, this information is not received because it is not its own.
3. As the name suggests, a switch uses exchange as its main function. It works on the OSI Layer 2 (data link layer) and forwards data based on the MAC address. Each port of the vswitch belongs to a conflict domain, while all the ports of the hub belong to a conflict domain. After the switch obtains the target MAC address, find the address table (the port corresponding to the MAC address) stored in the vswitch, confirm the port on which the NIC with this MAC address is connected, and then send the packet to the corresponding port, effectively suppress IP broadcast storms. In addition, the information package is in parallel state, with high efficiency. If the target Mac does not exist, the switch broadcasts all the ports. After receiving the port response, the switch "learns" the new address and adds it to the internal address table. The forwarding delay of a vswitch is very small, mainly because the hardware design mechanism is very efficient. To support the maximum data transmission rate of each port, the bandwidth of the forwarding packet inside the vswitch must be much larger than the port bandwidth, with a powerful overall throughput, each workstation can be provided with higher bandwidth and higher network utilization, meeting the parallel processing requirements of massive data in a large network environment.
4. Both bridge bridges and switches work on the Layer 2 (data link layer) of the OSI model. They can be seen as a Layer 2 router (the real router works at the network layer, forward packets by IP address ). A bridge can effectively connect two LAN networks and forward Frames Based on the MAC address (physical address), so that local communication is restricted within this segment, and forward the corresponding signal to another network segment, the bridge is usually used to connect a small number of, the same type of network segment. Basic Features of bridges 1. the bridge implements LAN interconnection on the data link layer; 2. the bridge can interconnect two local networks that use different data link layer protocols, different transmission media, and different transmission rates. 3. the bridge implements communication between interconnected networks by receiving, storing, filtering and forwarding addresses. 4. the network to be connected by the bridge uses the same protocol above the data link layer. A bridge can separate the traffic between two networks to improve the performance and security of the interconnected network.
5. Different from hubs and vswitches, a router works on the layer 3 (Network Layer) of OSI and forwards data packets according to IP addresses. A vro is a network device that can connect multiple networks or CIDR blocks. It can convert data between different networks or CIDR blocks (such as a LAN-large network, it also allocates the most appropriate path for packet transmission so that data can be transmitted between them to form a larger network. The reason why a router is at a critical position in the interconnect network is that it is at the network layer. On the one hand, it can span different physical network types (DDN, FDDI, Ethernet, etc ), logically, the entire interconnected network is divided into logically independent network units, so that the network has a certain logical structure. The main task of a router is to find an optimal transmission path for each data frame passing through the router and transmit the data to the destination site effectively. The basic function of a vro is to transmit data (IP packets) to the correct network. The segments include: 1. IP datagram forwarding, including datagram path finding and transmission; 2. subnet isolation to prevent broadcast storms. 3. Maintain route tables and exchange route information with other routers. This is the basis for IP packet forwarding; 4. IP datagram error handling and simple congestion control; 5. Filtering and accounting of IP datagram.
Summary: Layer 1: repeater, Hub Layer 2: Switch, bridge Layer 3: Router note: the hub can also be classified as Layer 2 trunk cable according to its function
