HUB, also known as hub, works in the first physical layer of OSI seven-layer structure, belongs to * * * enjoyment equipment, receives data broadcast and sends it out. In a local area network, it is generally a star connection topology, and each workstation is connected to a hub. Because of the bandwidth sharing characteristics of hubs, the network utilization efficiency is extremely low, and large and medium-sized networks generally do not use hubs. At present, hubs are basically full-duplex mode, and the common hub transmission rate in the market is generally 100Mbps.
Second, the switch
As the name implies, the switch takes switching as its main function, works at the second layer of OSI (data link layer) and forwards data according to MAC address. Each port of a switch belongs to a collision domain, while all ports of a hub belong to a collision domain. By analyzing the header information of Ethernet packets (including source MAC address, target MAC address, information length, etc. ), the switch obtains the target MAC address, looks up the address comparison table stored by the switch (the port corresponding to the MAC address), confirms which port the network card of the MAC address is connected to, and then sends the data packet to the corresponding port, thus effectively suppressing the IP broadcast storm. The data packet is in a parallel state, which is efficient.
The forwarding delay of the switch is very small, mainly due to the high efficiency of its hardware design mechanism. In order to support the maximum data transmission rate of each port, the bandwidth of the backboard for forwarding data packets inside the switch must be much larger than the port bandwidth, and it has a strong overall throughput, so as to provide higher bandwidth and higher network utilization for each workstation and meet the requirements of large-scale network environment for parallel processing of a large number of data.
Third, the router
Unlike hubs and switches, routers work at the third layer (network layer) of OSI, addressing and forwarding packets according to IP. Router is a kind of network equipment that can connect multiple networks or network segments. It can convert data information between different networks or network segments (such as LAN-large network), allocate the most suitable path for packet transmission, and make data transmit between them, thus forming a larger network.
Routers have two main functions, namely, data channel function and control function. Data channel functions include forwarding decision, backplane forwarding and output link scheduling, which are generally completed by specific hardware; Control functions are generally realized by software, including information exchange with neighboring routers, system configuration, system management and so on.
Fourth, the repeater
Repeater works in the first layer (physical layer) of OSI. Repeater is the simplest network interconnection equipment, which connects two or more network segments of the same network and mainly completes the functions of the physical layer. Repeater is responsible for transmitting information bit by bit on the physical layer of two network nodes, completing the functions of signal replication, adjustment and amplification, thus increasing the signal transmission distance, extending the network length and coverage area, and supporting long-distance communication.
Generally speaking, the network part at both ends of the repeater is a network segment, not a subnet. The repeater only sends the data on any cable segment to another cable segment, regardless of whether there is wrong data or data unsuitable for the network segment. Network repeater is the most frequently contacted by everyone, including microwave repeater, laser repeater and infrared repeater. In communication. The mechanism is similar, and analogy bypasses.
Verb (abbreviation of verb) gate
Gateway is also called protocol converter. The concept of gateway is actually different from the above equipment types, and it is introduced here for convenience of reference.
Gateway is a complex network connection device, which can support the conversion between different protocols and realize the interconnection between different protocol networks. The gateway can convert incompatible advanced protocols. In order to realize the communication between heterogeneous devices, the gateway needs to translate and convert different link layer, special session layer, presentation layer and application layer protocols. So the gateway has the characteristics of router, bridge and repeater.
In order to connect two completely different networks (heterogeneous networks), gateways are generally used, and the two networks are also interconnected by computers called gateways in the Internet. The computer can decide whether to send the information sent by the user outside the local network according to the IP address of the user's communication target computer. At the same time, it also receives information sent by the outside world to computers belonging to the local network. It is a channel connecting one network with another. In order to make the TCP/IP protocol addressable, the channel is given an IP address, which is called the gateway address.
Therefore, the role of the gateway is to connect two network segments with different protocols and translate and convert the data with different transmission protocols in the two network segments. In interconnected devices, due to the complexity of protocol conversion, generally only one-to-one conversion or conversion of a few specific application protocols can be performed.
Sixth, the bridge
Bridges, like switches, work in the second layer of OSI model (data link layer) and can be regarded as two-layer routers (real routers work in the network layer and forward packets according to IP addresses). Bridge can effectively connect two LANs, forward frames according to MAC address (physical address), limit local communication to this network segment, and forward corresponding signals to another network segment. Bridges are usually used to connect a small number of network segments of the same type.