Hub, also known as HUB, working in the OSI seven-layer structure of the first layer of the physical layer, belonging to the *** enjoyment of the type of equipment to receive data broadcasting sent out in the local area network are generally star-connected topology, each workstation is connected to the hub. Due to the hub's bandwidth *** enjoyment characteristics lead to network utilization efficiency is extremely low, generally in large and medium-sized network will not be used to the hub. Now the hub is basically a full-duplex mode, the common hub transmission rate on the market are generally 100Mbps.

Switch

Switch as the name implies to switch as the main function, working in the OSI layer 2 (data link layer), according to the MAC address of the data forwarding. Each port of a switch belongs to a conflict domain, while all ports of a hub belong to a conflict domain. The switch analyzes the packet header information of the Ethernet packet (which contains the source MAC address, destination MAC address, message length, etc.), obtains the destination MAC address, looks up the address cross-reference table stored in the switch (the port corresponding to the MAC address), confirms which port the NIC with this MAC address is connected to, and then sends the packet to the corresponding port, effectively suppressing IP broadcasting Storm. And the information packets are in parallel state, which is more efficient.

The switch's forwarding delay is very small, mainly due to its hardware design mechanism is very efficient, in order to support the maximum data transfer rate of each port, the backplane bandwidth of the switch's internal forwarding packets must be much larger than the port bandwidth, with a strong overall throughput rate, in order to provide higher bandwidth for each workstation and higher network utilization, which can meet the requirements of large-scale network environments for large amounts of data processing.

Three, router

Router with hubs and switches are different, is working in the third layer of OSI (network layer), according to the IP address forwarding packets. A router is a network device that can connect multiple networks or network segments, converting data information between different networks or network segments (e.g., a LAN - a large network) and assigning the most appropriate path for packet transmission so that data can be transmitted between them to form a larger network.

Routers have two primary functions, the data channel function and the control function. The data channel function includes forwarding decisions, backplane forwarding, and output link scheduling, which are generally accomplished by specific hardware; the control function is generally realized by software, including information exchange with neighboring routers, system configuration, and system management.

Four, Repeater

Repeater (Repeater) work in the first layer of the OSI (physical layer), the repeater is the simplest network interconnection equipment, connecting the same network of two or more network segments, the main completion of the physical layer of the function is responsible for the physical layer in the two network nodes to transmit information by bit, to complete the replication of signals, adjustments and amplification of the function, thus increasing the distance of signal transmission, extending the distance of signal transmission. This increases the distance of signal transmission, extends the length and coverage area of the network, and supports long-distance communication.

Generally, the portion of the network at each end of a repeater is a network segment, not a subnet. Repeaters only send data on any cable segment to another segment, and do not care if the data contains erroneous data or data that is not appropriate for the network segment. The most common thing that people come across are network repeaters, and in communications there are also microwave repeaters, laser repeaters, infrared repeaters, and so on, with similar mechanisms and touchstones.

Fifth, the gateway

Gateway (Gateway), also known as the protocol converter, the concept of the gateway is actually not the same type of equipment with the above issues, but for ease of reference or to put it here and introduced.

Gateway is a complex network connection device, can support the conversion between different protocols, to achieve the interconnection between different protocol networks. Gateway has the ability to convert incompatible high-level protocols, in order to realize the communication between heterogeneous devices, the gateway needs to translate and convert different link layer, dedicated session layer, representation layer and application layer protocols. Therefore, gateways have the characteristics of routers, bridges, and repeaters.

To connect two completely different networks (heterogeneous networks) together, a gateway is generally used, and in the Internet the two networks are also interconnected by a computer called a gateway. This computer can be based on the IP address of the user's communication target computer, decide whether to send the information sent by the user out of the local network, at the same time, it will also be sent to the outside world belongs to the local network of computers to receive the information, it is a network with another network connected to the channel. In order for the TCP/IP protocol to address it, the channel is given an IP address, which is called a gateway address.

So the role of a gateway is to be a device that connects two network segments that use different protocols, translating and converting data from the two network segments that use different transport protocols to each other. In interconnecting devices, due to the complexity of protocol conversion, it is generally only possible to perform one-to-one conversion, or conversion of a few application-specific protocols.

Six, bridge

Bridge and switch are working in the same OSI model of the second layer (data link layer), can be regarded as a layer 2 router (the real router is working in the network layer, according to the IP address of the packet forwarding). Bridges effectively connect two local area networks (LANs), forwarding frames based on MAC addresses (physical addresses), limiting local traffic to the segment, and forwarding the appropriate signals to the other segment. Bridges are typically used to connect a small number of network segments of the same type.