Doppler effect
The Doppler effect is a phenomenon in which the frequency of the wave received by the observer is different from the frequency emitted by the wave source when the wave source and the observer move relative to each other. The whistle sound of the train rushing over from a distance becomes shrill (that is, the frequency becomes higher, and the wavelength becomes shorter), while the whistle of the train away from us becomes deep (that is, the frequency becomes lower, and the wavelength becomes longer). The phenomenon of the Puller effect also occurs in the ringing of private cars and the ringing of train bells.
Doppler effect (Doppler Shift)
Doppler Shift (Doppler Shift) means that when the mobile station moves in a certain direction at a constant rate, the phase and frequency will change due to the difference in propagation distance. This change is usually called Doppler Frequency shift. It reveals the law that the properties of waves change in motion. The receiving frequency of the wave becomes higher when the wave source moves toward the observer, and the receiving frequency becomes lower when the wave source moves away from the observer.
Doppler effect (Gateway)
Gateway (Gateway) is also called network connector and protocol converter.
Everyone knows that to walk from one room to another, one must pass through a door. Similarly, to send information from one network to another, it must pass a "gateway", which is the gateway. As the name implies, a gateway is a "gateway" connecting one network to another.
The gateway is essentially an IP address from a network to other networks. For example, there are network A and network B, the IP address range of network A is "192.168.1.1-192. 168.1.254", the subnet mask is 255.255.255.0; the IP address range of network B is "192.168.2.1~192.168. 2.254", the subnet mask is 255.255.255.0. Without a router, TCP/IP communication is not possible between two networks. Even if the two networks are connected to the same switch (or hub), the TCP/IP protocol will be based on the subnet mask (255.255). .255.0) Determine that the hosts in the two networks are in different networks. To realize the communication between these two networks, it must pass through the gateway. If the host in network A finds that the destination host of the data packet is not in the local network, it forwards the data packet to its own gateway, which then forwards it to the gateway of network B, and the gateway of network B forwards it to a certain network in network B. Host. The process of network B forwarding data packets to network A is the same.
Therefore, only by setting the IP address of the gateway, the TCP/IP protocol can realize the mutual communication between different networks. So which machine's IP address is this IP address? The IP address of the gateway is the IP address of the device with routing function. The devices with routing function include routers, routing protocol-enabled servers (essentially equivalent to a router), and proxy servers (also equivalent to a router).
The default gateway means that if a host cannot find an available gateway, it will send the data packet to the default designated gateway, and this gateway will process the data packet. The gateway used by the host now generally refers to the default gateway.
Router (Router)
A router (also known as a router) is a telecommunications network device responsible for path finding. It provides two important mechanisms: routing and forwarding. It can determine the routing path (between host and host) that a data packet traverses from source to destination. Transmission path), this process is called routing; the data packet at the input end of the router is transferred to the appropriate output end of the router (inside the router), which is called forwarding.
It finds a network path with the least amount of communication from multiple paths in the interconnection network to provide users with communication. Routers use static routing or dynamic routing to determine the shortest path between networks. Static routing needs to be manually set by the administrator, while dynamic routing uses some protocols to dynamically discover paths between networks and determine the shortest path. Generally, static routing is used for small networks, and dynamic routing is used for large complex networks.
Routers are used to connect multiple logically separated networks. To provide users with the best communication path, the router uses a routing table to select a path for data transmission. The routing table contains a list of network addresses and distances between addresses. The router uses the routing table to find the correct path for the data packet from the current location to the destination address. The router uses the least time algorithm or the optimal path algorithm to adjust the path of information transmission. If a network path fails or is blocked, the router can choose another path to ensure the normal transmission of information. Routers can convert data formats and become necessary equipment for network interconnection between different protocols.
The router uses the path finding protocol to obtain network information, and uses the path finding algorithm and criteria based on the "path finding matrix" to select the optimal path. According to the OSI reference model, the router is a network layer system. Routers are divided into single-protocol routers and multi-protocol routers.
For example, the ones you mentioned are more popular: if you give you an IP address of 116.24.143.126 and a subnet mask of 255.255.255.224, that is, there are 32 addresses in this address, 30 of which are available, remove Gateway, there are 29 assignable. The address is from 116.24.143.96-127, the first available IP is 97, and the last is 126. In this example, you use 126 as the gateway, so 29 from 97 to 125 Addresses can be allocated by you. Similarly. 116.24.143.126, mask 255.255.255.0, then you have 253 addresses that can be allocated by you. That is 1-125, 127-254. 116.24.143.166, the mask is 255.255.255.128, that is, there are 125 addresses that can be allocated by you. That is, 129-165,167-254. How many addresses are available in each segment, not the last digit of the IP, but the subnet mask
1. The gateway is the network A role in refers to an exit in a "network".
2. A router is a device.
3. The router can realize the function of a gateway, but the router function is not only a gateway
4. The gateway can be realized by a router, but also Not only implemented by routers