What is a gateway?

What is a gateway?

Gateway (Gateway) is also known as network connector and protocol converter. The gateway is on the transport layer to achieve network interconnection. It is the most complex network interconnection device and is only used for the interconnection of two networks with different high-level protocols. The structure of the gateway is also similar to the router, except for the interconnection layer. The gateway can be used for both WAN interconnection and LAN interconnection.

What is the gateway? how to use? Is it related to the router?
Answer: The gateway is Gateway, which is a device that connects networks based on different communication protocols so that files can be transferred between these networks. In addition to transmitting information, the gateway converts this information into a form approved by the protocol used by the receiving network. It has a close relationship with routers.

Everyone knows that walking from one room to another must pass through a door. Similarly, when sending information from one network to another, it must pass through a "gate", which is the gateway.

What is a gateway, as the name implies, a gateway is a "gateway" where one network connects to another network.
[Gate of two different protocol networks]

According to different classification standards, there are many kinds of gateways. The gateway in the TCP / IP protocol is the most commonly used. Here, the "gateway" refers to the gateway under the TCP / IP protocol.

So what exactly is a gateway? The gateway is essentially the IP address of a network that leads to other networks-for a long time, is the gateway an address?

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, there is no TCP / IP communication between the 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 on different networks. To achieve communication between these two networks, you must pass through the gateway.

If the host in network A finds that the destination host of the packet is not in the local network, it forwards the packet to its own gateway, and then the gateway forwards it to the gateway of network B, and the gateway of network B forwards it to some of network B. Host (as shown in the figure). The same is true for the process of network B forwarding packets to network A.

Therefore, only by setting the IP address of the gateway can the TCP / IP protocol communicate with each other. So which machine's IP address is this IP address?
The IP address of the gateway is the IP address of a device with a routing function. The device with a routing function includes a router, a server with routing protocols enabled (essentially equivalent to a router), and a proxy server (also equivalent to a router).

The gateway cannot be completely classified as a kind of network hardware. In general terms, they should be a combination of software and hardware that can connect to different networks. In particular, they can connect two systems using different formats, communication protocols, or structures. The gateway actually repackages the information so that they can be read by another system. In order to accomplish this task, the gateway must be able to run on several layers of the OSI model. The gateway must communicate with the application, establish and manage sessions, transmit the encoded data, and parse the logical and physical address data.

The gateway can be set on the server, microcomputer or mainframe. Because gateways have powerful functions and are mostly application-dependent, they are more expensive than routers. In addition, because the transmission of gateways is more complex, they transmit data at a lower speed than bridges or routers. Because of the slowness of the gateways, they may cause network congestion. However, on certain occasions, only the gateway can do the job. In your online career, you will most likely hear a discussion about gateways in an email system environment. Common gateways, including email gateways, are described as follows:
Email gateway: Through this gateway, data can be transferred from one type of system to another. For example, an email gateway can allow people using Eudora email to communicate with people using Group Wise email.
IBM mainframe gateway: Through this gateway, communication can be established and managed between a personal computer and an IBM mainframe.
Internet Gateway: This gateway allows and manages access between the local area network and the Internet. Internet gateways can restrict certain LAN users from accessing the Internet. vice versa.
LAN gateway: Through this gateway, LAN segments running different protocols or operating on different layers of the OSI model can communicate with each other. The router can even act as a LAN gateway with just one server. The LAN gateway also includes a remote access server. It allows remote users to access the LAN by dialing.

In order to facilitate friends to understand the "gateway", today I added several explanations from other websites, the meaning is the same, the expression is different.

Solve cross-gateway technology

Why use a gateway?

The current IPV4 IP address is 32 bits, and is divided into three types of addresses according to the first few digits: A, B, and C. However, due to the rapid development of the Internet, IP resources are gradually depleted, and fewer and fewer IPs are available for distribution. There is a serious conflict with the development of the Internet for a long time. In the case where IPV6 is still far from being fully upgraded, only the proxy server can be used to implement the conversion of the internal network address and the public network address to achieve access to the Internet.

The intermediary proxy server is a gateway, that is, this gateway brings endless troubles to the current multimedia communication system. In the case of poor IP resources, the only way to access the broadband network is through a gateway or even a multi-layer gateway, because the multimedia communication system protocols such as H.323 and other parties who want to conduct business must have one party with a public IP address, but now How many users of broadband can meet this requirement? MICOSOFT's NETMEETING and other multimedia communication systems are in this awkward position; cross-gateway becomes a headache.

Cross-gateway: The network data passes through layers of gateways, subject to the speed of the gateway node, and the network speed is greatly reduced. The cross-gateway technology is based on the underlying network protocol, breaking through the gateway bottleneck and realizing customer point-to-point communication.