The gateway is also called the Internet connector and the protocol converter. Gateway is the most complex network interconnection device that implements network interconnection above the network level. It is only used for two high-level protocols and different network interconnections. Gateway can not only be used for WAN interconnection, but also for LAN interconnection. Gateway is a computer system or device that acts as a transformation task. Gateway is a translator between two systems which are completely different in different communication protocols, data formats or languages. Unlike bridges that simply convey information, gateways repackage incoming information to meet the needs of the target system.
As we all know, going from one room to another is bound to pass through a door. Similarly, sending information from one network to another must go through a gateway, which is gateway. As the name implies, gateway is a gateway that a network connects to another network. That is, the network level.
The gateway is also called the Internet connector and the protocol converter. The default gateway is the most complex network interconnection device on the network layer to achieve network interconnection. It is used for two high-level protocols and different network interconnections. The structure of gateway is also similar to router, which is different from interconnect layer. Gateway can not only be used for WAN interconnection, but also for LAN interconnection.
[Description: for historical reasons, many of the documents about TCP/IP used network layer routers as gateways. In today's many LAN uses access to the network, so the gateway is usually the IP of the router. ]
There are two kinds of gateways in OSI: one is connection oriented gateway, the other is connectionless gateway. When there is a certain distance between the two subnets, a gateway is usually divided into two halves, which is connected by a link in the middle. We call it a half gateway.
According to different classification standards, gateways also have many kinds. The gateway in the TCP/IP protocol is the most commonly used. The gateway we refer to here refers to the gateway under the TCP/IP protocol.
So what is the gateway? Gateway is essentially a network IP address to other networks. For example, there are network A and network B, the IP address of the network A is "192.168.1.1~192. 168.1.254", and the subnet mask is 255.255.255.0; the IP address range of the network B is "192.168.2.1~192.168.2.254", and the subnet mask is 255.255.255.0. In the absence of a router, there is no TCP/IP communication between the two networks, and even if two networks are connected to the same switch (or hub), the TCP/IP protocol also determines that the hosts in the two networks are in a different network based on the subnet mask (255.255.255.0). To achieve the communication between the two networks, we must go through the gateway. If the host in the network A finds that the destination host of the packet is not in the local network, the packet is forwarded to its own gateway, then the gateway is forwarded to the gateway of the network B, and the gateway of the network B is reforwarded to a host of the network B (as shown in the attached diagram). The process of forwarding packets to network B by network A.
Therefore, only by setting up the IP address of the gateway, TCP/IP protocol can realize the communication between different networks. Which machine's IP address is this IP address? The IP address of the gateway is the IP address of a device with routing functions. The devices with routing functions are routers, servers that enable Routing Protocols (essentially a router), and proxy servers (as well as a router).
In the context of interaction with the Novell NetWare network, the gateway plays a bridge between the server information block (SMB) protocol used in the Windows network and the NetWare core protocol (NCP) used by the NetWare network. The gateway is also called a IP router.
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