Gateway

Gateway also known as gateways, protocol converters. Gateway at the transport layer to achieve network interconnection, network interconnection is the most complex equipment, only two high-level protocol for interconnection of different networks. Both can be used for wide area network gateway interconnects can also be used for LAN interconnection. Conversion is a responsibility to act as the gateway computer system or device. In the use of different communication protocols, data format or language, or even completely different architecture between the two systems, the gateway is a translator. And the bridge to convey information simply different, the gateway to the information received to re-packaged to suit the purpose systems. Meanwhile, the gateways can also provide filtering and security features. Most gateway protocol running on top of OSI 7 layer - application layer.
We all know, from one room to another room, must go through a door. Similarly, from one to another network to send information, but also must go through a "gateway", which is the gateway road crossings. As the name implies, Gateway (Gateway) is a network connection to another network's "gateway."
In OSI, the gateway there are two: one is connection-oriented gateway, a gateway is no connection. When the distance between the two subnets, often a gateway into two halves, separated by a connecting link, which we call half-gateway.
According to different classification criteria, there are many gateways. TCP / IP protocol in the gateway is the most commonly used, here we are talking about "gateway" refer to TCP / IP protocol under the gateway.
So the gateway in the end what is it? Gateway is essentially a network IP address leading to other networks. Such as a network A and network B, network A, the range of IP addresses "192.168.1.1 ~ 192. 168.1.254", a subnet mask of 255.255.255.0; network IP address range B, "192.168.2.1 ~ 192.168. 2.254 ", a subnet mask of 255.255.255.0. The case in the absence of a router, between two networks can not be TCP / IP communications, even if the two networks connected to the same switch (or hub), TCP / IP protocol will be based on the subnet mask (255.255.255.0) to determine the two hosts on the network in a different network in the. In order to achieve communication between two networks, it must be through the gateway. If the host A network packet that the destination host is not on the local network, put forward the packet to its own gateway, and then forwarded by the gateway the gateway to the network B, network gateway sub-distributed network of B B, a host (such as the photo below). A network B forwards the packet to the network process.
Therefore, only set the IP address of the gateway, TCP / IP protocol to achieve communication between different networks. Then the IP address of the machine which IP address? Gateway IP address is a routing device IP address, routing devices with a router, enable the routing protocol of the server (essentially equivalent to a router), the proxy server (also equivalent to a router).
And Novell NetWare networks in the context of interaction, the network gateway used in the Windows Server Message Block (SMB) protocol and the NetWare Core Protocol NetWare network use (NCP) play a bridge role between. Also known as the gateway IP router.