What is a gateway? Common Gateway Types

　　1, what is the gateway

According to different classification criteria, there are many kinds of gateways. The gateway in the TCP/IP protocol is the most commonly used, where we speak of "gateways" that refer to the TCP/IP protocol gateway. What is a gateway? A gateway is essentially a network IP address that leads to other networks. For example, network A and network B, network A's IP address range 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 "and the subnet mask is 255.255.255.0. In the absence of a router, TCP/IP traffic is not possible between two networks, even if the two networks are connected to the same switch (or hub), and the TCP/IP protocol determines that the hosts in the two networks are in different networks based on the subnet mask (255.255.255.0). To achieve communication between the two networks, you must pass through the gateway. If the host in Network a discovers that the destination host of the packet is not on the local network, the packet is forwarded to its own gateway, and then the gateway is forwarded to Network B's gateway, and Network B's gateway is forwarded to a host of network B (as shown in the attached figure). The same is true for Network B's forwarding of packets to network A. Therefore, only if the IP address of the gateway is set up, TCP/IP protocol can realize the communication between different networks. So what is the IP address of the machine? The IP address of the gateway is the IP address of the device with the routing capability, and the device with the routing capability has a router, a server with a routing protocol enabled (essentially the equivalent of a router), a proxy server (also equivalent to a router).

A gateway is a facility operated on the OSI Transport layer in an interconnection network, so called a facility because the gateway is not necessarily a device, and it is possible to implement gateway functionality in a single host. Of course, also do not rule out the use of a computer to specifically implement the Gateway has the protocol conversion function.

Because gateways are the facilities for interconnection, interoperability, and application interoperability. Often it is used to connect proprietary systems, so there has never been an advertisement or company selling gateways on the market. So, in this sense, a gateway is a concept, or a function of abstraction. The scope of the gateway is very wide, in the TCP/IP network, the gateway is sometimes referred to as the router, while in the MHS system, in order to achieve ccittx.400 and smtpl Simple Mail Transport protocol interoperability between the concept of the gateway. SMTP is the e-mail message used in the TCP/IP environment, the standard is RFC-822, and the ccittx.400 that conform to international standards are developed later, but they are supported by Europe-pioneer worldwide. To interconnect the two systems, the TCP/IP standard-setting group specifically defines the transformation standard RFC987 between X.400 and RFC-822 (for 1984 X.400) and RFC1148 (for 1988 X.400). The facilities for implementing the above transformation standard are also called gateways.

　　2. Common Gateway Types

(1) Internet gateway: In the Internet, the previous gateway is now called a router. Gateway now refers to a system that transforms network and application protocols so that users and applications on both TCP/IP and non-TCP/IP networks can communicate with each other. NET Guan Ye refers to the translation device between applications. A proxy server gateway is a firewall that allows users of the intranet to access the Internet while prohibiting Internet users from accessing the intranet. A full-featured firewall provides advanced screening, authentication, and proxy capabilities to prevent hackers and attackers from entering the internal system.

(2) LAN Gateways: LAN gateways provide a channel for data transfer between LANs. Typically, an intermediary LAN uses a different protocol, and the data needs to be converted to pass. Many routers provide Ethernet connections to FDDI and can act as such. In addition, there are gateways that provide AppleTalk with TCP/IP, IPX, and TCP/IP protocol conversions.

(3) IBM host Gateway: Connects LAN workstations to IBM host systems. The first gateway simulates the IBM host's 320 terminals, making the LAN workstation a terminal for the host. A more complex gateway allows a PC to transfer files between hosts, or a client/server run mode that allows a PC to access the host's database. IBM's APPN protocol provides the same-tier networking services that make hosts part of the network. The current trend is that hosts also support TCP/IP, connect directly with TCP/IP or through a Web server to users, and no longer require a dedicated gateway.

(4) e-mail Gateway: Responsible for the conversion of mail information between different vendor applications, enabling users to share letters from different e-mail applications on the Web. A common e-mail gateway converts private information formats into X.400 formats.