As we all know, walking from one room to another is bound to go through a door. Similarly, sending information from one network to another must go through a "gateway", that is, a gateway. As the name implies, a gateway is a "gateway" for one network to connect to another. ?
There are many kinds of gateways according to different classification standards. The gateway in TCP/IP protocol is the most commonly used, and the "gateway" we say here refers to the gateway under TCP/IP protocol. ?
So what exactly is a gateway? A gateway is essentially the IP address of a network to other networks. For example, there are network A and network B, and the IP address range of network A is "192.168.1~192." 168. 1.254 ",and 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 255.255.0. Without a router, there would be no TCP/IP communication between the two networks. Even if two networks are connected to the same switch (or hub), the TCP/IP protocol will determine that the hosts in the two networks are in different networks according to the subnet mask (255.255.255.0). In order to realize the communication between the two networks, it is necessary to 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 will forward the packet to its own gateway, which will then forward the packet to the gateway in network B, which will then forward the packet to the host in network B (as shown in the attached figure). 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 realize the communication between different networks. So which machine's IP address is this IP address? The IP address of gateway is the IP address of devices with routing function, including routers, servers with routing protocol enabled (essentially equivalent to routers) and proxy servers (also equivalent to routers).
With what? Novell？ NetWare？ Where is the gateway in the context of network interoperability? Windows？ Server information blocks used in the network? (SMEs)? Agreement and? NetWare？ Internet use? NetWare？ Core agreement? (NCP)？ It acts as a bridge. Gateway is also called. IP？ Router.
What is the function of computer host gateway?
Suppose your name is Tiny, you live in a big yard, your neighbors have many small partners, and there is a janitor at the door. Uncle Li is your door. When you want to play with your little friend in the yard, as long as you call his name in the yard, he will respond to you and run out to play with you.
But you are not allowed to go out of the gate. If you want to have any contact with the outside world, you must contact Uncle Li (gateway) at the door by telephone. I want to chat with my classmate Xiao Ming. Xiao Ming lives in another yard far away, and there is also a doorman in his yard (at Xiao Ming's door). But you don't know Xiaoming's telephone number, but your class teacher has a list of all the students in your class and a telephone number comparison table. Your teacher is your DNS server. So you dialed the telephone of Uncle Li's house and had the following conversation:
One inch: Uncle Li, can I ask the class teacher to check Xiaoming's phone number?
Uncle Li: OK, you wait. (Then Uncle Li hung up a phone call to your class teacher and asked for Xiao Ming's phone number. ) Yes, his home phone number is 2 1 1.99.99.99.
Xiaoyi: Great! Uncle Li, I'm looking for Xiaoming. Please help me contact Xiaoming again.
Uncle Li: No problem. (Then Uncle Li sent a request to the telephone office to connect Xiao Ming's home phone. The last pass is, of course, transferred to Uncle Wang in Xiaoming's yard, and then Uncle Wang transferred the phone to Xiaoming's home. )
So you contacted Xiao Ming.
Solve cross-gateway technology?
The current IP address of IPV4 is 32 bits, which can be divided into three types according to the first few bits: A, B and C; However, due to the rapid development of the Internet, IP resources are increasingly exhausted, and there are fewer and fewer IP addresses available for allocation, which seriously conflicts with the rapid development of the Internet. In the case that IPV6 is far from being fully upgraded, Internet access can only be realized if the proxy server converts the internal network address and the public network address. ?
The proxy server acting as an intermediary is a gateway, which brings endless troubles to the multimedia communication system at this stage. In the case of poor IP resources, the only way to access broadband networks is to use gateways or even multi-layer gateways. Because the protocol of multimedia communication system, such as H.323, must have the IP address of public network, but how many broadband users can meet this requirement now? Microsoft's NETMEETING and other multimedia communication systems are in this embarrassing situation; Crossing the pass has become a headache. ?
Cross-gateway: Network data passes through layers of gateways, which is limited by the speed of gateway nodes, and the network speed is greatly reduced. ? Cross-gateway technology is based on the underlying network protocol, which breaks through the bottleneck of gateway and realizes customer point-to-point communication. ?
What is the default gateway?
If you figure out what a gateway is, the default gateway will be easy to understand. Just as a room can have multiple doors, a host can also have multiple gateways. Default gateway means that if the host can't find an available gateway, it will send the packet to the default gateway, and the default gateway will process the packet. The gateway used by the host now usually refers to the default gateway.
[1][2] gateway type
1, transport gateway. The transmission gateway is used to establish the transmission connection between two networks. By using the transport gateway, hosts on different networks can establish cascaded point-to-point transport connections across multiple networks. For example, the commonly used router is the transmission gateway. The function of "gateway" is to connect two different network segments or two different routing protocols, such as RIP, EIGRP, OSPF, BGP, etc.
2. Application gateway. The application gateway performs protocol conversion at the application layer. For example, one host is implementing the ISO e-mail standard, and the other host is implementing the Internet? E-mail standard, if these two hosts need to exchange e-mail, they must go through an e-mail gateway for protocol conversion. This e-mail gateway is an application gateway. For example, in and? Novell？ NetWare？ Where is the gateway in the context of network interoperability? Windows？ Server information blocks used in the network? (SMEs)? Agreement and? NetWare？ Internet use? NetWare？ Core agreement? (NCP)？ It acts as a bridge. NCP is a protocol working in the seventh layer of OSI, which is used to control the interaction between client station and server, and mainly completes the functions of opening, closing and reading files in different ways.
Now the classification of gateway products is more and more detailed, including signaling gateway, trunk gateway and access gateway:
Signaling gateway SG is mainly used to relay signaling messages between No.7 signaling network and IP network. At the beginning of 3G, messages (RANAP message between 3G and BSSAP message between 3G and 2G) can be passed between access side and core network switch, and ISUP message can also be passed between MSC/GMSC of 2G and soft switch. ?
Trunk gateway, also known as IP gateway, is a VoIP device that meets the needs of telecom operators and enterprises. Trunk gateway (IP Gateway) is built on the basis of relay board and media gateway board. The single board can provide at most 128 media conversion, two Ethernet ports, and the framework adopts the industry-leading CPCI standard, which is convenient to expand and has the characteristics of high stability, high reliability, high density and large capacity.
Access gateway is a media access gateway for voice/fax services based on IP, which provides efficient and high-quality voice services and VoIP solutions for operators, enterprises, communities and residents.