Shulou(Shulou.com)06/03 Report--

1. Agent (Proxy)

Proxy, also known as network agent, is a special network service that allows a network terminal (usually a client) to make an indirect connection with another network terminal (usually a server) through this service. Some network security devices such as gateways and routers have conditional network agent functionality. It is generally felt that the proxy service is beneficial to ensure the privacy protection or security of the network terminal and avoid attack.

The proxy server is both server and client. The client sends a request message to the agent, and the server agent must, like the network server, properly handle post requests and connections, and then respond back. At the same time, the agent itself sends a request to the server, so it must behave like the correct client, sending the request and receiving the response.

Characteristics of proxy server:

The client doesn't know who the real server is, and the server doesn't know what the client is like.

The client has the same communication protocol with the proxy server, the proxy server and the server.

The proxy server parses the received request, re-encapsulates it and then sends it to the server; after the server responds, it parses the response, re-encapsulates it and then sends it to the client.

2. Gateway (Gateway)

In the computer network, the gateway (English: Gateway) is the network server that forwards the communication data of other network servers. When receiving the post request sent from the client, it processes the request like the source network server with its own resources. Sometimes pc clients may not even realize that their communication target is a gateway.

In traditional TCP/IP terminology, there are only two types of network devices, one is the gateway, the other is the host. Gateways can forward packets between networks, but hosts cannot forward packets. In the host (also known as terminal system, end system), the packet needs to be processed by the TCP/IP four-layer protocol, but in the gateway (also known as intermediary system, intermediate system) only needs to reach the internetwork layer (Internet layer) and determine the path before it can be forwarded. At that time, there was no difference between a gateway and a router (router).

In modern network terminology, the definition of gateway is different from that of router. Gateways (gateway) can move data between different protocols, while routers (router) move data between different networks, which is equivalent to the traditional IP gateway (IP gateway).

The characteristics of the gateway server:

The client doesn't know who the real server is, and the server doesn't know what the client is like.

The communication protocol or version of the communication protocol used between the client and the proxy server, the proxy server and the server is different.

The proxy server parses the received request, converts the protocol and then sends it to the server; after the server response, it parses the response, converts the protocol and then sends it to the client.

3. Tunnel Protocol (Tunneling Protocol)

Tunnel protocol (English: Tunneling Protocol) is a network communication protocol, in which a network protocol (sending protocol) is used to encapsulate a different network protocol in the load part. The reason for using tunneling is to transfer data on incompatible networks or to provide a secure path over insecure networks.

Features of the tunnel:

The protocol is written to carry traffic other than the protocol itself.

Allow data to move from one network to another

Only care about the transmission of the traffic, not parse the carrying traffic

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