Introduction to Agency services

Forward Proxy

If not specifically stated, the general Agent technology refers to forward proxy, that is, the forward agent. The proxy server is located between the client and the server (server), and in order to obtain the content from the server, the client sends a request to the proxy server and specifies the target server, then the proxy The server forwards the request to the server and returns the obtained content to the client. Typically, the client must have a certain configuration (such as configuring the IP address, port of the forward proxy) before the forward proxy can be used.

Application Scenarios :

1. access to the local server is not directly accessible , the most common scenario is: Enterprise intranet access to the Internet, Proxy server has two network cards, a piece of the network is configured to address, a piece is an external network. The company does not allow the intranet to access the Internet directly, by configuring the agent in the browser to access the Internet through the proxy.
2. caching , this very common, Internet site performance improvement tool. Server-side data will be cached on the agent, on the one hand speed up the user's access speed, on the other hand, but also reduce the consumption of network bandwidth.

3. Access Authorization , client A/b to access the server, but need to be authorized to, if the proxy server is configured with a allow, B deny rules, then a through the proxy can access the server, and B access, because the unauthorized, the packet arrives at the proxy, the packet is discarded directly.

Transparent proxy

The literal meaning is that the client does not know that there is a proxy server, and proxy server modifies the content of your request and transmits the real IP.

Application Scenarios :

The company now accesses certain websites. For example, to avoid employee work hours browsing the shopping site, a company blocked access to those sites. When employees connect to the Web, they get a "not allowed access" prompt when they visit these sites. This is the application of transparent proxies. The company inserted a transparent proxy in the middle of the network and the outside network, and set the rule of forbidden access on the proxy, and the request to match the rule was redirected to the prompt page by crawling the request content.

Reverse Proxy

Use an example to understand the reverse proxy. We have a server with a domain name of www.dt.com, which can easily cause the server to be unsafe if a malicious user tries to attack the server by technical means. In this way, a proxy server is added between the malicious user and the server to impersonate the server, and the firewall policy is set on the server, which only allows the proxy server to access the server, then for the malicious user, proxy The server is the server he wants to destroy, so it can protect the real server. The function that proxy server implements here is the reverse proxy.
Application Scenarios :

1. load balancing , such as the common Apache/nginx implementation of the reverse proxy and load balancing, the proxy service can determine the request to which machine room according to the source of the request, and according to the configured policy, so that the computer room in the same amount of access to each of the machines.

2. The original server masquerading , the user accesses the www.dt.com, the request produces the URL is Http://www.dt.com?query=jay, after the DNS resolves the domain name, the request is sent to the B server, the B server receives the request, The URL is reorganized into a http://1.1.1.1?query=jay, sent to a server, a machine receives the request, the firewall checks whether the request is from B, if not, a server gets Query=jay to process, results result, A server sends result to the B server, and B servers send result to the user. The b server here disguises a to process the user's request.

differences from forward proxies :

For client, Proxy server is the original server, and the client does not need to make any configuration.

Introduction to Agency services