Web server with HTTP collaboration-proxy, Gateway, tunnel

1. Virtual Host

(1) http/1.1 specification allows a single HTTP server to build multiple Web sites;

(2) on the Internet, the domain name through the DNS service mapped to the IP address (domain name resolution) after the visit to the target site, that is, when the request was sent to the server, the IP address is already accessed;

(3) If two domain names are deployed on a single server (the same IP address), the access IP is the same after the DNS service is used to resolve the domain name;

(4) Under the same IP address, the host name or the URI of the domain name must be fully specified in the host header when sending an HTTP request because the virtual host can store multiple Web sites with different hostname and domain names.

2. Agent(1), definition

A proxy is an application that has a forwarding function that acts as a "middleman" between the server and the client, receives a request sent by the client and forwards it to the server, and also receives the response returned by the server and forwards it to the client.

(2), Characteristics

A), the agent does not change the request URI, will be sent directly to the front of the target server holding resources;

b), in the HTTP communication process, you can cascade multiple proxy servers. When forwarding, additional via header fields are required to mark the host information that passes through.

(3), function

Using caching techniques to reduce network bandwidth traffic, the organization's internal access control for specific Web sites, to obtain access logs for the primary purpose.

(4), classification

The agent has two classification baselines: one is whether the cache is used, or whether the message is modified.

A) When the proxy forwards the response, the cache proxy pre-saves a copy of the resource (cache) on the proxy server. When the agent receives a request for the same resource again, it can not get the resource from the source server, but instead returns the previously cached resource as a response.

b) When forwarding a request or response, the proxy type that does not make any processing of the message is called a transparent proxy.

3. Gateway(1), definition

A gateway is a server that forwards traffic to other servers, and when it receives a request sent from a client, it processes the request as if it were a resource server that owns the resource. Sometimes the client is unaware that its communication target is a gateway.

(2), Characteristics

Gateways work in a very similar mechanism to proxies. The gateway enables the server on the communication line to provide non-HTTP protocol services.

Using a gateway can improve the security of the communication because it can be encrypted on the communication line between the client and the gateway to ensure the security of the connection. For example, a gateway can connect to a database and query data using SQL statements. In addition, when a credit card is settled on a Web site shopping site, the gateway can be linked to the credit card clearing system.

4. Tunnel(1), definition

A tunnel is an application that relays between a client and a server that is far apart and maintains a communication connection between the two sides.

(2), Characteristics

The tunnel itself does not parse the HTTP request, which is the server that the request remains as it was transferred to.

Web server with HTTP collaboration-proxy, Gateway, tunnel