Schematic HTTP protocol (Chapter Five Web server with HTTP collaboration)

Today I saw the network protocol (5) Web server.

In the second chapter, we understand how a simple client interacts with the server. Now let's see what improvements are being made in practice.

1 Keyword: mapping. This mapping allows the client and server to be separated. A client corresponding to a DNS mapping, and then through the map to send his request to the server, it feels like an ancient matchmaker, she must be in deep harmonic two habits of thinking. Translate this word "map" to the other side.

22 big heads OK, so how do they communicate? Yes, by mapping. But who's going to do it? That leads to the few small meat. Proxies, gateways, and tunnels.

Look at the agent first. The agent is like a middleman, because sometimes the client and the server is far away, such as you in the Yangtze River head, I am in Sicily. What to do? This can be done by proxy, something like a file broker. Then a section of the request passed, the Red man riding a concubine smile, no one knows is litchi.

That's the reason. So, since it's a transit point, it's the inn that can make the request for a temporary stop. So what does he do? Since it's a pub. Then there must be some features. Like what:

"Cache function", the Inn is not to let people rest and recharge, so he can put resources, so as to communicate.

"Transparent and opaque features". Is that some inn in order to promote their own brand, in the guest (request) walk will send some of their own inn as a promotion, such as send a pocket above the "Tong Fu Inn" or something.

Say another one: the Gateway. You can think of network management, check, in short, he gives a person's feeling is to be able to check that feeling. Let me see what the gateway is.

(from 360 Questions and answers, address http://wenda.so.com/q/1367802894068897) Gateways are also known as inter-network connectors and protocol converters. Gateway on the transport layer to achieve network interconnection, is the most complex network interconnection devices, only for two high-level protocols different network interconnection. Gateways can be used for both WAN interconnection,

can also be used to interconnect LAN. A gateway is a computer system or device that acts as a transformation task. The gateway is a translator between two systems that use different communication protocols, data formats or languages, and even architectures that are completely different. Unlike bridges, which simply convey information, the Gateway will repackage the information received,

To meet the needs of the target system. The gateway can also provide filtering and security features. Most gateways run on the top layer of the OSI 7 layer protocol-the application layer.

Like a door, responsible for filtering and security, in fact, agents have these functions.

Next look at the tunnel. This is a program that is responsible for providing security features.

His characteristic is, to be foolish, because he does not parse the HTTP protocol, can only transfer the request intact. But he can provide encryption mechanism and security mechanism, is not very reassuring? This will allow you to defend against many attacks.

Next, say, cache.

The cache is divided into

Proxy Server cache (INN)

Client-Side Caching

But the cache has a time limit, and when the deadline is exceeded, he goes to the server to request resources. To achieve common progress in a timely manner.

Schematic HTTP protocol (Chapter Five Web server with HTTP collaboration)