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HTTP (Hypertext Transfer Protocol) Hypertext transfer Protocol is an application protocol for distributed collaboration and multimedia information statistics. HTTP is the communication foundation of Word Wide Web, where html documents point to hyperlinks to other resources that users can easily post, for example, by clicking the mouse or clicking on the screen in a Web browser.

The Development of HTTP Protocol

HTTP/0.9

The first version of http protocol is only suitable for the brief exchange of data information, that is, only text transmission, only GET request mode, and does not support the request header, because it does not support POST mode, most sensitive information can not be exchanged, so the client can not transmit too much information to the server.

Disadvantages: the type of information is too single to meet the demand, serial processing

HTTP/1.0

The first version of HTTP protocol, which specifies the version number in communication, is often used in proxy servers and becomes a transaction-oriented application layer protocol. This protocol requires a connection to be established and dismantled in response to each request. 1.0 introduces POST and HEAD commands, which is a typical serial connection transaction compared to a version that ensures the security of data transmission to a certain extent.

Disadvantages: serial processing, low efficiency

HTTP/1.1

The persistent connection mechanism is introduced and adopted by default, and it works better with the proxy server. It also supports sending multiple requests at the same time under the same connection in the pipeline mode, in order to reduce the line load and improve the transmission speed. New methods: PUT, PATCH, OPTIONS, DELETE

Disadvantages: in the same TCP connection, all communications are carried out sequentially, and the server can only process responses sequentially. If the previous processing is too slow, many requests will be queued, resulting in head-of-line blocking (Head-of-line blocking).

HTTP/2.0

Header information and data body are binary, called header information frame and data frame.

Multiplexing TCP connections, in which both the client and the browser can send multiple requests or responses at the same time without having to correspond one by one in order, thus avoiding "head-of-line congestion". This two-way real-time communication is called Multiplexing.

The header information compression mechanism (header compression) is introduced, in which the header information is compressed by gzip or compress and then sent; both the client and the server maintain a header information table, all fields are stored in this table, and an index number is generated. Instead of sending the same field, only the index number is sent to improve the speed.

HTTP/2 allows the server to actively send resources, namely server push (server push), to the client without request.

Add:

The HTTP protocol is stateless and the server cannot trace the source.

Solution method

Cookie client storage

Session server storage

HTTP transaction: the process of one visit

Request: request

Response: response

The relationship between HTTP2.0 and SPDY

HTTP2.0 is an upgraded version of SPDY

HTTP2.0 supports plaintext HTTP transmission, while SPDY enforces the use of HTTPS

The compression algorithm for HTTP2.0 headers uses HPACK instead of DEFLATE, which is adopted by SPDY

Brief comparison diagram of HTTP protocol connection

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