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This article shares with you the content of the sample analysis of HTTP3. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

HTTP3 is the latest version of the HTTP protocol. Since its inception, HTTP has been the preferred application layer protocol for exchanging hypertext documents. Over the years, HTTP has made several major upgrades to keep up with the development of the Internet and the increase in the types of content exchanged on WWW, and HTTP/3 is the latest version.

HTTP 2 problem

The previous article has introduced HTTP 2 as a whole, so this article only talks about the problem of HTTP/2.

In the case of using TCP at the bottom, the slow start of TCP and the sharp decline of performance caused by unreasonable setting of congestion window size have not been solved. Gene here, can not change HTTP 2 multiplexing only reduces the number of connections, the problem of head-of-line blocking has not been completely solved. If the packet loss rate of TCP exceeds 2%, the performance of HTTP1.1 will not be as good as that of HTTP. Because HTTP1 is a separate TCP connection, the comparison is shown in the following diagram:

HTTP 3

HTTP 3 is developed based on QUIC. The bottom layer uses UDP for data transmission, but the upper layer still uses HTTP/2. There is a QUIC layer before HTTP2 and UDP, and the TLS encryption process is handled in this layer. There are two versions of QUICK. The QUIC at the head of the early Google is called gQUIC,IETF standardization and then IQUIC. Compared with HTTP, the overall HTTP/3 is as follows:

The comparison of the entire HTTP family is as follows:

HTTP3 features:

Using UDP as the transport layer to communicate ensures the security of the protocol itself. QUIC completes the TLS encrypted handshake to establish the connection in the process of establishing the connection. Normally, only 1RTT is needed to establish the connection. If the previous secret information is cached, the connection is verified and established directly, which is the process of 0RTT. A connection can also be established with a small amount of business data. Instead of binding to the specific underlying connection, QUIC allocates a unique ID to both ends of each connection, and the upper connection only recognizes this pair of logical ID. When the network is switched or disconnected, you only need to continue to send packets to complete the establishment of the connection. Use QPACK for header compression, because HPACK requires an orderly transmission process, which will lead to head-of-line blocking. However, this problem does not exist in QPACK. HTTP/3 defines a new header:Alt-Svc: H4 = ": 20003" in header: it means that the server has opened a port 20003 on port 20003 for HTTP/3 service supplement.

Use the following code to determine whether HTTP/2 is used or not

(function () {/ / guarantee that this method only executes if (window.chrome & & typeof chrome.loadTimes = 'function') {var loadTimes = window.chrome.loadTimes (); var spdy = loadTimes.wasFetchedViaSpdy; var info = loadTimes.npnNegotiatedProtocol | | loadTimes.connectionInfo in chrome browsers that support loadTimes / / use "h3" as the identification if (spdy & & / ^ h3/i.test (info)) {return console.info ('this site uses HTTP/2');}} console.warn (' this site does not use HTTP/2');}) ()

Thank you for reading! This is the end of this article on "sample Analysis of HTTP3". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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