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HTTP/2 Protocol Support

Last updated: 2021-01-14 19:01:27

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    What is HTTP/2?

    • HTTP/2 (Hypertext Transfer Protocol Version 2) is a major revision of the HTTP network protocol used by the World Wide Web.
    • HTTP/2 is designed to address the performance issues in HTTP1.X to better use network resources and reduce network application latency.
    • HTTP/2 is backward compatible with HTTP1.X.

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    Why should I use HTTP/2?

    Compared with HTTP1.X, HTTP/2 can make the response be more fast and efficient. HTTP/2 has the following advantages:

    • Multiplex: concurrent processing brings a faster response.
    • Server push: the server proactively pushes resources needed by the client, reducing the number of requests.
    • More features include bandwidth limit, request priority, header compression, and binary framing.

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    How does the billing work?

    CLB supports the HTTP/2 protocol without charging extra fees.

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    How do I enable HTTP/2 on CLB?

    1. Enable HTTP/2 on HTTPS listeners
      • CLB instance: you can enable or disable the HTTP/2 protocol in a CLB instance. For more information, please see Configuring an HTTPS Listener.
      • Classic CLB instance: HTTPS listeners created for a classic CLB instance before April 2018 do not support HTTP/2. HTTPS listeners created after April 2018 support but cannot disable HTTP/2.
    2. Agree on the protocol at client access
      When the client accesses an HTTP/2-enabled listener, the protocol version will be negotiated during the handshake process of HTTPS. The client uses ALPN (Application-Layer Protocol Negotiation) to inform the server of a list of supported protocols. The server selects HTTP/2 or HTTP1.X according to the protocol list. If the client does not support HTTP/2, the server will be automatically backward compatible without requiring additional configuration.


    1. The HTTP listener does not support HTTP/2. Mainstream browsers and web servers only support the TLS-based HTTP/2 protocol.
    2. The HTTP1.X protocol is still used between the CLB instance and the real server.

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    Which regions support HTTP/2?

    Currently, all regions support HTTP/2.

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