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How to enable QUIC on LiteSpeed Web Server

QUIC (or, Quick UDP Internet Connection) is an experimental protocol initially developed by Google in 2012, and announced publicly the following year. QUIC is a good choice for those looking to reduce connection-establishment time and improve congestion control. Since version 5.2, LiteSpeed provides the first production-grade mass-market QUIC implementation available for the public. If you want to serve your web content using the QUIC protocol, LiteSpeed is the solution.

The followings explain the requirements and steps to enable QUIC on LSWS.

Enabling QUIC is easy

To enable QUIC, there is no configuration change in LSWS. For control panel, QUIC is turned on by default for Apache HTTPS vhosts.

All user need to do is open UDP port 443.

Firewall Configuration

QUIC itself should auto listen on 443 on UDP. The only thing you should do is to open it in any firewall they may be running.

QUIC (Quick UDP Internet Connections) runs a stream-multiplexing protocol over Transport Layer Security (TLS) on top of UDP instead of TCP. Be sure you've enabled the port with both TCP and UDP.

Most of the time, tcp 443 should have been enabled. You will need to identify which firewall is running, such as firewalld, iptables, csf, or even any external firewalls.

You can quickly check to make sure it is listening by running

netstat -lupn | grep 443

How to verify QUIC is enabled

Understanding QUIC

Requirements

Understanding the Priority of the Settings

QUIC can be enabled or disabled at three different levels. It's important to understand how these settings affect each other.
If QUIC is not explicitly turned off at any level, then priority for enabling QUIC is given at the most specific level: Virtual Host, then Listener, then Server.
If QUIC is explicity turned off at any level, then none of the more specific levels may turn it on. In other words, if QUIC is turned off at the Server level, then it cannot be turned on at the Listener level or at the Virtual Host level.

Put another way:

For a particular Virtual Host, QUIC will be ON if:

For a particular Virtual Host, QUIC will be OFF if:

Here is an example setup:

QUIC Directives