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CDN:What is the QUIC protocol?

Last Updated:Sep 22, 2023

The Quick UDP Internet Connections (QUIC) protocol provides enhanced security for data transmission between clients and points of presence (POPs) and accelerates content delivery. This topic introduces QUIC and the billing rules, and describes how to enable QUIC.

What is QUIC?

QUIC is an experimental transport layer network protocol that provides the same security capabilities as TLS/SSL and reduces connection and transmission latency. QUIC is developed based on UDP and has excellent performance in case of weak network connections. When packet loss and network latency issues are severe, QUIC can still ensure service availability. QUIC can implement different congestion control algorithms at the application layer regardless of the operating system or kernel that is used. Compared with TCP, QUIC supports flexible changes based on service requirements. QUIC is a suitable alternative when TCP optimization encounters bottlenecks.

Alibaba Cloud CDN supports QUIC that is implemented at Layer 7.

QUIC types

Alibaba Cloud CDN supports IETF QUIC and Google QUIC (gQUIC). Supported versions of gQUIC are Q39, Q43, and Q46.

  • IETF QUIC is a standard Internet protocol.

  • IETF QUIC is compatible with gQUIC versions G39, Q43, and Q46. We recommend that you use IETF QUIC.

How it works

The following figure shows how QUIC works with Alibaba Cloud CDN.原理图

Client requirements

QUIC has the following requirements for clients:

  • If you use Google Chrome, you can send QUIC requests to Alibaba Cloud CDN since Alibaba Cloud CDN supports HTTP/3.

  • If you use a self-developed app, the app must be integrated with a network protocol library that supports QUIC, such as lsquic-client, Cronet, ngtcp2, or quiche.

Billing rules

QUIC is a value-added service. You are charged based on the number of QUIC requests. For more information, visit the CDN pricing page.

  • Alibaba Cloud CDN identifies QUIC requests based on whether they are transmitted over UDP.

  • QUIC requests whose header specifies QUIC: Alibaba Cloud CDN identifies whether the request is a QUIC request. If so, you are charged for a QUIC request. If not, you are charged for an HTTPS request.

How to identify QUIC requests

In the following example, Google Chrome is used to show how to identify QUIC requests.

Procedure: Right-click a blank space on a web page and choose Inspect > Network. If the value in the Protocol column of a request is h3-29, the request is a QUIC request.


If the Protocol column is not displayed, refresh the page, right-click a row, and then choose Header Options > Protocol.

The following figure shows that the Protocol column displays h3, which indicates that the request is a QUIC request.