Global Accelerator:Use HTTP/3 with Global Accelerator (GA)

QUIC and HTTP/3 features

QUIC (Quick UDP Internet Connections) is a UDP-based, low-latency transport protocol that addresses TCP and TLS performance bottlenecks in high-latency and multiplexed connections.

QUIC is the transport layer for HTTP/3 and is widely adopted by major browsers and web servers.

HTTP/3 use cases

• Web browsing: Reduces page load times for resource-heavy pages through multiplexing.

• Real-time communication: Benefits latency-sensitive applications (instant messaging, video conferencing, online gaming) with fast error recovery.

• Mobile devices: Connection migration handles network switches gracefully, maintaining stable connections.

• Streaming media: Reduces buffering and interruptions for video and audio playback.

• High concurrency: Multiplexing handles large numbers of concurrent requests without HTTP/2's head-of-line blocking.

Supported protocol versions and client requirements

GA supports h3. Ensure your client supports a compatible HTTP/3 version:

• Google Chrome 87 or later. For other browsers, verify HTTP/3 support.

• For other clients (such as self-developed apps), integrate a QUIC-compatible network library such as lsquic-client, Cronet, ngtcp2, or quiche.

How GA and clients negotiate HTTP/3

HTTP/3 is negotiated automatically during the TLS 1.3 handshake — no explicit configuration is needed.

HTTP/3 is a standalone protocol based on QUIC, not an extension of HTTP/1.1 or HTTP/2. Modern clients handle protocol negotiation and fallback automatically.

GA and a client negotiate an HTTP/3 connection as follows:

1. After the Maximum HTTP Version of an HTTPS listener in a GA instance is set to HTTP/3, GA will announce support for HTTP/3 to the client. The support is announced in the Alt-Svc HTTP response header, and the value of the Alt-Svc header is: Alt-Svc : h3=":$quic_port"; ma=3600.

2. The client attempts to establish an HTTP connection with GA. Note the following:

   • If the client cannot establish an HTTP/3 connection, it always falls back to HTTP/1.1 or HTTP/2.

   • The client supports caching cookies related to HTTP/3.

   • An HTTP/3 connection may fail for the following reasons:

     • The HTTP/3 version supported by the client is not compatible with the version supported by GA.

     • GA detects that UDP traffic is blocked or rate-limited, which prevents HTTP/3 from working.

     • The client does not support HTTP/3 and therefore does not attempt to negotiate an HTTP/3 connection.

3. Enabling or disabling HTTP/3 support in GA does not affect basic client connectivity because clients automatically fall back to HTTP/2 or HTTP/1.1.

Step 1: Configure GA and enable HTTP/3

1. Log on to the GA console.

2. On the Instances page, click Create GA Instance > Pay-as-you-go Standard Instance in the upper-left corner.

3. On the Basic Instance Configuration page, enter a name for the GA instance. Then, click Next.

4. On the Configure Acceleration Area page, select China (Beijing) for Acceleration Area. You can use the default values for other parameters or adjust as needed. Then, click Next.

   Important

   If the peak bandwidth is set too low, throttling may occur and result in dropped traffic. Plan the peak bandwidth to ensure that it meets your business requirements.

   

5. On the Configure Listener page, configure the following parameters. You can use the default values for other parameters or adjust as needed. Then, click Next.

   Parameter	Description
   Protocol	Select HTTPS.
   Maximum HTTP Version	Select HTTP/3. Note If your pay-as-you-go GA instance does not provide the option to configure the Maximum HTTP Version, your instance may be running on a version that does not support this feature. To use this feature, contact your account manager to request an instance upgrade. If a client does not support HTTP/3, GA accepts requests over HTTP/2 or HTTP/1.1 as a fallback.
   Port	Select the default HTTPS port 443.
   Server Certificate	Select the SSL certificate that is associated with your domain name.

   

6. On the Configure an Endpoint Group page, configure the following parameters. You can use the default values for other parameters or adjust as needed. Then, click Next.

   Parameter	Description
   Region	Select Germany (Frankfurt).
   Endpoint Configuration	Select Backend Service Type for Backend Service Type. Select your application server for Backend Service.
   Port Mapping	If the listener port is different from the endpoint port, you need to configure port mapping. In this topic, the listener port is set to 443 and the endpoint port is set to 80.
   Cross-border Acceleration Settings	In this scenario, if your business involves cross-border acceleration between the Chinese mainland and other countries or regions, read and select Compliance Commitments Regarding Cross-border Data Transfers.

   

   

7. On the Configuration Review page, review the configurations and click Submit. Wait for the instance to be created.

Step 2: Configure DNS resolution

Map your domain name to the CNAME of the GA instance to route traffic through GA.

1. Log on to the GA console.

2. Find the GA instance for which you want to configure DNS resolution and copy its CNAME address.

3. Add a CNAME record.

   1. On the Alibaba Cloud DNS page, find your domain name and click Actions in the Actions column.

      Note

      If your domain name was not registered with Alibaba Cloud, add the domain name to the Alibaba Cloud DNS console before configuring DNS records.

   2. On the Configure page, click Add Record.

   3. In the Add Record panel, configure the following parameters to add the CNAME record. Then, click Confirm.

      Parameter	Description
      Type	Select CNAME from the drop-down list.
      Host	The prefix of your domain name.
      DNS Request Source	Select Default.
      TTL	Time to Live — how long a DNS record is cached. Use the default value for this example.
      Value	Enter the CNAME address that you copied from the GA instance.

Step 3: Verify HTTP/3 and acceleration performance

Test video acceleration performance from a client in the China (Beijing) acceleration area.

1. Test the GA acceleration performance with HTTP/3:

   Open browser developer tools and navigate to https://<your domain name>. Disable browser cache to prevent caching from affecting HTTP/3 negotiation (in Chrome, select Disable cache).

   

2. Test the GA acceleration performance without HTTP/3:

   Modify the HTTPS listener configuration of the GA instance. Change the value of Maximum HTTP Version to HTTP/2.

   Open browser developer tools and navigate to https://<your domain name>.

   

3. Test the performance without GA acceleration:

   If the server lacks a public IP address, bind an Elastic IP Address (EIP) first.

   Open browser developer tools and navigate to http://<public IP address>:<port>.

   

4. Compare the acceleration performance:

   Test data shows GA with HTTP/3 improves video access speed.

   Scenario	Initial load time (3.3 MB)	Full video load time (112 MB)	Initial load comparison (Time saved / % improvement)	Video load comparison (Time saved / % improvement)
   Scenario 1: Use GA with HTTP/3	16.86 seconds	3.8 minutes	0.78s / 4.42% (vs. Scenario 2)	0.4 min / 9.52% (vs. Scenario 2)
   Scenario 2: Use GA without HTTP/3	17.64 seconds	4.2 minutes	48.36s / 73.27% (vs. Scenario 3)	34.4 min / 89.12% (vs. Scenario 3)
   Scenario 3: Do not use GA	1.1 minutes	38.6 minutes	N/A	N/A

   Note

   Data shown is for reference only. Actual performance depends on your environment.