Resolved HTTP 3 is not used despite NGINX Only hosting

[FloLa]

Server operating system version

Debian 10.13

Plesk version and microupdate number

v18.0.61_build1800240528.05

I saw that HTTP 3 is now possible for NGINX.
All my servers have NGINX only hosting. Now I wanted to activate it according to the instructions, i.e.:

Plesk Guide

I also installed the firewall etc. but the HTTP 3 protocol is not being used for me, various test sites also show that it is not installed, what can I do?
The following are my settings:

 

[AYamshanov]

Hi!

Do you see "alt-svc: h3=":443"; ma=86400" header in server's answers?
Have you tried to get website content over http/3 protocol only (e.g.: `curl --http3-only`)?
Do you have any firewalls outside of your server (like a cloud firewall provided by a hoster)?

We have discussed a similar topic in this thread, Resolved - http/3 supported by plesk?. Makes sense to check that a browser is informed about the ability to use HTTP/3 with a website and check that 443/udp traffic is really allowed to and from the server in firewall(s).

 

[FloLa]

Hi!


Many thanks for your response.

I tried to do a check via CURL, unfortunately without success.
When I look at the Plesk site I see an Alt-SVC header, when I open my website I don't get such a header.
So it definitely doesn't work, the browser can do it too.

I don't have an external firewall or anything active either, really just everything from the Plesk installation.

My Server:

Plesk Website:

 

[FloLa]

Does anyone else have this problem?

 

[AYamshanov]

Just ideas what makes sense to check to narrow down the area to look for the problem.
Since there is no the "alt-svc" header, need to dig deeper to figure out why it is missed.

• Check that the nginx webserver is listening for HTTP/3 connections (443/udp). In this example, I use a website with the domain "practical-fermat.192-0-2-1.plesk.page".

# grep -2 'h3=' /var/www/vhosts/system/practical-fermat.192-0-2-1.plesk.page/conf/nginx.conf 
server {
        listen 192.0.2.1:443 quic;
        add_header Alt-Svc 'h3=":443"; ma=86400';
        listen 192.0.2.1:443 ssl;
        http2 on;

# netstat -lunp | grep nginx
udp        0      0 192.0.2.1:443           0.0.0.0:*                           2097/nginx: master  
[...]

• Do you have ability to create a new website with technical domain (like https.//practical-fermat.192-0-2-1.plesk.page) to check how it works without customizations on a blank website,

If something is different, need to check the webserver settings. If everything is ok, need to check website.

 

[FloLa]

I just found one thing, see screenshot:

Only the following is present in the file

Why is this?

 

[FloLa]

Am I the only one having this problem?

 

[MartinT]

Hi,

I got a similar prblem, no solution. Erverything looks like a Firewall in front of the serve by hosting provider. I asked mine, they say no. firewalls at my server are open, all the given check in this thead are ok. That alll is a big questiomark.

I only sometimes get on a picture .svg or an banner an h3. When I hoover with the mouse over it, it say. this date won the race against h2. So maybe h3 is at my servers to slow and the browser take h2.

 

[learning_curve]

@FloLa / @MartinT Have you read this (and other posts) in this long thread: Resolved - http/3 supported by plesk?

 

[FloLa]

@learning_curve Yes, I read but unfortunately there is no solution.

 

[FloLa]

Hi,

I got a similar prblem, no solution. Erverything looks like a Firewall in front of the serve by hosting provider. I asked mine, they say no. firewalls at my server are open, all the given check in this thead are ok. That alll is a big questiomark.

I only sometimes get on a picture .svg or an banner an h3. When I hoover with the mouse over it, it say. this date won the race against h2. So maybe h3 is at my servers to slow and the browser take h2.

Unfortunately, for some reason H3 doesn't work for me even when I explicitly try to use it.

 

[FloLa]

What is the difference between the command:

plesk bin http3_pref --enable -nginx

And:

plesk bin http3_pref --enable -panel -nginx

Is it just the Plesk panel?

 

[Kaspar@Plesk]

Is it just the Plesk panel?

Yes, that correct. The former command enables HTTP/3 for connections to Plesk Panel.

 

[learning_curve]

What is the difference between the command:

plesk bin http3_pref --enable -nginx

And:

plesk bin http3_pref --enable -panel -nginx

Is it just the Plesk panel?

This was covered in that previous thread that you've looked at, plus the later changes made by Plesk, which disabled the panel from http/3 anyway.

Assuming that you have Curl that will function with http/3 (Cloudfare can assist, if you don't / need to re-config) then please post your curl tests on here, as they are more informative than the images that have been posted so far.

As stated in that post (that's linked in our previous post), currently, it's quite easy to be mis-informed by browser tests, even if, you think that you have correctly configured them fopr http/3.

 

[learning_curve]

@FloLa

Two very simple curl / http/3 tests:

$ curl --http3 https://**your-fqdn** -I

and

curl -vDI https://**your-fqdn** --http3-only

Sanitize them (by removing your fqdn) and then post those results on here

 

[FloLa]

After the last update "Plesk Obsidian 18.0.61 Update 5" and deactivating and activating it again, HTTP3 now seems to work.
At least it works with CURL, I still get the wrong result on the "HTTP/3 Check" page, but that shouldn't bother me.

For whatever reason, my server also prefers to use HTTP2 over HTTP3.

 

[learning_curve]

After the last update "Plesk Obsidian 18.0.61 Update 5" and deactivating and activating it again, HTTP3 now seems to work.
At least it works with CURL, I still get the wrong result on the "HTTP/3 Check" page, but that shouldn't bother me.

You've now proved that HTTP/3 is active on your server. That's the critical part. At present it's almost a guarantee that some browsers, will sometimes, on some sites...(!) provide a false HTTP/3 response. That will improve over time, as HTTP/3 becomes the new 'default' as opposed to it being classed as 'experimental'.

For whatever reason, my server also prefers to use HTTP2 over HTTP3.

The answer may be this:

HTTP version negotiation is required before using HTTP/3​

HTTP/3 generally doesn’t work for the first request because browsers assume by default that the server doesn’t support HTTP/3 and send the first request via either HTTP/2 or HTTP/1.1 on a TCP connection. If the server supports HTTP/3, it responds with an Alt-Svc (Alternative Service) header that informs the client that it can send HTTP/3 requests. The browser can respond in different ways: it can open a QUIC connection right away or wait until the TCP connection is closed. Either way, an HTTP/3 connection is only set up after the initial resources have been downloaded over an HTTP/1.1 or HTTP/2 connection.

This ^^ is taken from this detailed and informative page: A Comprehensive Guide To HTTP/3 And QUIC | DebugBear

 

[FloLa]

@learning_curve You are absolutely right, thank you for the detailed explanation.

This thread can be closed or marked as Resolved. Thanks to everyone for the answers.

 

[Paulo_o]

Unfortunately, for some reason H3 doesn't work for me even when I explicitly try to use it.

I have solved the problem changing NGINX.conf worker_processes auto; to worker_processes 1;

Now all browsers shows "h3" protocol.

Also see this post.

 

[FloLa]

@Paulo_o I currently have worker_processes = 8 or worker_processes = 12, it depends on the server, in principle I just want all cores to be used.

HTTP3 works for me with Curl but it just doesn't show up in the browser.
But as long as there isn't a stable version of it, the module is uninteresting anyway, until then the details will be out.