anchor.diff:  
   [NOTE]
   ====
  -Spring Boot does not support `h2c`, the cleartext version of the HTTP/2 protocol.
  -So you must <<howto-configure-ssl, configure SSL first>>.
  +Spring Boot does not advise using `h2c`, the cleartext version of the HTTP/2 protocol.
  +As a result, the next sections require to <<howto-configure-ssl, configure SSL first>>.
  +If you still choose to use `h2c`, you can check <<howto-configure-http2-h2c, the dedicated section>>.
   ====
   
   
  -
  -[[howto-configure-http2-undertow]]
  -==== HTTP/2 with Undertow
  -As of Undertow 1.4.0+, HTTP/2 is supported without any additional requirement on JDK8.
  +[[howto-configure-http2-tomcat]]
  +==== HTTP/2 with Tomcat
  +Spring Boot ships by default with Tomcat 9.0.x which supports HTTP/2 out of the box when using JDK 9 or later.
  +Alternatively, HTTP/2 can be used on JDK 8 if the `libtcnative` library and its dependencies are installed on the host operating system.
  +
  +The library folder must be made available, if not already, to the JVM library path.
  +You can do so with a JVM argument such as `-Djava.library.path=/usr/local/opt/tomcat-native/lib`.
  +More on this in the https://tomcat.apache.org/tomcat-9.0-doc/apr.html[official Tomcat documentation].
  +
  +Starting Tomcat 9.0.x on JDK 8 without that native support logs the following error:
  +
  +[indent=0,subs="attributes"]
  +----
  +	ERROR 8787 --- [           main] o.a.coyote.http11.Http11NioProtocol      : The upgrade handler [org.apache.coyote.http2.Http2Protocol] for [h2] only supports upgrade via ALPN but has been configured for the ["https-jsse-nio-8443"] connector that does not support ALPN.
  +----
  +
  +This error is not fatal, and the application still starts with HTTP/1.1 SSL support.
   
   
   
  
positive.code: 
  Spring Boot manages the version for the `io.netty:netty-tcnative-boringssl-static` "uber jar", containing native libraries for all platforms.
  Developers can choose to import only the required dependencies using a classifier (see https://netty.io/wiki/forked-tomcat-native.html[the Netty official documentation]).
  
  
  
  
negative.code: ==== HTTP/2 with Jetty
  As of Jetty 9.4.8, HTTP/2 is also supported with the https://www.conscrypt.org/[Conscrypt library].
  To enable that support, your application needs to have two additional dependencies: `org.eclipse.jetty:jetty-alpn-conscrypt-server` and `org.eclipse.jetty.http2:http2-server`.
  
  
  
  