DOC: Describe reuse safe for HOL handling
Explain the special case of server connections using a protocol subject
to HOL on http-reuse safe mode.
diff --git a/doc/configuration.txt b/doc/configuration.txt
index e9bde91..a1a743f 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -6611,7 +6611,12 @@
closes the connection when the request is being sent, the
browser can decide to silently retry it. Since it is exactly
equivalent to regular keep-alive, there should be no side
- effects.
+ effects. There is also a special handling for the connections
+ using protocols subject to Head-of-line blocking (backend with
+ h2 or fcgi). In this case, when at least one stream is
+ processed, the used connection is reserved to handle streams
+ of the same session. When no more streams are processed, the
+ connection is released and can be reused.
- "aggressive" : this mode may be useful in webservices environments where
all servers are not necessarily known and where it would be