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+Switch the connection to a different protocol. Redis version 6 or greater are
+able to support two protocols, the old protocol, RESP2, and a new one introduced
+with Redis 6, RESP3. RESP3 has certain advantages since when the connection is
+in this mode, Redis is able to reply with more semantical replies: for instance
+`HGETALL` will return a _map type_, so a client library implementation no longer
+requires to know in advance to translate the array into a hash before returning
+it to the caller. For a full coverage of RESP3 please
+[check this repository](https://github.com/antirez/resp3).
+
+Redis 6 connections starts in RESP2 mode, so clients implementing RESP2 do not
+need to change (nor there are short term plans to drop support for RESP2).
+Clients that want to handshake the RESP3 mode need to call the `HELLO` command,
+using "3" as first argument.
+
+    > HELLO 3
+    1# "server" => "redis"
+    2# "version" => "6.0.0"
+    3# "proto" => (integer) 3
+    4# "id" => (integer) 10
+    5# "mode" => "standalone"
+    6# "role" => "master"
+    7# "modules" => (empty array)
+
+The `HELLO` command has a useful reply that will state a number of facts about
+the server: the exact version, the set of modules loaded, the client ID, the
+replication role and so forth. Because of that, and given that the `HELLO`
+command also works with "2" as argument, both in order to downgrade the protocol
+back to version 2, or just to get the reply from the server without switching
+the protocol, client library authors may consider using this command instead of
+the canonical `PING` when setting up the connection.
+
+This command accepts two non mandatory options:
+
+- `AUTH <username> <password>`: directly authenticate the connection other than
+  switching to the specified protocol. In this way there is no need to call
+  `AUTH` before `HELLO` when setting up new connections. Note that the username
+  can be set to "default" in order to authenticate against a server that does
+  not use ACLs, but the simpler `requirepass` mechanism of Redis before
+  version 6.
+- `SETNAME <clientname>`: this is equivalent to also call `CLIENT SETNAME`.
+
+@return
+
+@array-reply: a list of server properties. The reply is a map instead of an
+array when RESP3 is selected. The command returns an error if the protocol
+requested does not exist.