diff --git a/docs/backup-protocol.rst b/docs/backup-protocol.rst
index 2d78f375..ec594c7c 100644
--- a/docs/backup-protocol.rst
+++ b/docs/backup-protocol.rst
@@ -1,5 +1,42 @@
 Backup Protocol
 ===============
 
-.. todo:: add introduction to HTTP2 based backup protocols
+Proxmox Backup Server uses a REST based API. While the management
+interface use normal HTTP, the actual backup and restore interface use
+HTTP/2 for improved performance. Both HTTP and HTTP/2 are well known
+standards, so the following section assumes that you are familiar on
+how to use them.
 
+
+Backup Protocol API
+-------------------
+
+To start a new backup, the API call ``GET /api2/json/backup`` needs to
+be upgraded to a HTTP/2 connection using
+``proxmox-backup-protocol-v1`` as protocol name::
+
+  GET /api2/json/backup HTTP/1.1
+  UPGRADE: proxmox-backup-protocol-v1
+
+The server replies with HTTP 101 Switching Protocol status code,
+and you can then issue REST command on that updated HTTP/2 connection.
+
+Please use the `API Viewer <api-viewer/index.html>`_ for details about
+available REST commands.
+
+
+Restore/Reader Protocol API
+---------------------------
+
+To start a new reader, the API call ``GET /api2/json/reader`` needs to
+be upgraded to a HTTP/2 connection using
+``proxmox-backup-reader-protocol-v1`` as protocol name::
+
+  GET /api2/json/reader HTTP/1.1
+  UPGRADE: proxmox-backup-reader-protocol-v1
+
+The server replies with HTTP 101 Switching Protocol status code,
+and you can then issue REST command on that updated HTTP/2 connection.
+
+Please use the `API Viewer <api-viewer/index.html>`_ for details about
+available REST commands.