diff --git a/specification/push_gateway.rst b/specification/push_gateway.rst
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+Push Gateway API
+================
+
+Clients may want to receive push notifications when events are received at
+the homeserver. This is managed by a distinct entity called the Push Gateway.
+A client's homeserver forwards information about the event to the push gateway
+and the gateway submits a push notification to the push notification provider
+(e.g. APNS, GCM).
+
+
+::
+
+                                   +--------------------+  +-------------------+
+                  Matrix HTTP      |                    |  |                   |
+             Notification Protocol |   App Developer    |  |   Device Vendor   |
+                                   |                    |  |                   |
+           +-------------------+   | +----------------+ |  | +---------------+ |
+           |                   |   | |                | |  | |               | |
+           | Matrix homeserver+----->  Push Gateway  +------> Push Provider | |
+           |                   |   | |                | |  | |               | |
+           +-^-----------------+   | +----------------+ |  | +----+----------+ |
+             |                     |                    |  |      |            |
+    Matrix   |                     |                    |  |      |            |
+ Client/Server API  +              |                    |  |      |            |
+             |      |              +--------------------+  +-------------------+
+             |   +--+-+                                           |             
+             |   |    <-------------------------------------------+             
+             +---+    |                                                        
+                 |    |          Provider Push Protocol                        
+                 +----+                                                        
+                                                                               
+         Mobile Device or Client                                               
+
+
+Homeserver behaviour
+--------------------
+
+This describes the format used by "HTTP" pushers to send notifications of
+events to Push Gateways. If the endpoint returns an HTTP error code, the
+homeserver SHOULD retry for a reasonable amount of time using exponential backoff.
+
+{{push_notifier_http_api}}