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+### White Rabbit network provides two services:
+
+  - network-wide high-accuracy time distribution (synchronization) - in
+    most cases a reference time provided by atomic clock or/and GPS
+    receiver is distributed over White Rabbit Network. A device which
+    connects White Rabbit Network with time reference (atomic clock/GPS
+    receiver) is called **Timing Master**
+  - deterministic and reliable data distribution (delivery) - in most
+    cases a controller-node sends control messages to controlled-nodes.
+    A device which implements a controller function and sends critical
+    data onto White Rabbit network is called a **Data Master**
+
+-----
+
+### Timing Master
+
+  - a WR Switch or a WR Node connected (and synchronized) to a time
+    reference (atomic clock or/and GPS receiver)
+  - acts as a PTP Grandmaster
+  - multiple Timing Masters in a single White Rabbit Network are allowed
+
+### Data Master
+
+  - a WR Node (maybe WR Switch) that implements a functionality of a
+    controller to the WR Nodes connected by the White Rabbit Network
+  - multiple Timing Masters in a single White Rabbit Network are allowed
+
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 3 July 2012