[++doc] add benchmark design

doc/graphviz/netpfgadesign.dot

@@ -4,7 +4,7 @@ graph G {
 
     x520_1 [ label="X520: IPv4" ];
     x520_2 [ label="X520: IPv6" ];
-    x520_nsg [ label="X520: Controller" ];
+    x520_nsg [ label="X520: P4 Controller" ];
 
     netpfga1 [ label="NetFPGA Port 1" ];
     netpfga2 [ label="NetFPGA Port 2" ];

doc/graphviz/softwarenat64design.dot

@@ -0,0 +1,27 @@
+graph G {
+    node [ shape="box"];
+    rankdir="LR";
+
+    x520_1 [ label="X520: IPv4" ];
+    x520_2 [ label="X520: IPv6" ];
+    x520_nsg_1 [ label="X520: IPv4" ];
+    x520_nsg_2 [ label="X520: IPv6" ];
+
+    subgraph cluster_esprimo {
+        label="Load generator";
+
+        x520_1;
+        x520_2;
+    }
+
+    subgraph cluster_nsg {
+        label="NAT64 Host";
+
+        x520_nsg_1;
+        x520_nsg_2;
+    }
+
+    x520_1--x520_nsg_1;
+    x520_2--x520_nsg_2;
+
+}