have explicit network map data type and do calculation from there

shared/management/networkmap/nmdata/network.go

@@ -0,0 +1,16 @@
+package nmdata
+
+import "net"
+
+// Network is the slim twin of types.Network.
+type Network struct {
+	Identifier string
+	Net        net.IPNet
+	NetV6      net.IPNet
+	Dns        string
+	Serial     uint64
+}
+
+func (n *Network) CurrentSerial() uint64 {
+	return n.Serial
+}