diff --git a/views/ngXosViews/diagnostic/src/js/config.js b/views/ngXosViews/diagnostic/src/js/config.js
index 99112b1..db1d832 100644
--- a/views/ngXosViews/diagnostic/src/js/config.js
+++ b/views/ngXosViews/diagnostic/src/js/config.js
@@ -6,6 +6,14 @@
     widthMargin: 20,
     heightMargin: 30,
     duration: 750,
+    // elWidths: { // this is the fixed width for elements
+    //   devices: 20,
+    //   subscribers: 20,
+    //   router: 20,
+    //   network: 104,
+    //   rack: 105
+    // },
+    elWidths: [20, 104, 105, 104, 20, 20],
     circle: {
       radius: 10,
       r: 10,
@@ -18,7 +26,7 @@
       y: -10
     },
     rack: {
-      width: 60,
+      width: 105,
       height: 50,
       x: -30,
       y: -25
@@ -26,12 +34,15 @@
     computeNode: {
       width: 50,
       height: 20,
+      margin: 5,
+      labelHeight: 10,
       x: -25,
       y: -10
     },
     instance: {
       width: 40,
       height: 16,
+      margin: 5,
       x: -20,
       y: -8
     }
diff --git a/views/ngXosViews/diagnostic/src/js/logicTopology.js b/views/ngXosViews/diagnostic/src/js/logicTopology.js
index b689b89..afe61a8 100644
--- a/views/ngXosViews/diagnostic/src/js/logicTopology.js
+++ b/views/ngXosViews/diagnostic/src/js/logicTopology.js
@@ -16,8 +16,21 @@
 
         var svg;
 
+
+        const handleSvg = (el) => {
+
+          svg = d3.select(el)
+          .append('svg')
+          .style('width', `${el.clientWidth}px`)
+          .style('height', `${el.clientHeight}px`);
+        }
+
         $scope.$watch(() => this.subscribers, (subscribers) => {
           if(subscribers){
+
+            // TODO
+            // build here the full data structure
+
             LogicTopologyHelper.addSubscribers(svg, angular.copy(subscribers));
           }
         });
@@ -28,14 +41,6 @@
           }
         });
 
-        const handleSvg = (el) => {
-
-          svg = d3.select(el)
-          .append('svg')
-          .style('width', `${el.clientWidth}px`)
-          .style('height', `${el.clientHeight}px`);
-        }
-
         handleSvg($element[0]);
         LogicTopologyHelper.drawTree(svg);
       }
diff --git a/views/ngXosViews/diagnostic/src/js/logicTopologyHelper.js b/views/ngXosViews/diagnostic/src/js/logicTopologyHelper.js
index d33de36..411da49 100644
--- a/views/ngXosViews/diagnostic/src/js/logicTopologyHelper.js
+++ b/views/ngXosViews/diagnostic/src/js/logicTopologyHelper.js
@@ -31,6 +31,45 @@
     };
 
     /**
+     * Calculate the horizontal position for each element.
+     * subsrcribers, devices and routers have the same fixed width 20
+     * network have a fixed width 104
+     * rack have a fixed width 105
+     * build and array of 6 elements representing the position of each element in the svg
+     * to equally space them
+     */
+
+    this.computeElementPosition = (svgWidth) => {
+
+      let xPos = [];
+
+      let totalElWidth = lodash.reduce(serviceTopologyConfig.elWidths, (el, val) => val + el, 0);
+
+      let remainingSpace = svgWidth - totalElWidth - serviceTopologyConfig.widthMargin;
+
+      let step = remainingSpace / (serviceTopologyConfig.elWidths.length - 1);
+
+      lodash.forEach(serviceTopologyConfig.elWidths, (el, i) => {
+
+        // get half of the previous elements width
+        let previousElWidth = 0;
+        if(i !== 0){
+          previousElWidth = lodash.reduce(serviceTopologyConfig.elWidths.slice(0, i), (el, val) => val + el, 0) / 2;
+        }
+
+        let elPos =
+          serviceTopologyConfig.widthMargin // right margin
+          + (step * i) // space between elements
+          + (el / 2) // this el width
+          + previousElWidth; // previous elements width
+
+        xPos.push(svgWidth - elPos);
+      })
+
+      return xPos
+    };
+
+    /**
     * from a nested data structure,
     * create nodes and links for a D3 Tree Layout
     */
@@ -38,10 +77,12 @@
       let nodes = layout.nodes(data);
 
       // Normalize for fixed-depth.
-      nodes.forEach(function(d) {
+      nodes.forEach((d) => {
         // position the child node horizontally
-        const step = ((svgWidth - (serviceTopologyConfig.widthMargin * 2)) / 7);
-        d.y = (6 - d.depth) * step;
+        // const step = ((svgWidth - (serviceTopologyConfig.widthMargin * 2)) / 7);
+        // d.y = (6 - d.depth) * step;
+        d.y = this.computeElementPosition(svgWidth)[d.depth];
+        console.log(d.id, d.y);
       });
 
       let links = layout.links(nodes);
diff --git a/views/ngXosViews/diagnostic/src/js/rackHelper.js b/views/ngXosViews/diagnostic/src/js/rackHelper.js
new file mode 100644
index 0000000..037ecdd
--- /dev/null
+++ b/views/ngXosViews/diagnostic/src/js/rackHelper.js
@@ -0,0 +1,85 @@
+(function () {
+  angular.module('xos.serviceTopology')
+  .service('RackHelper', function(serviceTopologyConfig, lodash){
+
+    this.getComputeNodeLabelSize = () => {
+      return serviceTopologyConfig.computeNode.labelHeight + (serviceTopologyConfig.instance.margin * 2)
+    }
+
+    /**
+    * Given a list of instance should get the Compute Node size.
+    * They are placed in rows of 2 with 5px margin on each side.
+    */
+   
+    this.getComputeNodeSize = lodash.memoize((instances) => {
+      const width = (serviceTopologyConfig.instance.margin * 3) + (serviceTopologyConfig.instance.width *2);
+
+      const rows = Math.round(instances.length / 2);
+
+      const labelSpace = this.getComputeNodeLabelSize();
+
+      const height = (serviceTopologyConfig.instance.height * rows) + (serviceTopologyConfig.instance.margin * (rows + 1)) + labelSpace;
+      return [width, height];
+    });
+
+    /**
+    * Give a list on Compute Node should calculate the Rack Size.
+    * Compute nodes are placed in a single column with 5px margin on each side.
+    */
+    this.getRackSize = (nodes) => {
+
+      let width = 0;
+      let height = serviceTopologyConfig.computeNode.margin;
+
+      lodash.forEach(nodes, (node) => {
+        let [instanceWidth, instanceHeight] = this.getComputeNodeSize(node.instances);
+
+        width = instanceWidth + (serviceTopologyConfig.computeNode.margin * 2);
+        height += (instanceHeight + serviceTopologyConfig.computeNode.margin);
+      });
+
+      return [width, height];
+    };
+
+    /**
+    * Given an instance index, return the coordinates
+    */
+   
+    this.getInstancePosition = (position) => {
+      const row = Math.floor(position / 2);
+      const column = (position % 2) ? 1 : 0;
+
+      // add ComputeNode label size
+      const labelSpace = this.getComputeNodeLabelSize();
+
+      // x = margin + (width * column) + ( maring * column)
+      const x = serviceTopologyConfig.instance.margin + (serviceTopologyConfig.instance.width * column) + (serviceTopologyConfig.instance.margin * column);
+
+      // y = label + margin + (height * row) + ( maring * row)
+      const y = labelSpace + serviceTopologyConfig.instance.margin + (serviceTopologyConfig.instance.height * row) + (serviceTopologyConfig.instance.margin * row);
+      return [x, y];
+    };
+
+    /**
+    * Given an Compute Node index, return the coordinates
+    */
+
+    this.getComputeNodePosition = (nodes, position) => {
+      const x = serviceTopologyConfig.computeNode.margin;
+
+      let previousElEight = lodash.reduce(nodes.slice(0, position), (val, node) => {
+        return val + this.getComputeNodeSize(node.instances)[1]
+      }, 0);
+
+      console.log('previousElEight ' + previousElEight);
+      const y =
+        serviceTopologyConfig.computeNode.margin
+        + (serviceTopologyConfig.computeNode.margin * position)
+        + previousElEight;
+
+
+      return [x, y];
+    };
+
+  });
+})();
diff --git a/views/ngXosViews/diagnostic/src/js/rest_services.js b/views/ngXosViews/diagnostic/src/js/rest_services.js
index 87db711..8c3e317 100644
--- a/views/ngXosViews/diagnostic/src/js/rest_services.js
+++ b/views/ngXosViews/diagnostic/src/js/rest_services.js
@@ -39,7 +39,7 @@
                 node.instances = list[i];
                 return node;
               });
-
+              console.log(res.data);
               deferred.resolve(res.data);
             })