var json = 
     {
  "name": "Start",
  "display" : "Entry",
  "parent": "null",
  "children": [
    {
      "name": "Swith-1",
      "display": "United States of America Entry Swith",
      "parent": "Start",
      "children": [
        {
          "name": "Swith-1.1",
        "display": "IL Entry Swith",
          "parent": "Swith-1",
           "children": [
        {
          "name": "Swith-1.1.1",
        "display": "Chicago Entry Swith",
          "parent": "Swith-1.1"
        },
        {
          "name": "Swith-1.1.2",
        "display": "Springfield Entry Swith",
          "parent": "Swith-1.1"
        }
      ] 
        },
        {
          "name": "Swith-1.2",
        "display": "CA Entry Swith",
          "parent": "Swith-1"
        }
      ]
    },
    {
      "name": "Swith-2",
      "display": "External gateways",
      "parent": "Start"
    }
  ]
};

var width = 700;
var height = 650;
var maxLabel = 150;
var duration = 500;
var radius = 5;
    
var i = 0;
var root;

var tree = d3.layout.tree()
    .size([height, width]);

var diagonal = d3.svg.diagonal()
    .projection(function(d) { return [d.y, d.x]; });

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)
        .append("g")
        .attr("transform", "translate(" + maxLabel + ",0)");

root = json;
root.x0 = height / 2;
root.y0 = 0;

root.children.forEach(collapse);

function update(source) 
{
    // Compute the new tree layout.
    var nodes = tree.nodes(root).reverse();
    var links = tree.links(nodes);

    // Normalize for fixed-depth.
    nodes.forEach(function(d) { d.y = d.depth * maxLabel; });

    // Update the nodes…
    var node = svg.selectAll("g.node")
        .data(nodes, function(d){ 
            return d.id || (d.id = ++i); 
        });

    // Enter any new nodes at the parent's previous position.
    var nodeEnter = node.enter()
        .append("g")
        .attr("class", "node")
        .attr("transform", function(d){ return "translate(" + source.y0 + "," + source.x0 + ")"; })
        .on("click", click);

    nodeEnter.append("circle")
        .attr("r", 0)
        .style("fill", function(d){ 
            return d._children ? "lightsteelblue" : "white"; 
        });

    nodeEnter.append("text")
        .attr("x", function(d){ 
            var spacing = computeRadius(d) + 5;
            return d.children || d._children ? -spacing : spacing; 
        })
        .attr("dy", "3")
        .attr("text-anchor", function(d){ return d.children || d._children ? "end" : "start"; })
        .text(function(d){ return d.name; })
        .style("fill-opacity", 0);

    // Transition nodes to their new position.
    var nodeUpdate = node.transition()
        .duration(duration)
        .attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });

    nodeUpdate.select("circle")
        .attr("r", function(d){ return computeRadius(d); })
        .style("fill", function(d) { return d._children ? "lightsteelblue" : "#fff"; });

    nodeUpdate.select("text").style("fill-opacity", 1);

    // Transition exiting nodes to the parent's new position.
    var nodeExit = node.exit().transition()
        .duration(duration)
        .attr("transform", function(d) { return "translate(" + source.y + "," + source.x + ")"; })
        .remove();

    nodeExit.select("circle").attr("r", 0);
    nodeExit.select("text").style("fill-opacity", 0);

    // Update the links…
    var link = svg.selectAll("path.link")
        .data(links, function(d){ return d.target.id; });

    // Enter any new links at the parent's previous position.
    link.enter().insert("path", "g")
        .attr("class", "link")
        .attr("d", function(d){
            var o = {x: source.x0, y: source.y0};
            return diagonal({source: o, target: o});
        });

    // Transition links to their new position.
    link.transition()
        .duration(duration)
        .attr("d", diagonal);

    // Transition exiting nodes to the parent's new position.
    link.exit().transition()
        .duration(duration)
        .attr("d", function(d){
            var o = {x: source.x, y: source.y};
            return diagonal({source: o, target: o});
        })
        .remove();

    // Stash the old positions for transition.
    nodes.forEach(function(d){
        d.x0 = d.x;
        d.y0 = d.y;
    });
}

function computeRadius(d)
{
    if(d.children || d._children) return radius + (radius * nbEndNodes(d) / 10);
    else return radius;
}

function nbEndNodes(n)
{
    nb = 0;    
    if(n.children){
        n.children.forEach(function(c){ 
            nb += nbEndNodes(c); 
        });
    }
    else if(n._children){
        n._children.forEach(function(c){ 
            nb += nbEndNodes(c); 
        });
    }
    else nb++;
    
    return nb;
}

function click(d)
{
    if (d.children){
        d._children = d.children;
        d.children = null;
    } 
    else{
        d.children = d._children;
        d._children = null;
    }
    update(d);
}

function collapse(d){
    if (d.children){
        d._children = d.children;
        d._children.forEach(collapse);
        d.children = null;
    }
}

update(root);

html{
    font: 10px sans-serif;
}

svg{
    border: 1px solid silver;
}

.node{
    cursor: pointer;
}

.node circle{
    stroke: steelblue;
    stroke-width: 1.5px;
}

.link{
    fill: none;
    stroke: lightgray;
    stroke-width: 1.5px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>
<div id=tree></div>