added customization on virtual nodes

examples/B01-dns-component/README.md

@@ -51,6 +51,17 @@ dns.getZone('twitter.com.').addRecord('@ A 1.1.1.1')
 dns.getZone('google.com.').addRecord('@ A 2.2.2.2')
 ```
 
+##  Customization for visualization
+
+When the nodes are displayed on the map, we would like to display a more 
+friendly name, instead of the unique name assigned to each virtual node. 
+We can do the following. When this virtual node is bound to a physical 
+node, the display name will be inherited by the physical node. 
+
+```
+emu.getVirtualNode('a-root-server').setDisplayName('Root-A')
+```
+
 ##  Saving the DNS component to File
 
 After adding the DNS layer to the emulator, we can save the entire DNS

examples/B01-dns-component/dns-component.py

@@ -36,6 +36,22 @@
 dns.getZone('syr.edu.').addRecord('@ A 128.230.18.63') 
 dns.getZone('weibo.cn.').addRecord('@ A 5.5.5.5').addRecord('www A 5.5.5.6')
 
+# Customize the display names (for visualization purpose)
+emu.getVirtualNode('a-root-server').setDisplayName('Root-A')
+emu.getVirtualNode('b-root-server').setDisplayName('Root-B')
+emu.getVirtualNode('a-com-server').setDisplayName('COM-A')
+emu.getVirtualNode('b-com-server').setDisplayName('COM-B')
+emu.getVirtualNode('a-net-server').setDisplayName('NET')
+emu.getVirtualNode('a-edu-server').setDisplayName('EDU')
+emu.getVirtualNode('a-cn-server').setDisplayName('CN-A')
+emu.getVirtualNode('b-cn-server').setDisplayName('CN-B')
+emu.getVirtualNode('ns-twitter-com').setDisplayName('twitter.com')
+emu.getVirtualNode('ns-google-com').setDisplayName('google.com')
+emu.getVirtualNode('ns-example-net').setDisplayName('example.net')
+emu.getVirtualNode('ns-syr-edu').setDisplayName('syr.edu')
+emu.getVirtualNode('ns-weibo-cn').setDisplayName('weibo.cn')
+
+
 ###########################################################
 emu.addLayer(dns)
 emu.dump('dns-component.bin')