The Virtual Network Layer
A virtual network is a network of virtual machines running on a single physical machine that are connected logically to each other so that they can send data to and receive data from each other. Each virtual network is serviced by a single virtual switch (vSwitch). Typically, every vSwitch is associated with one/more port groups; a port group specifies port configuration options such as bandwidth limitations and VLAN tagging policies for each logical port on the vSwitch, and thus defines how a connection to the network is made via the vSwitch.
The Virtual Network layer provides insights into the composition of the virtual networks on a vSphere/ESX server and the traffic to and from each of the virtual networks, so that administrators can promptly detect overloads, accurately identify the vSwitch-port group combination which handled the heavy traffic, and instantly isolate the VM in the virtual network to/from which the data was transmitted.
Figure 1 : The Virtual Network Layer