NSX

NSX provides a virtualized network overlay that runs in the ESXi kernel that facilitates virtual firewall, router and switch components.  It uses VxLAN to provide the networks and largely uses extensions to the vSphere Distributed Switch to do it.  You still need physical switches and routers once you leave the vSphere world but with the VxLAN protocol you are riding 'on top' of standard packets when connecting between two virtual data centers running NSX.  It also provides for micro segmentation and 'East-West' firewalls.

NSX de-couples the network functions from the physical devices, in a way that is analogous to de-coupling virtual machines (VMs) from physical servers.  In order to de-couple the new virtual network from the traditional network, NSX natively re-creates the traditional network constructs in virtual space --- these constructs include ports, switches, routers, firewalls, etc.

NSX pools networking hardware like routers and switches and allows them to be reconfigured and managed entirely through software.  Customers who use the NSX product or rival software don't need to purchase new hardware as their needs change as had been the case in the past.

NSX is sold in a bundle with other VMware products including VMware Cloud Foundation which lets companies run applications across data centers and clouds.  And it will also be part of the upcoming "VMware cloud on AWS" that will enable customers to run VMware-based applications on Amazon Web Services public cloud.

                                NSX Security

Management Plane
NSX Manager
VMware vSphere

Control Plane
NSX Controller
User World Agent

Data Plane
NSX vSwitch
VXLAN
Distributed Logical Router
Distributed Firewall
NSX Edge Services Gateway
VMware vSphere Distributed Switch