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Saturday, January 4, 2014

Openstack Neutron architecture explained based on OVS and VMware NVP plugin comparison

There are 3 recorded meetup videos that were organized by the onlinemeetup Openstack group ( These are an excellent source of information into network virtualization, nova-network, Neutron OVS and NVP plugins.

The recorded sessions can be found on YouTube here:

OpenStack Networking - Theory Session, Part 1
OpenStack Networking - Theory Session, Part 2
OpenStack Networking - Hands-On Lab, Part 3

Network virtualization basic

Nova Networking

The first version of network implemented in Openstack is called nova-networking and can be still used. Some of the advantages and limitations can be seen below.

The most complex deployment architecture used VLANs to implemented tenant and isolation. This scenario has a lot ideas that are then later shared in Neutron plugins.

OVS plugin

As you can see the architecture looks very similar. There are some subtle differences although like: instead of VLAN we use GRE tunnels, instead of Linux bridge we use the OpenVswitch (OVS). The important thing to note is that we don't use OpenFlow protocol to control the OVS switches. The switch will be pre-programmed by the agent running on the hypervisor.

NVP plugin

To describe and explain how NVP works it is good to compare its architecture to OVS plugin above. The first slide shows what component are not being used.

The network communication model with NVP provides new component.

The main differences are:
  • OVS switches will be programmed by the NVP cluster using OpenFlow protocol
  • Instead of GRE we use STT tunneling
  • Security groups will be natively implemented in OVS (no need for iptables)
  • The virtual router is highly available and is implemented on external nodes 

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