OVS and OVN

Posted by Manish Panchmatia on Wednesday, September 16, 2020 Labels: ,

Let's understand first OVS and OVN

 Limitation of OpenStack networking
- L2 population, 
- local ARP responder, 
- L2 Gateway and 
- DVR 
https://networkop.co.uk/blog/2016/10/13/os-dvr/
https://networkop.co.uk/blog/2016/05/21/neutron-l2gw/
https://networkop.co.uk/blog/2016/05/06/neutron-l2pop/

OVN is 
- a distributed SDN controller 
- implementing virtual networks 
- with the help OVS. 

OVN provides
- L2/L3 Virtual networking
- firewall service

Architecture Same as VMWare's NSX

* dedicated Linux bridge between the VM and the OVS integration bridge for implementation of security group
* dedicated NS for DHCP agent
* dedicated NS for routing
* NAT = network namespaces + iptables + proxy-ARP.

OVN implements inside a single OVS bridge:
- security groups, 
- distributed virtual routing, 
- NAT and 
- distributed DHCP server

Flow/path
Neutron data model -> 
OVN ML2 plugin -> 
OVN Northbond DB (DB Node) : QoS, NAT and ACL settings -> 
OVN northd (DB Node) -> 
OVN southbond DB (DB Node): L2 Datapath and L3 Datapath -> 
OVN Controller (Worker Node): Distributed SDN Contoller -> 
local OVS over openflow. (Worker Node)

Network: a virtual L2 broadcast domain
Subnet: attached to the network.
Router: provides connectivity between all directly connected subnets
Port: VM’s point of attachment to the subnet

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