Neutron's explicit congestion notification support

Network congestion can be very common in large data centers generating huge traffic from multiple hosts. Though each hosts can use IP header TOS ECN bit functionality to implement explicit congestion notification (http://en.wikipedia.org/wiki/Explicit_Congestion_Notification) but this will be a redundant effort.

This proposal talks about exploring OVS capability of achieving ECN on behalf of each host. This will help in making the solution centralized and can be done per tenant level. In addition to this traffic classification for applying ECN functionality can also be achieved via specific filtering rules, if required. Almost all the leading vendors support this option to ensure QoS. Each vendor can update their plug-in's for using the proposed QoS API extension for their cloud service environment orchestrated via openstack.