Imagine a scenario where you have to apply certain traffic management rules for a dozen compute node instances. Therefore, assigning a certain set of rules for a specific group of nodes will be much easier instead of going through each node at a time. Security groups enclose all the aspects of the rules that are applied to the ingoing and outgoing traffic to instances, which includes the following:
The source and receiver, which will allow or deny traffic to instances from either the internal OpenStack IP addresses or from the rest of the world
Protocols to which the rule will apply, such as TCP, UDP, and ICMP
Egress/ingress traffic management to a Neutron port
In this way, OpenStack offers an additional security layer to the firewall rules that are available on the compute instance. The purpose is to manage traffic to several compute instances from one security group. You should bear in mind that the networking security groups are more granular-traffic-filtering-aware than the...