In order to understand how SDN fits into the OpenStack ecosystem, let's revisit some of the learnings from the earlier sections of this chapter:
Network abstractions are required in order to provide a flexible environment for cloud-based applications
Networking must support programmatic APIs in order to dynamically provision the resources needed for applications and to integrate effectively with compute and storage resources
Centralized management of SDN is critical to support multi-vendor based cloud infrastructure
As seen in the previous chapter, OpenStack supports simple abstractions such as network, subnet, router, firewall, and so on. These abstractions help cloud users to define applications and the required infrastructure as software entities. The advantage of this approach is that underlying physical infrastructure is unaware and independent of the applications running on it. Sophisticated orchestration entities and SDN controllers...