SDN policy-driven service chain placement in OpenStack

Abstract

Network functions virtualization requires automatic deployment and scaling of components. This raises the question of where to place instances of a function, for instance in the OpenStack cloud system. Data plane functions can forward large amounts of traffic. In this case, network-aware placement can avoid an inefficient use of host bandwidth, and a chain of functions can benefit from co-locating instances on a host. However, a practical challenge is that the bandwidth utilization or traffic demand matrix is not always known before the deployment of an instance. A promising remedy is to leverage existing Software Defined Networking (SDN) policies to derive connectivity weights between components. In this paper, we present this novel solution to the online instance placement problem. We have developed an extension of the OpenStack scheduler that uses SDN forwarding policies to rank potential hosts. For a given type of virtual machine, the corresponding forwarding policies can be retrieved from an SDN controller prior to the placement decision. Our prototype identifies potential communication peers and weighs the forwarding rules to prefer hosts that already run communication peers. We present heuristics for such weighing, and we also discuss limitations of the approach. A testbed implementation proofs that even in a simple example our solution can double the service chain throughput.