In-Band Control for an Ethernet-Based Software-Defined Network

Abstract

A distinguishing characteristic of a software-defined network is separation of the network's control plane from its data plane. Especially when the granularity of control is an individual network flow, such separation entails frequent communications between these two planes. This communication pattern demands the same level of resilience from the control plane as that from the data plane, and thus calls into question the conventional out-of-band control network design as used in many existing SDN systems. Peregrine is an Ethernet-based software-defined network that was originally designed as the internal network of a container computer, and unifies storage access, inter-server communication, and network control into a single network comprising only commodity off-the-shelf Ethernet switches. To fully utilize all available physical network links, Peregrine treats the physical network as an explicitly routed mesh and equalizes the loads of its links using a global load-balancing routing algorithm running on a centralized controller. The in-band control architecture of Peregrine leads to two issues: (1) how to evolve a Peregrine network from its initial bootstrapping mode to the explicit routing mode at run time, and (2) how to support fast fail-over for physical failures that break both the control and data plane. This paper describes how Peregrine addresses these two issues, and shows its effectiveness with performance measurements collected from a fully operational test-bed.