Rethinking host network stack architecture

As the gap between the speed of networks and processor cores increases, the software alone will not be able to handle all incoming data without additional assistance from the hardware. The network interface controllers (NICs) evolve and add supporting features which could help the system increase its scalability with respect to incoming packets, provide Quality of Service (QoS) guarantees and reduce the CPU load. However, modern operating systems are ill suited to both efficiently exploit and effectively manage the hardware resources of state-of-the-art NICs. The main problem is the layered architecture of the network stack and the rigid interfaces. This dissertation argues that in order to effectively use the diverse and complex NIC hardware features, we need (i) a hardware agnostic representation of the packet processing capabilities of the NICs, and (ii) a flexible interface to share this information with different layers of the network stack. This work presents the Dataflow graph based model to capture both the hardware capabilities for packet processing of the NIC and the state of the network stack, in order to enable automated reasoning about the NIC features in a hardware-agnostic way. It also describes the implementation of the Dragonet network stack which uses the dataflow model to support the diversity and complexity in the NICs. Dragonet enables effective use of the available hardware features in a portable way by using the dataflow model to share the packet processing capabilities of a particular NIC configuration with the runtime system, which can then automatically specialize the network stack based on this information. Furthermore, the dataflow model enables systematic exploration of the hardware configuration space and allows reasoning about the hardware capabilities in the context of application requirements. Thus, allowing policy-based management of the NIC’s resources. The dissertation shows the effectiveness of the dataflow model by implementing several high-level policies for managing different hardware resources on two separate NICs.