Vagabond: Dynamic Network Endpoint Reconfiguration in Virtualized Environments

One of the biggest challenges of virtualization today is to efficiently share and manage network devices among different virtual machines (VMs). Software-based network virtualization solutions like device emulation and split driver device models have advantages of resource sharing and fine grained hypervisor resource control. However, software based approaches have performance and scalability impediments due to the software interventions for every I/O activity. Recent hardware advancements in network devices allow in-device partitioning and assignment of network functions to different guest operating systems. The nature of the assignment is static which gives rise to inflexibility in efficient network resource management. Additionally, fine grained hypervisor control on the network device is compromised because of the direct hardware assignment to the guest virtual machine. In this work, we propose Vagabond, an alternate network virtualization model that supports flexible and dynamic assignment of network resources to guest VMs. The most significant advantage of the proposed model is to facilitate a framework to manage network resources efficiently when the number of hardware in-device partitions are less than the number of VMs. Additionally the advantages of software based network virtualization are kept intact to overcome the difficulties posed due to direct hardware assignment to the guest. Our experimental evaluation shows that the CPU resource overhead with Vagabond is up to 2x lower than the software approach. Compared to the direct hardware assignment, Vagabond incurs an additional overhead of 17% in the best case. We demonstrate the applicability and usage of Vagabond with two use cases: live migration of VMs connected to hardware in-device partitions and a fair-share network resource allocation scheme.