Challenges for Scalable Networking in a Virtualized Server

The virtualization of I/O presents new challenges to the already formidable problem of network scalability for servers. The basic problem being addressed is that a finite set of networking resources within a server need to be shared among a number of guest virtual machines, and these network resources need to scale in order to satisfy the aggregate network throughput requirements of those guest virtual machines. Multiple approaches for network and I/O virtualization are being developed. We focus on the IO Virtual Machine (IOVM) model for network virtualization that uses specialized virtual machines that are dedicated for the purpose of sharing the network devices among a set of guests. In this paper, we show how the IOVM architecture maps onto multi-core server platforms, and we present empirical results and analysis on a Xen test-bed that implements a 'scale-up' strategy for network I/O based on the IOVM model.