Experiences Implementing Live VM Migration over the WAN with Multi-Path TCP

Abstract

Live VM Migration allows a running virtual machine or service to be moved from one host to another without the need to be shut down. This critical process offers many benefits for Internet services, including load balancing and service availability especially during host maintenance. Nevertheless, VM migration has been limited to layer 2 environments where the VM's IP address can be migrated with the VM. This is because the IP address must remain reachable after the migration. This necessarily restricts the ability to migrate VMs, limiting their potential and utility.In this paper, we show how a new Internet standard, Multi-Path TCP, can be used to seamlessly migrate live VMs across WAN boundaries. This allows services to migrate closer to their clients while preserving active TCP connections, improving performance, responsiveness, and user engagement. We show this by designing and implementing LSM-MPTCP, a system for VM Migration over the WAN. We demonstrate how our approach can improve throughput and latency in a real cloud environment, achieving throughput improvements up to 6 times and reducing round-trip times by 99%. We also expose subtle networking issues related to migration that can heavily affect loss rates.