VMware vSphere Encrypted vMotion Architecture, Performance and Best Practices

Executive Summary

With the rise in popularity of hybrid cloud computing, where VM-sensitive data leaves the traditional IT environment and traverses over the public networks, IT administrators and architects need a simple and secure way to protect critical VM data that traverses across clouds and over long distances.

The Encrypted vMotion feature available in VMware vSphere® 6.5 addresses this challenge by introducing a software approach that provides end-to-end encryption for vMotion network traffic. The feature encrypts all the vMotion data inside the vmkernel by using the most widely used AES-GCM encryption standards, and thereby provides data confidentiality, integrity, and authenticity even if vMotion traffic traverses untrusted network links.

Experiments conducted in the VMware performance labs using industry-standard workloads show the following:

  • vSphere 6.5 Encrypted vMotion performs nearly the same as regular, unencrypted vMotion.
  • The CPU cost of encrypting vMotion traffic is very moderate, thanks to the performance optimizations added to the vSphere 6.5 vMotion code path.
  • vSphere 6.5 Encrypted vMotion provides the proven reliability and performance guarantees of regular, unencrypted vMotion, even across long.

Introduction

VMware vSphere® vMotion® [1] provides the ability to migrate a running virtual machine from one vSphere host to another, with no perceivable impact to the virtual machine’s performance. vMotion brings enormous benefits to administrators—it reduces server downtime and facilitates automatic load-balancing.

During migration, the entire memory and disk state associated with a VM, along with its metadata, are transferred over the vMotion network. It is possible during VM migration for an attacker with sufficient network privileges to compromise a VM by modifying its memory contents during the transit to subvert the VM’s applications or its guest operating system. Due to this possible security risk, VMware highly recommended administrators use an isolated or secured network for vMotion traffic, separate from other datacenter networks such as the management network or provisioning network. This protected the VM’s sensitive data as it traversed over a secure network.

Even though this recommended approach adds slightly higher network and administrative complexity, it works well in a traditional IT environment where the customer owns the complete network infrastructure and can secure it. In a hybrid cloud, however, workloads move dynamically between clouds and datacenters over secured and unsecured network links. Therefore, it is essential to secure sensitive vMotion traffic at the network endpoints. This protects critical VM data even as the vMotion traffic leaves the traditional IT environment and traverses over the public networks.

vSphere 6.5 introduces Encrypted vMotion, which provides end-to-end encryption of vMotion traffic and protects VM data from eavesdropping occurrences on untrusted network links. Encrypted vMotion provides complete confidentiality, integrity, and authenticity of the data transferred over a vMotion network without any requirement for dedicated networks or additional hardware.

The sections that follow describe:

  • vSphere 6.5 Encrypted vMotion technology and architecture
  • How to configure Encrypted vMotion from the vSphere Client
  • Performance implications of encrypting vMotion traffic using real-life workload scenarios
  • Best practices for deployment

Encrypted vMotion Architecture

vMotion uses TCP as the transport protocol for migrating the VM data. To secure VM migration, vSphere 6.5 encrypts all the vMotion traffic, including the TCP payload and vMotion metadata, using the most widely used AES-GCM encryption standard algorithms, provided by the FIPS-certified vmkernel vmkcrypto module.
Workflow Encrypted vMotion

Encryption Protocol

Encrypted vMotion does not rely on the Secure Sockets Layer (SSL) or Internet Protocol Security (IPsec) technologies for securing vMotion traffic. Instead, it implements a custom encrypted protocol above the TCP layer. This is done primarily for performance, but also for reasons explained below.
SSL is compute intensive and completely implemented in user space, while vMotion, which constitutes core ESXi, executes in kernel space. This means, if vMotion were to rely on SSL, each encryption/decryption call would need to traverse across kernel and user spaces, thereby resulting in excessive performance overhead. Using the encryption algorithms provided by the vmkernel vmkcrypto module enables vMotion to avoid such a performance penalty.

Although IPSec can be used to secure vMotion traffic, its usability is limited in the vSphere environment because ESXi hosts support IPsec only for IPv6 traffic, but not for IPv4 traffic. Besides, implementing a custom protocol above the TCP layer gives vMotion the ability to create the appropriate number of vMotion worker threads, and coordinate efficiently among them to spread the encryption/decryption CPU load across multiple cores.

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