VMware and Citrix Systems are competing head-to-head to gain ground in the next round of virtualization in the enterprise, but they're going about it in decidedly different ways.

Their competition, along with rapidly emerging third-party toolsets for managing virtual machines, will be evident in the keynotes and sessions of Interop in Las Vegas, May 17 - 21.

VMware is focused on converting the data center into a more virtualized environment through its layer of software products. If it has its way, every data center eventually will look more like a cloud computing center.

Citrix does many of the same things VMware does, but for now, it's focused on converting the enterprise, starting with the end user, and moving up. It seeks to flank today's IT-centric data center with a more consumer-like approach to virtualization's end users.

As VMware CTO Stephen Herrod said at the company's Palo Alto, Calif., headquarters in April, virtualization software is directly taking over some tasks that used to be done in highly specialized hardware configurations. Many of these functions are being built into VMware's vSphere 4 suite.

One piece is vSphere's Fault Tolerance, which "spins up a shadow VM of the one running, mimicking everything the primary one is doing. If production virtual machine fails, it seamlessly cuts over to the shadow VM without anyone noticing" the changeover, he said.

VMware will be emphasizing aspects of the virtual data center operating system at Interop. Herrod will give a keynote address on virtualization's future at 8:30 a.m. Tuesday. Fellow VMware CTO for management Ben Verghese will speak at a session, "Virtualization Management Futures: The Final Frontier?" at 3:15 p.m. on Wednesday. Citrix System, the leader in virtualizing end user applications, is building on its Presentation Server presence in the enterprise. Presentation Server virtualized hundreds of Windows applications on central servers, where end users access them. Any application or desktop that currently can be virtualized under Citrix XenServer, Citrix XenApp, and Citrix Desktop can be made accessible to end users through a new Citrix product, Dazzle, a lightweight storefront for distributing virtualized applications and desktops.