Within the last ten days, Citrix Systems and VMware have each landed surprise blows in a fight that has heated up from an us-vs.-them platform debate to a real sparring match in the cloud and virtual desktop arenas.\nThe most recent is a surprising partnership announced today between Citrix and Cisco Systems to bundle Cisco's Unified Computing System (UCS) with Citrix' XenDesktop virtual desktop infrastructure (VDI) product. [ For timely virtualization news and expert advice on strategy, see CIO.com's Virtualization Drilldown section. ]The bundle, called the Cisco Desktop Virtualization Solution with Citrix XenDesktop, includes hardware, software and licenses to support 300 virtual desktop users, according to Citrix vice president Sumit Dhawan and Cisco VP Jackie Ross, who conducted a teleconference announcing the deal. It's available now. \nThe UCS package includes a chassis with 10GB\/sec interconnect fabric linking five blade servers\u2014two B200 models designed to support virtual applications and three B250 M1 models whose extended memory doubles to 100 the capacity of each blade to support virtual-desktop users, Ross says. \nExpansion Packs include four more B250 expanded-memory blades with which customers can add 400 VDI users at a time up to a total of "tens of thousands"\u2014as many as 320 blades in a series of UCS chassis connected by lossless 10GB\/sec Ethernet, linked to the rest of the network via Cisco Nexus 5000 top-of-rack Nexus Ethernet switches and native support for Fibre Channel, Ethernet and Fibre Channel Over Ethernet (FCOE), Ross says.A Surprise Cisco AllianceThe announcement is surprising to some because Cisco has been a close ally and part ownerof VMware long before VMware's virtualization platform became a lead attraction on UCS when it was launched in March, 2009. \nThe alliance with Citrix makes sense for both Citrix and Cisco in the fast-growing virtual desktop market, however, according to Chris Wolf, senior analyst at Burton Group. \n"Cisco is offering UCS as a backend platform for server-hosted virtual desktops, and there's interest in Citrix among their customer base, so it would be a poor business decision to only show allegiance to VMware," Wolf says. "Cisco has made abundantly clear they do not discriminate against a particular hypervisor; they support XenServer today."\nIn the teleconference announcing the partnership, Citrix also made abundantly clear that its version of the UCS virtualization platform would support either XenServer or VMware's vSphere virtual servers on the backend, though only Citrix' VDI package on the front. \n"VMware's probably not going to like that, but it probably won't be that big a deal," according to Ian Song, enterprise virtualization analyst at IDC. "Citrix is focused on converting its user base to XenDesktop and there's not that big an overlap with VMware server users." \nThere is increasing overlap in the customer base both companies want to convert from physical desktop computers to virtual, however, and in that competition Citrix is clearly dominant, Song says. The punch\/counter-punch marketing has confused the scoring a bit, he says. VMware's New AmmoVMware was able to pull even with XenDesktop on the certification front with the release of VMware View 4.5 at VMworld. The release brought VMware's desktop virtualization suite to full compliance with Burton Group's Server Hosted Virtual Desktop evaluation criteria, which only Citrix had achieved until then. \nVMware scored a major coup, at least on its technology road map and development plan, by announcing a hosted service code-named "Project Horizon" that replicates the VDI-on-any-device capability of Citrix' Dazzle and Receiver products, but extends the concept further than just letting users view virtual desktops from an iPhone, Wolf says. \n"The real differentiator is that it integrates with SaaS solutions, allows connections to applications published on a VMware applciation farm, includes a single sign-on component for applications that could be a XenApp application that can all be seen and managed from a single pane of glass," Wolf says. "That kind of raised the bar for virtual desktops." \nIf Project Horizon let VMware steal a march on Citrix on the desktop, it was only stealing back the one Citrix snatched on VMworld's opening day by announcing it had acquired VMlogix, whose main product serves almost exactly the same function as VMware's highly touted, long-awaited vCloud Director the cloud-management product. \nAnnouncing it acquired existing technology to match a product VMware hasn't shipped helped Citrix gain ground dominated by VMware even as VMware tried to expand its reach into the virtual desktop dominated by Citrix, Song says. \nBoth companies are pursuing similar goals, but doing it in much different ways\u2014Citrix focusing on current products and technology, while VMware draws a more comprehensive picture of the virtual desktop tied into and managed through the cloud, all based on its virtualization platform, Song says. \nVMware's weakness, and Citrix' strength, is that VMware is planning for the long term and laying out a roadmap of products that may not be available until 2011 or even 2012, Song says. \nFrom a customer's point of view, however, things could work the other way as well. \n"Enterprise clients understand no single vendor can do everything they want today," Wolf says. "They also understand if they commit to a desktop virtualization platform it's almost as sticky as server virtualization, so they want to make the right choice. \n"It's important where the vendor is right now, but it's also very important where the vendor is going," Wolf says. "Transparency in roadmaps and development is critical for these companies, which are being very methodoical about architecting their next-den desktop and selecting solutions that might include SaaS and server-hosted desktops and other services as well, all converged in one infrastructure." \nFollow everything from CIO.com on Twitter @CIOonline.