The advantages of a Virtual Desktop Infrastructure (VDI) are pretty clear - lower costs, ease of management, lower overheads and better security at the desktop.

1. Clarifying VDI – Faster Ways to Implementation
The advantages of a Virtual Desktop Infrastructure (VDI) are pretty clear - lower costs, ease of management, lower
overheads and better security at the desktop.
But its take-up has been much slower than predicted. A recent NCC survey reported that only 5% of companies were
using VDI extensively and almost 40% were still at the stage of planning or evaluating it.
There are many explanations for the slow uptake, but chief among them is confusion about the many and varied
protocols on offer. The lack of a standard VDI protocol is a significant factor, with IT departments reluctant to commit
to a specific technology, in case their choice is superseded or sidelined by another protocol.
The industry’s nascent Video Electronics Standards Agency is looking to develop a standard protocol set (Net2Display),
but this is some way off and it is far from clear whether the resulting protocols will be broadly adopted.
VDI in itself is not a particularly new concept. Tools such as Laplink and PC Anywhere were its forerunners, allowing
users to link PCs and work remotely. Citrix and Microsoft’s Terminal Server changed server-based computing
massively and brought with them a proliferation of protocols, many of which are still used today. Despite the diverse
options available, the market seems to have settled on a few “favourites”, notably:
Citrix ICA: Citrix has been developing products to provide remote access to DOS and Windows applications
on multi-user platforms since the early 1990s. Currently one of the most widely used protocols Citrix ICA has
been developed over the last 15 years as a result of continuous enhancements to the Citrix Metaframe and
Presentation Server products.
Microsoft Remote Desktop Protocols (RDP) 5, 6 (and soon) 7: The first version of RDP (version 4) was
introduced by Microsoft in 1998 with the launch of Windows NT 4.0 Terminal Server. Later versions added
support for a range of features including printing to local printers, improving bandwidth use and support for
enhanced graphics and colours.
Teradici: A relative late-comer to the market, Teradici launched its PCoIP chip technology in 1997 to deliver
PC-like experience over the network. This technology allows users to run complex applications that need high
graphic-intensive cards (e.g. CAD products). The graphic stream is split between the server and end point
device. The protocol looks at the amount of bandwidth available and continuously adjusts the end-user’s
image quality accordingly. The more bandwidth available the better the quality of the screen image.
HDX: The newest form of the Citrix ICA client, it streams 3D graphics, Flash and is good for end-users with
rich media applications. This protocol is aware of the environment (content and infrastructure) in which it is
being used, (i.e. LAN or WAN) so takes account of variations in available bandwidth. It provides functionality
for plug-and-play devices via USB ports.
PCoIP:
This is one of the more recent protocols that combines aspects of VMware and Teradici. Essentially, it is very
similar to Citrix HDX, but PCoIP has been gaining ground rapidly, as it allows streaming of multimedia, Flash,
HD graphics and audio at a speed and quality not previously possible on desktop virtualisation. There appear
few compatibility issues with PCoIP: VMware View includes “log in as current user” functionality which is
integrated with active directory, and Version 4.0.1 provides single-sign on support for PCoIP using third party
providers such as Sentillion and Imprivata. Whilst not yet available, support for VoIP is planned for the future.
VDI has probably also been slow to take-off because of other concerns such as bandwidth availability and latency in
the network.
Bandwidth availability is a key issue when using HDX and PCoIP for VDI: both need far more than the traditional ICA
and RDPs to ensure the end-user experience meets expectations, particularly for home or remote working. Older
protocols can function effectively with less than 64kbps of bandwidth compared with new ones whose demands can

2. reach several megabytes. As a result, the more traditional protocols are ideal for office or remote working, but the
newer protocols are only really suitable for LANs, until there are solutions which can provide effective acceleration and
reduce the amount of bandwidth they need.
WAN latency is another concern, with recent research showing that delays of more than 200milliseconds are likely to
be detrimental to application performance for end-users. Addressing your network’s latency via WAN optmisation
issues before starting any VDI implementation is the only sure way to resolve these potential performance limitations.
This may be more difficult than you’d initially think, as there are currently no optimisation or acceleration capabilities
for the newer protocols – and many of them use some form of proprietary encryption. Currently, this is something of
a stumbling block, but organisations such as Riverbed and Blue Coat are now looking to develop solutions to
overcome these difficulties.
Focus on the user
One of the easiest ways to speed your VDI implementation is selecting a vendor that you are already working with, or
know well. By understanding their techniques and shortcuts, your learning curve can be relatively shallow. Choosing a
new vendor with exceptional technology can bring quick returns, but it means a steeper learning curve.
Whilst protocols such as HDX and PCoIP are currently seen as the emerging protocols for the future, all the evidence
suggests that RDP and ICA still play a major role in successful VDI implementations. Almost 80% of end-users with
virtual desktops do not actually need any further functionality to use their existing applications for their everyday
activities.
Given this, perhaps the route to a fast, trouble-free VDI deployment involves taking the time to assess users’ needs
and expectations, rather than immediately opting for the latest protocols to deliver functionality that may not be
wanted, relevant or effective.
Author: Nick Garlick
Nebulas Solutions Group
February 2010