What is DaaS, Thin Client Computing / Desktop as a Service

Desktop as a Service (DaaS) is a cloud service in which the back-end of a virtual desktop infrastructure (VDI) is hosted by a cloud service provider.

What is a Client?

In computing terminology, a ‘client’ is a hardware or software component in a network that relies on a more powerful computer, a server, to perform specified operations. This means that not all processing needs to be performed by a user’s device or applications. The client simply provides a window, or interface, to view and use applications on a personal computer, workstation or other device. Clients most commonly connect to servers through the Internet.
Thin Clients

A ‘thin’ client relies on a server to do most or all of its processing. A common example is a web application that uses a browser to present the application to the user. Thin computers are far simpler than standard PCs, and usually contain just enough information to start up and connect to the server.
Thick Clients

A ‘thick’ client is a computer with many locally stored programs and resources and little dependence on network resources. A common example of a ‘thick client’ is where the interface of the application must be downloaded to the desktop computer.
Benefits of Thin Client Computing

The advantages of thin client computing include:

Reduced cost – simpler devices are lower in price. In a situation where many people perform a similar task, it is more cost-effective to have one network server computer and many cheap client computers, than to have many complete devices.
Ease of maintenance – a standard computer has a lot of parts, and a thin client only has a few, which means fewer things can go wrong. The simplicity makes it easier to diagnose and repair problems.
Ease of use – reduced complexity for users.
Security – security is centralized and easier to manage.

Thin client computers are increasingly replacing standard PCs in the workplace.
Virtual Desktop Infrastructure (VDI)

A virtualized desktop means that a standard desktop computer’s operating system, applications and other resources required for the interface are delivered from a host server. A VDI enables users to access their desktop from remote locations, including on mobile devices, because a central server executes the user interface. It is increasingly common for the standard Windows interface to be virtualized, rather than housed on the user’s device.

Desktop as a Service (DaaS)

Desktop as a Service (DaaS) is where an external cloud service provider’s servers – rather than in-house servers – provide the operations for a virtual desktop infrastructure (VDI). The DaaS service provider takes on responsibility for data storage, backup, security and upgrades, which reduces pressure on internal IT staff. DaaS is purchased on a subscription basis, usually for a set monthly fee.

DaaS is a great alternative for smaller to mid-sized businesses seeking the benefits of a VDI, but lacking the budget and resources required to set up an in-house VDI. The monthly pay-per-use of DaaS avoids the need for high upfront capital expenditure, making it a more affordable way to access newer technology.

First what is a remote desktop protocol ?

When it comes to virtual desktop infrastructure, administrators have a lot of choices. You may have wondered about the differences between VDI software options, remote display protocols or all the licenses out there. In this series, we tackle some of the biggest head-scratchers facing VDI admins to help you get things straight.

In VDI environments, the remote display protocol has a big responsibility: to transmit data from a data-center-hosted desktop to the endpoint.

Popular remote display protocols offer high-resolution sessions, multimedia stream remoting, multi-monitor support, dynamic object compression, USB redirection, drive mapping and more. Microsoft’s Remote Desktop Protocol (RDP), VMware’s PC-over-IP (PCoIP) and Citrix’s HDX are the most commonly used, but there are other protocols from companies such as Ericom and Hewlett-Packard.

Each remote display protocol works differently depending on the network and which applications are being delivered, so you need to know how the major protocols diverge. Let’s get this straight.

What’s under the hood of a remote display protocol?

RemoteFX, HDX and PCoIP are Layer 7 protocols that are based on two Open Systems Interconnection (OSI) stack Layer 4 protocols: the User Datagram Protocol (UDP) and Transmission Control Protocol (TCP). TCP divides data into packets and reassembles them at the endpoint, while UDP does not sequence the packets.

TCP is more reliable because it makes sure that a connection is maintained until all the data is delivered. Plus, if an error occurs, TCP sends the affected data again. UDP does not confirm that all packets are received at the endpoint, but that means it’s faster for delivering media-heavy messages such as video.

Remote display protocols have their limitations, especially when it comes to delivering graphics-intensive applications. Great performance requires a lot of bandwidth, which can clog the network. Plus, if you want low CPU use, your protocol will hog bandwidth and weaken end user performance. As desktop virtualization expert Brian Madden says, you can have “low bandwidth, good experience, low CPU … pick any two.”

Microsoft RDP/RemoteFX

RemoteFX, an enhancement to Microsoft’s Remote Desktop Protocol, was released with Windows Server 2008 R2 to boost high-definition graphics rendering. RemoteFX works on Hyper-V only, although Citrix Systems Inc. does support the protocol for use in XenDesktop environments. Windows Server 2012 RemoteFX allows Remote Desktop Services to use UDP when necessary, while previous versions could only use TCP.

RemoteFX and Windows Server 2012
RDP was initially for LAN-only delivery, but the latest version adds WAN optimization. RemoteFX in Windows Server 2012 also comes with multitouch support and Adaptive Graphics, a feature that does visual element-rendering on the host rather than the client.

Citrix ICA and HDX protocols

Citrix started the whole remote display protocol industry with its independent computing architecture, or ICA protocol. Citrix more recently put a vast amount of development effort into transforming ICA into the HDX protocol — which is a group of several remote display technologies that work together — used in XenDesktop and XenApp since 2009

In the early days, the only way to get good USB redirection, Windows multi-monitor support or video playback was by using third-party software. But over the years, Citrix has continuously made improvements to ICA/HDX to turn it into a modern remote display protocol. There are no significant features missing from HDX.

Additionally, Citrix HDX includes technologies that focus on specific aspects of remote desktop and application delivery. For example, HDX 3D Pro helps IT deliver a quality user experience for employees using remote 3D or other resource-intensive applications. Another HDX subgroup, HDX Mobile, improves the user experience when accessing Windows apps and virtual desktops on mobile devices.

VMware Blast protocol and PCoIP

VMware signed a license agreement with Teradici in 2008 to use the PC-over-IP (PCoIP) protocol in its Horizon end-user computing suite. Teradici has a long engineering history in remote graphics delivery, which is why PCoIP has always supported USB redirection, video playback and multi-monitor well. PCoIP was originally designed for hardware clients, so it did not originally support client printers or disk drives on the client. However, over the past eight years VMware and Teradici have co-developed a lot of enhancements to PCoIP to keep pace with Citrix HDX and Microsoft RemoteFX. Not all of these features are available to other PCoIP licensees. For example, the AWS WorkSpaces DaaS offering only includes basic PCoIP protocol.

Comparison Of Industry DaaS Leaders

When considering a DaaS solution, there are a couple of things you need to examine. First, is the hypervisor, which supplies the software platform that runs the virtual machines. The other is the cloud service provider that supplies and mans the cloud running said hypervisor. Hypervisors vary in their capabilities; cloud providers vary in their offerings.

Currently, there are three major DaaS providers:

VMware’s Horizon Air can provide users with a Windows XP, Windows 7, Windows 8, Windows Server 2008, or Windows Server 2012 R2 virtual desktop. For a server OS, prices include licensing. For clients such as Windows 7 or 8, you will have to bring your own licenses. The cloud-hosted desktops can be integrated with Active Directory.

VMware offers three service tiers ranging from $35 per month to $100 per month with a minimum order of 50 users, billed monthly or annually, with volume discounts available. Desktops can be persistent or non-persistent and utilize the PCoIP protocol (also supports RDP). Service is provided by VMware or authorized service providers, and pricing may vary depending on which option you choose and the services offered.

VMware offers a free seven day trial of their DaaS offering for prospective buyers.

WorkSpaces by Amazon only delivers the Windows 7 Experience via Windows Server 2008 R2. As a result of Microsoft’s SPLA, no other licensing is needed. Amazon also offers Active Directory integration.

Several pricing tiers are available ranging from $35 per month to $75 per month depending on hardware and software options with no order minimum. WorkSpaces is based on a heavily modified version of the open-source Xen hypervisor, providing only persistent desktops, and utilizing the PCoIP protocol.

Citrix XenDesktop offers Windows Server 2008 R2, Windows Server 2012 R2, and Windows XP, 7, 8,10 client desktops. It runs on the HDX protocol, and service can be obtained through authorized service providers. Prices vary depending on the provider.

One may wonder why Microsoft is not in this discussion ?

Microsoft plans to continue supporting existing Azure RemoteApp customers through August 31, 2017, after which time the service will be discontinued. Purchases of Azure RemoteApp has end October 1, 2016.

Microsoft and Citrix are now providing a common platform called Citrix XenApp Essentials Service”  that deliver virtual apps from the Microsoft Azure Marketplace powered by the Citrix Cloud XenApp Essentials Service.




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