Are you confused about Microsoft Terminal Services, Citrix Presentation Server, Citrix Access Essentials, and what the difference is between them? No worries. In this article, I give a brief overview of each and the relationship between them.

First, let start with the foundation – Microsoft Terminal Services. Terminal Services is the core technology that allows you to run multiple user sessions on a server, remoting the display and input over the network. Terminal Services has been around for some time, in various forms. Originally a Citrix technology, it now owned by Microsoft. NT4 Terminal Server Edition was the first version from Microsoft, which was a seperate release from NT4. Over time, it become better integrated into the Operating System, so it now a key part of Windows XP Remote Desktop feature, as well as providing Remote Administration and it traditional desktop serving functionality in the Windows Server 2003.

In essence, that Terminal Services today – remote display of desktops. What about Citrix Presentation Server? One techy point that comes up early when discussing Presentation Server, is the ICA protocol. What does that bring to the party? The most notable thing, is that it allows you to remote individual applications that fit fairly seamlessly into your client device. They appear in the taskbar, you can switch back-and-forth between local and remote applications in a natural way. That and other features of the ICA protocol make using remote applications an experience that is much like using the applications locally, irrespective of the network.

Is that it? Presentation Server just brings you a different network protocol and a nicer experience? Nope – the really big thing Presentation Server adds is management infrastructure, allowing you to fit more sessions onto a servers, with farms of hundreds of servers. You also get the tools needed to monitor the health and performance of farms on that scale. On top of that, is layered the ability to restriction access to applications to specific users, SSL encryption, the ability to start applications from a web site, and more.

So that it – pretty simple. Terminal Services is remote desktops, Presentation Server adds a better experience and management. What else do you need? Well, Access Essentials, of course… (well, I would say that, wouldn I?)

Presentation Server provides for the scalability and flexibility requirements of larger organizations, who have a dedicated IT staff. If you have a modest number of users and limited IT staff (perhaps it just you, and you have your job to get done?), you can get overwhelmed by the options for how to deploy Presentation Server on your network. Following advice that makes great sense for 100+ server deployments, when you only have 50 employees can soon stack up the costs. Let face it, you also paying for that flexibility and scalability in the cost of the Presentation Server licenses. That where Access Essentials comes in.

Access Essentials takes the building blocks of Presentation Server and tailors them for customers that want the capabilities, but on a more modest scale. It easy to fall into the trap that smaller customers can make do with a less capable product – but I think that does small customers a dis-service. In Access Essentials, we aimed to add simplicity as a feature. That not to say that we been able to keep everything from Presentation Server, you have to trade some things to get simplicity.

The big trade in Access Essentials is to have just one server. The difference between one server and two is big. Two servers means you have to keep them in sync. Install a hotfix on one server, you should install it on the other. You also have to sort out replication and storage of User Profiles – if using an app on one server sets a registry key, you have to get that new value to the other server, the next time you start the app on it. A single server makes the deployment options simple, put everything on that box. Because of this, we can make the installation process a no-brainer. The management infrastructure of Presentation Server is still there, caged under the covers, so on your single server you get web-based access, per-user applications and all the other great things from Presentation Server, all bundled into a single server.

Sounds great, what the catch? Two biggies, but I think only one counts. You not going to get thousands of sessions running on one server. Since we limit Access Essentials to 75 Named Users, I hope that not a big issue for you . Reduced resiliency is the one that does count – if anything takes the server offline, that it, service gone. Having spoken to customers and resellers – the way to compensate for this is to use RAID arrays and regular backups. The other tip, is that if you have a seperate file server, use it – make sure that you store your documents on the file server.

So there you have it, my thoughts on the differences between Terminal Services, Presentation Server and Access Essentials. Hope you found it interesting, why not post a comment below, and let me know what you think.