It is worthwhile looking at the key element of Citrix licensing in connection with the two flagships XenApp and XenDesktop to understand the licence dilemma better. XenApp is a host-based application as well as a server desktop publishing system, which is based on Microsoft’s terminal server technology. It was written by Citrix and to date is maintained by Citrix, which can be read on the rather outdated maintenance contracts – End-of-Life of versions 4.5 and 5 end 2005, version 6 will only run another three years. XenApp is rarely sold as an individual licence. It is mainly bought as part of the XenDesktop Enterprise or Platinum Edition.
XenDesktop is a combination of XenApp and VDI technology, which provides an individual VM (Virtual Machine) for each user with a copy of a Windows desktop as operating system. As part of XenDesktop, Citrix offers user, device as well as concurrent licenses. Workspace Suite is a XenDesktop Platinum Edition, combined with a XenMobile Enterprise (with ShareFile) Edition. As per customer preference, this can be purchased with user as well as device licenses. The Workspace Bundle is also a XenDesktop Platinum Edition in combination with a XenMobile Enterprise (with ShareFile) Edition, which is offered with concurrent licences for simultaneous use by different people.
User, Device and Concurrent Licences
The demand for user and device licenses is determined using the Citrix licensing server and are afterwards also issued via the server. If more than one user logs onto the same device, then it should be issued with a device licence as only then any number of users can operate the device. If one user wants to be able to log onto several devices that do not have a device licence, then this person receives a user licence. These licenses cannot be claimed back for 90 days after the last login, not before a release has been done manually using a Citrix utility.
The following list illustrates how many licenses can be required in a standard case according to the licence formula:
A – C + B = Number of required user/device licenses
A= Total number of users
B= Total number of enabled devices
C= Total number of users, who use only enabled devices.
If 800 people work in an organisation, which has 300 enabled devices and 400 users, who only use the enabled devices, then you require 700 user/device licenses. In certain cases, concurrent licenses for simultaneous use are the better solution. However, these are twice the cost of user or device licenses. Extreme caution is to be exercised when deciding on a licence model. For example, if 1000 people work in an organisation, but only 400 of them log in at any given time, then concurrent licenses are the best option – as long as the ratio is more than 2 to 1 (when the licenses more than double).
Other Stumbling Blocks
There are other factors that need to be considered when choosing a licence model. With this licence concept, servers as well as the different groups of access licences have to be strictly kept separate from each other and maintained. This makes the use and tracking of the licenses harder and also gets in the way of cost transparency and compliance.
The fact that XenApp, XenDesktop VDI or both of them can be used by a certain user concurrently with one licence also does not shed any more light into the licence jungle. An unlimited number of hosts are permitted with both of these two products. Citrix only checks the user licenses. Usually, Citrix meets its customers by allowing an excess of 10 percent without any further licence restrictions. However, with the introduction of XenDesktop 7.6, this bonus is again relinquished in favour of a 15-day “grace period”. Then the compulsory implementation of licence numbers is waived until the maximum licence number is reached for the first time. From this point in time, additional users are condoned for 15 days. After 15 days, the strict implementation takes effect and no user, who is above the originally purchased licence number, is able to log on. This sounds easy on paper, however, in practice such bottle necks created by lack of licenses cause great damage; damage that could have been avoided by more transparency during licensing and better compliance assurance.
Citrix Licensing: https://www.citrix.de/buy/licensing/product.html
Citrix Licensing Demystified: http://www.whitehatvirtual.com/blog/citrix-licensing-demystified