User guide

© 2011 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information. Cisco Validated Design Page 19
Figure 18. Citrix XenDesktop on XenServer Architecture
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Web Interface: Web Interface provides the user interface to the XenDesktop environment. Web Interface
brokers user authentication, enumerates the available desktops and, upon launch, delivers an .ica file to
the Citrix Receiver on the user‘s local device to initiate a connection. Because Web Interface is a critical
component, redundant servers must be available to provide fault tolerance.
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License Server: The Citrix License Server is responsible for managing the licenses for all of the
components of XenDesktop 4 including XenServer 5.6 (Only XenServer 5.6 can use the License Server).
XenDesktop has a 90 day grace period which allows the system to function normally for 90 days if the
license server becomes unavailable. This grace period offsets the complexity involved with building
redundancy into the license server.
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Domain Controller: The Domain Controller hosts Active Directory, Dynamic Host Configuration Protocol
(DHCP) and Domain Name System (DNS). Active Directory provides a common namespace and secure
method of communication between all the servers and desktops in the environment. DNS provides IP Host
name resolution for the core XenDesktop infrastructure components. DHCP is used by the virtual desktop
to request and obtain an IP address from the DHCP service. DHCP uses Option 66 and 67 to specify the
bootstrap file location and filename to a virtual desktop. The DHCP service receives requests on UDP port
67 and sends data to UDP port 68 on a virtual desktop. The virtual desktops then have the operating
system streamed over the network utilizing Citrix Provisioning Services.
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Provisioning Services: Provisioning Services (PVS) creates and provisions virtual desktops from a single
desktop image (vDisk) on demand, optimizing storage utilization and providing a pristine virtual desktop to
each user every time they log on. Desktop provisioning also simplifies desktop images, provides the best
flexibility, and offers fewer points of desktop management for both applications and desktops. The Trivial
File Transfer Protocol (TFTP) and Pre-boot eXecution Environment (PXE) services are required for the
virtual desktop to boot off the network and download the bootstrap file which instructs the virtual desktop to
connect to the PVS server for registration and vDisk access instructions.
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Desktop Delivery Controller: The XenDesktop controllers are responsible for maintaining the proper level of
idle desktops to allow for instantaneous connections, monitoring the state of online and connected virtual
desktops and shutting down virtual desktops as needed. The primary XD controller is configured as the