Baseline Policy Design

Contributors

Author: Floris van der Ploeg

Overview

Policies provide the basis to configure and fine-tune Citrix Virtual Apps and Desktops environments. Policies allow organizations to control settings based on various combinations of users, devices, or connection types and include settings for:

  • Connections
  • Security
  • Bandwidth

When making policy decisions, consider both Microsoft and Citrix policies to include all user experience, security, and optimization settings. This article focuses on Citrix policies only. For a list of all Citrix-related policy settings, refer to the Citrix Policy Settings Reference.

Decision: Preferred Policy Engine

Organizations can configure Citrix policies either via Citrix Studio or through Active Directory group policy. Active Directory policies use Citrix ADMX files, which extend group policy and provide advanced filtering mechanisms.

Using Active Directory group policy allows organizations to manage both Windows policies and Citrix policies in the same location, and minimizes the administrative tools required for policy management. Group policies are automatically replicated across domain controllers, protecting the information, and simplifying policy application.

Use the Citrix administrative consoles if Citrix administrators do not have access to Active Directory policies. Select the method which is most appropriate for the organization’s needs and use that method consistently. Using a single method avoids confusion with multiple Citrix policy locations.

It is important to understand how the aggregation of policies, known as policy precedence, flows, to understand how a resultant set of policies is created. With Active Directory and Citrix policies, the precedence is as follows:

Policy Precedence Policy Type
Processed first (lowest precedence) Local machine policies
Processed second Citrix policies created using the Citrix administrative consoles
Processed third Site level AD policies
Processed fourth Domain level AD policies
Processed fifth Highest level OU in the domain
Processed sixth and subsequent Subsequent level OU in the domain
Processed last (highest precedence) Lowest level OU containing the object

Policies from each level aggregate into a final policy that is applied to the user or computer. In most enterprise deployments, Citrix administrators do not have permissions to change policies outside their specific OUs, which are typically the highest level for precedence. When exceptions are required, use the “block inheritance” and “no override” settings to manage which policy settings apply from higher up the OU tree. Block inheritance stops settings from higher-level OUs (lower precedence) from being incorporated into the policy. However, when configuring a higher-level OU policy with no override, the block inheritance setting does is not applied. For this reason, care must be taken in policy planning. Use available tools such as the “Active Directory Resultant Set of Policy” or the “Citrix Group Policy Modeling Wizard” to validate the observed outcomes with the expected outcomes.

Note:

Some Citrix policy settings, if used, need to be configured through Active Directory group policy. For example, Delivery Controllers and Delivery Controller registration port, are required for registration of the VDAs.

Decision: Policy Integration

When configuring policies, organizations often require both Active Directory policies and Citrix policies to create a fully configured environment. With the use of both policy sets, the resultant set of policies can become confusing to determine. Sometimes, particularly concerning Windows Remote Desktop Services (RDS) and Citrix policies, similar functionality can be configured in two different locations. For example, it is possible to enable client drive mapping in a Citrix policy and disable client drive mapping in an RDS policy. The ability to use the desired feature can be dependent upon the combination of RDS and Citrix policy. It is essential to understand that Citrix policies build upon functionality available in Remote Desktop Services. If the required feature is explicitly disabled in the RDS policy, the Citrix policy is not able to affect a configuration.

To avoid this confusion, Citrix recommends configuring RDS policies only where required, and there is no corresponding policy in the Citrix Virtual Apps and Desktops configuration. Only configure RDS policies if the configuration is needed for RDS use within the organization. Configuring policies at the highest common denominator simplifies the process of understanding the resultant set of policies and troubleshooting policy configurations.

Decision: Policy Scope

Once policies are created, apply the policies to groups of users, computers, or both, based on the required outcome. Policy filtering allows policies to be applied to the required user or computer groups. With Active Directory-based policies, a crucial decision is whether to apply a policy to computers or users within the Site, domain, or organizational units (OUs). Active Directory policies are broken down into user configuration and computer configuration. By default, the settings within the user configuration apply to users who reside within the OU at logon. Settings within the computer configuration are applied to the computer at system startup and affect all users who log on to the system. One challenge of policy association with Active Directory and Citrix deployments revolves around three core areas:

  • Citrix environment-specific computer policies
    Citrix servers and virtual desktops often have computer policies that are created and deployed specifically for the environment. Applying these policies is easily accomplished by creating separate OU structures for the servers and the virtual desktops. Specific policies can then be created and confidently applied only to the computers within the OU and below and nothing else. Based on requirements, divide virtual desktops and servers within the OU structure based on server roles, geographical locations, or business units.
  • Citrix specific user policies
    When creating policies for Citrix Virtual Apps and Desktops, several policies specific to user experience and security are applied based on the user’s connection. However, the user’s account might be located anywhere within the Active Directory structure, creating difficulty with simply applying user configuration based policies. It is not desirable to apply the Citrix specific configurations at the domain level as the settings would apply to every system to which any user logs on. Applying the user configuration settings at the OU where the Citrix servers or virtual desktops are located also doesn’t work. The user accounts are not located within that OU, therefore the settings not applied to the users. The solution is to apply a loopback policy. A loopback policy is a computer configuration policy that forces the computer to apply the assigned user configuration policy of the OU to any user who logs on to the server or virtual desktop. The user’s location within Active Directory does not affect the applied settings in a loopback policy. Loopback processing can be applied to either merge or replace mode. Using replace mode overwrites the entire user Group Policy Object (GPO) with the policy from the Citrix server or virtual desktop OU. Merge mode combines the user GPO with the GPO from the Citrix server or desktop OU. As the computer GPOs are processed after the user GPOs when merge mode is configured, the Citrix related OU settings have precedence. When using merge mode, Citrix related OU settings apply in the event of a conflict. For more information, refer to the Microsoft support article Loopback processing of Group Policy.
  • Active Directory policy filtering
    In more advanced cases, there can be a need to apply a policy setting to a small subset of users, such as Citrix administrators. In this case, loopback processing only applies to a subset of users, not all users who log on to the system. Use Active Directory policy filtering to specify specific users or groups of users to which the policy is applied. A policy can be created for a specific function. Also, a policy filter can be set to apply that policy only to a group of users. Policy filtering is accomplished using the security properties of each target policy.

Citrix policies created using Citrix Studio have specific filter settings available, used to address policy-filtering situations that are not available when using group policy. Apply Citrix policies using any combination of the following filters:

Filter Name Filter Description Scope
Access control Applies a policy based on the access control conditions through which a client connects. For example, users connecting through a Citrix NetScaler Gateway can have specific policies applied. User settings
Client IP address Applies a policy based on the IPv4 or IPv6 address of the user device used to connect to the session. Care must be taken with this filter if IPv4 address ranges are used to avoid unexpected results. User settings
Client name Applies a policy based on the name of the user device from which the session is connected. User settings
Delivery Group Applies a policy based on the delivery group membership of the desktop or server running the session. User and computer settings
Delivery Group type Applies a policy based on the type of machine running the session. For example, different policies can be set depending on whether a machine is private or shared. User and computer settings
NetScaler SD-WAN Applies a policy based on whether a session is launched through NetScaler SD-WAN. User settings
Organizational Unit (OU) Applies a policy based on the Organizational Unit (OU) of the desktop or server running the session. User and computer settings
Tag Applies a policy based on any tags applied to the machine running the session. Tags are strings that can be added to items, such as machines, in Citrix Virtual Apps and Desktops environments. These tags can be used to search for or limit access to desktops. User and computer settings
User or group Applies a policy based on the user or group membership of the user connecting to the session. User settings

Note:

Policies in a Citrix Virtual Apps and Desktops environment provide a merged view of settings that apply at the user and computer level. In the previous table, the Scope column identifies whether the specified filter applies to user settings, computer settings, or both.

Decision: Baseline Policy

A baseline policy contains all common elements required to deliver a high-definition experience to most users within the organization. A baseline policy creates the foundation for user access and any exceptions that are needed to address specific access requirements for groups of users. To create the simplest policy structure possible, configure the policy settings in the baseline to be comprehensive enough to accommodate as many use cases as possible. Set the priority of the baseline policy to lowest priority, for example, 99. A priority number of “1” is the highest priority. Enable all Citrix policy settings in the baseline configuration, even if those settings use the default value. Configuring these settings defines desired behavior and avoids confusion if the default settings change. Use Citrix policy templates to configure Citrix policies to effectively manage the end-user experience within an environment. Citrix Policy templates are a solid initial starting point for a baseline policy. Templates consist of pre-configured settings that optimize performance for specific environments or network conditions. The built-in templates included in Citrix Virtual Apps and Desktops are shown in the following table:

Template name Description
High Server Scalability Includes settings to provide an optimal user experience while hosting more users on a single server.
High Server Scalability-Legacy OS Equal to the “High Server Scalability” template, apply this policy to VDAs running a legacy Operating System like Windows 2008R2 or Windows 7 and earlier.
Optimized for NetScaler SD-WAN Includes settings to provide an optimized experience to users working from branch offices with NetScaler SD-WAN deployed.
Optimized for WAN Includes settings for providing an optimized experience to users with low-bandwidth or high-latency connections.
Optimized for WAN-Legacy OS Equal to the “Optimized for WAN” template, apply this policy to VDAs running a legacy Operating System like Windows 2008R2 or Windows 7 and earlier.
Security and Control Includes settings for disabling access to peripheral devices, drive mapping, port redirection, and Flash acceleration on user devices.
Very High Definition User Experience Includes settings for providing high-quality audio, graphics, and video to users.

For more information on Citrix policy templates, refer to Citrix Docs - Policy Templates.

Include Windows policies in a baseline policy configuration. Windows policies reflect settings that optimize the user experience and remove features that are not required or desired in a Citrix Virtual Apps and Desktops environment. One common feature turned off in these environments is Windows Update. In virtualized environments, mainly where desktops and servers are streamed and non-persistent, Windows Update creates processing and network overhead. Changes made by the update process do not persist after a restart of the virtual desktop or application server. Organizations often use Windows Software Update Service (WSUS) to control Windows Updates. In these cases, updates are applied to the master disk and made available by the IT department on a scheduled basis.

In addition to the preceding considerations, an organization’s final baseline policy includes settings to address the organization’s requirements. These requirements can be related to security, common network conditions, or to manage user devices or user profiles.

Design Decision: Administrative Delegation

Prevent unauthorized access by limiting the number of users who can access the policies. Leaving security too relaxed can lead to the exfiltration of the configuration details of the Citrix Virtual Apps and Desktops deployment. The method to restrict access depends on the engine used to configure the policies. When using Citrix Studio as the policy engine, assign roles to groups to delegate administrative access. For more information about scopes and roles, refer to the Delegated Administration documentation.

  • Use the built-in administrative roles
    Add Active Directory groups to the respective role to delegate the required level of control.

    • Full Administrator grants read and write access on all objects in the Citrix Virtual Apps and Desktops Site. Pay special attention when assigning the “Full Administrator” role. Besides policies, the “Full Administrator” role grants read and write access to all other objects within the entire Site as well.
    • Read Only Administrator provides read-only permissions on objects within the assigned scope in a Citrix Virtual Apps and Desktops Site. Assigning a group to the “Read Only Administrator” roles grants read-only access to all policies regardless of the assigned scope.
  • Create a custom administrative role
    For more granular control over access to policies, create custom roles. A custom role enables administrators to assign specific tasks to a group of administrators. Assign the “Manage Policies” or “View Policies” definition to delegate the appropriate permissions. As policies are not part of a specific scope, the scope assigned to the administrator does not affect access to the policies. Add Active Directory groups as Administrators and assign the custom role to delegate access.

When configuring Citrix policies using Active Directory group policies, administrators delegate access using the Group Policy Management Console. A single GPO can contain multiple Citrix policies. The granularity of the assigned permissions depends on the design of the GPO structure. Read or write access is granted to a user or group on a per-GPO basis. Access granted on GPO level grants permissions to all Citrix policies configured in that GPO.

Policy Design Recommendations

Based on experience from the field, Citrix developed leading practices related to Citrix policy design. The leading practices put together the design decisions taken from the previous chapters.

Baseline Policy

Leave the unfiltered policy empty and set it to disabled. Configure the unfiltered policy to have the lowest priority possible. The higher the priority number (for example, a priority of 99), the lower the priority. Create baseline computer and user policies named according to the company’s naming convention. Ensure that the baseline policies apply to most users and computers which connect to the Citrix Virtual Apps and Desktops environment. Configure all settings in the baseline policy, even if these settings use the default value.

Policy Layering

Create exceptions to the baseline policy based on the requirements of the end-users. Assign the policy exceptions based on the appropriate filter. Set the priority for the exception policies to be higher than the baseline policy. Create as few policies as possible and consolidate settings where possible. Defining too many policies can lead to complexity and unexpected outcomes.

Example:

In a Citrix Virtual Apps and Desktops deployment, users are not allowed to access the local drives on their endpoint devices inside the Citrix session. Active Directory group membership grants access to local drives. To achieve this behavior, set the “Client drive redirection” setting to “Prohibited” in the baseline policy. Create a policy with a higher priority and set the “Client drive redirection” setting to “Allowed” in the new policy. Add an Active Directory group in the assignments of the new policy. Only users who are a member of the Active Directory group have access to local drives. The default behavior is to deny access to local drives for all other users.

Policy Management

Do not mix-and-match policy engines. Choose one policy engine and configure all Citrix policies using that engine. For example, when using Active Directory group policies, do not use Citrix Studio to create other Citrix policies.

Document all policies, policy settings, and exceptions. Either use a company-internal documentation format or use the policy’s description field to keep track of changes. When using the description field, use a standardized form. For example, include the date, author, and description of the changes: 2020-04-17 - FvdP: Disabled Client Drive Mapping according to request SR422344.

Use policy description field for documentation