The Delivery Controller is responsible for brokering user sessions to the least-loaded Virtual Delivery Agent (VDA) within a Delivery Group. To make this decision, it relies on a "load index" value. This value is calculated directly on each VDA machine based on configured metrics such as session count, CPU, memory, and disk usage. The VDA periodically reports its calculated load index to the Delivery Controller. The Controller then uses this real-time information from all registered VDAs to determine which machine is the best candidate to host the next user session, ensuring optimal resource distribution.

B. Citrix Director: Citrix Director is a monitoring and troubleshooting tool that consumes data from the Controller; it does not provide real-time load data to the Controller for brokering decisions.

C. Citrix policies: Citrix policies are used to configure the parameters for how the load index is calculated on the VDA, but they do not provide the actual dynamic load value itself.

D. Site database: The Site database stores the site's configuration and historical data. While the Controller interacts with it, the live, real-time load index is reported directly from the VDA.

1. Citrix Virtual Apps and Desktops Product Documentation. Load management. "The load index is calculated on each Virtual Delivery Agent (VDA). The VDA reports the load index to the Delivery Controller. The Controller uses this information in its brokering decisions." (Citrix Docs, "Load management" section).

2. Citrix Virtual Apps and Desktops Product Documentation. Manage Delivery Groups. "Load balancing settings [...] The Delivery Controller selects a server based on the current load." This section implicitly confirms the Controller receives load data to make its selection, which is sourced from the VDAs as stated in the Load Management documentation. (Citrix Docs, "Manage Delivery Groups," section on "Load balancing").