When implementing Active Directory for authentication in enterprise applications like timekeeping systems, Microsoft's licensing model requires careful consideration. For your scenario with 5000 users, you'll need both server licenses and Client Access Licenses (CALs).

• Windows Server License: Required for each physical or virtual server running Active Directory Domain Services
• User CALs or Device CALs: Choose between licensing per user or per device accessing the AD
• External Connector License: If external users need access (not applicable in this internal case)

Here's how to verify authentication in your timekeeping system using C#:

using System.DirectoryServices;

public bool AuthenticateUser(string username, string password)
{
    try 
    {
        using (DirectoryEntry entry = new DirectoryEntry("LDAP://yourdomain.com", 
               username, password))
        {
            using (DirectorySearcher searcher = new DirectorySearcher(entry))
            {
                searcher.Filter = $"(sAMAccountName={username})";
                SearchResult result = searcher.FindOne();
                return (result != null);
            }
        }
    }
    catch
    {
        return false;
    }
}

For 5000 users, Microsoft's Enterprise Agreement (EA) or Select Plus programs typically offer the best value. Key factors:

• User CALs are generally cheaper than Device CALs when users access from multiple devices
• Windows Server Datacenter Edition allows unlimited virtual instances if you're virtualizing
• Software Assurance provides version upgrade rights

1. Maintain an accurate count of authenticated users/devices
2. Document your CAL type selection (User vs Device)
3. Consider future growth when purchasing licenses
4. Regularly audit authentication logs to verify license compliance

For pure authentication scenarios, Azure AD might offer simpler licensing:

Basic Tier: $1/user/month
Premium P1: $6/user/month

However, hybrid solutions require both on-prem and cloud licensing.

When integrating Active Directory (AD) authentication with enterprise systems like timekeeping software, the licensing requirements can be complex. Microsoft's licensing model operates on two fundamental components:

// Conceptual representation of AD licensing components
AD_License = {
    server_license: "Windows Server", 
    client_access: "CALs (Client Access Licenses)",
    additional_services: ["Directory Services", "Authentication Protocols"]
}

For a 5,000-user deployment authenticating against AD, you'll need:

• Windows Server licenses: Physical or virtual instances running AD DS
• Client Access Licenses (CALs): Required for each device or user accessing the server
• External Connector licenses: Alternative for non-employee access

Here's how you might structure authentication in code while maintaining license compliance:

// PowerShell example for AD authentication
$credential = Get-Credential
$timekeepingSystem = "TimeTracker01"

try {
    $adAuth = New-Object System.DirectoryServices.DirectoryEntry(
        "LDAP://yourdomain.com",
        $credential.UserName,
        $credential.GetNetworkCredential().Password
    )
    
    if ($adAuth.Name -ne $null) {
        # Licensed authentication successful
        Connect-TimekeepingSystem -Credential $credential -Server $timekeepingSystem
    }
}
catch {
    Write-Error "Authentication failed: $_"
}

For large deployments (5,000+ users), consider:

1. Volume licensing agreements
2. User CALs instead of Device CALs for roaming users
3. Proper AD forest/domain design to minimize required servers

The most cost-effective solution typically involves Windows Server licenses plus User CALs for each employee accessing the system, with External Connector licenses for any non-employee access.