Understanding Client Access Licenses

Microsoft doesn't make all of its money just selling software-it also makes a boat-load selling Client Access Licenses. Whether you are an administrator who manages hundreds of systems or a small business owner just trying to connect a few PCs to a server, understanding Client Access Licenses is the only way to ensure your company doesn't run afoul of Microsoft's End User License Agreements (EULAs).

What's a CAL?

When you buy Windows Server, you receive a server license that allows you to install the operating system on one computer. A server license by itself doesn't give you the legal right to allow others to connect to that computer, whether they work for your company or not. Instead, each user needs a Client Access License, or CAL. You might think that buying a copy of Windows XP or other Windows operating system gives you that CAL, but it doesn't. When you buy a Windows client operating system you have the legal right to install it on a computer and use it, but the Windows license does not give you the legal right to use it to connect to a Windows Server. That's where the CALs come in.

A CAL gives you the legal right to connect to a server application such as Windows Server. Not all CALs are created equal, however. A CAL is targeted to a specific server application.

For example, in order for ten users to connect to a Windows Server to access shared printers and folders, you need to purchase ten Windows CALs. Windows Server keeps track of the connections by computer, so multiple concurrent connections from one computer count only against one license. For example, you could open four shared folders and use two shared printers concurrently, and this would count as one connection rather than six.

Now, let's throw Exchange Server into the mix. If you have 25 users, you need to purchase 25 Exchange Server CALs in addition to 25 Windows CALs for that server. Likewise, other Microsoft server applications such as SQL Server, Project Server, Host Integration Server, and others, require their own CALs. Let's expand the example and say that you have 25 users who need access to the server for printing and file sharing. 20 of those users need access to Exchange Server, and 10 need access to SQL Server. You need 25 Windows CALs, 20 Exchange Server CALs, and 10 SQL Server CALs, for a total of 55 CALs.

Sounds simple enough, doesn't it? In an example like this it is simple, but what if several of your Exchange Server users need to access the server from a desktop computer, a notebook, and a PDA? What if you add a shop floor where 50 employees share 10 computers in different shifts? Now you need to consider licensing modes.

Choose Your Mode

Windows 2000 Server offers two licensing modes: per-server and per-seat. Windows Server 2003 replaces per-seat licensing with per-user / per-device. Let's take per-server first.

When you configure Windows Server for per-server mode, you specify the number of CALs you have purchased for the server and Windows Server allows up to that number of concurrent connections. Configure it for 100 CALs, for example, and Windows Server will support up to 100 concurrent connections. Additional connection attempts after the limit is reached fail. Windows Server counts administrator connections against the total but still allows administrators to connect after the limit is reached to allow them to manage the server (and potentially disconnect users if needed). With per-server licensing therefore, Windows Server actively controls connections based on the number of licenses for which you have configured it.

Per-user / per-seat mode is a bit different. A User CAL (per-user mode) allows a single user to connect to the server with any number of devices. If your users work with a desktop computer, notebook, PDA, and smart phone-all accessing an Exchange Server, for example-the logical choice would be to purchase User CALs. Each user could then connect with as many devices as needed.

A Device CAL allows one device to connect to the server application. For example, assume you have a training lab containing 20 computers that are shared by 200 students throughout the day. Rather than purchase 200 User CALs, you would instead purchase 20 Device CALs. Since User CALs and Device CALs cost the same, your licensing cost is only one-tenth what it would be if you purchased User CALs.

An important distinction between per-server and per-user / per-device licensing is that with the latter, Windows Server does not prevent connections even after the limit is reached. The License Logging service does monitor and report connections for both per-server and per-user / per-device, but only with per-server mode does Windows deny connections after the limit is reached.

I Don't Need No Stinking CAL!

There are a few situations where CALs are not needed. The first is when users access the server anonymously. For example, you don't need CALs to allow users to access your company's Web site. If you add a private area to the site that requires authentication, such as to allow access to key customers or business partners, you do need to add CALs for those users who will be authenticating.

Recognizing that companies might require a large number of customers or clients to access a server or server application, Microsoft introduced the External Connector License. An External Connector (EC) allows an unlimited number of external users to access a particular server application. ECs are not meant to allow company employees to connect remotely-you need traditional CALs for that. Instead, ECs are targeted at customers, clients, and business partners who need authenticated access to your servers and server applications.

ECs can be expensive if you don't have very many customers or partners at the moment who need access. If that's the case, you can purchase CALs and achieve the same legal goal. If the number of external users will grow over time, compare the cost of individual CALs against the cost of an EC to determine which option makes the most sense for your situation.

For more information about CALs and licensing, check out Microsoft's CAL Guide at its Software Asset Management site. You'll also find more information about licensing and license management in an article I wrote for TechRepublic on the subject. Finally, look for more articles here in the future on licensing and license management.

Jim

UPDATE: Terminal Services users click here to learn more about TS licensing.