What are Client Access Licenses and External Connectors?


I get this question a lot, so I thought I would share some info on CALs and ECs

Lets not forget that the choice to go with CALs or an EC<for external users/devices, I will explain further> is usually down to COST or Compliancy

Client Access Licenses – CALs

CALs are not software, they are the right to access the services of a server or servers

CALs are offered in Per User or Per Device mode, again, the choice is down to you, take the factors below into consideration before deciding, they cost the same!

Device CAL: Licenses a device for use by any user to access instances of the server software on licensed servers

User CAL: Licenses one user to use any device to access instances of the server software on licensed servers

CALs are version specific, If you have Windows Server 2003, you need Win 2003 CALs, Win 2000 CALs will NOT do!, you can of course use Windows 2003 CALs to cover access to a Win 2000 Server, they need to be Per Device though

CAL requirements

You must acquire and assign a CAL to each device or user that accesses your instances of the server software directly or indirectly. A hardware partition or blade is considered to be a separate device.

You do not need CALs for:

Any user or device that accesses your instances of the server software only through the Internet without being authenticated or otherwise individually identified by the server software or through any other means,

Any of your servers licensed to run instances of the server software, and

Up to two devices or users to access your instances of the server software only to administer those instances.

Did you know – you can temporarily reassign your device CAL to a loaner device while the first device is out of service or your user CAL to a temporary worker while the user is absent.

Which should I choose, Device or User or EC?

The choice is your own, here are some guidelines

You may choose Per Device simply because you have more USERS than devices, such as in a Call Centre with multiple shifts sharing the same device

You may choose Per User because you have a multi device infrastructure were your users each have a PC/Laptop/PDA or similar devices

You may choose EC because you have multiple external users/devices connecting to your servers, or you cannot keep a count of connection made to your server by external devices/users

More on EC

An External Connector (EC) license is an alternative to CALs for each server that external users will access.

An external user is a person who is not an employee, or similar personnel of the company or its affiliates, and is not someone to whom you provide hosted services using the server software

An EC license assigned to a server permits access by any number of external users, as long as that access is for the benefit of the licensee and not the external user.

Each physical server that external users access requires only one EC license regardless of the number of instances running.

EC licenses, like CALs, are version and functionality specific, They must be the same version or later than the server software being accessed.

You may use Cals in place of EC and vice versa for external users

The decision on whether to acquire CALs or an EC is primarily a financial one.

Did you know – The Windows CAL "breakpoint" for external users/devices is approx 69, so if you have 69+ external users/devices connecting to your server, it will be more cost effective to purchase a Windows EC

Which should I choose Standard or Standard+Enterprise CALs?

All products have a Standard CAL, but some of our server products have a choice between Standard and Standard+Enterprise CALs – MOSS/Exchange and OCS

The choice is based on the functionality you want at the DEVICE end

A Standard CAL allows client computers access to a limited set of fundamental services of the server

An Enterprise CAL allows client computers access to more advanced services of the server

It “adds to” rather than includes the functionality of the Standard CAL

Did you know – You do NOT require the ENTERPRISE edition of the Server to utilise the Enterprise CAL


More info on Standard/Enterprise CAL functionality to follow and an overview of Core CAL and Enterprise CAL Suite



  1. Thanks for this post. It clarifies, but also confuses me somewhat I must admit.As a school wishing to use MOSS to host an internet service for pupils, staff and parents to use, what are the licensing implications? The service requires authentication (AD accounts) and will also be used inside school by pupils and staff. We have a UK Schools Agreement.For some example numbers, let\’s say we have 200 staff, 1750 pupils and 2500 parentsI hope you can advise on this as my experience is that neither Microsoft employees nor resellers can truly grasp the intricacies of the licensing schemes.

  2. Thanks for the info.I have a question.. Is there any official definition for external user? In addition to the definition above: "An external user is a person who is not an employee, or similar personnel of the company or its affiliates, and is not someone to whom you provide hosted services using the server software" I have also found the following one: "Generally, an external user is defined as anyone who is not an employee of the organization. For example, external users can include clients, suppliers, and alumni of the organization. External users do not include independent contractors, agents, service providers, or other persons providing services to or on behalf of the organization holding the license. As an alternative to an EC license, some organizations may choose to license each external user with a separate CAL or CALs.". So, which one is correct and complete?Thanks,

  3. Hi VladislavThe definition in the PUR should be the most complete definition of External User that I would recommend you refer toFrom the current PUR “External users” means users that are not either: (i) your or your affiliates’ employees, or (ii) your or your affiliates’ onsite contractors or agents. If you are under a SPLA then the reference in th SPUR would sufficeThe individual agreements will also have extended info alsoHope this helpsEmma

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