Let’s begin by examining the features of each product:
- Microsoft Forefront Threat Management Gateway (TMG) 2010 is an integrated edge security gateway. An enterprise-class firewall (Common Criteria certification pending – ISA 2006 and ISA 2004 were both EAL4+ certified), it includes support for proxy services (forward and reverse proxy), content caching, and VPN (both remote access and site-to-site). It can be deployed in all of these roles, or any subset of them.
- Microsoft Forefront Unified Access Gateway (UAG) 2010 is a dedicated remote access gateway. It provides browser-based remote access to published applications via an SSL VPN portal. It includes limited support for traditional client access VPN with Secure Socket Tunneling Protocol (SSTP) and Network Connector (a proprietary UAG component that provides network-level access). UAG can also serve as a DirectAccess gateway, a deployment scenario for which the UAG provides incredible value.
Fundamentally, TMG is a network-centric access control solution. With it you can provide fine-grained control over all types of communication going through the firewall, both web-based and non web-based protocols. TMG controls access inbound and outbound, and allows for the configuration of multiple perimeter (DMZ) networks.
By contrast, UAG is an application-centric remote access solution. It provides inbound access only; there are no outbound access capabilities provided by UAG. This is a common source of confusion, as UAG includes TMG under the hood. Many administrators mistakenly believe they can leverage the underlying TMG installation to provide forward proxy or VPN services. This is not supported. Other than mail server publishing, TMG may not be used for any other purpose. It is installed to provide protection for the UAG application only.
UAG takes one of the TMG deployment roles, the VPN/remote access role, and supercharges it. UAG includes advanced application publishing capabilities not provided by TMG, such as endpoint configuration and health detection, customizable data manipulation, session clean up, and more. For example, an administrator can allow full access to a published application to any system that has anti-virus software running and up-to-date, has the firewall enabled, and has the latest system updates applied. If the system does not meet these requirements, the administrator can determine if access should be granted with reduced privileges, or perhaps denied access altogether. An administrator might mask specific data sent to a user (such as credit card numbers, social security numbers, etc.) if the user is accessing the published web application from an untrusted device (non-managed workstation, kiosk, etc.). When the user closes their session, all temporarily downloaded files are removed from the workstation, ensuring that no sensitive data is left behind.
So when do you deploy TMG and when do you deploy UAG? If you want to control outbound web access (forward proxy or firewall), TMG is your only option. If you want to publish multiple applications with a single URL (an application portal), UAG is the answer. There are, however, areas where there is overlap between TMG and UAG capabilities. For example, let’s say you want to publish a single application such as Outlook Web App (OWA). Which solution do you choose? TMG can publish OWA quite capably, as can UAG. The answer depends on your specific requirements. If you need to restrict access to only those systems that meet your specific configuration requirements, publishing OWA with UAG is the solution. If you wish to grant access to OWA to anyone who authenticates successfully, then TMG will suffice.
Licensing often plays a role in determining which solution to deploy for remote access. UAG is licensed using Client Access Licenses, or CALs. Each user of the system is required to have a UAG CAL. The UAG CAL is included in the Microsoft Enterprise CAL (eCAL), so this may not be an issue for larger enterprises. TMG is licensed per processor. There are no CALs required for users of TMG (advanced web protection features do require the Web Protection Services Subscription license, however, which is licensed per user or per device annually). For more information, refer to the licensing FAQs for TMG and UAG.
In summary, TMG is a rock-solid firewall, proxy, content cache, and VPN access gateway that has basic support for application publishing. UAG is an advanced remote access gateway dedicated to application publishing, and is highly customizable and limited in functionality only by your programming skills, creativity, and imagination.
In a nutshell, think of TMG and UAG like this:
TMG – Keeps the bad guys out.
UAG – Lets the good guys in.
UAG – Lets the good guys in.