It is the rare environment that has only one vendor's product. The dream of integrated network access control (NAC) is that network managers will be able to pick and choose best-of-breed components from different vendors to make a complete solution. It's a dream that started with Cisco and Microsoft, and now rests on standards from the Trusted Computing Group. Today, most NAC solutions are interoperable with Cisco or Microsoft technology.
A very large percentage of environments have some combination of Microsoft software and Cisco network devices. This was recognized early on when Microsoft and Cisco were starting to develop their NAC solutions, and the two companies pledged to support each other's efforts. Microsoft and Cisco also promised that their products would be interoperable with the Trusted Computing Group's Trusted Network Connect (TNC) standards.
Two years ago, it seemed those pledged efforts might be mostly marketing hype, as neither delivered solutions that followed up on the agreed-upon integration. I'm happy to report that there is a moderate level of integration today, though mixing and matching components from Microsoft Network Access Protection (NAP) and Cisco Network Admission Control (Cisco NAC) to form a complete solution still has a way to go, and it is questionable if integration efforts will ever reach the level sought by users. But there is a lot you can do and a variety of ways you can juggle components.
Open industry standards
First, how compatible are Microsoft's and Cisco's products with the TNC standard? According to Steve Hanna, Distinguished Engineer at Juniper Networks, co-chair of the Trusted Network Connect working group at the Trusted Computing Group (TCG), and co-chair of the Network Endpoint Assessment (NEA) working group in the Internet Engineering Task Force, Microsoft's NAP client is fully compliant.
After working with the TCG to conform to the TNC standard, Microsoft turned over its internal Statement of Health (SoH) format and protocol to the TCG; SoH is integral to checking and reporting a computer's health status to participating management devices. Microsoft's SoH is an implementation of the IF-TNCCS-SOH standard, which describes how a TNC-compliant client and server exchange messages.
Cisco aimed to comply with TNC standards as well, but didn't feel as comfortable working directly with the TCG. Cisco normally works with open standards defined by the Internet Engineering Task Force (IETF), so both Cisco and TCG agreed to push the TNC standards through the IETF. TCG's Steve Hanna and Cisco's Susan Thompson co-chair the IETF NEA working group heading up the IETF standard. According to both TCG and Cisco, the new standard is near completion, which should lead to improved future integration between all NAC vendors, as all can move ahead with future products and features without worrying about a technical tower of Babel.