Addendum to the ProCurve Access Control Security Design Guide

Microsoft NAP

NAP Enforcement Point

In AAA, a PEP provides network access to an endpoint and enforces a PDP’s decisions. Similarly, a NAP enforcement point stands between an endpoint and access to the network. NAP supports these enforcement points (some of which can also be AAA PEPs and some of which cannot):

HRA—controls network access by issuing certificates, which are required to authenticate communications in the unrestricted network

DHCP server—controls network access by assigning IP addresses to endpoints, allowing the endpoints to reach either all addresses or a restricted set of addresses

VPN server—controls network access by opening either unrestricted security associations (SAs) with remote endpoints or filtered SAs

802.1X authenticator—controls network access by placing ports (or wireless associations) in either an unrestricted or restricted VLAN

As you learned earlier, an endpoint has several NAP ECs, each of which correspond to a particular type of enforcement point (or, more precisely, an enforcement server [ES] on the enforcement point). The appropriate EC submits the endpoint’s SSoH to the NAP enforcement point.

Table A-2. NAP ECs and Corresponding NAP Enforcement Points

NAP EC

NAP Enforcement Point

IPsec NAP EC

HRA (on Windows Server 2008)

DHCP NAP EC

DHCP server (on Windows

 

Server 2008)

VPN NAP EC

VPN gateway

EAP NAP EC

802.1X authenticator

 

 

The enforcement point forwards the SSoH to the NPS using RADIUS (much as a PDP forwards a user’s credentials to a RADIUS server). After the NPS verifies the endpoint’s health and makes an access control decision, the NAP enforcement point applies the appropriate controls.

NPS

Like an AAA PDP, an NPS makes policy-based decisions about the level of network access that the endpoint should receive. For each NAP client SHA, the NPS has a system health validator (SHV), which contains the current requirements for system health. The NPS compares the values in the SHVs with the values in the endpoint’s SSoH.

A-16