All About Network Access Controls

If you’re planning to implement a network access control system (NAC) to ensure only authorized users can access corporate resources, you’re in good company.

If you’re planning to implement a network access control system to ensure that only authorized users with fully patched and virus-protected hardware can access corporate resources, then you’re in good company. About a third of large U.S. companies are intending to start adopting it this year, according to research conducted by Cambridge, Mass- based analyst Forrester.

The key drivers for these companies are compliance considerations having the capability to carry out network access control, and being able to prove that capability. There is also a financial driver in that manual access control is all about updating clients, and this can be very time-consuming and resource-intensive. Automating policy enforcement can free up a lot of people and cut calls to help desks dramatically.

Cost of network access controller implementation

A network access control implementation is likely to take about 18 months and cost anywhere from $100,000 to ten times that figure, and the key to a successful implementation, as always, is a thorough planning stage, according to Rob Whiteley, Forrester’s senior analyst.

Implementing Cisco’s Network Admission Control and Microsoft’s Network Access Protection will affect security policies, network infrastructure like switches, and, of course, desktop and portable devices and the software running on them. In other words, access control is as much a framework as a series of technologies. What this means is that for a successful implementation you need to ensure the whole IT department, including desktop support staff, network administrators and security people, is involved from the start.

Then it’s necessary to make some architectural decisions, and, specifically, you need to examine three choices. Are you going to implement access control though routing and switching hardware, by buying appliances or exclusively as a software solution? Each has it own benefits and drawbacks, but the three options can, to an extent, be mixed and matched.

Using network hardware gives the most granular control, tying policies to access control dynamically. Instead of telling a switch to admit or deny a device based on some fixed attribute such as its MAC address, it can make decisions based on policies that can vary, and on compliance with those policies, which can also vary. The benefits of this approach are that it offers the highest performance and it is the most scalable solution. The obvious downside is the cost of upgrading large parts of the network infrastructure. However, given that the refresh cycle of network hardware is typically five to seven years, the chances are that at least some of your switching gear is due for replacement anyway.

An alternative that avoids replacing relatively new switches is to adopt access control appliances to do the work “in a box”. This completely avoids touching the network infrastructure access control is effectively implemented as a hardware overlay and is likely to be considerably cheaper. The disadvantage of this approach is that it is less granular, less scalable and performance is likely to be lower.

The remaining possibility is to do the whole thing in software, and there are plenty of vendors such as McAfee, Check Point and Endforce that supply products to achieve this. Typically this software would be run close to the DHCP and Active Directory servers, and can be implemented quickly and cheaply. The downside is that whereas a network appliance has lockdown capabilities and can shut off access to a user at the network layer 2 or 3 level (effectively carrying out a function which has been offloaded from the switch) in software you don’t have this network control. The most likely scenario is that the software is used to prevent hosts being assigned an IP address, or only an address from a particular, restricted, range. In fact, the software could be used to issue commands to a piece of network hardware> However, few network professionals would be happy with this soft of hack.

It’s important to reiterate that these three architectures can be mixed and matched it’s perfectly feasible to install new switches at the corporate HQ, an appliance at one branch office and software solutions elsewhere in the organization. Or you could install appliances as an interim measure, and to replace them with new network hardware as it becomes time to replace it.

How to pick a network access controller

“The most important thing is to pick a vendor that is standards-based,” says Whiteley. “It’s no good putting in an appliance that has to be thrown out in two years you need to make sure that whatever you get is (Cisco) NAC or (Microsoft) NAP compatible.”

The obvious final question then is whether NAC or NAP will “win” in the long term. Both have their strengths. Cisco is good at enforcement and Microsoft is good at policy. The answer to the question was revealed last month when Cisco and Microsoft formally announced interoperability between the Cisco Network Admission Control (NAC) and Microsoft Network Access Protection (NAP) solutions. Interoperability will be supported with the release of NAP in the future version of Windows Server which is scheduled to be available in the second half of 2007. The interoperability architecture allows customers to deploy both NAC and NAP incrementally or concurrently.

If your company is involved in financial services, health care or government work, regulatory requirements make network access control something you should be looking to implement right away. But whatever industry your company works in, security considerations mean that network access control is something you are going to want to implement sooner or later. Given the length of time it takes to implement, now is the time to start making plans.

Did You Know…
Deploying both the Cisco Secure Access Control Server (ACS) and the Microsoft Network Policy Server (NPS) will be required for the initial interoperability release. However, Cisco and Microsoft have cross-licensed the NAC and NAP protocols, which provides the opportunity for both companies to respond to future market and customer requirements for a combined policy product. [Source]

Key Terms To Understanding Network Access Controls:

security policy
A security policy is a document that outlines the rules, laws and practices for computer network access.

network management
Refers to the broad subject of managing computer networks. There exists a wide variety of software and hardware products that help network system administrators manage a network.

Network Admission Control
Abbreviated as NAC, Cisco’s Network Admission Control is a set of technologies and solutions that use the network infrastructure to enforce security policy compliance on all devices seeking to access network computing resources.

Network Access Protection
Abbreviated as NAP, Microsoft’s Network Access Protection is a policy-enforcement platform built into the Microsoft Windows Vista and Windows Server Code Name “Longhorn” operating systems.

Paul Rubens is a frequent contributor to He writes regularly for, and

This article was originally published on November 10, 2006

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