Direct versus indirect routing

There are two types of routing: direct and indirect.

direct

When a machine can send an IP packet to another machine without going through a third machine, the route the packet will travel is said to be a ``direct route'' and the selection of that route is called ``direct routing''. In Figure 5-1, ``Example internetwork'', the machine columbia can trace a direct route to any of the machines on the 132.147.118 network (that is, seine, thames, and volga). The machine columbia cannot reach london or paris directly.

Figure 5-1 Example internetwork

indirect

When a machine wishing to send an IP packet to a second machine must send that packet through a third machine, the route the packet will travel is said to be an ``indirect route'' and the selection of the intermediary machine is called ``indirect routing''. The intermediary machine, a router, has connections to more than one network and is said to provide a gateway between the networks. Therefore, a router may also be called a ``network gateway''. In Figure 5-1, ``Example internetwork'', the machine volga is a network gateway between the 132.147.118 network and the 132.147.246 network. If the machine seine needs to send an IP packet to paris, it must send the packet to volga, which forwards the packet to paris.

Sometimes the source and destination hosts are more than one network away from each other.

Network Access Protection Design Guide

Updated: October 6, 2008

Applies To: Windows 7, Windows Server 2008, Windows Server 2008 R2, Windows Vista

Network Access Protection (NAP) is one of the most anticipated features of the Windows Server� 2008 operating system. NAP is a new platform that allows network administrators to define specific levels of network access based on a client�s identity, the groups to which the client belongs, and the degree to which the client complies with corporate governance policy. If a client is not compliant, NAP provides a mechanism for automatically bringing the client into compliance (a process known as remediation) and then dynamically increasing its level of network access. NAP is supported by Windows Server 2008 R2, Windows Server 2008, Windows 7, Windows Vista�, and Windows� XP with Service Pack 3 (SP3). NAP includes an application programming interface that developers and vendors can use to integrate their products and leverage this health state validation, access enforcement, and ongoing compliance evaluation. For more information about the NAP API, see Network Access Protection (http://go.microsoft.com/fwlink/?LinkId=128423).

The following are key NAP concepts:

NAP Agent. A service included with Windows Server 2008, Windows Vista, and Windows XP with SP3 that collects and manages health information for NAP client computers.
NAP client computer. A computer that has the NAP Agent service installed and running, and is providing its health status to NAP server computers.
NAP-capable computer. A computer that has the NAP Agent service installed and running and is capable of providing its health status to NAP server computers. NAP-capable computers include computers running Windows Server 2008, Windows Vista, and Windows XP with SP3.
Non-NAP-capable computer. A computer that cannot provide its health status to NAP server components. A computer that has NAP agent installed but not running is also considered non-NAP-capable.
Compliant computer. A computer that meets the NAP health requirements that you have defined for your network. Only NAP client computers can be compliant.
Noncompliant computer. A computer that does not meet the NAP health requirements that you have defined for your network. Only NAP client computers can be noncompliant.
Health status. Information about a NAP client computer that NAP uses to allow or restrict access to a network. Health is defined by a client computer's configuration state. Some common measurements of health include the operational status of Windows Firewall, the update status of antivirus signatures, and the installation status of security updates. A NAP client computer provides health status by sending a message called a statement of health (SoH).
NAP health policy server. A NAP health policy server is a computer running Windows Server 2008 with the Network Policy Server (NPS) role service installed and configured for NAP. The NAP health policy server uses NPS policies and settings to evaluate the health of NAP client computers when they request access to the network, or when their health state changes. Based on the results of this evaluation, the NAP health policy server instructs whether NAP client computers will be granted full or restricted access to the network.