Routing Information Protocol (RIP)

The Routing Information Protocol (RIP) facilitates the exchange of routing information on a NetWare internetwork. Like IPX, the RIP protocol was derived from XNS. However, an extra field, ``Number of ticks'', was added to the packet structure to improve the decision criteria for selecting the fastest route to a destination. This change prohibits the straight integration of NetWare's RIP with strictly conforming XNS implementations.

RIP broadcasts

The broadcast of RIP packets allows:

workstations to locate the fastest route to a network number.

routers to request routing information from other routers to update their own internal tables.

routers to respond to route requests from workstations and other routers.

routers to make sure that all other routers are aware of the internetwork configuration.

routers to detect a change in the internetwork configuration.

For more information on routers and the functions they perform, see the Novell NetWare documentation.

RIP packet structure

The RIP packet structure is shown in Figure 4-5. This structure is enveloped within the data area of IPX.

Figure 4-5 RIP packet structure

The packet contains the following fields:

Operation

indicates whether the packet is a request or a response. A 1 in this field indicates a request; a 2 indicates a response.

Network Number

Identifies the network segment the packet will be sent to.

Number of Hops

Indicates the number of routers the packet must pass through to reach a network number.

Number of Ticks

Indicates how much time is required for the packet to reach the specified network segment. The number in this field is always at least one. (A ``tick'' is approximately 1/18 of a second; there are 18.21 ticks in a second.)

The ``Operation'' field can be followed by one or more sets of information, each consisting of a network number and the number of hops and ticks to that network number. A RIP packet can contain a maximum of 50 sets of network number information.

The original XNS definition of the RIP did not include the ``Number of Ticks'' field. The ``Number of ticks'' field was added by the developers of NetWare so that the NetWare shell could estimate how long it should wait for a response from a file server. Also, if multiple routes exist to a network number, a router uses the route with the smallest number of ticks when forwarding packets to that network number.

If a RIP packet is a request for information, only the ``Network Number'' field applies; the ``Number of hops'' and ``Number of ticks'' fields are essentially nulled out. A response packet can be either a reply to a request from a router or workstation or a periodic broadcast by a router.

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.