Routing and Remote Access Service Architecture

Routing and Remote Access is built on a series of communications and management agents, transport protocols, forwarders, and APIs. These components have been built, expanded, and improved over the years to provide a secure, efficient, effective, and reliable communications system for client-to-server and server-to-server communications in a Windows networking environment.

Figure 26.1 diagrams the various components detailed through the balance of this section, noting each component and its role in the communications system.

Figure 26.1. The Routing and Remote Access Service.

SNMP Agent for RRAS

Windows Server 2003 RRAS supports the Simple Network Management Protocol (SNMP) management information bases (MIBs). The SNMP agent provides monitoring and alerting information for SNMP management systems. The SNMP agent is a critical component to the reliability and manageability of RRAS as a cornerstone to remote and mobile communications.

Management Applications

Management applications for RRAS include the Routing and Remote Access snap-in and the Netsh command-line utility. These applications are utilities that help an organization better administer the remote and mobile communications environment.

Authentication, Authorization, and Accounting

AAA is a set of components that provides authentication, authorization, and accounting for RRAS when it is configured for the Windows authentication provider or the Windows accounting provider. The local AAA components are not used when RRAS is configured for the RADIUS authentication or accounting provider. The AAA components are also used by the Internet Authentication Service (IAS).

Dynamic Interface Manager (Mprdim.dll)

The Dynamic Interface Manager component supports a Remote Procedure Call (RPC) interface for SNMP-based management functions used by management utilities such as the Routing and Remote Access snap-in. It communicates with the Connection Manager for demand-dial connections and configuration information to the router managers (such as the IP Router Manager and IPX Router Manager). The Dynamic Interface Manager also loads configuration information from the Windows Server 2003 Registry. In addition, it manages all routing interfaces, including local area network, persistent demand-dial, and IP-in-IP interfaces.

Connection Manager

The Connection Manager components manage WAN devices and establish connections by using TAPI. The Connection Manager also negotiates PPP control protocols, including Extensible Authentication Protocol (EAP) and also implements Multilink and Bandwidth Allocation Protocol (BAP).

Telephony Application Programming Interface

The Telephony Application Programming Interface (Telephony API or TAPI) provides services to create, monitor, and terminate connections independently of hardware. The Connection Manager uses TAPI to create or receive demand-dial connections.

IP Router Manager (Iprtmgr.dll)

The IP Router Manager component obtains configuration information from the Dynamic Interface Manager. It loads and communicates configuration information to IP routing protocols, such as RIP for IP and OSPF supplied with Windows Server 2003. It also communicates IP packet filtering configuration information to the IP filtering driver as well as communicates IP routing configuration information to the IP forwarder in the TCP/IP protocol. The IP Router Manager also maintains an interface database of all IP routing interfaces. In addition, it initiates demand-dial connections for routing protocols by communicating with the Dynamic Interface Manager.

IPX Router Manager (Ipxrtmgr.dll)

The IPX Router Manager obtains configuration information from the Dynamic Interface Manager and maintains an interface database of all IPX routing interfaces. It communicates IPX packet filtering configuration information to the IPX filtering driver as well as communicates IPX routing configuration information to the IPX forwarder driver. The IPX Router Manager loads and communicates configuration information to IPX routing protocols (RIP for IPX, SAP for IPX). In addition, it initiates demand-dial connections for routing protocols by communicating with the Dynamic Interface Manager.

Unicast Routing Protocols

RRAS provides the following four unicast routing protocols:

• RIP for IP (Iprip2.dll) The RIP for IP routing protocol communicates RIP for IPlearned routes by using the Route Table Manager. It also uses Winsock to send and receive RIP for IP traffic and exports management APIs to support MIBs and management applications through the IP Router Manager.

• OSPF Routing Protocol (Ospf.dll) The OSPF routing protocol communicates OSPF-learned routes by using the Route Table Manager. It uses Winsock to send and receive OSPF traffic as well as exports management APIs to support MIBs and management applications through the IP Router Manager.

• RIP for IPX (ipxrip.dll) The RIP for IPX routing protocol communicates RIP for IPXlearned routes by using the Route Table Manager. It uses Winsock to send and receive RIP for IPX traffic. It also exports management APIs to support MIBs and management applications through the IPX Router Manager.

• SAP for IPX (ipxsap.dll) The SAP for IPX routing protocol communicates SAP for IPXlearned routes by using the Route Table Manager. It uses Winsock to send and receive SAP for IPX traffic and also exports management APIs to support MIBs and management applications through the IPX Router Manager.

IP Multicast Routing Protocols

The IP multicast routing protocol that RRAS uses is IGMP (versions 1, 2, and 3). IGMP communicates multicast group membership information to the Multicast Group Manager. It also uses Winsock to send and receive IGMP traffic and exports management APIs to support MIBs and management applications through the Multicast Group Manager.

Route Table Manager (Rtm.dll)

The Route Table Manager maintains a user-mode route table for all routes from all possible route sources. It displays APIs for adding, deleting, and enumerating routes that are used by the routing protocols. The Route Table Manager also communicates only the best routes to the appropriate forwarder driver. The best routes are those that have the lowest preference level (for IP routes) and the lowest metrics. The best routes become the routes in the IP forwarding table and IPX forwarding table.

Multicast Group Manager

The Multicast Group Manager maintains all multicast group memberships and communicates multicast forwarding entries (MFEs) in the IP Multicast Forwarder. It also reflects group membership between IP multicast routing protocols.

IP Filtering Driver (Ipfltdrv.sys)

The IP filtering driver obtains configuration information from the IP Router Manager. It also applies IP filters after the IP forwarder has found a route.

IP Unicast Forwarder

The IP Unicast Forwarder, a component of the TCP/IP protocol (Tcpip.sys), obtains configuration information from the IP Router Manager. It stores the IP forwarding table, a table of the best routes obtained from the Route Table Manager. It can also initiate a demand-dial connection and forward unicast IP traffic.

IP Multicast Forwarder

The IP Multicast Forwarder, which is a component of the TCP/IP protocol (Tcpip.sys), stores multicast forward entries obtained from IP multicast routing protocols through the Multicast Group Manager. It is based on multicast traffic received and communicates new source or group information to the Multicast Group Manager. It also forwards IP multicast packets.

IPX Filtering Driver (Nwlnkflt.sys)

The IPX filtering driver obtains configuration information from the IPX Router Manager and applies IPX filters after the IPX forwarder driver has found a route.

IPX Forwarder Driver (Nwlnkfwd.sys)

The IPX forwarder driver obtains configuration information from the IPX Router Manager and also stores the IPX forwarding table, a table of the best routes obtained from the Route Table Manager. The IPX forwarder driver can initiate a demand-dial connection as well as forward IPX traffic.