Multilink and BAP

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Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

A server running Routing and Remote Access supports Multilink and the Bandwidth Allocation Protocol (BAP). With Multilink, multiple physical links appear as a single logical link over which data is sent and received. A good example is the aggregation of both B channels of an ISDN Basic Rate Interface (BRI) connection. Multilink is the recommended method of combining multiple B channels of a BRI connection because the support for bonding, the combining of ISDN B channels through hardware support, is specific to the ISDN adapter. You can use Multilink for any ISDN adapter. Multilink must be supported on both sides of the connection.

While Multilink allows for multiple physical links to be aggregated, Multilink does not provide a mechanism to adapt to changing bandwidth conditions by adding extra links when needed or terminating extra links when unneeded. This additional capability is provided by the Bandwidth Allocation Protocol (BAP).

For example, a Multilink and BAP-enabled remote access client and remote access server create a Multilink connection that consists of a single physical link. As the utilization of the single link rises to a configured level, the remote access client uses a BAP request message to request an additional link. The BAP request message specifies the type of link desired, such as analog phone, ISDN, or X.25. The remote access server then sends a BAP response message that contains the phone number of an available port on the remote access server of the same type as specified by the remote access client in the BAP request.

To enable Multilink and BAP, you must do the following:

  1. Enable dynamic bandwidth control on the remote access server by using Routing and Remote Access. For more information, see Enable BAP and BACP. Multilink and BAP are enabled by default.

  2. Enable Multilink on the appropriate remote access policy. For more information, see Configure multilink options. By default, the policy profile is configured to use the settings of the remote access server.

  3. Configure Multilink and BAP behavior on the remote access client. For more information, see Configuring multiple device dialing.

To set the phone number on a port that is sent back to a BAP-enabled client, see Set the phone number on a port.

Note

  • When Multilink and BAP are used in combination with the callback feature set to always call back to the same number, a concentrator must exist on the caller side that can distribute incoming calls to the same number on various ports.