Remote Access Server

Bandwidth Allocation Protocol (BAP)

While MP allows for multiple physical links to be aggregated, MP does not provide a mechanism to adapt to changing conditions by adding extra links when needed or terminating extra links when unneeded. This additional capability is provided by the Bandwidth Allocation Protocol (BAP) and the Bandwidth Allocation Control Protocol (BACP) defined in RFC 2125. BAP is a PPP control protocol that is used on an MP connection to dynamically manage links. BAP uses the PPP Protocol of ID 0xC0-2D.

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

When the utilization on the second link drops to a specific level, either the remote access client or the remote access server can send a BAP Link-Drop-Query-Request message to drop the link.

BAP also supports a Callback-Request message where the requesting peer specifies the link type and the number to call back to. For more information about BAP messages, see RFC 2125.

Table 7.17 lists BAP LCP options negotiated by Microsoft PPP peers.

Table 7.17 BAP LCP Options

Option Name	Option Type	Option Length	Description
BAP Link Discriminator	23 or 0x17	4	A unique number used to identify a particular link in a Multilink PPP connection.

Multilink PPP and BAP are enabled on the remote access server through the PPP tab on the properties of the remote access router in the Routing and Remote Access snap-in. Properties of Multilink and BAP are configured from the Multilink tab on the properties of a remote access policy profile.

To set the phone number of a port that is sent in the BAP Call-Response message

Use the Routing and Remote Access snap-in to obtain properties on the Ports object.
Select the desired port, and click Configure.
Type the phone number in the Phone number of this device text box.