Bandwidth Allocation Protocol, or BAR, is a remote access protocol that dynamically controls how bandwidth can be allocated.
What is BAP (Bandwidth Allocation Protocol)?
Bandwidth Allocation Protocol (BAP) is a multilink remote access protocol supported by Microsoft Windows 2000 that dynamically controls how bandwidth can be allocated for multilink connections using the Point-to-Point Protocol (PPP).
Bandwidth Allocation Protocol (BAP) makes multilink connections more efficient by allocating lines only as required, thus eliminating wasted bandwidth. This is especially useful if the telecommunications carrier being used for the PPP connection charges by the amount of bandwidth being utilized by the customer.

BAP allows the administrator to configure the PPP server to specify which particular Multilink PPP (MPPP) lines can be added or dropped. The administrator also specifies which bandwidth thresholds must be crossed before additional lines are added or existing ones are dropped. BAP is especially useful over Integrated Services Digital Network (ISDN) connections because these dial-up services can almost instantly add or drop lines.
BAP is provided in Windows 2000 as an additional enhancement to the Routing and Remote Access Service (RRAS) of Windows NT 4.0. BAP is defined in Request for Comments (RFC) number 2125.