
Configuring Dial Services
7-4 114062 Rev. B
PPP Bandwidth Allocation Protocol
The PPP Bandwidth Allocation Protocol (BAP), defined in RFC 2125, manages
the dynamic allocation of bandwidth across links in a multilink bundle. It provides
a flexible yet powerful method of managing bandwidth between two routers.
BAP is only available for bandwidth-on-demand service across ISDN lines.
BAP does the following:
• Coordinates the addition and removal of links from a bundle
• Enables a router to pass information to its peer, so the peer knows which
phone number to dial to activate a connection
• Defines call control packets that enable the router to add or remove bandwidth
effectively
BAP has the following advantages:
• Ensures effective use of bandwidth.
• Allows the Bay Networks routers to work together or with other vendors’
routers.
• Minimizes the configuration of outgoing phone numbers because only one
number is required. The peer passes other phone numbers to the router, which
the router then uses to make calls.
• Uses call requests to determine whether bandwidth is available, which saves
the cost of placing a call to find out this information.
Call requests are BAP protocol messages and are unrelated to ISDN call
requests. When the router sends a BAP call request, it uses active lines, so
there is no call attempt and no phone charge.
• Ensures that both routers agree to activate and deactivate the lines, so there are
no allocation conflicts.
The Bandwidth Allocation Control Protocol (BACP) is the control protocol. It
negotiates the use of BAP, enabling BAP data to be exchanged between the peer
routers. If BACP negotiation fails, the router will not use BAP for
bandwidth-on-demand service.
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