network protocols handbook.pdf

178Protocols GuideWAN - PPP ProtocolsProtocol NameBAP: PPP Bandwidth AllocationProtocol (BAP)BACP: PPP Bandwidth AllocationControl Protocol (BACP)Protocol DescriptionThe Bandwidth Allocation Protocol (BAP) can be used to managethe number of links in a multi-link bundle. BAP defines datagramsto coordinate adding and removing individual links in amulti-link bundle, as well as specifying which peer is responsiblefor various decisions regarding managing bandwidth during amulti-link connection. The Bandwidth Allocation Control Protocol(BACP) is the associated control protocol for BAP. BACPdefines control parameters for the BAP protocol to use.As PPP multilink implementations become increasingly common,there is a greater need for some conformity in how to managebandwidth over such links. BACP and BAP provide a flexibleyet robust way of managing bandwidth between 2 peers.BAP does this by defining Call-Control packets and a protocolthat allows peers to co-ordinate the actual bandwidth allocationand de-allocation. Phone number deltas may be passed in theCall-Control packets to minimize the end user’s configuration.BAP defines packets, parameters and negotiation procedures toallow two endpoints to negotiate gracefully adding and droppinglinks from a multilink bundle. BAP allows two peer implementationsto manage the bandwidth available to the protocols usingthe multilink bundle by negotiating when to add and drop links.Use of the negotiation features of BAP makes it unnecessary torequire a ‘common’ algorithm for determining when to add andremove links in a multilink bundle.After BACP reaches the opened state, either peer MAY requestthat another link be added to the bundle by sending a BAP CallorCallback-Request packet. A Call-Request packet is sent if theimplementation wishes to originate the call for the new link, anda Callback-Request packet is sent if the implementation wishesits peer to originate the call for the new link. The implementationreceiving a Call- or Callback-Request MUST respond with aCall- or Callback-Response with a valid Response Code.Protocol StructureBAP Packet structure:BACP packet structure:8 16 32bit VariableCode Identifier Length Data• Code - Decimal value which indicates the type ofBACP packet.• Identifier - Decimal value which aids in matching requestsand replies.• Length - Length of the BACP packet, including theCode, Identifier, Length and Data fields.• Data - Variable length field which may contain one ormore configuration options.Related protocolsPPP, PPPoE, PPPoA, SLIP, CHAP, HDLC, LCP, NCPSponsor SourceBAP and BACP are defined by IETF (http://www.ietf.org) .Referencehttp://www.javvin.com/protocol/rfc2125.pdfThe PPP Bandwidth Allocation Protocol (BAP) / The PPP BandwidthAllocation Control Protocol (BACP)8 16bit VariableType Length Data• Type - Indicates the type of the BAP Datagram Option.This field is binary coded Hexadecimal.