
Configuring Dial Services
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117353-B Rev. 00
Multilink Fragmentation
Multilink fragmentation splits datagrams into smaller packets when necessary and
sends these packets across links in a multilink bundle. Fragmentation improves the
distribution of data across multilink lines and uses buffer resources more
efficiently, thereby improving communication over bandwidth circuits. Bay
Networks routers comply with RFC 1717, which defines PPP multilink.
Packets sent across links in a multilink bundle have an outer header packet that
contains a unique packet sequence number and allows for the following:
• Fragmentation of the original packets
• Assignment of sequence numbers to each fragment
• Transmission across links in a multilink bundle
• Reassembly of the original sequence and packet size at the destination router
For more information about multilink and fragmentation, see Configuring PPP
Services.
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.
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