Additional bandwidth is often required to complete certain tasks, but it is not always required.
The purchase of specialized hardware and expensive communication lines might not be justified. The PPP Multilink Protocol (MP) groups multiple PPP links together to form a single virtual link or bundle. The aggregation of multiple links increases the total effective bandwidth between two systems by using standard modems and telephone lines. You can include up to six links in an MP bundle. To establish a multilink connection, both ends of the PPP link must support the multilink protocol. The multilink protocol is documented as a Request for Comment (RFC) standard RFC-1990.
The ability to dynamically add and remove physical links allows a system to be configured to supply bandwidth only when it is needed. This approach is commonly referred to as Bandwidth on Demand and allows you to only pay for the additional bandwidth when you actually use it. To realize the benefits of Bandwidth on Demand, at least one peer must be capable of monitoring utilization of the total bandwidth currently in an MP bundle. Links can be added to or removed from the bundle when bandwidth utilization exceeds values defined by configuration. The Bandwidth Allocation Protocol allows peers to negotiate adding and removing links in an MP bundle. RFC-2125 documents both the PPP Bandwidth Allocation Protocol (BAP) and Bandwidth Allocation Control Protocol (BACP).