Borrowing is a unique feature of CBQ that provides bandwidth cost savings with extremely efficient sharing of link bandwidth. Each traffic class can be specifically authorized to borrow, or not borrow, from any idle bandwidth on the link. If a class is allowed to borrow, it can burst above its committed rate to meet periodic bursts in demand. It then has access to any idle bandwidth on the link. The efficiency of borrowing results in reduced cost as well as increased revenue potential for network service providers.
Cost is reduced as user traffic more efficiently shares the total available link bandwidth.
Revenue can increase as network service providers create tiered service offerings allowing, for example, a committed minimum bandwidth rate with borrowing, a fixed rate with no borrowing, or a steady-state bandwidth rate with borrowing. As a traffic class is shaped, or trained, to meet its specified bit rate, the rate at which TCP acknowledgments are returned to the source will cause TCP flow control mechanisms to naturally, and in a fully standard way, slow the connection down. As a TCP connection begins to request more bandwidth, it will be allowed if bandwidth is currently available for that class of traffic. This mechanism of slowing down and increasing the rate of a TCP flow is central to ensuring the highest possible efficiency in network link utilization. Bandwidth policies can be established on any interface in the Access Point system, which means traffic can be shaped as it enters and leaves a customer site or a service point of presence.