In data communications, the bandwidth-delay product is the product of a data link's capacity (in bits per second) and its round-trip delay time (in seconds).
The bandwidth-delay product was originally proposed[2] as a rule of thumb for sizing router buffers in conjunction with congestion avoidance algorithm random early detection (RED).
As defined in RFC 1072, a network is considered an LFN if its bandwidth-delay product is significantly larger than 105 bits (12,500 bytes).
Ultra-high speed local area networks (LANs) may fall into this category, where protocol tuning is critical for achieving peak throughput, on account of their extremely high bandwidth, even though their delay is not great.
A high bandwidth-delay product is an important problem case in the design of protocols such as Transmission Control Protocol (TCP) in respect of TCP tuning, because the protocol can only achieve optimum throughput if a sender sends a sufficiently large quantity of data before being required to stop and wait until a confirming message is received from the receiver, acknowledging successful receipt of that data.
Protocols that hope to succeed in this respect need carefully designed self-monitoring, self-tuning algorithms.