TCP tips & tricks

Glossary

DBP — delay-bandwidth product (~ RTT * throughtput)

TCP tricks

The DBP is important for TCP connections. This is because TCP is able to transmit a large number of packets into the network without having to wait for an acknowledgement for each one. Similarly, a TCP can receive a large number of packets without necessarily acknowledging them all. In fact, TCP only has to acknowledge the most recent packet; the sender can assume that all earlier packets are implicitly acknowledged.

How does all this apply to sizing of TCP socket buffers? It basically means that there is little point in making the buffers (both transmit and receive) larger than the expected maximum DBP of the communications channel. For connections which are expected to traverse the Internet, you may need quite large buffers. For local Ethernet only, the buffers need not be larger than, say, two packets.

DBP is important for TCP connections. This is because TCP is able to transmit a large number of packets into the network without having to wait for an acknowledgement for each one. Similarly, a TCP can receive a large number of packets without necessarily acknowledging them all. In fact, TCP only has to acknowledge the most recent packet; the sender can assume that all earlier packets are implicitly acknowledged.