Compute in-flight data, a receive-window throughput ceiling and explicit exponential timeout waits.
Networking
TCP bandwidth-delay and retry calculator
Compute in-flight data, a receive-window throughput ceiling and explicit exponential timeout waits.
Example inputs · Replace these with your measurements to build your plan.
Method, example and sources
Multiply bandwidth by RTT and divide by eight to obtain BDP bytes.
Convert binary MiB window bytes into a window/RTT rate ceiling.
Limit the ceiling by the entered path bandwidth.
Double consecutive timeout waits up to the explicit cap and sum them.
Worked example. 1 Gbps across 40 ms needs 5,000,000 bytes in flight. A 4 MiB window caps this model near 838.861 Mbps. Three 1/2/4-second waits total seven seconds.
Bandwidth-delay product is the in-flight data needed to fill the entered path. Window/RTT is only one throughput ceiling.
Bandwidth-delay product
5,000,000bytes
BDP in binary units
4.7684MiB
Window-limited throughput
838.8608Mbps
Cumulative timeout waits
7,000ms
TCP bandwidth-delay and retry calculator: detailed result
Timeout
Wait (ms)
1
1000
2
2000
3
4000
Actual TCP also depends on congestion window, loss, pacing, receive-window scaling, ACK behavior and application limits. A zero receive window stops data in this simple model.
Retry waits illustrate exponential backoff with an explicit cap of at least 60 seconds; this is not an adaptive RTT estimator or a promise about an operating system's retry policy.
From the catalog
Network Interface Cards
Explore related listings, then confirm the exact model requirements against your plan. These listings are not an automatic compatibility or capacity verdict.
Use the catalog search inside the worksheet to choose a model or compare the full product family.
A fast link can remain underused when insufficient data is allowed in flight across its round-trip delay. Bandwidth-delay product makes that amount visible in bytes and binary mebibytes. The receive-window calculation is a ceiling for the entered path, rather than a prediction that changing a system setting will achieve that throughput.
What to verify next
Congestion control, loss, pacing, acknowledgments and application behavior may impose tighter limits. The separate retry table illustrates exponential timeout backoff with an explicit cap; real TCP computes an adaptive retransmission timer and follows implementation-specific retry policies. Compare packet captures and endpoint configuration before changing production buffers, and keep receive-window bytes distinct from application file sizes.
Worked example
1 Gbps across 40 ms needs 5,000,000 bytes in flight. A 4 MiB window caps this model near 838.861 Mbps. Three 1/2/4-second waits total seven seconds.
TCP bandwidth-delay and retry calculator — Uniqcli
