# Equations¶

## Impacts of delay on TCP throughput¶

The throughput of a single TCP session is not only constrained by the available bandwidth, but also by delay and packet loss rate. Any layer 2 error correction method needs to find the right balance between adding delay and accepting packet loss.

The Mathis formula gives an upper bound:Max DATA throughput rate < (MSS/RTT)*(1 / sqrt(p))

- MSS: maximum segment size
- RTT: round trip time
- p: packet loss rate

RfC 3819, Section 8.5 gives a more accurate estimate:

MSS BW = -------------------------------------------------------- RTT*sqrt(1.33*p) + RTO*p*[1+32*p^2]*min[1,3*sqrt(.75*p)] where BW is the maximum TCP throughout achievable by an individual TCP flow MSS is the TCP segment size being used by the connection RTT is the end-to-end round trip time of the TCP connection RTO is the packet timeout (based on RTT) p is the packet loss rate for the path (i.e., .01 if there is 1% packet loss)