9.1. TCP Error-Recovery Features

TCP’s error-recovery features are our best tools for locating, diagnosing, and eventually repairing high latency on a network. In terms of computer networking, latency is a measure of delay between a packet’s transmission and its receipt.

Latency can be measured as one-way (from a single source to a destination) or as round-trip (from a source to a destination and back to the original source). When communication between devices is fast, and the amount of time it takes for a packet to get from one point to another is low, the communication is said to have low latency. Conversely, when packets take a significant amount of time to travel between a source and destination, the communication is said to have high latency. High latency is the number one enemy of all network administrators who value their sanity (and their job).