In one or more embodiments, an apparatus includes a first power-line communication circuit to communicate data with a second power-line communication circuit over power lines and using a communication protocol requiring that one of the first power-line communication circuit or the second power-line communication circuit join into regular communications in response to an initiation message received over the power lines. The first power-line communication circuit communicates data regularly with the second power-line communication circuit over the power lines after being joined into regular communications by an initiation message received over the power lines, the initiation message being communicated over the power lines at an initiation time interval, the initiation time interval being based on a random interval that is within an interval range and that is based on a relative time at which at least two of the plurality of endpoint devices are designated to join within an interval range.