In 802.15.4 beacon-enabled mode, each node employs two system parameters: beacon order (BO) and Superframe Order (SO). This determines the sleep/wake cycle
The parameter BO decides the length of beacon interval (BI), where BI = aBaseSuperframeDuration × 2^BO symbols and 0 ≤ BO ≤ 14; while the parameter
SO decides the length of superframe duration (SD), where SD = aBaseSuperframeDuration × 2^SO symbols and 0 ≤ SO ≤ BO ≤ 14.
SD is the active (wake) while BI - SD is the inactive (sleep) period.
Obviously both the control plane operations (or RPL) and the data forwarding would only occur in the active (Wake) cycle of the sensor.