This document defines the "IPv6 over the TSCH mode of IEEE 802.15.4e" (6TiSCH) Operation Sublayer (6top) Protocol (6P), which enables distributed scheduling in 6TiSCH networks. 6P allows neighbor nodes to add/delete Time-Slotted Channel Hopping (TSCH) cells to/on one another. 6P is part of the 6TiSCH Operation Sublayer (6top), the layer just above the IEEE Std 802.15.4 TSCH Medium Access Control layer. 6top is composed of one or more Scheduling Functions (SFs) and the 6top Protocol defined in this document. A 6top SF decides when to add/delete cells, and it triggers 6P Transactions. The definition of SFs is out of scope for this document; however, this document provides the requirements for an SF.