Universidad Diego Portales Politecnico di Bari University of Luxembourg University of California Berkeley This document describes the environment, problem statement, and goals of On-The-Fly (OTF) scheduling, a Layer-3 mechanism for 6TiSCH networks. The purpose of OTF is to dynamically adapt the aggregate bandwidth, i.e., the number of reserved soft cells between neighbor nodes, based on the specific application constraints to be satisfied. When using OTF, softcell reservation is distributed: through the 6top interface, neighbor nodes negotiate the cell(s) to be (re)allocated/ deleted, with no intervention needed of a centralized entity. This document aims at defining a module which uses the functionalities provided by the 6top sublayer to (i) extract statistics and (ii) determine when to reserve/delete soft cells in the schedule. The exact reservation and deletion algorithm, and the number and type of statistics to be used in the algorithm are out of scope. OTF deals only with the number of softcells to be reserved/deleted; it is up to 6top to select the specific soft cells within the TSCH schedule.