In smart factory applications, sensors, actuators, field devices, and supervision systems often require a high degree of reliability and timeliness in information exchange. The Quality of Service provided by the underlying industrial communication network is a key requisite for Quality of Control. In this context, the WirelessHART, ISA100.11a, and IEEE802.15.4e Timeslotted Channel Hopping (TSCH) standards contribute novel protocols to support quasi-deterministic services, based on wireless shortrange communication technologies. The recently created IETF 6TiSCH working group binds IPv6 to this market. Within the 6TiSCH architecture, the 6top sublayer manages the way communication resources are scheduled in time and frequency. The On-The-Fly (OTF) bandwidth reservation module plays a complementary role; it is a distributed approach for adapting the scheduled bandwidth to network requirements. This article first describes the OTF module and its interactions with the 6top sublayer. It then presents simulation results of OTF, drawn from a realistic 50-sensor mote multi-hop network that models a small industrial plant. Results show that OTF can attain an end-to-end latency of the order of a second, with over 99% endto- end reliability. The first real-world OTF implementation in OpenWSN is presented to demonstrate it can easily be added within the 6TiSCH architecture.