Optical Burst Switching (OBS) offers a promising switching technique to support huge bandwidth requirements in optical backbone networks that use Wavelength Division Multiplexing. This book details the quality of service (QoS) issue in OBS networks. It examines the basic mechanisms to improve overall QoS in OBS networks as well as discusses the relative QoS differentiation among multiple service classes in OBS networks. Coverage also details absolute QoS provisioning in OBS networks, end-to-end QoS provisioning in OBS networks, and some non-mainstream research issues and future research directions in OBS networks.