Mobile Ad-Hoc Network (MANET) is a collection of mobile nodes, dynamically forming a temporary network without pre-existing network infrastructure or centralized administration. Due to the bandwidth constraint and dynamic topology of MANETs, supporting quality of Service (QoS) in MANETs is a challenging task. MANETs have certain unique characteristics that pose several difficulties in provisioning QoS. Most routing protocols for MANETs are designed without explicitly considering QoS of the routes. QoS-aware routing requires to find a route that satisfies the end-to-end QoS requirement. QoS in MANETs is a rapidly growing area of research interest.In this report, the challenges of QoS support for MANETs are discussed first.Then the current research on QoS support in MANETs is reviewed, followed by extensive discussion and analysis of QoS models and QoS routing. Finally, one of the QoS models - SWAN is studied to provide a qualitative assessment of the applicability of the model.