Qos is basically the quality of service which is being used for providing the level of predictability and controlling behavior of the current internet protocol services. The performance attributes of these services include service availability, delay, delay variations, through puts and packet loss rates. It works on the principle of service level agreements. There are 3 main protocols on which the QoS works and they are reservation protocol ie RSPV protocol, Multi protocol labeling switching ie MPLS protocol and Subnet bandwidth management ie SBM protocol. The main protocol is the RSPV protocol which is a kind of transparent protocol which enables a network for providing differential level of services which are specific in providing the flow of data. They have different performance requirements and these differences are necessary for the detection of the levels of the performances required for the different applications to work properly.