Network based services are expanding scale at an unprecedented speed currently. With the continuously strengthen of user’s dependence on these, performance issues are becoming more and more important. Service Level Agreement (SLA) is a negotiated contract between service provider and customer in the way of service quality, priority, responsibility, etc. In this thesis, we designed and implemented a prototype for a SLA driven transmission service, which can deliver a file from one host to another, using a combination of different transport protocols. The proposed service measures the network conditions, and based on these and user’s requirement, it dynamically evaluates if it can meet the user SLA. Once a transmission has been accepted, it uses this information to adjust the usage of different transfer layer protocols, in order to meet the agreed SLA. The thesis work is based on the investigating of network theory and experimental results. We research how the SLA driven transmission service is affected by various factors, they include user’s requirements, network conditions, and service performance, etc. We design and implement an evaluation model for the network performance. It reveals how network performance is influenced by different network metrics, such as Round-Trip-Time (RTT), Throughput, and Packet Loss Rate (PLR), etc. We implement a transmission service on real test-bed, which is a controllable environment. We can alter the network metrics and measuring frequency of our evaluation model. Then, we evaluate these changes with our evaluation model and improve the performance of the transmission service. After that, we propose a calculating method for the service cost. At last, we can summarize the feasibility of this SLA driven transmission service. In the experiments, we obtain the variable delivery time and packet loss of the transmission service, which are changed with RTT and PLR of network. We analyze the different performance of transmission service, which uses TCP, UDP, and SCTP separately. Also a suitable measuring frequency and the cost for the usage of transmission service on this frequency are pointed out. Statistical analysis on the experiment results show that such SLA driven transmission service is feasible. It brings improved performance for user’s requirements. In addition, we come up with some useful suggestions and future work for the transmission service.