Design of traffic conditioner using marking algorithm on DiffServ-over-MPLS

Differentiated service (Diffserv) is the most attention-getting method which does not require excessive changes in existent Internet infrastructure. In order to assure high QoS, the transmission rate should be offered according to SLA (service level agreement) between the user and ISP. However, TCP often fails to support bandwidth in a steady rate to a certain degree, because of intrinsic features of TCP flow-control algorithm. In spite of the fact that SLA must be kept to a certain degree, TCP problems can occur when transfers exceed SLA due to surplus of bandwidth and the congestion of traffic drops the transmission rate down. In this paper, a traffic conditioner is designed to improve the imbalance problems in using TCP and UDP, and control actively the transmission rate according to the availability of remained rate. We set the upper bound of SLA at the input point of the conditioner and used marking algorithm to minimize the TCP's rising tendency of escaping from SLA. The new algorithm proposed will make total transmission rate reach the average rate to minimize low utilization occurred at DiffServ due to the special feature of TCP. This algorithm proportionally calculates and assigns excess bandwidth quotas according to each flow's target rate when excess bandwidth occurs in the network.