Fair early drop marker for improving TCP fairness in multiple domain DiffServ networks

Abstract

The differentiated services (DiffServ) model, proposed as a scalable way of providing quality of service in the Internet, provides packet level service differentiation on a per-hop basis. To provide the end-to-end service differentiation more efficiently for the assured services, as as a source marker, an interdomain marker placed at the boundary edge routers connecting network domains is necessary because an Internet connection usually spans through a path involving one or more network domains. Such an interdomain marker should be operated at the aggregate flow level due to the scalability problem. The random early demotion and promotion (REDP) marker was proposed as an interdomain marker. It introduces randomness and early decisions on the three-color packet marking process at the aggregate flow level to remove the phase effect that brings about the unfairness in the demotion and promotion among different flows. The REDP marker achieves good UDP fairness in demoting and promoting packets through random and early marking decisions on packets. However, TCP fairness of the REDP marker is not obvious as for UDP sources. In this paper, we propose a new interdomain marker to resolve the problem of the REDP marker. Instead of unfair packet droppings at the RIO buffers in the core routers which cause unfairness of TCP flows, it fairly drops the green packets of each TCP flow with a token filling rate configuration method before they enter into the core routers. By doing this fair early packet dropping, it increases TCP fairness at a minor expense for the total throughput. (c) Elsevier B.V. All rights reserved.