A random early demotion and promotion marker for assured services

The differentiated services (DiffServ) model, proposed to evolve the current best-effort Internet to a quality-of-service-aware Internet, provides packet level service differentiation on a per-hop basis. The end-to-end service differentiation may be provided by extending the per-hop behavior over multiple network domains through service level agreements between domains. The edge routers of each of the domains monitor the aggregate flow of the incoming packets and demote packets when the aggregate incoming traffic exceeds the negotiated interdomain service agreement. A demoted packet may encounter other edge routers on its path that have sufficient resources to route the packet with its original marking. In this paper, we propose a random early demotion and promotion (REDP) technique that works at the aggregate traffic level and allows (1) fair demotion of packets belonging to different flows, and (2) easy and fair detection and promotion of the demoted packets. Using early and random decisions on packets REDP ensures fairness in promotion and demotion. It uses a three color marking mechanism, reserving one color fur differentiating between a demoted packet and a packet with the original out-of-profile marking. We experiment with the proposed REDP scheme using the ns2 simulator for both TCP and UDP streams. The results demonstrate the fairness of REDP scheme in demoting and promoting packets. Furthermore, we show a variety of results that demonstrates that REDP provides better assured services compared to the previously proposed RIO scheme with or without the provision of promotion.