Assured Forwarding Per Hop Behavior Research Articles

Improving fairness in a WRED-based DiffServ network: A fluid-flow approach

The DiffServ architecture has been proposed as a scalable approach for upgrading the Internet, adding service differentiation functionalities. However, several aspects of this architecture still have to be analyzed and solved. For this reason, network designers need to be provided with tools which are able to estimate the average behavior of a DiffServ network with a high level of accuracy and in a short time. In this paper a fluid-flow model of a DiffServ network supporting Assured Forwarding Per-Hop Behavior (PHB) and loaded with TCP flows is proposed. At the edge of the network, two rate three color markers (TRTCM) are employed as profile meters, while within the network core routers implement a Weighted RED (WRED) buffer management mechanism. In order to demonstrate the high accuracy of the proposed model, a comparison between model and simulation results is performed, taking into account not just a bottleneck link, but a complex network topology. The proposed analytical framework is then used to analyze the impact of several factors on the fair sharing of network resources between traffic aggregates with the same traffic profile, and to achieve some guidelines for WRED parameter settings with the aim of reducing unfairness.

Bandwidth sharing under the assured forwarding Per-Hop behavior

The DiffServ’s Assured Forwarding (af) Per-Hop Behavior (phb) Group defines a differentiated forwarding of packets in four independent classes, each class having three levels of drop precedence. Specific end-to-end services based on thisphb are still being defined. A particular type of service that could assure a given rate to a traffic aggregate has been outlined elsewhere. In such a service, a fair distribution of bandwidth is one of the main concerns.

Experimental TCP Performance Evaluation on Diffserv AF PHBs over ATM SBR Service

In these days, IP network customers become sensitive to the QoS guarantee provided by the network. Amongst many QoS guarantee schemes, Diffserv (Differentiated Services) is the one of the most practical candidates for the next generation IP networks. Under these circumstances, the commercial network venders have already provided the Diffserv routers that support EF (Expedited Forwarding) PHB (Per Hop Behavior). However, AF (Assured Forwarding) PHB in Diffserv still has not been provided by commercial routers. Therefore, it is a realistic solution that SBR3 (Statistical Bit Rate 3) of ATM emulates AF PHB, but it is not clear whether TCP traffic over AF PHB emulated by ATM is differentiated from the best effort TCP traffic over DF (Default Forwarding) PHB. To confirm the differentiation, we have experimentally studied TCP performance through the link into which TCP connections over AF PHB and DF PHB are aggregated. This paper describes the experimental results and discusses the possibility of the TCP performance differentiation between AF PHB and DF PHB over ATM.