Abstract—With the protiferation of high-speed networks and networked services, prov~loning dfierentiated serviees to a d]verse user base with heterogeneous QoS requirements has beeome an important]problem. The traditional approach of resouree reservation and admiksion control provides both guarantees and graded serviee+%however, at the cost of potentially underutilized resources and tindted sealabltity. In thu paper, we describe a WAN QoS prov~]on areMtecture that adaptively organizes be-at-effort bandwidth into stratified services with graded QoS properties such that the QoS needs of a diverse user base ean be effectively met. Our mdriteetu~BS (Stratitied Best-effort Service)--pmmotes a simple user/shnple network reatkation where neither the user nor the network is burdened with complex comprrtationat responsibitities. SBS is scalablq efficient and adaptive, and it complements the guaranteed service archL teeturq sharing a common network substrate comprised of GPS routers. It is also a functional complemen ~ pmvi&oning QoS efficiently commensurate with user needs, albt4t at the cost of weaker pmteetilon. SBS is suited to noncooperative network envimnrnerrts where users belhave seltishly and resouree contention reaohrtion k m~rated by the principle of competitive interaction. A principat feature of SBS is the transformation of user-centric QoS prevision mechanisms—a defining characteristic of competitive interaction entaiting intimate user control of internal networlk rmourees-into network.eentrie mechanisms while preserving the former’s resouree atloeation

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The need for automated traceability support has been advocated by various researchers and practitioners alike, as manual traceability is cumbersome and error-prone. Thus, many tools and approaches have been developed to overcome the limitations of manual traceability detection and usage. However, the large amount of available traceability tools is lacking suitable means for reasonable comparison based on welldefined criteria, which in turn complicates the process of choosing the appropriate tool. We propose and discuss a framework for classifying traceability tools, demonstrate its feasibility by organizing three tools according to its criteria, and illustrate how its criteria can be used when searching for a suitable tool. 1