A Per-Flow Measurement and Estimation Method for DiffServ Implementations

Providers of data network services are in search of new solutions for service offerings over integrated service packet networks (ISPN) which can accommodate voice and video traffic in addition to data traffic. The goal is to enable cutting-edge services such as IP telephony, video conferencing, video on demand (VoD), tele-medicine, etc. As the traditional design of data networks has had little or no support for providing the required traffic characteristics to voice and video streams, architectures for quality of service have been defined. Of these architectures, differentiated services are seen as a significant contributor to the migration of current data network to next-generation networks capable of providing a broader range of services. However, the way they have been defined, these architectures lack precise formal specifications, and therefore their performance is strongly related to the quality of each implementation. This paper presents an abstract model for differentiated services with assured forwarding per-hop behavior (PHB). The model is meant for a better illustration of the dynamics of quality of service (QoS) parameters. After a thorough review of existing methodologies for performance measurements for differentiated services, the paper proposes a dynamic model for assured forwarding and validates it against generated traffic on a live network (NCIT*net 2). This work is the starting point for the detailed specification of differentiated services PHBs. A series of following papers will introduce and develop necessary concepts for modeling and estimation of QoS parameters which are associated with these services.