Quantifying the quality of service of streaming media in differentiated services networks

Quality of service (QoS) support in the current Internet is indispensable because of QoS-sensitive real-time applications such as voice-over-IP, IP-TV, video conferencing, online gaining etc. Since the introduction of the differentiated services (Diff-Serv) architecture there has been considerable work reported in literature on its performance evaluation. However, none of them have addressed the basic issue of quantification of QoS for supporting streaming media. The main contribution in this paper is the quantification of the QoS of streaming media in terms of mean opinion score (MOS) values. A test bed has been implemented using off-the-shelf components. The experimental results and MOS values are used to show that in a DiffServ assured forwarding network architecture, with class based weighted fair queue scheduling discipline, the QoS of streaming media is not compromised when the load exceeds the reserved capacity, even in case of congestion.

1. Introduction

Internet's traditional best-effort service model cannot provide guarantees required by streaming video, Voice-over-IP (VoIP) and quality sensitive business applications. Therefore it is necessary to offer service differentiation based on the requirements of users and applications. The Differentiated Services (DiffServ) architecture, see [26], has recently become the preferred method to address QoS issues in IP networks. This packet marking based approach to IP-QoS is attractive due to its simplicity and scalability. An end-to-end differentiated service is obtained by concatenation of per-domain services and Service Level Agreements (SLA) between adjoining domains along the path that the traffic crosses in going from source to destination. Per domain services are realized by traffic conditioning at the edge and simple differentiated forwarding mechanisms at the core of the network. Two of the more popular proposed forwarding mechanisms are Expedited Forwarding (EF) and Assured Forwarding (AF) per hop behavior (PHB). The basic concept of AF-based services is simple mark and drop mechanisms to assure QoS. The AF approach will provide better than best effort service by controlling the drop preference of packets at the time of congestion. In the presented work we have implemented the DiffServ AF architecture to ensure the QoS of streaming media in presence of other interfering traffic, including VoIP and FTP traffic. In recent years, experimental work on DiffServ architectures, is mainly reported in terms of network parameters, such as e.g. throughput, delay, jitter.