Service level Indication: A proposal for QoS monitoring in SLA -based multidomain networks

The offering of QoS based communication services has to face several challenges. Among these, the provisioning of an open and formalised framework for the collection and interchange of monitoring and performance data is feit as one of the most important issues to be solved. Indeed, this is true in seenarios where multiple providers are teaming (intentionally or not) for the construction of a complex service to be sold to a final user, like in the case of the creation of a virtual private network spanning multiple network Operators and infrastructures. In this case, failures in providing certain required Ievels in the quality parameters should be dealt with an immediate attribution of responsibility across the different entities involved in the end-to-end provisioning of the service. But also in cases apparently much simpler, for example when an user requires a video strearning service across a single operator network infrastructure, there is a demand for mechanisms for the measurement of the received quality of service across all the elements involved in the service provisioning: the server system, the network infrastructure, the dient terminal and the user application. lt is clear that this is a complex problem, involving different technologies, disciplines and research areas. In this paper, starting from the ongoing work in the definition of standard interfaces for the Quality of Service negotiation (Service Level Agreements) and control (Service Level Specifications), as weil as from the work ongoing in the IPFIX and IPPM working groups from the IETF, we introduce a new document specifically for delivering monitoring information to user applications. We called such a document Service Level Indication. We here aim at sketching a possible starting point for a research discussion. © 2003 by Springer Science+Business Media Dordrecht

A comparative study of in-band and out-of-band VOIP protocols in layer 3 and layer 2.5 environments

For more than a century the classic circuit-switched telephony in the form of PSTN (Public Service Telephone Network) has dominated the world of phone communications (Varshney et al., 2002). The alternative solution of VoIP (Voice over Internet Protocol) or Internet telephony has increased dramatically its share over the years though. Originally started among computer enthusiasts, nowadays it has become a huge research area in both the academic community as well as the industry (Karapantazis and Pavlidou, 2009). Therefore, many VoIP technologies have emerged in order to offer telephony services. However, the performance of these VoIP technologies is a key issue for the sound quality that the end-users receive. When making reference to sound quality PSTN still stands as the benchmark.Against this background, the aim of this project is to evaluate different VoIP signalling protocols in terms of their key performance metrics and the impact of security and packet transport mechanisms on them. In order to reach this aim in-band and out-of-band VoIP signalling protocols are reviewed along with the existing security techniques which protect phone calls and network protocols that relay voice over packet-switched systems. In addition, the various methods and tools that are used in order to carry out performance measurements are examined together with the open source Asterisk VoIP platform. The findings of the literature review are then used in order to design and implement a novel experimental framework which is employed for the evaluation of the in-band and out-of-band VoIP signalling protocols in respect to their key performance networks. The major issue of this framework though is the lack of fine-grained clock synchronisation which is required in order to achieve ultra precise measurements. However, valid results are still extracted. These results show that in-band signalling protocols are highly optimised for VoIP telephony and outperform out-of-band signalling protocols in certain key areas. Furthermore, the use of VoIP specific security mechanisms introduces just a minor overhead whereas the use of Layer 2.5 protocols against the Layer 3 routing protocols does not improve the performance of the VoIP signalling protocols