Search

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-ofband 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.

Cloud computing has been the subject of many researches. Researches shows that cloud computing permit to reduce hardware cost, reduce the energy consumption and allow a more efficient use of servers. Nowadays lot of servers are used inefficiently because they are underutilized. The uses of cloud computing associate to virtualization have been a solution to the underutilisation of those servers. However the virtualization performances with cloud computing cannot offers performances equal to the native performances. The aim of this project was to study the performances of the virtualization with cloud computing. To be able to meet this aim it has been review at first the previous researches on this area. It has been outline the different types of cloud toolkit as well as the different ways available to virtualize machines. In addition to that it has been examined open source solutions available to implement a private cloud. The findings of the literature review have been used to realize the design of the different experiments and also in the choice the tools used to implement a private cloud. In the design and the implementation it has been setup experiment to evaluate the performances of public and private cloud. The results obtains through those experiments have outline the performances of public cloud and shows that the virtualization of Linux gives better performances than the virtualization of Windows. This is explained by the fact that Linux is using paravitualization while Windows is using HVM. The evaluation of performances on the private cloud has permitted the comparison of native performance with paravirtualization and HVM. It has been seen that paravirtualization hasperformances really close to the native performances contrary to HVM. Finally it hasbeen presented the cost of the different solutions and their advantages.

The Information and Communication Technology (ICT) sector represent two to three percentsof the world energy consumption and about the same percentage of GreenHouse Gas(GHG) emission. Moreover the IT-related costs represent fifty per-cents of the electricity billof a company. In January 2010 the Green Touch consortium composed of sixteen leading companies and laboratories in the IT field led by Bell's lab and Alcatel-Lucent have announced that in five years the Internet could require a thousand times less energy than it requires now. Furthermore Edinburgh Napier University is committed to reduce its carbon footprint by 25% on the 2007/8 to 2012/13 period (Edinburgh Napier University Sustainability Office, 2009) and one of the objectives is to deploy innovative C&IT solutions. Therefore there is a general interest to reduce the electrical cost of the IT infrastructure, usually led by environmental concerns. One of the most prominent technologies when Green IT is discussed is Cloud Computing (Stephen Ruth, 2009). This technology allows the on-demand self service provisioning by making resources available as a service. Its elasticity allows the automatic scaling of thedemand and hardware consolidation thanks to virtualization. Therefore an increasing number of companies are moving their resources into a cloud managed by themselves or a third party. However this is known to reduce the electricity bill of a company if the cloud is managed by a third-party off-premise but this does not say to which extent is the powerconsumption is reduced. Indeed the processing resources seem to be just located somewhere else. Moreover hardware consolidation suggest that power saving is achieved only during off-peak time (Xiaobo Fan et al, 2007). Furthermore the cost of the network is never mentioned when cloud is referred as power saving and this cost might not be negligible. Indeed the network might need upgrades because what was being done locally is done remotely with cloud computing. In the same way cloud computing is supposed to enhance the capabilities of mobile devices but the impact of cloud communication on their autonomy is mentioned anywhere. Experimentations have been performed in order to evaluate the power consumption of an infrastructure relying on a cloud used for desktop virtualization and also to measure the cost of the same infrastructure without a cloud. The overall infrastructure have been split in different elements respectively the cloud infrastructure, the network infrastructure and enddevices and the power consumption of each element have been monitored separately. The experimentation have considered different severs, network equipment (switches, wireless access-points, router) and end-devices (desktops Iphone, Ipad and Sony-Ericsson Xperia running Android). The experiments have also measured the impact of a cloud communication on the battery of mobile devices. The evaluation have considered different deployment sizes and estimated the carbon emission of the technologies tested. The cloud infrastructure happened to be power saving and not only during off-peak time from a deployment size large enough (approximately 20 computers) for the same processing power. The power saving is large enough for wide deployment (500 computers) that it could overcome the cost of a network upgrade to a Gigabit access infrastructure and still reduce the carbon emission by 4 tonnes or 43.97% over a year and on Napier campuses compared to traditional deployment with a Fast-Ethernet access-network. However the impact of cloud communication on mobile-devices is important and has increase the power consumption by 57% to 169%.