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The Infrastructure-as-a-Service (IaaS) model is one of the fastest growing opportunities for cloud-based service providers. It provides an environment that reduces operating and capital expenses while increasing agility and reliability of critical information systems. In this multitenancy environment, cloud-based service providers are challenged with providing a secure isolation service combining different vertical segments, such as financial or public services, while nevertheless meeting industry standards and legal compliance requirements within their data centers. In order to achieve this, new solutions are being designed and proposed to provide traffic isolation for a large numbers of tenants and their resulting traffic volumes. This paper highlights key challenges that cloudbased service providers might encounter while providing multi-tenant environments. It also succinctly describes some key solutions for providing simultaneous tenant and network isolation, as well as highlights their respective advantages and disadvantages. We begin with Generic Routing Encapsulation (GRE) introduced in 1994 in "RFC 1701", and will conclude with today's latest solutions. We detail fifteen of the newest architectures and then compare their complexities, the overhead they induce, their VM migration abilities, their resilience, their scalability, and their multi data center capacities. This paper is intended for, but not limited to, cloud-based service providers who want to deploy the most appropriate isolation solution for their needs, taking into consideration their existing network infrastructure. This survey provides details and comparisons of various proposals while also highlighting possible guidelines for future research on issues pertaining to the design of new network isolation architectures.

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Voice over Wireless LAN (VoWLAN) is becoming more and more helpful in our life and is expected to be among the most important applications in next generation networks. However, the maximum number of VoIP sessions that a WLAN can ensure is very small. Moreover, when the WLAN reaches its capacity the addition of one VoIP session affects the QoS parameters of all VoIP sessions. In this paper, we propose an adaptive technique to ensure the active VoIP sessions of users with high priority (from a provider perspective). Thus, in order to guarantee the quality of high priority sessions, we propose to downgrade the quality (low but acceptable MOS) of user sessions with low priority by changing their used codecs (e.g., ITU G729 instead of ITU G711). This technique and all related monitoring functions are defined into the proposed session-based QoS management architecture [1]. In order to validate our approach a complete test-bed is made up by which we have performed some feasibility and gain tests.