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Existing network virtualization systems share a few characteristics, namely they target one data center of a single operator and only offer traditional networking services. As such, their support for critical applications that need to be deployed across multiple trust domains, while enforcing diverse security requirements, is limited. This paper enhances the state-of-the-art by presenting a multi-cloud network virtualization system, allowing the provision of virtual networks of containers. Our solution enables a provider to enrich its network substrate with public and private cloud-based resources, increasing flexibility and the range of supplied services. One challenging aspect that we tackle is the embedding of virtual network requests to the substrate infrastructure, as existing work is unfit to a modern data center context, scales poorly or does not consider the security of virtual resources. We propose a scalable heuristic that considers security as a first-class citizen and is specifically tailored to a hybrid multi-cloud domain. We evaluate our algorithm with large-scale simulations that consider realistic network topologies and our prototype in a substrate composed of one private data center and two public clouds. The system scales well for networks of thousands of switches employing diverse topologies and improves on the virtual network acceptance ratio, provider revenue, and embedding delays. Our results show that the acceptance ratios are less than 1% from the optimal and that the system can provision a 10 thousand container virtual network in approximately 2 minutes.

One of the major concerns of IPTV network deployment is channel change delay (also known as zapping delay). This delay can add up to 2 s or more, and its main culprits are synchronisation and buffering of the media streams. Proving the importance of the problem is the already significant amount of literature addressing it. We start this paper with a survey of techniques proposed to reduce IPTV channel change delay. Then, by analysing an extensive dataset from an operational IPTV provider – comprising 255 thousand users, 150 TV channels, and covering a 6-month period – we have observed that most channel switching events are relatively predictable: users very frequently switch linearly, up or down to the next TV channel. This fact motivated us to use this dataset to analyse in detail a specific type of solutions to this problem, namely, predictive pre-joining of TV channels. In these schemes each set top box (STB) simultaneously joins additional multicast groups (TV channels) along with the one that is requested by the user. If the user switches to any of these channels the switching latency is virtually eliminated, not affecting therefore user's experience. We start by evaluating a simple scheme, where the neighbouring channels (i.e., channels adjacent to the requested one) are pre-joined by the STB during zapping periods. Notwithstanding the simplicity of this scheme, trace-driven simulations show that the zapping delay can be virtually eliminated for a significant percentage of channel switching requests. For example, when sending the previous and the next channel concurrently with the requested one, for only 1 min after a zapping event, switching delay is eliminated for close to half of all channel switching requests. Importantly, this result is achieved with a negligible increase of bandwidth utilisation in the access link. Other more complex schemes where user behaviour is tracked were also evaluated, but the improvement over the simple scheme was insignificant.