How Unstable Can Be a Heterogeneous Multimedia Network under Adversarial Attacks That Change Dynamically Link Slowdowns?

Multimedia communication networks, such as the Internet, are heterogeneous in their nature due to the usage of different methods for content distribution. The efficiency of multimedia distribution depends on the variety of communication protocols that are simultaneously running (composed) over different network hosts in order to resolve packet conflicts. A very natural question that arises in such common settings of multimedia networks concerns the degradation of network stability under adversarial attacks that change dynamically network link slowdowns. A packet-switched network is stable if the number of packets in the network remains bounded at all times against any adversary. In this work, we study this question adopting an enhanced adversarial framework, where an adversary controls the rates of packet injections, determines packet paths and manipulates network link slowdowns. Such adversarial attacks can be considered as a type of denial of service attacks. Within this framework, we study network stability under specific compositions of contention-resolution protocols trying to characterise this property in terms of network topologies. The examined network topologies have been proved forbidden for stability when network link slowdowns are fixed and packet paths do not contain repeated edges, but they can contain repeated nodes. Interestingly, our results suggest that dynamic adversarial attacks changing link slowdowns may be worse than adversarial attacks with unit slowdowns for specific protocol compositions. We feel that this study could help on the design and maintenance of trustworthy multimedia networks.