Mobile network operators are experiencing a tremendous increase in data traffic due to the growing popularity of bandwidth-intensive video services. This challenge can be faced either by boosting the capacity of the network infrastructure, or by means of offloading traffic from the backhaul and core network and serving contents from distributed cache servers close to the users. Network operators can extend the coverage of traditional CDNs by making usage of caching locations much closer to the users than traditional CDNs. Additionally, network operators can optimize the caching and delivery of contents by exploiting the complete knowledge of their network for designing a cost-effective infrastructure able to achieve both improved user satisfaction and cost savings. This article provides thoroughly justified design principles for a highly distributed operator-owned CDN while focusing on four key aspects: the optimal location of cache servers, mechanisms for request routing, content replica placement, and content outsourcing and retrieval

As other signaling protocols in the past, also SIP suffers of server overload leading to performance collapse. In this framework, recent Internet drafts propose the improvements of overload control mechanisms already presented in SIP and/or a closed loop system model for overload avoidance. In this framework, the paper presents the system simulator developed extending the Network Simulator (ns-2) with logical for local overload control. Furthermore, the paper proposes a new queueing discipline obtained combining the simple First In First Out (FIFO) service discipline with the priority one. Then the paper presents a simulation analysis, aimed at evaluating the impact on system performance of different queueing structures, service disciplines, and buffer sizes. Simulation results clearly show that the proposed queueing discipline produces good system performance with a low complexity increase. Finally, the simulation results point out the weakness of the 503 Service Unavailable message mechanism, which does not introduce significant improvement when combined with the proposed solution.

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