Section: New Results

Open Network Architecture

Storage on Wheels: Offloading Popular Contents Through a Vehicular Cloud

Participants: Luigi Vigneri and Chadi Barakat.

The increasing demand for mobile data is overloading the cellular infrastructure. Small cells and edge caching is being explored as an alternative, but installation and maintenance costs for sufficient coverage are significant. In this work, we perform a preliminary study of an alternative architecture based on two main ideas: (i) using vehicles as mobile caches that can be accessed by user devices; compared to small cells, vehicles are more widespread and require lower costs; (ii) combining the mobility of vehicles with delayed content access to increase the number of cache hits (and reduce the load on the infrastructure). Contrary to standard DTN-type approaches, in our system max delays are guaranteed to be kept to a few minutes (beyond this deadline, the content is fetched from the infrastructure). We first propose an analytical framework to compute the optimal number of content replicas that one should cache, in order to minimize the infrastructure load. We then investigate how to optimally refresh these caches to introduce new contents, as well as to react to the temporal variability in content popularity. Simulations suggest that our vehicular cloud considerably reduces the infrastructure load in urban settings, assuming modest penetration rates and tolerable content access delays. This work is currently under submission; it is the result of collaboration with the Mobile Communications Department at Eurecom in the context of a PhD thesis funded by the UCN@SOPHIA Labex.

Geographically Fair In-Network Caching for Mobile Data Offloading

Participant: Chadi Barakat

Data offloading from the cellular network to low-cost WiFi has been the subject of several research works in the last years. In-network caching has also been studied as an efficient means to further reduce cellular network traffic. In this contribution, done jointly with the Maestro project-team, we consider a scenario where mobile users can download popular contents (e.g., maps of a city, shopping information, social media, etc.) from WiFi-enabled caches deployed in an urban area. We study the optimal distribution of contents among the caches (i.e., what contents to put in each cache) to minimize users’ access cost in the whole network. We argue that this optimal distribution does not necessarily provide geographic fairness, i.e., users at different locations can experience highly variable performance. In order to mitigate this problem, we propose two different cache coordination algorithms based on gossiping. These algorithms achieve geographic fairness while preserving the minimum access cost for end users. More details on this contribution can be found in [12] .

Virtual Service Providers (vSP)

Participant: Damien Saucez

The ability of SOHO networks to connect to the Internet through several Internet service providers, gives high potential to enable rich cloud-based network services for enterprises. Nevertheless, it remains a huge challenge for SOHOs to leverage such multi-homing and cloud networking capabilities. For such a reason, we introduced the vSP concept (virtual Service Provider). The idea of vSP is to hide the technical complexity inherent to multi-homing and allow SOHOs to seamlessly use their cloud resources. The role of the vSP is to orchestrate traffic between the different Internet Services Providers (ISPs) in order to maximize the cloud service performance without requiring any intervention of the SOHO network administrator. This ongoing work is done in collaboration with Telecom ParisTech, Ericsson, LISPERS.net, and Cisco Systems and is presented in two papers [19] , [20] and detailed in one IETF Internet-draft [19] .

Rules Placement Problem in OpenFlow Networks

Participants: Xuan Nam Nguyen, Damien Saucez, Chadi Barakat and Thierry Turletti

Software-Defined Networking (SDN) abstracts low-level network functionalities to simplify network management and reduce costs. The OpenFlow protocol implements the SDN concept by abstracting network communications as flows to be processed by network elements. In OpenFlow, the high-level policies are translated into network primitives called rules that are distributed over the network. While the abstraction offered by OpenFlow allows to potentially implement any policy, it raises the new question of how to define the rules and where to place them in the network while respecting all technical and administrative requirements. We proposed a comprehensive study of the so-called OpenFlow rules placement problem with a survey of the various proposals intending to solve it [11] and developed an offline optimization framework for this problem with a polynomial time approximation in [13] .