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 has been published in [24]. It is the result of collaboration with Thrasyvoulos Spyropoulos from the Mobile Communications Department at Eurecom in the context of a PhD thesis funded by the UCN@Sophia Labex.

In another work, published in [25], and always in the context of the same collaboration with Thrasyvoulos Spyropoulos, we studied the feasibility of the approach using the popular video streaming case. In this work, we assume such a vehicular cloud is in place to provide video streaming to users, and that the operator can decide which content to store in the vehicle caches. Users can then greedily fill their playout buffer with video pieces of the streamed content from encountered vehicles, and turn to the infrastructure immediately when the playout buffer is empty, to ensure uninterrupted streaming. Our main contribution is to model the playout buffer in the user device with a queuing approach, and to provide a mathematical formulation for the idle periods of this buffer, which relate to the bytes downloaded from the cellular infrastructure. We also solve the resulting content allocation problem, and perform trace-based simulations to finally show that up to 50% of the original traffic could be offloaded from the main infrastructure.

SDN for QoE-based network optimization and management

Participants: Vitalii Poliakov, Damien Saucez.

The naive approach of the networking community is to always increase network capacity to absorb the traffic. In this thesis, we take the counterpoint of this approach claiming that it is possible to better use network resources if we take into account the Quality of Experience (QoE) of users while making routing decisions. The idea is that each network service (e.g., video streaming, web, chat) has different requirements in terms of network performances such as bandwidth or delay and that modern networks present high path diversity, particularly 5G. Our work is thus to provide mechanisms to decide how to route traffic in the network, potentially using multiple paths in parallel, based on their real impact on the QoE. For example, if the experience of a user is not negatively impacted if their traffic is diverted on a slow path, we can use it to free resources for traffic that really needs the high speed path. Initial results for this new activities are published in [27] and [21].

Measurements of LISP

Participant: Damien Saucez.

  To face the new challenges of the Internet such as the Cloud and mobility the Locator/ID Separation Protocol (LISP) leverages the separation of the identifier and the locator roles of IP addresses. Contrarily to the classical BGP-based routing architecture, LISP relies on a pull model. In particular, routing information is pulled from a new network element, the Mapping System, to provide the association between the identifier (i.e., the address used to identify a host inside a domain) and a list of locators (i.e., the addresses to locate an attachment point) upon an explicit query. We evaluate a LISP Mapping System deployment in the public LISP Beta Network deployment from two aspects: Stability and Consistency. Our measurements show that the mapping information is stable over time and consistent between the different mapping entities and the vantage points. Due to the presence of few cases where the Mapping System is unstable and/or inconsistent, we propose a taxonomy in order to classify such instabilities and/or inconsistencies and investigate them in depth to provide hints on how to improve LISP performance. Results are published in [26].

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 [17].

Scalable Multicast Service in Software Defined ISP networks

Participants: Hardik Soni, Thierry Turletti, Walid Dabbous.

In the context of the SDN-based multicast mechanisms activity, we have proposed an architectural solution to provide scalable multicast service in ISP networks. In fact, new applications where anyone can broadcast video are becoming very popular on smartphones. With the advent of high definition video, ISP providers may take the opportunity to propose new high quality broadcast services to their clients. Because of its centralized control plane, Software Defined Networking (SDN) seems an ideal way to deploy such a service in a flexible and bandwidth-efficient way. But deploying large scale multicast services on SDN requires smart group membership management and a bandwidth reservation mechanism to support QoS guarantees that should neither waste bandwidth nor impact too severely best effort traffic. We have proposed a Network Function Virtualization based solution for Software Defined ISP networks to implement scalable multicast group management. We also propose in the same paper a routing algorithm called Lazy Load balancing Multicast (L2BM) for sharing the network capacity in a friendly way between guaranteed-bandwidth multicast traffic and best-effort traffic. Our implementation of the framework made on Floodlight controllers and Open vSwitches is used to study the performance of L2BM. A paper on this work is under submission [37].

Towards unifying content level and network level operations

Participants: Amine Loukili, Damien Saucez, Thierry Turletti.

Programmability of the network to provide content level operations is highly desirable.  With the advent of virtualization and network function softwarization, the networking world shifts to Software Defined Networking (SDN) and OpenFlow is one of the most suitable candidates to implement the southbound API (the interface allowing the SDN-controller to program network devices). In the meanwhile, the generalization of broadband Internet has led to massive content consumption. However, while content is usually retrieved via layer 7 protocols, OpenFlow operations are performed at lower layers (layer 4 or lower) making the protocol ineffective to deal with contents. To address this issue, we define an abstraction to unify network level and content level operations and present a straw-man logically centralized architecture proposal to support it. Our implementation demonstrates the feasibility of the solution and its advantage over fully centralized approach. This work has been published in the CoNext student workshop [19]. A demonstration was also presented at IEEE SDN/NFV conference [32].

Resiliency in Service Function Chaining

Participants: Ghada Moualla, Damien Saucez, Thierry Turletti.

In the context of the dynamic placement of Virtual Network Functions in the network activity, we have studied the importance of resiliency in service functions chaining. When deploying network service function chains the focus is usually given on metrics such as the cost, the latency, or the energy and it is assumed that the underlying cloud infrastructure provides resiliency mechanisms to handle with the disruptions occurring in the physical infrastructure. In a position paper on this topic published in PROCON 2016 [20], we advocate that while usual performance metrics are essential to decide on the deployment of network service function chains, the notion of resiliency should not be neglected as the choice of virtual-to-physical placement may dramatically improve the ability of the service chains to handle with failures of the infrastructure without requiring complex resiliency mechanisms.

SDN for Public Safety Networks

Participants: Damien Saucez, Xuan Nam Nguyen, Thierry Turletti.

Commercial users of modern communications networks have benefited from a huge progress of the related technologies. However, Public Safety Networks (PSNs) and devices did not follow the same trend. Very often, they still rely on voice or low speed data communications, tempting first responders to use their own private devices when they need to exchange real-time video or geolocation information. Under this consideration, national authorities and specialized organizations have recently initiated the integration of more recent technologies, such as cellular Long Term Evolution (LTE), even though they need further developments to cope with the harsh usages that safety personnel may face. We wrote a report showing the evolution of these networks towards the recent evolution of networking technologies started with Software Defined networking (SDN) and Network Functions Virtualization (NFV). Based on the requirements derived from a standardized earthquake scenario and a study of the main improvements brought by this network softwarization, it analyzes how SDN and NFV can solve part of the issues raised with commercial LTE and enhance PSN communications. The capabilities of these new technologies are applied to a list of characteristics required by mission-critical networks, e.g., rapid deployment, reliability, security or resilience, taking advantage of features such as the separation between control and data planes or the simplified dynamic resources management. The resulting enhancements are then illustrated using example frameworks published in the literature for Cloud Radio Access Networks, resilient backhaul solution, isolated base stations, SDN-based architecture or Service Function Chaining [28].

Standardization Activities

Participant: Damien Saucez.

The Locator/ID Separation Protocol (LISP) aims to improve the Internet routing by leveraging separating the roles of IP addresses. In RFC7834 [36] we studied the impact that the deployment of LISP would have on both the routing infrastructure and the end user if it was largely deployed in today’s Internet. In addition, as bringing new protocols to the Internet opens new security questions, in RFC7835 [35] we provide an exhaustive threat analysis of LISP. Both RFCs are used as insights to extend the architecture of LISP to make it more efficient and safer.

Information Centric Networking (ICN) is a radically new way to conceive networks by promoting content information as routing primitives, instead of content location. In RFC7927 [31], we list the research challenges hidden behind this revolutionary approach of networking. This RFC aims to be the baseline for the development of ICN solutions.