Vasilis Sourlas

Distributed Cache Management in Information-Centric Networks

The main promise of current research efforts in the area of Information-Centric Networking (ICN) architectures is to optimize the dissemination of information within transient communication relationships of endpoints. Efficient caching of information is key to delivering on this promise. In this paper, we look into achieving this promise from the angle of managed replication of information. Management decisions are made in order to efficiently place replicas of information in dedicated storage devices attached to nodes of the network. In contrast to traditional off-line external management systems we adopt a distributed autonomic management architecture where management intelligence is placed inside the network. Particularly, we present an autonomic cache management approach for ICNs, where distributed managers residing in cache-enabled nodes decide on which information items to cache. We propose four on-line intra-domain cache management algorithms with different level of autonomicity and compare them with respect to performance, complexity, execution time and message exchange overhead. Additionally, we derive a lower bound of the overall network traffic cost for a certain category of network topologies. Our extensive simulations, using realistic network topologies and synthetic workload generators, signify the importance of network wide knowledge and cooperation.

Exploiting Caching and Multicast for 5G Wireless Networks

The landscape toward 5G wireless communication is currently unclear, and, despite the efforts of academia and industry in evolving traditional cellular networks, the enabling technology for 5G is still obscure. This paper puts forward a network paradigm toward next-generation cellular networks, targeting to satisfy the explosive demand for mobile data while minimizing energy expenditures. The paradigm builds on two principles; namely caching and multicast. On one hand, caching policies disperse popular content files at the wireless edge, e.g., pico-cells and femto-cells, hence shortening the distance between content and requester. On other hand, due to the broadcast nature of wireless medium, requests for identical files occurring at nearby times are aggregated and served through a common multicast stream. To better exploit the available cache space, caching policies are optimized based on multicast transmissions. We show that the multicast-aware caching problem is NP-hard and develop solutions with performance guarantees using randomized-rounding techniques. Trace-driven numerical results show that in the presence of massive demand for delay tolerant content, combining caching and multicast can indeed reduce energy costs. The gains over existing caching schemes are 19% when users tolerate delay of three minutes, increasing further with the steepness of content access pattern.

Pursuing a Software Defined Information-centric Network

The areas of Software-Defined Networking (SDN) and Information-Centric Networking (ICN) have gained increasing attention in the wider research community, while gaining credibility through corporate interest and investment. With the promise of SDN to simplify the deployment of alternative network architectures, the question arises how SDN and ICN could concretely be combined, deployed and tested. In this paper, we address this very question within a particular architectural context for ICN. We outline a possible realization in a novel design for ICN solutions and point to possible test bed deployments for future testing.

Multicast-aware caching for small cell networks

The deployment of small cells is expected to gain huge momentum in the near future, as a solution for managing the skyrocketing mobile data demand growth. Local caching of popular files at the small cell base stations has been recently proposed, aiming at reducing the traffic incurred when transferring the requested content from the core network to the users. In this paper, we propose and analyze a novel caching approach that can achieve significantly lower traffic compared to the traditional caching schemes. Our cache design policy carefully takes into account the fact that an operator can serve the requests for the same file that happen at nearby times via a single multicast transmission. The latter incurs less traffic as the requested file is transmitted to the users only once, rather than with many unicast transmissions. Systematic experiments demonstrate the effectiveness of our approach, as compared to the existing caching schemes.

Storage planning and replica assignment in content-centric publish/subscribe networks

Content-centric publish/subscribe networking is a flexible communication model that meets the requirements of the content distribution in the Internet, where information needs to be addressed by semantic attributes rather than origin and destination identities. In current implementations of publish/subscribe networks, messages are not stored and only active subscribers receive published messages. However, in a dynamic scenario, where users join the network at various instances, a user may be interested in content published before its subscription time. In this paper, we introduce a mechanism that enables storing in such networks, while maintaining the main principle of loose-coupled and asynchronous communication. Furthermore, we propose a new storage placement and replica assignment algorithm which differentiates classes of content based on their popularity and minimizes the clients response latency and the overall traffic of the network. We also present and compare two replica assignment alternatives and examine their performance when both the locality and the popularity of users request change. The performance of our proposed placement and replica assignment algorithm and the proposed storing mechanism is evaluated via simulations and insights are given for future work. The proposed mechanism is compared with mechanisms from the CDN (Content Delivery Networks) context and performs as close as 1-15% (depending on the conducted experiment) to a greedy (near optimal) approach installing up to 3 times less storage servers in the network and providing the necessary differentiation among the classes of the content.

Autonomic cache management in Information-Centric Networks

Recent research efforts in the area of future networks indicate Information-Centric Networking (ICN) as the dominant architecture for the Future Internet. The main promise of ICN is that of shifting the communication paradigm of the internetworking layer from machine endpoints to information access and delivery. Optimized content dissemination and efficient caching of information is key to delivering on this promise. Moreover, current trends in management of future networks adopt a more distributed autonomic management architecture where management intelligence is placed inside the network with respect to traditional off-line external management systems. In this paper, we present an autonomic cache management approach for ICNs, where distributed managers residing in cache-enabled nodes decide on which items to cache. We propose three online cache management algorithms with different level of autonomicity and compare them with respect to performance, complexity, execution time and message exchange overhead. Our extensive simulation-based experimentation signifies the importance of network wide knowledge and cooperation.

Mobility Support Through Caching in Content-Based Publish/Subscribe Networks

In a publish/subscribe (pub/sub) network, message delivery is guaranteed for all connected subscribers at publish time. However, in a dynamic mobile scenario where users join and leave the network, it is important that content published at the time they are disconnected is still delivered when they reconnect from a different point. In this paper, we enhance the caching mechanisms in pub/sub networks to enable client mobility. We build our mobility support with minor changes in the caching scheme while preserving the main principles of loose coupled and asynchronous communication of the pub/sub communication model. We also present a new proactive mechanism to reduce the overhead of duplicate responses. The evaluation of our proposed scheme is performed via simulations and testbed measurements.

A novel cache aware routing scheme for Information-Centric Networks

Information-Centric Networking (ICN) has attracted the attention of the research community, which has argued that content, instead of end-points, must be at the center stage of attention. The research issues addressed by most of the proposed architectures are related to persistent/unique naming, efficient content distribution and discovery through name-based addresses, in-network caching and security. Given this emergence of ICN-oriented solutions, the relevant management needs in terms of performance have not been extensively studied with most efforts focusing on the performance of the in-network caching schemes. Moreover, little attention has been given on designing efficient routing mechanisms suitable for ICNs, since most of the approaches assume either traditional shortest path or inefficient flooding schemes. In this paper, we describe how a resource management system can be deployed on two of the most prominent ICN network architectures. We propose an intra-domain cache aware routing scheme that computes the paths with the minimum transportation cost based on the information item demands and the caching capabilities of the network. Particularly, we initially present a dynamic programming approach for the computation of the minimum transportation cost paths when the caching capabilities of the network are independent of the selected routing scheme, as well as an iterative algorithm for those cases where the caching capabilities of the network are strongly coupled to the routing scheme. Finally, we derive analytically the communication and computational complexity of the proposed approach and we evaluate its performance through simulations. Our results indicate that our cache aware routing scheme adapts efficiently to the ever-changing ICN environment caused by the volatility of the user requests.

Caching in Content-Based Publish/Subscribe Systems

In a publish/subscribe network, message delivery is guaranteed for all active subscribers at publish time. However, in a dynamic scenario where users join and leave the network, a user may be interested in content published before the subscription time. In this paper, we introduce mechanisms that enable caching in such networks, while maintaining the main principle of loose-coupled and asynchronous communication. Furthermore we investigate two caching policies; caching in all candidate brokers (basic caching) which yields high survivability and low delay and caching in leaf brokers (leaf caching) which maintains low overhead and querying complexity. The comparison is performed via simulations and testbed measurements and insights are given for future work.

Scalable Cache Management for ISP-Operated Content Delivery Services

Content delivery networks (CDNs) have been the prevalent method for the efficient delivery of content across the Internet. Management operations performed by CDNs are usually applied only based on limited information about Internet Service Provider (ISP) networks, which can have a negative impact on the utilization of ISP resources. To overcome these issues, previous research efforts have been investigating ISP-operated content delivery services, by which an ISP can deploy its own in-network caching infrastructure and implement its own cache management strategies. In this paper, we extend our previous work on ISP-operated content distribution and develop a novel scalable and efficient distributed approach to control the placement of content in the available caching points. The proposed approach relies on parallelizing the decision-making process and the use of network partitioning to cluster the distributed decision-making points, which enables fast reconfiguration and limits the volume of information required to take reconfiguration decisions. We evaluate the performance of our approach based on a wide range of parameters. The results demonstrate that the proposed solution can outperform previous approaches in terms of management overhead and complexity while offering similar network and caching performance.