Lorenzo Saino

Hash-routing schemes for information centric networking

Hash-routing has been proposed in the past as a mapping mechanism between object requests and cache clusters within enterprise networks. In this paper, we revisit hash-routing techniques and apply them to Information-Centric Networking (ICN) environments, where network routers have cache space readily available. In particular, we investigate whether hash-routing is a viable and efficient caching approach when applied outside enterprise networks, but within the boundaries of a domain. We design five different hash-routing schemes which efficiently exploit in-network caches without requiring network routers to maintain per-content state information. We evaluate the proposed hash-routing schemes using extensive simulations over real Internet domain topologies and compare them against various on-path caching mechanisms. We show that such schemes can increase cache hits by up to 31% in comparison to on-path caching, with minimal impact on the traffic dynamics of intra-domain links.

CCTCP: A scalable receiver-driven congestion control protocol for content centric networking

Content Centric Networking (CCN) is a recently proposed information-centric Internet architecture in which the main network abstraction is represented by location-agnostic content identifiers instead of node identifiers. In CCN each content object is divided into packet-size chunks. When a content object is transferred, routers on the path can cache single chunks which they can use to serve subsequent requests from other users. Since content chunks in CCN may be retrieved from a number of different nodes/caches, implicit-feedback transport protocols will not be able to work efficiently, because it is not possible to set an appropriate timeout value based on RTT estimations given that the data source may change frequently during a flow. In order to address this problem, we propose in this paper a scalable, implicit-feedback congestion control protocol, capable of coping with RTT unpredictability using a novel anticipated interests mechanism to predict the location of chunks before they are actually served. Our evaluation shows that our protocol outperforms similar receiver-driven protocols, in particular when content chunks are scattered across network paths due to reduced cache sizes, long-tail content popularity distribution or the adoption of specific caching policies.

Name-Based Replication Priorities in Disaster Cases

In the immediate aftermath of a natural disaster, network infrastructure is likely to have suffered severe damages that challenge normal communications. In addition to that, traffic substantially increases as a result of people attempting to get in touch with friends, relatives or the rescue teams. To address such requirements of a challenged network, we propose a communication framework based on messages that exploits name-based replication of content and enables ad-hoc communications with spatial and temporal scoping and prioritisation of named messages. We evaluate our design against less sophisticated replication strategies and show that important messages (e.g., from first responders) get disseminated to more nodes than less important messages.

Hierarchical Content Stores in High-Speed ICN Routers: Emulation and Prototype Implementation

Recent work motivates the design of Information-centric routers that make use of hierarchies of memory to jointly scale in the size and speed of content stores. The present paper advances this understanding by (i) instantiating a general purpose two-layer packet-level caching system, (ii) investigating the solution design space via emulation, and (iii) introducing a proof-of-concept prototype. The emulation-based study reveals insights about the broad design space, the expected impact of workload, and gains due to multi-threaded execution. The full-blown system prototype experimentally confirms that, by exploiting both DRAM and SSD memory technologies, ICN routers can sustain cache operations in excess of 10Gbps running on off-the-shelf hardware.

Efficient Hash-routing and Domain Clustering Techniques for Information-Centric Networks

Hash-routing is a well-known technique used in server-cluster environments to direct content requests to the responsible servers hosting the requested content. In this work, we look at hash-routing from a different angle and apply the technique to Information-Centric Networking (ICN) environments, where in-network content caches serve as temporary storage for content. In particular, edge-domain routers re-direct requests to in-network caches, more often than not off the shortest path, according to the hash-assignment function. Although the benefits of this off-path in-network caching scheme are significant (e.g., high cache hit rate with minimal co-ordination overhead), the basic scheme comes with disadvantages. That is, in case of very large domains the off-path detour of requests might increase latency to prohibitive levels. In order to deal with extensive detour delays, we investigate nodal/domain clustering techniques, according to which large domains are split in clusters, which in turn apply hash-routing in the subset of nodes of each cluster. We model and evaluate the behaviour of nodal clustering and report significant improvement in delivery latency, which comes at the cost of a slight decrease in cache hit rates (i.e., up to 50% improvement in delivery latency for less than 10% decrease in cache hit rate compared to the original hash-routing scheme applied in the whole domain).

Revisiting Resource Pooling: The Case for In-Network Resource Sharing

We question the widely adopted view of in-network caches acting as temporary storage for the most popular content in Information-Centric Networks (ICN). Instead, we propose that in-network storage is used as a place of temporary custody for incoming content in a store and forward manner. Given this functionality of in-network storage, senders push content into the network in an open-loop manner to take advantage of underutilised links. When content hits the bottleneck link it gets re-routed through alternative uncongested paths. If alternative paths do not exist, incoming content is temporarily stored in in-network caches, while the system enters a closed-loop, back-pressure mode of operation to avoid congestive collapse. Our proposal follows in spirit the resource pooling principle, which, however, is restricted to end-to-end resources and paths. We extend this principle to also take advantage of in-network resources, in terms of multiplicity of available sub-paths (as compared to multihomed users only) and in-network cache space. We call the proposed principle In-Network Resource Pooling Principle (INRPP). Using the INRPP, congestion, or increased contention over a link, is dealt with locally in a hop-by-hop manner, instead of end-to-end. INRPP utilises resources throughout the network more efficiently and opens up new directions for research in the multipath routing and congestion control areas.

Understanding sharded caching systems

Sharding is a method for allocating data items to nodes of a distributed caching or storage system based on the result of a hash function computed on the item identifier. It is ubiquitously used in key-value stores, CDNs and many other applications. Despite considerable work has focused on the design and the implementation of such systems, there is limited understanding of their performance in realistic operational conditions from a theoretical standpoint. In this paper we fill this gap by providing a thorough modeling of sharded caching systems, focusing particularly on load balancing and caching performance aspects. Our analysis provides important insights that can be applied to optimize the design and configuration of sharded caching systems.

Augustus: a CCN router for programmable networks

Despite the considerable attention that the ICN paradigm received so far, its deployment has been hindered by the scale of upgrades required to the existing infrastructure. Software programmable networking frameworks would constitute a remarkable opportunity for ICN as they enable fast deployment of novel technologies on commodity hardware. However, a software ICN router implementation for commodity platforms guaranteeing adequate packet processing performance is not available yet. This paper introduces Augustus, a software architecture for ICN routers, and detail two implementations, stand-alone and modular, released as open-source code. We deployed both implementations on a state-of-the-art hardware platform and analyzed their performance under different configurations. Our analysis shows that with both implementations it is possible to achieve a throughput of approximately 10 Mpps, saturating 10 Gbit/s links with packet as small as 100 bytes. However, to achieve such performance, routers must be carefully configured to fully exploit the capabilities of the hardware platforms they run on.

On information exposure through named content

The proposed shift from host-centric to information-centric networking (ICN) has triggered extensive research in the area of content naming. Efforts have so far focused on the scalability and security properties that can make content objects routable and self-certifying. In this paper, we argue that the information that is exposed through explicitly naming content objects has been overlooked, although several operational and performance issues depend on the information that a name holds. We therefore revisit content naming design decisions taking into account information exposure and deployability of the ICN paradigm.