Cyclic or general overlays may provide multiple paths between publishers and subscribers. However, an advertisement tree and a matching subscription activates only one path for notifications routing in publish subscribe systems. This poses serious challenges in handling network conditions like congestion, and link or broker failures. Further, content-based dynamic routing of notifications requires instantaneous updates in routing paths, which is not a scalable option. This paper introduces a clustering approach with a bit-vector technique for inter-cluster dynamic routing of notifications in a structured cyclic topology that provides multiple paths between publishers and interested subscribers. The advertisement forwarding process exploits the structured nature of the overlay topology to generate advertisement trees of length 1 without generating duplicate messages in the advertisement forwarding process. Issued subscriptions are divided into multiple disjoint subgropus, where each subscription is broadcast to a cluster, which is a limited part of the structured cyclic overlay network. We implemented novel static and intra-cluster dynamic routing algorithms in the proposed overlay topology for our advertisement-based publish subscribe system, called OctopiA. We also performed a pragmatic comparison of our two algorithms with the state-of-the-art. Experiments on a cluster testbed show that our approach generates fewer inter-broker messages, and is scalable.
In Fig. 1(a), publisher P is connected to Broker 1, while an interested subscriber S, is connected to Broker 6. Broker 1, which is also root of the tree of the advertisement issued by P, assigns a unique TID to advertisement before forwarding it to other brokers. After receiving the advertisement from Broker 4, Broker 5 discard duplicate of the same advertisement when received from Broker 2. Similarly, Broker 6 discards the duplicate when received from Broker 3 @cite_19 . This indicates that despite using unique TID for each advertisement, extra inter-broker messages (IMs) still generate to detect duplicates. The advertisement tree shown in Fig. 1(a) is of the shortest length, which may also reduces lengths of the subscription trees. In this case, publications are processed by a fewer number of brokers in the routing paths, which improves throughput and reduces latency.
@cite_19
1498290244 1488414089 2070085078 1608885791
Users of content-based publish subscribe systems (CBPS) are interested in receiving data items with values that satisfy certain conditions. Each user submits a list of subscription specifications to a broker, which routes data items from publishers to users. When a broker receives a notification that contains a value from a publisher, it forwards it only to the subscribers whose requests match the value. However, in many applications, the data published are confidential, and their contents must not be revealed to brokers. Furthermore, a user's subscription may contain sensitive information that must be protected from brokers. Therefore, a difficult challenge arises: how to route publisher data to the appropriate subscribers without the intermediate brokers learning the plain text values of the notifications and subscriptions. To that extent, brokers must be able to perform operations on top of the encrypted contents of subscriptions and notifications. Such operations may be as simple as equality match, but often require more complex operations such as determining inclusion of data in a value interval. Previous work attempted to solve this problem by using one-way data mappings or specialized encryption functions that allow evaluation of conditions on ciphertexts. However, such operations are computationally expensive, and the resulting CBPS lack scalability. As fast dissemination is an important requirement in many applications, we focus on a new data transformation method called Asymmetric Scalar-product Preserving Encryption (ASPE) [1]. We devise methods that build upon ASPE to support private evaluation of several types of conditions. We also suggest techniques for secure aggregation of notifications, supporting functions such as sum, minimum, maximum and count. Our experimental evaluation shows that ASPE-based CBPS incurs 65 less overhead for exact-match filtering and 50 less overhead for range filtering compared to the state-of-the-art. With the rapid progress of mobile Internet and the growing popularity of smartphones, location-aware publish subscribe systems have recently attracted significant attention. Different from traditional content-based publish subscribe, subscriptions registered by subscribers and messages published by publishers include both spatial information and textual descriptions, and messages should be delivered to relevant subscribers whose subscriptions have high relevancy to the messages. To evaluate the relevancy between spatio-textual messages and subscriptions, we should combine the spatial proximity and textual relevancy. Since subscribers have different preferences - some subscribers prefer messages with high spatial proximity and some subscribers pay more attention to messages with high textual relevancy, it calls for new location-aware publish subscribe techniques to meet various needs from different subscribers. In this paper, we allow subscribers to parameterize their subscriptions and study the location-aware publish subscribe problem on parameterized spatio-textual subscriptions. One big challenge is to achieve high performance. To meet this requirement, we propose a filter-verification framework to efficiently deliver messages to relevant subscribers. In the filter step, we devise effective filters to prune large numbers of irreverent results and obtain some candidates. In the verification step, we verify the candidates to generate the answers. We propose three effective filters by integrating prefix filtering and spatial pruning techniques. Experimental results show our method achieves higher performance and better quality than baseline approaches. We consider a state-dependent three-terminal full-duplex relay channel with the channel states noncausally available at only the source, that is, neither at the relay nor at the destination. This model has application to cooperation over certain wireless channels with asymmetric cognition capabilities and cognitive interference relay channels. We establish lower bounds on the channel capacity for both discrete memoryless (DM) and Gaussian cases. For the DM case, the coding scheme for the lower bound uses techniques of rate-splitting at the source, decode-and-forward (DF) relaying, and a Gel'fand-Pinsker-like binning scheme. In this coding scheme, the relay decodes only partially the information sent by the source. Due to the rate-splitting, this lower bound is better than the one obtained by assuming that the relay decodes all the information from the source, that is, full-DF. For the Gaussian case, we consider channel models in which each of the relay node and the destination node experiences on its link an additive Gaussian outside interference. We first focus on the case in which the links to the relay and to the destination are corrupted by the same interference; and then we focus on the case of independent interferences. We also discuss a model with correlated interferences. For each of the first two models, we establish a lower bound on the channel capacity. The coding schemes for the lower bounds use techniques of dirty paper coding or carbon copying onto dirty paper, interference reduction at the source and decode-and-forward relaying. The results reveal that, by opposition to carbon copying onto dirty paper and its root Costa's initial dirty paper coding (DPC), it may be beneficial in our setup that the informed source uses a part of its power to partially cancel the effect of the interference so that the uninformed relay benefits from this cancellation, and so the source benefits in turn. This paper develops content-based publish subscribe algorithms to support general overlay topologies, as opposed to traditional acyclic or tree-based topologies. Among other benefits, publication routes can adapt to dynamic conditions by choosing among alternate routing paths, and composite events can be detected at optimal points in the network. The algorithms are implemented in the PADRES publish subscribe system and evaluated in a controlled local environment and a wide-area PlanetLab deployment. Atomic subscription notification delivery time improves by 20 in a well connected network, and composite subscriptions can be processed with 80 less network traffic and notifications delivered with about half the end to end delay.