Using publish/subscribe for message routing in mobile environments

Publish/subscribe is a mature communication paradigm to route and deliver events from publishers to interested subscribers. Initially conceived for large scale systems, e.g., the Internet, it has been used more recently in new scenarios, e.g., wireless sensor networks and the Internet of Things (IoT), where mobility and dynamicity are the norm. The loose-coupling and asynchronicity of publish/subscribe makes it an interesting choice for IoT scenarios, i.e., each node in an IoT network can choose a different role depending on its location, capabilities, etc. This paper presents MFT-PubSub, a fully mobile and fault tolerant content-based publish/subscribe protocol. Our proposal is a purely reactive solution for mobility in a publish/subscribe system without any kind of limits on the mobility patterns of the nodes. A wireless ad hoc network is created without the need of any previous connections or knowledge on the nodes. Handling the mobility, be it physical or logical, of both clients and brokers. We prove the validity of our solution by experimentation, and compare it with AODV, a routing protocol for mobile ad hoc networking. The simulations show an improvement on message delivery rate over previously used protocols.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. Research supported by grant TIN2016-79897-P funded by MCIN/AEI/10.13039/501100011033 and by the European Union, and by the Department of Education, Universities and Research of the Basque Government, grant IT-1437-22 (ADIAN)

Vitis: A Gossip-based Hybrid Overlay for Internet-scale Publish/Subscribe

Peer-to-peer overlay networks are attractive solutions for building Internet-scale publish/subscribe systems. However, scalability comes with a cost: a message published on a certain topic often needs to traverse a large number of uninterested (unsubscribed) nodes before reaching all its subscribers. This might sharply increase resource consumption for such relay nodes (in terms of bandwidth transmission cost, CPU, etc) and could ultimately lead to rapid deterioration of the system’s performance once the relay nodes start dropping the messages or choose to permanently abandon the system. In this paper, we introduce Vitis, a gossip-based publish/subscribe system that significantly decreases the number of relay messages, and scales to an unbounded number of nodes and topics. This is achieved by the novel approach of enabling rendezvous routing on unstructured overlays. We construct a hybrid system by injecting structure into an otherwise unstructured network. The resulting structure resembles a navigable small-world network, which spans along clusters of nodes that have similar subscriptions. The properties of such an overlay make it an ideal platform for efficient data dissemination in large-scale systems. We perform extensive simulations and evaluate Vitis by comparing its performance against two base-line publish/subscribe systems: one that is oblivious to node subscriptions, and another that exploits the subscription similarities. Our measurements show that Vitis significantly outperforms the base-line solutions on various subscription and churn scenarios, from both synthetic models and real-world traces

Design and implementation of an advanced MQTT broker for distributed pub/sub scenarios

MQTT is one of the most popular communication protocols for Internet of Things applications. Based on a publish/subscribe pattern, it relies on a single broker to exchange messages among clients according to topics of interest. However, such a centralized approach does not scale well and is prone to single point of failure risks, calling for solutions where multiple brokers cooperate together in a distributed fashion. In this paper, we present a complete solution for a distributed MQTT broker systems. We target several functional primitives which are key in such a scenario: broker discovery and failure recovery, overlay tree network creation and message routing. Moreover, we also focus on the case where multiple topics are present in the system. In such a scenario, a single tree-based overlay network connecting the different brokers may not be the most efficient solution. To cope with this issue, we propose a topic-based routing scheme for MQTT distributed brokers. The proposed solution creates multiple overlay networks in the distributed system, each one linking together only the brokers whose connected clients have interest in the same topics. We implement the complete system as an extension of the popular HiveMQ MQTT broker and perform several experiments to test its performance in scenarios characterized by a different publishers/subscribers configurations as well as number of topics existing in the system

VCube-PS: A Causal Broadcast Topic-based Publish/Subscribe System

In this work we present VCube-PS, a topic-based Publish/Subscribe system built on the top of a virtual hypercube-like topology. Membership information and published messages are broadcast to subscribers (members) of a topic group over dynamically built spanning trees rooted at the publisher. For a given topic, the delivery of published messages respects the causal order. VCube-PS was implemented on the PeerSim simulator, and experiments are reported including a comparison with the traditional Publish/Subscribe approach that employs a single rooted static spanning-tree for message distribution. Results confirm the efficiency of VCube-PS in terms of scalability, latency, number and size of messages.Comment: Improved text and performance evaluation. Added proof for the algorithms (Section 3.4

Towards a fully mobile publish/subscribe system

93 p.This PhD thesis makes contributions to support mobility and fault tolerance in a publish/subscribe system. Two protocols are proposed in order to support mobility of all devices in the system, including inside the event notification service. The protocols are designed with the idea that any change due to mobility is completely beyond our control and ability to predict. Moreover, the proposed solutions do not need to know neither the amount of nodes in the system nor their identities before starting, the system is able to adapt to new devices or disconnections and is able to keep operating correctly in a partitioned network. To do so we extend a previously proposed framework called Phoenix that already supported client mobility. Both protocols use a leader election mechanism to create a communication tree in a highly dynamic environment, and use a characteristic of that algorithm to detect topology changes and migrate nodes accordingly

Towards a fully mobile publish/subscribe system

93 p.This PhD thesis makes contributions to support mobility and fault tolerance in a publish/subscribe system. Two protocols are proposed in order to support mobility of all devices in the system, including inside the event notification service. The protocols are designed with the idea that any change due to mobility is completely beyond our control and ability to predict. Moreover, the proposed solutions do not need to know neither the amount of nodes in the system nor their identities before starting, the system is able to adapt to new devices or disconnections and is able to keep operating correctly in a partitioned network. To do so we extend a previously proposed framework called Phoenix that already supported client mobility. Both protocols use a leader election mechanism to create a communication tree in a highly dynamic environment, and use a characteristic of that algorithm to detect topology changes and migrate nodes accordingly

Hybrid application layer and in-network content-based filtering in SDN

Content-routing as provided by publish/subscribe systems has evolved as a key paradigm for interactions between loosely coupled application components (content publishers and subscribers). Using content-based forwarding rules (also called content filters) installed on content-based routers (also termed brokers), bandwidth-efficiency is increased by only forwarding content to the subset of subscribers who are actually interested in the published content. Software Defined Networking (SDN) is a method that enables installation of filters directly on the TCAM memory of network routers. Compared to traditional broker networks, SDN can significantly reduce the latency until events can be received by subscribers: i) the matching time is significantly reduced, and ii) the communication path can be adapted to directly reflect the underlying network topology and therefore reduce the number of forwarding hops for packets. Initial studies have shown that content-routing protocols based on spatial indexing are very well suited to realize a mapping of filtering operations to header-based packet matching performed in TCAM memory. Filters are represented by identifiers constituting the matching field of flows on switches. However, the limited number of available bits for content representation and the limited number of flows available on the TCAM memory for pub/sub traffic limits the expressiveness of these filters, resulting in false positives or unnecessary traffic in the system. The objective of this thesis, is to design and implement a hybrid pub/sub middleware that allows for filtering of events both on the application layer as well as on the network layer. However, this leads to a trade-off between expressiveness and line-rate performance. In particular, this thesis investigates mechanisms to reduce false positives in the system while maintaining end-to-end latency guarantees at subscribers

Confidentiality-Preserving Publish/Subscribe: A Survey

Publish/subscribe (pub/sub) is an attractive communication paradigm for large-scale distributed applications running across multiple administrative domains. Pub/sub allows event-based information dissemination based on constraints on the nature of the data rather than on pre-established communication channels. It is a natural fit for deployment in untrusted environments such as public clouds linking applications across multiple sites. However, pub/sub in untrusted environments lead to major confidentiality concerns stemming from the content-centric nature of the communications. This survey classifies and analyzes different approaches to confidentiality preservation for pub/sub, from applications of trust and access control models to novel encryption techniques. It provides an overview of the current challenges posed by confidentiality concerns and points to future research directions in this promising field

A Semantic Overlay for Self- Peer-to-Peer Publish/Subscribe

International audiencePublish/Subscribe systems provide a useful platform for delivering data (events) from publishers to subscribers in an anonymous fashion in distributed networks. In this pa-per, we promote a novel design principle for self-* dynamic and reliable content-based publish/subscribe systems and perform a comparative analysis of its probabilistic and de-terministic implementations. More specifically, we present a generic content-based publish/subscribe system, called DPS (Dynamic Publish/Subscribe). DPS combines classi-cal content-based filtering with self-* (self-organizing, self-configuring, and self-healing) subscription-driven cluster-ing of subscribers. DPS gracefully adapts to failures and changes in the system while achieving scalable events deliv-ery. DPS includes a variety of fault-tolerant deterministic and probabilistic content-based publication/subscription schemes. These schemes are targeted toward scalability, and aim at reducing and distributing the number of mes-sages exchanged. Reliability and scalability of our system are shown through analytical and experimental evaluation