Composable Mediation for Security-Aware Mobile Services

This article shows how service mediation can be used to add security features to services in a mobile service platform. This base platform takes care of security, charging, and other basic functions, which are then configured for services at runtime using a pluggable mediator framework. Service providers can focus on content, and thus leverage the signaling and mediation capabilities of the core platform. Mediators add specific functionality to a service, and are a specific form of service composition and selection. We examine how security technologies for authentication and authorization are integrated by mediators into a single policy infrastructure with a homogeneous interface for services. We consider here the Web services SAML and the 3GPP GBA security bootstrapping standard in the context of mobile services. We give an example using a video on demand service, and discuss how and when security concerns of services can be transferred from the services to mediators.     

Secure push for mobile airline services

In this paper, we propose an architecture for secure push services for mobile users that supports common-of-the-shelf (COTS) WLAN base stations. The architecture focuses on the creation of flexible access networks based on easily deployable base stations. The push functionality is realized using client-initiated connections with SIP, and TLS or dTLS for security. The central building block of the distributed system is the edge proxy, which manages and implicitly authenticates all inbound connections, and performs privacy enhancement. The main driving force of our architecture has been airline services, but the system is applicable also for other service domains.     

PTCP Incast in Data Center Networks

In recent years, dual-homed topologies have appeared in data centers in order to offer higher aggregate bandwidth by using multiple paths simultaneously. Multipath TCP （MPTCP） has been proposed as a replacement for TCP in those topologies as it can efficiently offer improved throughput and better fairness. However, we have found that MPTCP has a problem in terms of incast collapse where the receiver suffers a drastic goodput drop when it simultaneously requests data over multiple servers. In this paper, we investigate why the goodput collapses even if MPTCP is able to actively relieve hot spots. In order to address the problem, we propose an equally-weighted congestion control algorithm for MPTCP, namely EW-MPTCP, without need for centralized control, additional infrastructure and a hardware upgrade. In our scheme, in addition to the coupled congestion control performed on each subflow of an MPTCP connection, we allow each subflow to perform an additional congestion control operation by weighting the congestion window in reverse proportion to the number of servers. The goal is to mitigate incast collapse by allowing multiple MPTCP subflows to compete fairly with a single-TCP flow at the shared bottleneck. The simulation results show that our solution mitigates the incast problem and noticeably improves goodput in data centers.     

Optimizing content-based routers: posets and forests

Event-based systems are seen as good candidates for supporting distributed applications in dynamic and ubiquitous environments because they support decoupled and asynchronous one-to-many and many-to-many information dissemination. Event systems are widely used because asynchronous messaging provides a flexible alternative to RPC. They are typically implemented using an overlay network of routers. A content-based router forwards event messages based on filters that are installed by subscribers and other routers. This paper addresses the optimization of content-based routing tables organized using the covering relation and presents novel configurations for improving local and distributed operation. We present the poset-derived forest data structure and variants that perform considerably better under frequent filter additions and removals than existing data structures. The results offer a significant performance increase to currently known covering-based routing mechanisms. Sasu Tarkoma received his M.Sc. and Ph.Lic degrees in Computer Science from the University of Helsinki, Department of Computer Science. He has over 20 scientific publications and has also contributed to several books on mobile middleware. His research interests include distributed computing and middleware. Jaakko Kangasharju is a PhD student at the University of Helsinki and working as a researcher at the Helsinki Institute for Information Technology. His research is concentrated on XML messaging and processing in the mobile wireless environment. He has participated in related standardization efforts at the Object Management Group and the World Wide Web Consortium.     

Syxaw: Data Synchronization Middleware for the Mobile Web

In this paper, we present a middleware for synchronization of opaque and structured data in a mobile and resource-constrained environment. The presented Syxaw (Synchronizer with XML-awareness) system distinguishes itself from related proposals in that it interoperates transparently with resources on the World Wide Web, and by exhibiting a model of synchronization that is both easy to understand and well suited for weak devices in a mobile and ubiquitous environment. We demonstrate the feasibility of the proposed system by considering several usage scenarios, including working on the Web and collaborative XML editing. We consider system performance on a mobile wireless device, and examine the impact of different optimization techniques to the performance. According to our analysis, Web interoperability suggests that the data share model be kept simple and conservative, and that moving functionality onto the client is advantageous. We find that the techniques of operation bundling and concurrent use of network downlink and uplink improve network utilization, but that achieving full bandwidth usage with a weak client is challenging in practice.