One important aspect of ubiquitous environments is to provide users with the possibility to freely move about and continue to interact with the available applications through a variety of interactive devices such as cell phones, PDAs, desktop computers, intelligent watches, or digital television sets. Migratory applications are able to follow the user by sensing changes in the user's context and adapting to available devices, ideally without interrupting the user experience. However, applications themselves must contain functions to monitor context information, coordinate a migration, handle application adaptation, and interact with the user during the migration process. To make life easier for developers and users of migratory applications, an integrated Migration Service Platform (MSP) is proposed, where all the common migration functions are centralised. The authors show how the platform is realised as middleware that contains a server for the central functions and lightweight client-side running on the end-user devices. The authors show how migratory applications can interact with the platform and thereby do not have to contain migration functions themselves. The authors describe the challenges following the centralisation of a migration platform that can support different types of applications, both games and business applications, implemented with either web-technologies or as component-based applications.

This chapter introduces the various functionalities needed from the system to support generic service migration processes. The chapter focuses on the supporting parts of the platform related to the needed network network support. The chapter introduces entities, modules and components needed for providing the required network network support functionalities and detail their interaction, both internally as well as externally.

A dynamically changing state of the run-time environment impacts the performance of networked applications and furthermore influences the user-perceived quality of the applications. By migrating the application between the user's devices that give different user experiences, a good overall user experience can be maintained, without loosing the application session. It is non-trivial for a system to automatically choose the best device for migration. The choice must maximize the user experience quality and take into account that a migration delays the user's work-flow and even may fail. Moreover, the environment state is not directly observable, and needs to be estimated which leads to inaccuracy. We model the automatic migration trigger as a stochastic optimization problem and we propose to use a hidden Markov model combined with a Markov Decision Process (MDP) to solve the problem. The solution generates policies to choose target device for migration that gives the optimal user experience. We analyse these policies in simulation experiments and derive conclusions on which scenarios the model-based approach performs better than a greedy approach, also when considering inaccurate state estimation.

For the migration process a set of common operations and functionality can be identified. These are located in the Migration Service Platform in order to be able to reuse code, hereby reducing the coding effort required by application developers. These functions in particular focuses on networking issues and management of distributed information. In the following part of this chapter we elaborate these common functions, namely Mobility Support, Context Management, Migration Orchestration and Trigger Management functionalities.

One important aspect of ubiquitous environments is to provide users with the possibility to freely move about and continue to interact with the available applications through a variety of interactive devices such as cell phones, PDAs, desktop computers, intelligent watches or digital television sets. Migratory applications are able to follow the user by sensing changes in the user's context and adapting to available devices, ideally without interrupting the user experience. However, applications themselves must contain functions to monitor context information, coordinate a migration, handle application adaptation and interact with the user during the migration process. To make life easier for developers and users of migratory applications, we propose an integrated Migration Service Platform (MSP), where all the common migration functions are centralised. We show how the platform is realised as middleware that contains a server for the central functions and lightweight client-side running on the end-user devices. We show how migratory applications can interact with the platform and thereby do not have to contain migration functions themselves. By using the platform, they can register and be controlled by the platform to enrich the user experience with the application. We describe the challenges following the centralisation of a migration platform that can support different types of applications, both games and business applications, implemented with either web-technologies or as component-based applications.

In future ubiquitous communication environments, users expect to move freely while continuously interacting with the available applications through a variety of devices. Interactive applications will therefore need to support migration, which means to follow users and adapt to the changing context of use while preserving state. This paper focuses on the scenario of migration between two devices in which the actual migration procedure is executed over near-field communication (NFC) ad-hoc links. The NFC link is interesting as it gives the user the perception of trust and enables service continuity in cases where mid- or long-range wireless connectivity is unavailable. Based on an experimental performance analysis of a specific NFC platform, the paper presents a migration orchestration protocol with low overhead and low delays to be used with NFC links. Experimental results allow to conclude on the sizes of application state that can be expected to be feasible for such ad-hoc NFC migration.

Fault diagnosis is vital to initiate correct recovery actions in order to provide reliable end-to-end services in unreliable networking environments. In this paper we investigate end-node driven fault diagnosis assuming that no support functions in the network exist.Fault diagnosis in networking systems spanning wired and wireless links is complicated as faults are hidden in the network and observations are unreliable. To overcome this, we show how Bayesian Networks (BNs) can be applied for probabilistic fault diagnosis.We model a TCP end-to-end connection to estimate the state of the network and diagnose faults in the wireless and wired domain respectively. Estimation accuracy and diagnosis reactivity performance is evaluated from simulations and compared to a simple threshold based approach. We show how multiple unreliable cross-layer observations improve BN diagnosis performance and robustness to changes in the environment. Furthermore, we evaluate the BN approach and methods to extract features from network traffic to suggest improvements.