Sebastian Mies

S/Kademlia: A practicable approach towards secure key-based routing

Security is a common problem in completely decentralized peer-to-peer systems. Although several suggestions exist on how to create a secure key-based routing protocol, a practicable approach is still unattended. In this paper we introduce a secure key-based routing protocol based on Kademlia that has a high resilience against common attacks by using parallel lookups over multiple disjoint paths, limiting free nodeld generation with crypto puzzles and introducing a reliable sibling broadcast. The latter is needed to store data in a safe replicated way. We evaluate the security of our proposed extensions to the Kademlia protocol analytically and simulate the effects of multiple disjoint paths on lookup success under the influence of adversarial nodes.

The Underlay Abstraction in the Spontaneous Virtual Networks (SpoVNet) Architecture

Overlay-based services are a popular approach for providing functions like multicast, quality of service or security in the Internet without requiring infrastructure support. This paper presents the Underlay Abstraction Layer in the Spontaneous Virtual Networks (SpoVNet) architecture that enables easy and flexible creation of such services. Also building on an overlay approach, the Underlay Abstraction provides generic functionality to cope with mobility, multi-homing, and heterogeneity. It manages node mobility by separating node identifiers from network locators and it provides persistent connections by transparently switching locators. Multi-homing is supported by choosing the most appropriate pair of network locators for each connection. In order to cope with network and protocol heterogeneity, it uses dedicated overlay nodes, e.g., for relaying between IPv4 and IPv6 hosts. Since the functionality provided by the Underlay Abstraction can be used by several overlay-based services in parallel, redundant functionality is removed from services and applications.

Spontaneous Virtual Networks: On the road towards the Internet's Next Generation

Abstract Novel Internet applications demand global availability of complex services that can adapt dynamically to application requirements. At the same time, pervasive Internet usage and heterogeneous access technologies impose new challenges for service deployment. We present Spontaneous Virtual Networks (SpoVNet), a methodology that enables easy development of new services with transparent support for mobility, multi-homing, and heterogeneous environments. This article presents the overlay-based architecture of SpoVNet that supports the spontaneous deployment of new services as well as a seamless transition towards future networks. SpoVNet´s architecture offers support for the underlay aware adaptation of overlays by the use of cross-layer information. In the context of two exemplary services like a group communication service and an event service as well as two demanding applications – a realtime online game and a video streaming application – we illustrate how SpoVNet is of value in establishing services and applications for the Next Generation Internet.

Towards End-to-End Connectivity for Overlays Across Heterogeneous Networks

The incremental adoption of IPv6, middle boxes (e.g., NATs, Firewalls) as well as completely new network types and protocols paint a picture of a future Internet that consists of extremely heterogeneous edge networks (e.g. IPv4, IPv6, industrial Ethernet, sensor networks) that are not supposed or able to communicate directly. This increasing heterogeneity imposes severe challenges for overlay networks, which are considered as a potential migration strategy towards the future Internet since they can add new functionality and services in a distributed and self-organizing manner. Unfortunately, overlays are based on end-to-end connectivity and, thus, their deployment is hindered by network heterogeneity. In this paper, we take steps towards a solution to enable overlay connections in such heterogeneous networks, building upon a model of heterogeneous networks that comprises several connectivity domains with direct connectivity, interconnected by relays. As major contribution, we present a distributed protocol that detects the boundaries of connectivity domains as well as relays using a gossiping approach. Furthermore, the protocol manages unique identifiers of connectivity domains and efficiently handles domain splitting and merging due to underlay changes. Simulation studies indicate that the algorithm can handle splitting and merging of connectivity domains in reasonable time and is scalable with respect to control overhead.

Reconnecting the internet with ariba: self-organizing provisioning of end-to-end connectivity in heterogeneous networks

End-to-End connectivity in todays Internet can no longer be taken for granted. Middleboxes, mobility, and protocol heterogeneity complicate application development and often result in application-specific solutions. In our demo we present ariba: an overlay-based approach to handle such network challenges and to provide consistent homogeneous network primitives in order to ease application and service development.

On benchmarking routing protocols

While many other disciplines have developed defacto standards to benchmark solutions to their pressing problems, routing protocols are often evaluated in an ad-hoc manner. The resulting variations in the evaluation lead to diminished comparability between different proposals. In this paper, we present a simulation framework for reproducible benchmarking of routing algorithms under various metrics, e.g., stretch, convergence time, routing table size, and message overhead. The measurements are performed on a variety of network topologies and with variations in network dynamics in order to capture the behavior and the capabilities of a routing protocol. Our framework is based on the well-known discrete event simulator OMNeT++ and provides an easy-to-use modular interface, statistic collection for the important metrics as well as a set of network topologies including precalculated metrics. This set of network topologies may serve as an additional reference point in the evaluation of routing protocols complementing existing reference topologies. We provide this framework to the research community as open-source software to alleviate rapid development, testing, and comparison of new routing protocols.

Autonomous detection of connectivity

This paper contributes a protocol that measures underlay connectivity properties of nodes in an overlay network. The protocol autonomously assigns a unique random identifier to each subset of nodes that can communicate transitively using arbitrary underlay routing protocols (e.g., IPv4, IPv6, RFCOMM), denoted connectivity domain. We denote nodes in more than one connectivity domains relays, as they can forward messages between connectivity domains. This information is useful for overlay construction, as possible overlay neighbors must be in the same connectivity domain while relays enable communication between nodes in different connectivity domains. The general problem of identifying maximal connectivity domains is equivalent to the problem of finding all maximal cliques. We show that it can be efficiently approximated in an overlay setting with only partial knowledge of the network connectivity graph. The key observation is that in such scenario once all we discovered all relays remaining nodes can agree on a unique identifier per connectivity domain. We show by theoretical analysis and extensive simulations that the approach is accurate, scalable, resilient, and reactive to connectivity changes in the underlay network.