Peer-to-Peer and Overlay Networks


Overlay networks change the structure of a network to a structure of their need. Applications organize and manage their networks. Peer-to-Peer overlays allow to utilize resources at the edges of the network – resources from service providers as well as home users. The decentralized nature of the Peer-to-Peer paradigm allows new ideas, but also leads to additional problems with respect to security and service quality. We research on improving resilience with Peer-to-Peer methods, on security for overlay networks in general, spontaneous networks, and on the optimization of overlay networks using Cross-Layer information and measurements.

Resilience of P2P Systems

Peer-to-Peer networks provide a diversity of nodes and links that is unknown to the classic Client/Server Internet. This is beneficial for all services that profit from diversity. In the project ResumeNet we work on improving the resilience of networked service in future networks. The use of Peer-to-Peer methods is our first choice.

We adapted and studied the use of the Kademlia/KAD DHT to lookup services. Even when a lot of nodes fail a lookup can succeed. Future DNS service could also be more resilient with this kind of service resilience. Network resilience is based on the idea to use different additional route to the traditional IP routing. In case of failures or triangular inequality violations one may use overlay routes to improve performance or resolve failures.

Security and Privacy

Authentication and Authorization in Peer-to-Peer systems is usually delegated to a server. We developped new means to overcome this limitation and still provide reasonable security. The idea is to use social structures of humans behind the peers to form clusters of nodes that operate as one clique (or domain). The more scalable level of the cliques is used to build trust between the "servers" of different cliques. As trust establishment needs to deal with yet untrusted potentially insecure cases, we propose to include a risk assessment in the authentication and authorization process. Applications can then decide if they interact in order to build trust or skip the communication.

We also study attacks and defenses against Peer-to-Peer systems, in particular the Sybil and Eclipse attack. The increasing combination of social networks and Peer-to-Peer systems is not only used for security, but also studied in order to preserve the privacy of users.

Spontaneous Networks

Spontaneous Networks are formed spontaneously to provide a certain functionality for some time. Together with other partners we developped an architecture for such networks in the SpoVNet project. We expect that future services will utilize service-specific networks in a Future Internet. Given enough diversity, spontaneous interactions of hetergeneous systems will be a building-block in future networks.

Cross-Layer Measurement and Optimization

CLIO and UNISONO are our tools to collect and measure Cross-Layer information. UNISONO is a generic tool that operates within the system. CLIO adapts spontaneous overlays from the SpoVNet project to UNISONO. In SpoVNet, we use this to optimize multicast and video services.

Combining Server and P2P Infrastructures

The P2P paradigm has advantages and disadvantages. The Client/Server paradigm also has advantages and disadvantages. The idea here is that we could benefit from the advantages of both if we combine server and P2P system properly. The project CoSIP improve resilience for VoIP signalling using a server for performance and a P2P network for resilience when the server is unreachable. In other work we study the interaction of Cloud Computing and Peer-to-Peer. This may allow normal home users to benefit from the advent of Cloud Computing and lead to new kinds of applications.

Scientists: Prof. Dr. Ralph Holz, Richard von Seck

Projects: Multimedia Conferencing, SpoVNet, ResumeNet, OpenLab-Eclectic


2009-11-01 Dirk Haage, Ralph Holz, “Optimization of Distributed Services with UNISONO (ext. abstract),” in GI/ITG KuVS Fachgespräch NGN Service Delivery Platforms & Service Overlay Networks, Berlin, Germany, Nov. 2009. [Bib]
2009-11-01 Ralph Holz, Dirk Haage, “CLIO/UNISONO: Practical Distributed and Overlay-Wide Network Measurement (ext. abstract),” in 4th GI/ITG KuVS Workshop on The Future Internet and 2nd Workshop on Economic Traffic Management (ETM), Zürich, Switzerland, Nov. 2009. [Bib]
2009-03-01 Dirk Haage, Ralph Holz, Heiko Niedermayer, Pavel Laskov, “CLIO – A Cross-Layer Information Service for Overlay Network Optimization,” in Kommunikation in Verteilten Systemen (KiVS) 2009, Kassel, Germany, Mar. 2009. [Pdf] [Homepage] [Bib]
2007-07-01 Oliver Waldhorst, Roland Bless, Dirk Haage, et. al., “SpoVNet: An Architecture for Supporting Future Internet Applications,” in 7th Würzburg Workshop on IP: Joint EuroFGI and ITG Workshop on "Visions of Future Generation Networks", Würzburg, Germany, Jul. 2007. [Bib]

Student Theses

2015-08-01 Julius Bünger, “Implementation and Evaluation of Brahms in the GNUnet Framework.” BA, Aug-2015. Bartolomiej Polot, Sree Harsha Totakura [Pdf] [Bib]
2015-06-01 Markus Alexander Teich, “Group OTR and its Use-Cases.” IDP, Jun-2015. Sree Harsha Totakura [Bib]
2015-01-01 Daniel Hugenroth, “HRTP: A Broadcast-Based System for Unobservable Internet Telephony.” MA, 2015. Advisor: Lukas Schwaighofer, Supervisor: Prof. Georg Carle [Pdf] [Bib]