Universität Duisburg-Essen
Verteilte Systeme
Design, Implementation and Evaluation of a Framework to detect the Network Environment of a Peer
Prüfer Prof. Dr.-Ing. Torben Weis
Betreuer Dipl.-Inform. Sebastian Holzapfel
Bearbeiter Petyo Gadzhanov
Dauer 3 Monate

The peers@play project is a joint project of the distributed systems research group together with the universities of Mannheim and Hannover. Its goal is the creation of an interactive three-dimensional virtual world model. Such a model can be useful in virtual societies. They have gained much attention in the last years, in the World Wide Web (e.g. Web 2.0) as well as in 3D applications (e.g. Second Life or Sony Home). These systems are somewhat similar to portals, as they allow users to access a variety of goods and services. In Second Life, real and virtual goods are offered and exhibitions, concerts or even lectures take place. Technically, peers@play should be realized fully distributed based on a peer-to-peer architecture. We expect a high degree of heterogeneity of devices and communication networks, so users should be able to access our platform any time and any place to participate in the virtual society.

The most basic fact of peer-to-peer networks is that peers needs to communicate with each other. To do so, they have to create connections between each other. In typical private households, DSL or cable TV is used for Internet access. Computers connected to the Internet via a NAT-based router are very common, as they allow multiple devices to share one public IP address assigned by the Internet service provider. These NAT-based routers severely restrict the connectivity of a computer. In order to share a single IP address with multiple computers on the internal network the router has to modify the header information of any incoming and outgoing packet. Basically, it replaces for all outgoing packets the source IP address and port with its public IP address and a certain port (mapping). On the other hand, it has to replace the destination IP address and port of all incoming packets with the original ones. To do so, it needs to know the previously created mapping to forward the incoming packet to the right computer. Additionally, the router can provide firewall services and therefore it can filter incoming packets. To use so-called NAT traversal mechanisms successfully, a peer needs to know its own and also the network environment of the remote peer. This environment includes the public IP address, the assigned port and the mapping and filtering behavior of the NAT-based router. Therefore, in the context of this bachelor thesis we aim at the development of a framework that detects the network environment of a peer. The framework must be implemented using Gears4Net – a framework for developing distributed protocols designed and implemented at our department. The expected results of this thesis are two-fold: In the first stage the framework will be implemented (in the context of the peers@play source code). In the second stage, the implemented framework needs to be evaluated in detail. All results with explanations of all decisions need to be written in the written part of this thesis. Additionally, the implementation must be profoundly documented.


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