Helsinki University of Technology Department for Electrical and Communications Engineering Networking Laboratory

S-38.3119 Seminar on Delay-tolerant Networking


Today's communication protocols at virtually all layers largely make a common assumption: end-to-end connectivity exists, forwarding paths are relatively stable, and communication does not incur excessive latencies or losses. Transport and application protocols rely on these assumptions: for example, TCP performance may degrade quickly with large RTT or repeated non-congestion losses and application protocols perform poorly or even time out if the RTT increases significantly or the connectitivity is lost or interrupted before transactions were completed. Even for dynamic environments of mobile ad-hoc networking, it is often assumed that end-to-end paths can be found and that transmission latencies remain at most in the order seconds.

However, despite striving for ubiquitous connectivity (always-on or always best connected), we expect poor connectivity and disconnections to remain for many reasons: a communication peer or link may not be available, it may not be economic (i.e., too expensive) to utilize an available link for a certain task, device constraints (such as low battery) may prevent communications, or legal regulations (airplane, immigration) or social conventions (opera, theatre) may prohibit communications for some period of time. Some communication links may have inherently long propagation delays and/or may only be available infrequently. From an application's perspective, in fact, disconnections for some arbitrary time is nothing else than extra delay so that we can subsume unexpected disruptions and graceful disconnections under the same general term of delay.

This seminar on delay-tolerant networking addresses communications in environments with unusual caracteristics, i.e. properties that traditional design of communication protocols has not taken into account. Such "challenged networks" may exhibit, e.g., long communication delays, unpredictable link availability, and may not even provide an end-to-end path at all. These characteristics are partly inherent to certain link layer technologies (e.g. transmission error rate in wireless networks), but mostly stem from specific communication settings and system architectures (e.g. sensor networks connecting underwater equipment or planetary orbits). We will analyze numerous challenged networking environments and their communication characteristics. We will investigate (network,) transport, session, and application layer solutions to delay-tolerant networking as well as novel networking architectures dealing with such specific environments and also look into potential consequences for applications and user interaction paradigms.

This seminar addresses master and PhD students who (intend to) specialize in the area of networking, who have already have a sound understanding of networking protocols and architectures, and who are interested in detailed analysis, discussion, and further development of communication protocols.


Assignments and grading

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