Aalto University School of Electrical Engineering   Department of Communications and Networking   Research Group for Protocols, Services, and Software

Delay-tolerant Networking at Aalto University Comnet

Some quick references:

Delay-tolerant Networking (DTN)

DTN in an emerging research area that takes a different approach to (inter)networking and allows to work in stressed as well as in highly heterogeneous environments. DTN features a number of unique properties which make this concept applicable to challenged networking environments in which traditional communication paradigms would fail or perform rather poorly:

For encompassing information on DTN in general look at the DTN Research Group in the Internet Research Task Force (IRTF)

DTN RG Architecture

The DTNRG has developed an architecture for Delay-tolerant networking that has emerged from the efforts on Interplanetary Internet (IPI). The basic concepts find their application in sensor networks, interpersonal communication (people or "pocket-switched" networks), and in mobile Internet access.

Working with DTNs requires reconsidering the way in which application protocols operate since delays and disruptions have to be considered the default. This means that highly interactive application protocols do not operate well in DTN environments, nor do security or reliability mechanisms that require multiple end-to-end handshakes. And the otherwise ubiquitously available Internet infrastructure services (DHCP-based autoconfiguration, DNS lookups, certification validations, etc.) are likely out of reach or at least not directly accessible. At the same time, store-carry-and-forward operation of DTNs offers unique properties for enabling communication in challenged environments and for efficient cooperation between mobile nodes.

In our DTN research, we focus on applications run by (mobile) human users, with different degrees of mobility and changing mobility patterns. We specifically look at

General Publications

John Solis, Philip Ginzboorg, N. Asokan, Jörg Ott: Best-Effort Authentication for Opportunistic Networks. Proceedings of the International Workshop on Hot Topics on Wireless Network Security and Privacy (HotWiSec), 2011.

Jörg Ott, Ari Keränen, Esa Hyytiä: BeachNet: Propagation-based Information Sharing in Mostly Static Networks. Proceedings of ACM ExtremeCom, 2011. [PDF]

Ari Keränen, Mikko Pitkänen, Mikko Vuori, Jörg Ott: Effect of Non-cooperative Nodes in Mobile DTNs. Proceedings of IEEE WoWMoM Workshop on Autonomic and Opportunistic Communication (AOC), 2011. [PDF]

Jani Lakkakorpi, Mikko Pitkänen, Jörg Ott: Using Buffer Space Advertisements to Avoid Congestion in Mobile Opportunistic DTNs. Invited paper. 9th International Conference on Wired/Wireless Internet Communications (WWIC), 2011. [PDF]

Philip Ginzboorg, Valtteri Niemi, Jörg Ott: Message Fragmentation for Disrupted Links. Accepted for publication in the Proceedings of European Wireless, April 2011. [PDF]

Jani Lakkakorpi, Mikko Pitkänen, Jörg Ott: Adaptive Routing in Mobile Opportunistic Networks. Proceedings of the 11th ACM Symposium Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM), October, 2010. [PDF]

Philip Ginzboorg, Teemu Kärkkäinen, Aki Ruotsalainen, Mikael Andersson, Jörg Ott: DTN Communication in a Mine. Accepted for publication in the Proceedings of the 2nd Extreme Workshop on Communications, Dharamsala, India, September 2010. [PDF]

John Solis, N. Asokan, Kari Kostiainen, Philip Ginzboorg, Jörg Ott: Controlling Resource Hogs in Mobile Delay-tolerant Networks. Elsevier Journal of Computer Communications 33, pp 2-10, 2010.

Ari Keränen, Jörg Ott: DTN over Aerial Carriers. 4th ACM MobiCom Workshop on Challenged Networks, Beijing, China, September 2009. [PDF]

Mikko Pitkänen, Teemu Kärkkäinen, Janico Greifenberg, Jörg Ott: Searching for Content in Mobile DTNs. Proceedings of the 7th Annual IEEE International Conference on Pervasive Computing and Communications (PerCom), Galveston, Texas, March 2009. [PDF]

Jörg Ott: Delay Tolerance and the Future Internet (Invited paper). 11th International Symposium on Wireless Personal Multimedia Communications, Lapland, Finland, September 2008. [PDF]

Jouni Karvo, Jörg Ott: Time Scales and Delay-Tolerant Routing Protocols. Proceedings of the ACM MobiCom CHANTS Workshop, September 2008. San Francisco, September 2008. [PDF]

Mikko Pitkänen, Jörg Ott: Enabling Opportunistic Storage for Mobile DTNs. Journal on Pervasive and Mobile Computing, Elsevier, Vol 4, No 5, pp 579\-594, 2008.

Mikko Pitkänen, Ari Keränen, Jörg Ott: Message Fragmentation in Opportunistic DTNs. Proceedings of the Second WoWMoM Workshop on Autonomic and Opportunistic Communications (AOC) 2008. [PDF]

Mikko Pitkänen, Jörg Ott: Redundancy and Distributed Caching in Mobile DTNs. Second ACM SIGCOMM Workshop on Mobility in the Evolving Internet Architecture (MobiArch), Kyoto, August 2007. [PDF]

Jörg Ott, Mikko Pitkänen: DTN-based Content Storage and Retrieval. Accepted for publication at the First WoWMoM Workshop on Autonomic and Opportunistic Communications (AOC) 2007. [PDF]

Jörg Ott: Application Protocol Design Considerations for a Mobile Internet. 1st ACM MobiArch Workshop, San Francisco, December 2006. [PDF] [Slides]

DTN in Support of general application (e.g., for Drive-thru Internet)

In the Drive-thru Internet Project, we have developed a dedicated protocol architecture to support users potentially moving at high speeds and experiencing opportunistic intermittent connectivity in accessing Internet services. We have performed experiments with mail transmission and reception, with interactive web access, and are also looking into aspects of interactive services.

Code

A DTN-enabled web server will shortly be available for download here. It uses the Ruby DTN2 bindings developed Uni Bremen for the DTN Reference Implementation.

Publications

Jörg Ott, Dirk Kutscher: From Drive-thru Internet to Delay-tolerant Ad-hoc Networking. Book chapter in Marco Conti, Jon Crowcroft, Andrea Passarella (eds): "Mobile Ad-hoc Networks: From Theory to Reality." Nova Science Publishers, Inc., ISBN 978-60021-605-3, 2007.

Lauri Peltola: Enabling DTN-based Web Access: the Server Side. Msater Thesis, Helsinki University of Technology, Department of Communications and Networking, April 2008. [PDF]

Jörg Ott, Dirk Kutscher: Bundling the Web: HTTP over DTN. WNEPT Workshop 2006. [PDF]

Jörg Ott, Dirk Kutscher: Applying DTN to Mobile Internet Access: An Experiment with HTTP. Technical Report TR-TZI-050701, Technologiezentrum Informatik, Universität Bremen, July 2005. [PDF]

See also the Drive-thru Internet publications page.

Floating Content

Content sharing using personal web pages, blogs, or online social networks is a common means for people to maintain contact with their friends, colleagues, and acquain- tances. While such means are essential to overcome distances, using infrastructure services for location-based services may not be desirable. In this paper, we analyze a fully distributed variant of an ephemeral content sharing service, solely depen- dent on the mobile devices in the vicinity using principles of opportunistic networking.

The net result is a best effort service for floating content in which: 1) information dissemination is geographically limited; 2) the lifetime and spreading of information depends on interested nodes being available; 3) content can only be created and distributed locally; and 4) content can only be added, but not explicitly deleted. First we present our system design and summarize its analytical modeling. Then we perform extensive evaluation for a map-based mobility model in downtown Helsinki to assess the operational range for floating content, which, at the same time also validate the analytical results obtained for a more abstract model of the system.

See also the Floating Content project page.

Publications

Jörg Ott, Esa Hyytiä, Pasi Lassila, Jussi Kangasharju, Sougata Santra: Floating Content for Probabilistic Information Sharing. Elsevier Personal Wireless Communications (PMC), Volume 7, Issue 6, December 2011, Pages 671-689.

Esa Hyytiä, Jorma Virtamo, Pasi Lassila, Jussi Kangasharju, Jörg Ott: When Does Content Float? Characterizing Availability of Anchored Information in Opportunistic Content Sharing. Accepted for publication in the Proceedings of IEEE INFOCOM, April 2011. [PDF]

Jörg Ott, Esa Hyytiä, Pasi Lassila, Tobias Vaegs, Jussi Kangasharju: Floating Content: Information Sharing in Urban Areas. Accepted for publication in the Proceedings of IEEE PerCom, March 2011. [PDF]

Jussi Kangasharju, Jörg Ott, Ossi Karkulahti: Floating Content: Information Availability in Urban Environments. Work in Progress Session. Proceedings of the 8th Annual IEEE International Conference on Pervasive Computing and Communications (PerCom), Mannheim, Germany, March 2010. [PDF]

DTN for Mobile and Ad-hoc Networking

Mobile communication services rely on wireless infrastructure provided by third party operators even if communicating peers are in reasonable geographical proximity. Ad-hoc networking between powerful mobile devices may allow bypassing such infrastructure or partly replacing as a backup where no such infrastructure is available or the infrastructure is temporarily not (fully) operational.

However, mobile ad-hoc networking usually seeks to mimic IP-style connectivity because present applications require end-to-end communications. In practice, the limited effective node density makes the existence of an end-to-end (for a sufficient period of time) unlikely because

The DTN approach may provide one suitable mechanism to allow operation also in sparse (mostly or often disconnected) environments, provided that applications and application protocols are adapted to deal with the different conditions.

This research is carried out in close cooperating with Uni Bremen TZI where the Kasuari emulation framework has been developed which we have used for our joint work on DTN-MANET integration.

Publications

N. Asokan, Kari Kostiainen, Philip Ginzboorg, Jörg Ott, Cheng Luo: Applicability of Identity-based Cryptography for Disruption-Tolerant Networking. Proceedings of the First International MobiSys Workshop on Mobile Opportunistic Networking (MobiOpp), June 2007. [PDF]

Jörg Ott, Dirk Kutscher, Christoph Dwertmann: Integrating DTN and MANET Routing. Proceedings of the SIGCOMM CHANTS Workshop, September 2006. [PDF] [Slides]

Mobility Models and Simulations

We have designed the Opportunistic Network Environment (ONE) Simulator which provides a powerful tool for generating mobility traces, running DTN messaging simulations with different routing protocols, and visualizing both simulations interactively in real-time and results after their completion. The ONE simulator comprises three major components:

The ONE Simulator Code

The ONE simulator is written in Java. Design and implementation are by Ari Keränen. It is published under GPL and its version 1.4.1 is now available for download here.

Publications

Ari Keränen, Teemu Kärkkäinen, and Jörg Ott: Simulating Mobility and DTNs with the ONE. (Invited paper) Journal of Communiations, Academy Publisher, Vol 5 No 2, pp 92-105, February 2010.

Ari Keränen, Jörg Ott, Teemu Kärkkäinen: The ONE Simulator for DTN Protocol Evaluation. Proceedings of the 2nd International Conference on Simulation Tools and Techniques (SIMUTools), Rome, Italy, March 2009. [PDF]

Frans Ekman, Ari Keränen, Jouni Karvo, and Jörg Ott: Working Day Movement Model. 1st SIGMOBILE Workshop on Mobility Models for Networking Research, Hong Kong, May 2008. [PDF]

Frans Ekman: Mobility Models for Mobile Ad Hoc Network Simulations. Master Thesis, Helsinki University of Technology, Department of Communications and Networking, May 2008. [PDF]

Ari Keränen and Jörg Ott: Increasing Reality for DTN Protocol Simulations. Technical Report, Helsinki University of Technology, Networking Laboratory, July 2007. [prelimenary PDF] (official PDF with ISBN to come)

DTN for embedded mobile personal devices

To support DTN-based mobile (inter)personal communications, we are investigating, in addition to our aforementioned work on Drive-thru Internet, DTN for embedded mobile devices.

DTN for Nokia 770, N800, N810 Internet Tablets and N900, N950, and N950 mobile phones

We have done a simple and straightforward port to the Linux-based Nokia 770/800 Internet tablets. The Berkeley DTN reference implementation compiles quite nicely in the Scratchbox development environment. As applications, we are looking an email gatewaying and have a prototype of our dtntcp DTN-based web proxy/gateway working on a 770/800.

DTN for Symbian Mobile Phones

We have developed a Symbian-based implementation of the DTNRG bundle protocol and the TCP convergence layer spec from the DTN reference implementation. We have also include a Bluetooth convergence layer. Some characteristics:

DTN communication is presently restricted to WLAN and Bluetooth but we are working on convergence layers for GPRS and multimedia messaging, too. We are presenting the implementation at a demo at the RealMAN 2006 Workshop for which the paper and the poster are available.

Publications

Tuomo Hyyryläinen, Teemu Kärkkäinen, Cheng Luo, Valdas Jaspertas, Jouni Karvo, Jörg Ott: Opportunistic Email Distribution and Access in Challenged Heterogeneous Environments. Demo at the Second ACM SIGCOMM Workshop on Challenged Networks (CHANTS), Montreal, September 2007. [PDF]

N. Asokan, Kari Kostiainen, Philip Ginzboorg, Jörg Ott, Cheng Luo: Applicability of Identity-based Cryptography for Disruption-Tolerant Networking. First International MobiSys Workshop on Mobile Opportunistic Networking (MobiOpp) 2007. [PDF]

Omar Mukhtar: Design and Implementation of Bundle Protocol Stack for Delay-Tolerant Networking. Master Thesis, Helsinki University of Technology, 2006. [pdf]

Omar Mukhtar, Jörg Ott: Backup and Bypass: Introducing DTN-based Ad-hoc Networking to Mobile Phones. Demonstration (short paper) at the RealMAN Workshop 2006. [pdf]

DASM Code

The code of the DTN Symbian implementation is available for download. Tuomo Hyyryläinen is maintaining and enhancing the code now.

(Mobile) DTN Applications

We have developed a couple of DTN applications mostly for use with the DTN reference implementation.

DTN-enabled Blogger

A proxy for a mobile device which is contacted by the mobile user's web browser and then encapsulates blog-postings (with optional attachments) in DTN bundles and transfers them to a backend which unpacks them and posts them to a regular blogging site.

Publication

Lauri Peltola: DTN-based Blogging. Special Assignment, TKK Networking Laboratory, 2007. [PDF].

DTN-enabled Web

As an MSc thesis project, we have developed an open source DTN-capable web server. See the DTN web server project page for details and download.

Publication

Mikko Pitkänen, Teemu Kärkkäinen, and Jörg Ott: Opportunistic Web Access via WLAN Hotspots. Proceedings of the 8th Annual IEEE International Conference on Pervasive Computing and Communications (PerCom), Mannheim, Germany, March 2010. [PDF]

Lauri Peltola: Enabling DTN-based Web Access: the Server Side. Msater Thesis, Helsinki University of Technology, Department of Communications and Networking, April 2008. [PDF]

DTN Mail

We have developed a set of mail applications in support of DTN-based communications. This includes a personal mail proxy connecting existing mail clients (such as Thunderbird) via SMTP and POP3, a simple native DTN mail client for the Nokia Internet tablet, and an infrastructure mail gateway to translate between traditional SMTP and DTN-based mail traffic.

Publication

Tuomo Hyyryläinen, Teemu Kärkkäinen, Cheng Luo, Valdas Jaspertas, Jouni Karvo, Jörg Ott: Opportunistic Email Distribution and Access in Challenged Heterogeneous Environments. Demo at the Second ACM SIGCOMM Workshop on Challenged Networks (CHANTS), Montreal, September 2007. [PDF]

All components are open source under an Apache-style license. The code release is yet to come.

DTN-based Voice Communication: The DT-Talkie and Adaptive VoIP

The DT-Talkie is a push-to-talk-style application for the Nokia N800 and N810 Internet tablets. It allows holding (delay-tolerant) conversations over a DTN network (e.g., using a WLAN) by encapsulating talk spurts into bundles and exchanging them between peers. Simple conversations can make use of the hardware buttons of the N810; a GUI allows managing contacts and maintaining multiple conversation contexts.

For further information see the DT-Talkie project web page.

Publications

Nagasai Panchakarla, Jörg Ott: Delay-tolerant Adaptive Real-time Communication: A Case Study for Voice Proceedings of ExtremeCom 2012. [PDF]

Jörg Ott: Towards More Adaptive Voice Applications. (Invited paper) To be published in the Proceedings of the 4h International Symposium On Leveraging Applications of Formal Methods, Verification and Validation, Amirandes, Heraclion, Crete, October, 2010. [PDF]

Md. Tarikul Islam, Anssi Turkulainen, Jörg Ott: Voice Messaging for Mobile Delay-Tolerant Networks. Proceedings of IEEE COMSNETS, January 2011. [PDF]

Practical Voice Communications in Challenged Networks. Accepted for publication at the 1st Extreme Workshop on Communications. Padjelanta National Park, Lapland, August 2009. [PDF]

Md. Tarikul Islam: DT-Talkie: Interactive Voice Messaging for Heterogeneous Groups in Delay-Tolerant Networks. Demo at IEEE CCNC 2009. [PDF]

Md. Tarikul Islam: DT-Talkie: Push-to-Talk in Challenged Networks. Demo presentation at ACM MobiCom 2008. [PDF]

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