Routing in Delay Tolerant Networks

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This presentation covers some of the routing protocols for Delay Tolerant Networks (DTN) along with the overview of the Opportunistic Networking Environment which can be used for performance evaluation/comparison of/among these DTN protocols.
P.S. This presentation is for educational purpose only. It is not meant for any commercialization at all.

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Routing in Delay Tolerant Networks

  1. 1. Seminar by Anubhav Mahajan 06111502709 C.S.E. 7th Sem
  2. 2.      Delay Tolerant Networks(DTNs) are promising new development in network research field. DTNs are those networks where instantaneous end-to-end paths among nodes may not be possibly established or are absent for a long period of time. Purpose of this study was to survey DTN routing problem. It includes study of DTN routing protocols each of which aims at increasing the message delivery probability as well as reducing , as much as possible, the overheads incurred during the whole delivery process of the message. Henceforth, performance of these routing protocols will be evaluated using the ONE simulator which is designed specifically to simulate these routing protocols.
  3. 3.     Delay Tolerant Networks are wireless networks where disconnections and delays may occur frequently due to propagation phenomena such as node mobility, power outages etc. DTN comes into play when delays are observed due to nonexistence or long absence of instantaneous end-to-end paths among nodes. One of the main reasons behind these are untimely and random movement of intermediate nodes (mobile hosts) that have to carry data from any source to destination. In order to achieve data delivery, a “store-and-forward” approach is taken where data is incrementally moved and stored throughout the network in “hopes” that it will eventually reach its destination.
  4. 4.  To survey DTN routing problem.  To study different DTN routing protocols.  To study ONE simulator.  Performance evaluation of DTN routing protocols using the ONE simulator.
  5. 5.   DTN comes into play when instantaneous end-to-end paths among network nodes may not be possible to establish or are absent for a very long time. A “store-and-forward” approach is taken where data is incrementally moved and stored throughout the network in “hopes” that it will eventually reach its destination.
  6. 6.     DTN can be rendered as a special case of Ad-hoc networks where network partitions occurs very frequently and that too for a long period of time. Traditional Ad-hoc networking routing protocols requires an pre-existing instantaneous end-to-end path between source and destination nodes either directly or indirectly through intermediate mobile nodes. But if an instantaneous end-to-end connectivity is failed to get established, these protocols fails along with them. These failures also includes the cases where at the time of origination of a message there was an instantaneous endto-end connectivity between source and destination which may not be present at the time when the message is travelling through the path and results in loss of message.
  7. 7.  Interplanetary Internet.  Mobile posts around the planet including space stations or posts on terrain such as Antarctica.  Deep sea communication.  Mobile military deployments across seas and desserts.
  8. 8.  Routing protocols will be used to move messages end-toend across the network which is time varying as well as whose dynamics are not known in advance.  Goals of a DTN routing protocol are to: 1.) maximize message delivery rate 2.) minimize message latency 3.) minimize the total resources consumed in message delivery such as buffer sizes within mobile hosts(carriers) devoted to store other host’s messages ,energy of the host(carrier) consumed in storage and transmission of that message etc.
  9. 9.    A flooding based DTN routing protocol. Simply based on random pair-wise exchanges of messages that takes place among mobile hosts and among islands of mobile hosts to ensure eventual message delivery. Copies of a message will spread like some epidemic of a disease in the network, ultimately reaching to its destination.
  10. 10.    SV : Summary vector Summary vector of a mobile host is a brief summary of messages that are currently present in the buffer of a mobile host. When two mobile hosts come into contact with each other, they decide which messages are to be exchanged between them by looking at other host’s summary vector.
  11. 11.  A controlled flooding based DTN routing protocol but with no random pair-wise exchanges.  Message exchanges are based on delivery predictability which indicates how likely is that this node will be able to deliver a message to its particular destination.  Delivery predictability is measured on the basis of the number of times two hosts comes into contact or the number of times a host has successfully delivered a message to a particular destination through transitivity.  A message will be transferred from first node to second node if and only if the second node have a higher value of delivery predictability than the first node for the destination of that message.
  12. 12.      Not a flooding based technique. It consists of two phases :Spray phase and Wait phase. Spray phase: Source node will spray a limited number of copies of the message into those nodes that have much higher delivery predictability than the source node in hope that one of the sprayed node is destination itself. Wait phase : If the destination is not found in the spraying phase, each of the nodes carrying a message copy tries to performs direct transmission (i.e. will forward the message only to its destination). If still not successful then spraying phase will begin again after waiting for some pre-specified time period.
  13. 13.  Based on formation of social groups.  Assumes that nodes that are assigned to the same social network (classroom, project team) will regularly interact with members of that social group.  With these groups identified, consistent routes towards particular destinations are identified based on the delivery history of a group or node.  To deliver a message to a member or members of a particular group , simply transfer the message to a node which regularly interacts with any member of that group.  Rest, that member of the group will spread the message to all the members of that group.
  14. 14.    Simulation tool, developed in Java, used for processing of DTN routing protocols. It has been designed specifically for DTN routing protocols and applications. Provides interactive visualization and post-processing tools.
  15. 15.    First we write implementation of a DTN routing protocol in the form of JAVA classes which are fed into ONE simulator, which itself is a collection of java classes and packages. ONE simulates the protocol as per our specifications. As a result, it generates a detailed report on performance evaluation of the protocol as per simulation.
  16. 16. Feeded Java Classes Simulation Data Specifications Report
  17. 17.  Performance of DTN routing protocols will be evaluated on the basis of some specified parameters.  These are : 1.) Percent messages delivered using that protocol. 2.) Average latency of delivered messages. 3.) Total number of transmissions. 4.) Hop count per message. 5.) Average overhead per message.  After simulating a DTN protocol, as per our pre-specified configurations, the report of performance of the protocol will be generated in terms of these parameters.
  18. 18. First we provide a configuration to ONE over which these protocols will be simulated turn by turn.  This configuration includes : 1.) The map/scenario over which nodes will roam. 2.) The number of nodes in the scenario. 3.) The buffer size at each node.  Then on the basis of following two criteria, performance of each DTN routing protocol will be evaluated and compared. These are : 1.) Parameter vs. Variable Buffer Size keeping number of nodes fixed in the scenario. 2.) Parameter vs. Variable node count keeping buffer size of each node fixed in the scenario. 
  19. 19.  Successful survey of DTN routing problem.  Successful study of different DTN routing protocols.  Successful study of the ONE simulator and its working.  Successful performance evaluation of DTN routing protocols using the reports generated by the ONE simulator.
  20. 20.  Investigations for other forwarding strategies that can enhance the performance of DTN further.  There is much scope for addition of more maturity to the ONE simulator . This includes more functionalities such as automatic comparisons among DTN protocols on the basis of parameters rather than making us do manual comparisons.  Standardization of data which is used for simulating DTN protocols on the ONE simulator.
  21. 21.  [1] A. Vahdat and D. Becker, “Epidemic routing for partially connected adhoc networks,” Duke University, Tech. Rep., 2000.  [2] Roy Cabaniss, Sanjay Madria, George Rush, Abbey Trotta and Srinivasa S. Vulli Department of Computer Science, “Dynamic Social Grouping Based Routing in a Mobile Ad-Hoc Network”Missouri University of Science and Technology, Rolla, Missouri 65401, School of Computing and Engineering,University of Missouri, Kansas City, Missouri 64110  [3] Thrasyvoulos Spyropoulos, Konstantinos Psounis and Cauligi S. Raghavendra, “Spray and Wait: An Efficient Routing Scheme forIntermittently Connected Mobile Networks”  [4] Sushant Jain, Kevin Fall, Rabin Patra “Routing in a Delay Tolerant Network”  [5] Anders Lindgren, Avri Doria, Olov Schel´en “Probabilistic Routing in Intermittently Connected Networks”
  22. 22. [6] https://www.netlab.tkk.fi/tutkimus/dtn/theone/ [7] https://crawdad.cs.dartmouth.edu/data.php [8] https://www.wikipedia.org

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