Presentation is loading. Please wait.

Presentation is loading. Please wait.

Scalable Routing In Delay Tolerant Networks Mohammad Reza Faghani 1.

Similar presentations

Presentation on theme: "Scalable Routing In Delay Tolerant Networks Mohammad Reza Faghani 1."— Presentation transcript:

1 Scalable Routing In Delay Tolerant Networks Mohammad Reza Faghani 1

2 An Outer Space Network Mars Jupiter station Earth Mars 2

3 What is Delay Tolerant Networks ? Intermittent link (dis)connection No guarantees on End-to-End path Frequent long duration partitioning A B E D F C 3

4 What is Delay Tolerant Networks ? High latency, low data rate Order of hours latency Long queuing times Because of disconnections (Store and Forward) Extremely large (hours, even days) Constraints on end node Limited power, limited buffer How packets route !? 4

5 Routing in DTN DTN Routing Challenges. Instantaneous end to end path may not exist. Large queuing delays. Buffer limitations at intermediate nodes. Large messages. 5

6 Routing in DTN Routing Goals: Eventual Delivery (delivery ratio) Minimizing delivery delay Scalability Cost-effective 6

7 The Routing Problem in DTN Nodes with finite storage capacity Links with dynamic behavior Time varying capacity (c(t)) C(t) = 0, if link is down Message Src, Dst, start-time, size Output: Compute path(s) for every message Objective: Minimize delay Other objectives: message delivery ratio, minimize $$ cost 7

8 The Routing Problem in DTN Edge parameterized by Source Destination capacity function delay function. Define link costs and find minimum cost path. Cost varies with time. Compute minimum cost paths over this dynamic cost assignment Modified Dijkstra by taking into account time of arrival 8

9 Input variable used in Routing Contacts Complete link time variant datas Contacts summary : Time independent information Average waiting time until the next contact Queuing : Link queues, available storage Traffic Demand 9

10 Routing input vs. Performance Input variable used Performance Contacts Summary Contacts + Local Queuing MED ED EDLQ EDAQ LP distributed Contacts + Global Queuing Contacts + Global Queuing + Traffic Demand 10

11 Routing in large networks As the network size grows, number of contacts increases. These algorithms are not scalable for large networks. Using the idea used in static scalable routing. The hierarchical routing 11

12 Scalable Routing in DTNs Cong et. al. proposed a simple DTN model. This makes hierarchical routing possible For scalability, defined two contact information compression methods. 12

13 Simplified DTN model Static nodes (white) Mobile nodes with repetitive motion Motion cycle: T 1 =2 mins, T 3 =T 4 =3 mins Contact: a time period for communication. Persistent contacts: (2,1), (3,4), & (5,6) Persistent contact: (n i n j - - -) Predicted contacts: (1,3), (3,6), & (4,5) Predicted contact: (n i n j T ij t start t duration )

14 Hierarchical Routing in Static Networks Hierarchical network Uses multilevel clustering. Offers scalable management of routing tables. Hierarchical routing Uses the hierarchical network as a topology abstraction A top-down process: the decision made in a higher level is more important Clustering & Clusterhead

15 Hierarchical Clustering in Static Networks Level 2 Level 1 Level

16 Hierarchical Clustering in Static Networks Level 2 Level 1 Level 0

17 Hierarchical Clustering in Static Networks Before any routing each node in the network needs to obtain the topology information of its clusters in all levels. Source should know the hierarchy address of destination. 17

18 Hierarchical Clustering in Static Networks Level 2 Level 1 Level 0 Node 6 1 represents the cluster of nodes 6 0,8 0,24 0 All nodes have their own hierarchy address e.g. node 6 HA equals (1 3, 2 2, 6 1, 8 0 ).

19 Hierarchical Routing in Static Networks Source Destination Level 2 Level 1 Level 0

20 Hierarchical Routing in DTNs Hierarchical routing Similar to that in static networks Multilevel clustering Clusterhead selection Links: contact information aggregation Contact information compression methods 20

21 Cluster head Selection Objective Clusterhead: the center (in terms of delay) of a cluster Cluster members are close to their clusterheads Absolute priority D(i,j) is the weighed average delay between nodes i and j Higher if n is closer to the shortest paths among its neighbors Clusterheads that have the highest APs are self-selected. Relative priority Node i selects a nearby clusterhead n who has a high AP 21

22 Contact information aggregation Hierarchical links have time-variant delays They contain aggregate contact information Contact information in a level k+1 link are aggregated from the related level k links

23 Contact information compression Aggregation level (L a ) Above L a, each link contain only a constant delay 23

24 Contact information Compression Contact information aggregated to link (6,7) is shown in (c). There are two possible shortest paths across the time as shown in (d) & (e) The contact information stored by link (6,7) after contact information removal 24

25 Hierarchical Routing in DTNs Similar to Hierarchical Routing in static networks Hop by hop routing A top-down decision making within each hop Step 1: top-down routing When the routing process is above L a Step 2: Routing with contact information Routes on the combined contact information in all clusters below L a 25

26 Simulation An example network Static nodes Mobile nodes Mobile node Whose trajectory travels several random waypoints within a random square bound 26

27 Simulation Results Route length Distribution 27

28 Simulation Results Hop-count ratio 70/30 28

29 Simulation Results Delay ratio 70/30 29

30 Simulation Results DHR+CIR Delay ratio 70/50 30

31 Simulation Results Storage communication overhead 31

32 Summary Routing performance is close to the optimal routing result in terms of hop-count and delay Routing performance improves as aggregation level (L a ) increases Routing performance improves as the source and destination distance increases Storage and communication overhead is reduced by the compression methods while desirable routing performance and scalability is achieved. 32

33 References [1] Liu C,Wu Jie. Scalable Routing in Delay Tolerant Networks.In proc. of the 8th ACM International Symposium on Mobile Ad Hoc Networking and Computing (MobiHoc), 2007 [2] S. Jain, K.Fall, and R.Patra. Routing in Delay Tolerant networks. In Proc. of ACM SIGCOMM, 2004 [3] Leonard Kleinrock, Farok Kamoun, "Hierarchical Routing for Large Networks, Performance Evaluation and Optimization", Computer Networks, Vol. 1, No. 3, pp. 155–174, January

34 Questions !? 34

Download ppt "Scalable Routing In Delay Tolerant Networks Mohammad Reza Faghani 1."

Similar presentations

Ads by Google