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A Comprehensive Evaluation of RPL under Mobility Kevin Lee, Raghuram Sudhaakar, Jianxia Ning, Lillian Dai, Sateesh Addepalli, Flavio Bonomi * Paper accepted.

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Presentation on theme: "A Comprehensive Evaluation of RPL under Mobility Kevin Lee, Raghuram Sudhaakar, Jianxia Ning, Lillian Dai, Sateesh Addepalli, Flavio Bonomi * Paper accepted."— Presentation transcript:

1 A Comprehensive Evaluation of RPL under Mobility Kevin Lee, Raghuram Sudhaakar, Jianxia Ning, Lillian Dai, Sateesh Addepalli, Flavio Bonomi * Paper accepted by Consumer Communications And Networking Conference (CCNC 2012) Special Session Information Dissemination in Vehicular Networks * Extended paper submitted to Focus Issue on Vehicular Ad-hoc Networks in International Journal of Vehicular Technology in February 2012

2 Introduction Traffic offloading from 3G to WiFi AP to save money Multihop-to-infrastructure WiFi access reduces the number of AP deployments Intuitively, tree structure is formed with root of the tree at the AP Consider Routing Protocol for Low power and lossy networks (RPL)

3 What About Other Ad Hoc Routing? Reactive routing protocols are susceptible to route breaks Link state routing protocols unscalable because of flooding global topology information

4 RPL Operation DIO Directed Acyclic Graph (DAG) Information Option (DIO) messages are broadcast to build the tree; includes a nodes rank (its level), ETX, etc. ETX probe is sent periodically to probe neighboring ETX

5 RPL Summary RPL forms a Destination Oriented Directed Acyclic Graph (DODAG), with the root of the tree being the AP DODAG minimizes the cost to the root per Objective Function; used ETX here Directed Acyclic Graph (DAG) Information Option (DIO) messages are broadcast to build the tree; includes a nodes rank (its level), ETX, etc. A node selects a parent based on the received DIO msgs and calculates its rank Destination Advertisement Option (DAO) msg sent periodically to notify parent about routes to downward nodes

6 RPL Fine Tuning for VANETs Timer fine-tuning: – Immediate ETX probing for a new neighbor – Immediate broadcasting DIO msg upon new parent election – Immediate broadcasting DAO msg upon new parent election Loop avoidance and detection: – Stamp DIO msg with parents ID; – If a node that receives the DIO msg is equal to the parents ID in the DIO msg, itll discard the DIO msg

7 Loop Avoidance and Detection

8 Qualnet Evaluation Setup Lillian Dai, Sateesh, Raghu, Kevin Lee AP 5000m 2500m 25mph, 45mph, 65mph Packet delivery ratio (PDR) and overhead are obtained with varied DIO msg period and ETX probe period Car 1Car 2Car 3Car 7

9 Rank Change & Duration wrt Time and Speed Lead car (Car 1) establishes 25mph/65mph Rank duration is 22s for 25mph and 9s for 65mph 25mph65mph

10 ETX Probe Period on PDR The packet delivery ratio decreases as ETX probe interval increases -- delayed response to changing topology

11 ETX Probe Period on Overhead As the probe period increases, the number of ETX probes decreases PDR does not degrade as much for ETX probe period 1s, 3s, and 5s => topology change is on the level of 5s granularity => An adaptive timer approach for ETX probe recommended

12 DIO Msg Period and Speed on PDR PDR drops as DIO msg period increases PDR drops as speed increases for a given DIO msg period Diminishing return with decreasing DIO msg period suggests trickle

13 The lower the DIO msg period, the higher the DIO msg overhead DIO Msg Period and Speed on Overhead DIO msg overhead increases with increasing speed

14 PDR before and after changes The improvement is about 20% Modified RPL Improvement

15 Conclusion Studied the impact of DIO msg period and ETX probe period on PDR and overhead => Show the value and advantage of trickle timer Fine tune RPL and improve its performance in vehicular networks by 20% Future work: – More complex sim. scenario – Consider speed and direction in forming a tree – Consider trickle timer for ETX probe period


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