Mobility, traffic engineering and redundancy using RPL

Traffic engineering, redundancy and mobility with RPL
and several border routers
Maxime Denis
Département d’Informatique
Université de Mons
June 21th 2013
Director : Pr. Bruno Quoitin External experts : M. Sébastien Dawans
Reviewers : Pr. Sébastien Bette M. Laurent Deru
M. Mathieu Michel

Summary
Outline
1 Introduction
2 Background
3 Multi-BR problematic
4 State of the art
5 Validation
6 Conclusion
Maxime Denis (UMONS) Traﬃc engineering, redundancy and mobility with RPL June 21th 2013 2 / 29

Introduction
Introduction
Figure 1 : WSN layout on the bridge[1].
Wireless Sensors Network (WSN)
Set of sensors, i.e., devices with limited capabilities, often with energy
constraints and wireless interface.
Internet of Things (IoT)
Allows Internet connectivity for any devices : Smart Cities, Smart Building,
Smart Grids, Smart . . .IoT = interconnection of WSNs.

Introduction
Interfacing WSNs with classical networks
With Border Routers (BRs)
A sensor with two stacks, bridging the WLAN and the WSN ;
Most of the time a more capable sensor without energy
constraints ;
In this master thesis : interconnection between IEEE 802.15.4 and
Ethernet.

Introduction
Master thesis subject
Study the interconnection through multiple BRs with a focus on :
1 Redundancy ;
2 Mobility ;
3 Traﬃc engineering.
using RPL and Contiki.

Background
Outline
1 Introduction
2 Background
IPv6
Stacks
RPL
Contiki
4 State of the art
5 Validation
6 Conclusion

Background IPv6
IPv6
IPv6 [2, 3, 4]
large address space (2128 adresses) ;
minimal MTU (1280 Bytes) ;
autoconﬁguration process (NDP) ;
...
Neighbor Discovery Protocol [5]
contains ARP (IPv4) ;
Autoconﬁguration using the Duplicate Address Detection (DAD)
mechanism ;
Reachability detection using the Neighbor Unreachability Detection
(NUD).

Background Stacks
Stacks
IPv6
ICMP
NDP UDP TCP
802.3 MAC layer
802.3 PHY layer
Figure 2 : Classical stack.
IPv6
ICMP
RPL UDP TCP
802.15.4 MAC layer
802.15.4 PHY layer
6LoWPAN layer
Figure 3 : WSN stack.

Background RPL
Routing Protocol for Lossy networks (RPL)
Lightweight distance vector protocol [6] used in WSNs.
Description
Collect oriented : designed to collect data from sensors to sink.
Topology covered by a tree with a single root.
Datapath validation : no periodical messages.
Two concepts : instances and DODAGs (Destination Oriented
Directed Acyclic Graphs).
Traﬃc
RPL allows three kinds of traﬃc : Peer-to-Peer, Peer-to-Multi-Peer and
Multi-Peer-to-Peer.

Background RPL
DODAGs
DODAG : tree covering and partitioning the WSN.
Root : node managing the DODAG ;
Upward routes : created by DIOs, to reach the root ;
A node owns a parent which leads to the root ;
Downward routes : created by DAOs, to reach the sensor ;
Node’s rank means the distance between the node and the root ;
Metrics are used to qualify links and choose parents ;

Background RPL
Instances
Set of DODAGs, optimized for a QoS or designed for a constraint.
Rules
A node can join only a single DODAG per instance ;
A node can join all the instances available ;
A node may not join an instance if the QoS is not appropriate.

Background Contiki
Contiki : a lightweight operating system for WSNs
Description
Real time operating system [7], for embedded platforms.
What Contiki brings
uIP stack : small IPv6 (or IPv4) compliant stack, few RAM, single
interface support ;

Multi-BR problematic
Outline
1 Introduction
2 Background
Mobility
Redundancy
Traﬃc engineering
Extracted RPL root
4 State of the art
5 Validation
6 Conclusion

Multi-BR problematic Mobility
Mobility
Mobility case
Parent failure : switching to another parent in the DODAG.
Mobility : new neighborhood : DODAG ? Instance ?
In multi-BR case...

Multi-BR problematic Redundancy
Redundancy
Redundancy consequences
Border router failures : recovery increased ;
RPL overhead on sensors (several DODAGs).

Multi-BR problematic Traffic engineering
Traffic engineering
Force paths on the WSN to balance the traffic among several paths.
Solutions
Multi-instance to balance traffic over sensors ;
Multi-instance over several channels to balance traffic over channels.

Multi-BR problematic Extracted RPL root
Implementation : extracted RPL root over Ethernet
1 RPL root over Ethernet ;
2 Border routers running in a single DODAG per instance ;
3 Mobility and redundancy increased, complexity decreased.

State of the art
Outline
1 Introduction
2 Background
4 State of the art
6LBR
5 Validation
6 Conclusion

State of the art
Existing 6LoWPAN border router solutions
Computer dependant
Contiki’s border router integrated solution ;
Jackdaw USB stick [8] ;
Computer independant
Grinch project[9] ;
6LoWPAN-ND on Hogaza platform[10] ;
CETIC’s 6LBR[11, 12].

State of the art 6LBR
6LBR
Features
6LoWPAN border router using RPL ;
Support of two interfaces in Contiki (ﬁltering rules and translation).
Platforms
Linux native (PC, Raspberry Pi, BeagleBone), Redwire Econotag with
Ethernet controller.

Validation
Outline
1 Introduction
2 Background
4 State of the art
5 Validation
Conﬁguration
Experimentations
Results
6 Conclusion

Validation Configuration
Scenarios
Platforms
Zolertia Z1 (N1, N2, BR2) ;
Crossbow TelosB (BR1) ;
Four scenarios captured in five experimentations. Traffic capture done
using sniffer[13]. Traces in pcap format and sequence diagrams,
performance indication (values measured in traces).

Validation Experimentations
Scenario 1 (S1) : Multi-instance advertisement
Multi-instance advertisement and the route creation with packet
exchange between the WSN and the Ethernet using the extracted RPL
root. A single BR and a single sensor are used in this scenario.

BR 802.15.4EthernetRPL Root
DIO(instance=2)
DIO(instance=2)
DAO(instance=2, target=BR)
DAO(instance=1, target=BR)
DIO(instance=1)
DIO(instance=1)
DIO(instance=2)
DIO(instance=1)
DAD(global)
DAD(link-local)
Visual Paradigm for UML Standard Edition(University of Mons)

1
2
3
(3) Time
Sensor
802.15.4RPL Root Ethernet BR
UDP(Ack)
UDP(Ack)
UDP UDP
DIO(instance=1)
DIO(instance=1)
DAO(instance=1, target=Sensor)
DIS
Sensor turned on
DIO(instance=2)
DIO(instance=1)
DAO(instance=1, target=Sensor)
DIO(instance=2)
DIO(instance=1)
sual Paradigm for UML Standard Edition(University of Mons)

Scenario 4 (S4) : Mobility
A single instance with two BRs and a single sensor. Simulation of mobility
between two BRs.

between two BRs.
Ethernet 802.14.5
Sensor
BR1RPL root
DIO
DIO
DIO
DIO
DIO
DIO
DAD(global)
DAD(link-local)
UDP
DAO(target=Sensor)
UDP
UDP
DAO(target=Sensor)
UDP
DAO(target=BR1)
DAO(target=BR1)
UDP(Ack)UDP(Ack)

between two BRs.
2
1
(1) Time
802.14.5Ethernet
BR2
SensorBR1RPL root
UDP UDP
UDP UDP
DAO(target=Sensor)
DIO
DAO(target=BR2)
DIS
UDP
DIO
DIS
UDP UDP
UDP(Ack)
DAO(target=Sensor)
UDP(Ack)
UDP
UDP
UDP
UDP(Ack)UDP(Ack)

Validation Results
Results - S1 and S4
Summary of the main values gathered during scenarios
Route creation (S1) : about 7s ;
Retransmissions in mobility (S4) : about 30 ;
Route recreation after switch (S4) : about 18s.

Conclusion
Outline
1 Introduction
2 Background
4 State of the art
5 Validation
6 Conclusion
Contributions
Future work

Conclusion Contributions
Contributions
1 Complete description of the background notions used : RPL,
IPv6, NDP, 6LoWPAN and IEEE 802.15.4. ;
2 State of the art of the existing BRs solutions ;
3 The multi-BR problematic developed using redundancy, mobility
and traﬃc engineering ;
4 Design and implementation of the extracted RPL root and the
border routers ;
5 Four scenarios with traces and sequence diagrams ;
6 Multi-instance validation.

Conclusion Future work
Future work
1 Implementation of several instances using several channels ;
2 Dynamic load balancing implementation ;
3 Dynamic instance determination for Ethernet traﬃc ;
4 Validation using other applications (e.g., Pings, HTTP) ;
5 Bigger testbed and simulation validation ;
6 More realistic topologies (border routers and RPL root connected
through a backbone network) ;
7 ...

Thank you for your attention

[1] Sukun Kim, Shamim Pakzad, David Culler, James Demmel, Gregory
Fenves, Steven Glaser, and Martin Turon, “Health Monitoring of Civil
Infrastructures Using Wireless Sensor Networks.” http:
//www.cs.berkeley.edu/~binetude/work/ipsn07_ggb.pdf (last
access : 12/05/13).
[2] J.-P. Vasseur and A. Dunkels, Interconnecting smart objects with IP.
Morgan Kauﬀman, 2012.
[3] B. Quoitin, “IPv6.” Computer Networks course (UMONS).
[4] Internet Engineering Task Force, “RFC 2460 : Internet Protocol,
Version 6 (IPv6) Speciﬁcation.”
http://tools.ietf.org/html/rfc2460 (last access : 16/03/13).
[5] Internet Engineering Task Force, “RFC 4861 : Neighbor Discovery for
IP version 6 (IPv6).”
https://datatracker.ietf.org/doc/rfc4861/ (last access :
2/10/12).

[6] Internet Engineering Task Force, “RFC 6550 : RPL : IPv6 Routing
Protocol for Low-Power and Lossy Networks.”
https://datatracker.ietf.org/doc/rfc6550/ (last access :
2/10/12).
[7] “Contiki 2.6 Doxygen.”
http://contiki.sourceforge.net/docs/2.6/ (last access :
17/09/12).
[8] “Jackdaw USB stick.”
http://dak664.github.com/contiki-doxygen/a01677.html
(last access : 2/10/12).
[9] “Grinch - simple 6lowpan RPL border router.”
http://sixpinetrees.blogspot.be/2011/06/
grinch-simple-6lowpan-rpl-border-router.html (last access :
2/10/12).

[10] L. M. Ara, “Neighbor Discovery Proxy-Gateway for 6LoWPAN-based
Wireless Sensor Networks.” KTM Information and Communication
Technology.
[11] Maxime Denis, “6LoWPAN Border Router prototype on a Redwire
Econotag,” February 2013.
[12] CETIC, “A deployment-ready 6LoWPAN Border Router solution
based on Contiki.” https://github.com/cetic/6lbr (last access :
23/02/13).
[13] David Hauweele, “Wsn tools.”
https://github.com/gawen947/wsn-tools (last access :
22/05/13).

Mobility, traffic engineering and redundancy using RPL

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