Internship end

6LoWPAN border router :Internship

Maxime DENIS

UMONS

6 December 2012

Masters : Sebastien DAWANS Director : Pr. Bruno QUOITINLaurent DERU

Maxime DENIS (UMONS) 6LoWPAN border router : Internship 6 December 2012 1 / 41

Summary

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesis

7 Conclusion

8 ReferencesMaxime DENIS (UMONS) 6LoWPAN border router : Internship 6 December 2012 2 / 41

Introduction Internship subject

Starting point

CETIC border router prototype

The CETIC border router interconnects a WLAN (IPv6) and a WSN(6LoWPAN) using RPL for routing.

FIGURE 1 : The border router in a typical topology.

ModesRouter, hybrid bridge and full bridge.



Phases of the internship

1 Documentation :a state of the art ;b documentation of the current implementation.

2 Evaluation :a scenarios : use cases with sequence diagrams ;b performance ;c mobility ;d etc.

3 Implementation :a optimizations ;b adding functionalities.



Platforms

FIGURE 2 : Redwire Econotag [1] and ENC28J60[2] Ethernet controller (left),Crossbow Telos B [3] (right).Configuration

Redwire Econotag running the CETIC BR application and an UDPserver on Contiki ;Crossbow Telos B running a simple webserver (Sky websense)and an UDP sender on Contiki.



Testbed

FIGURE 3 : CETIC testbed topology allowing multi-hop routing.


Introduction Notions

6LoWPAN and RPL

6LoWPAN[4, 5]Constitutes an adaption layer between IPv6 and IEEE 802.15.4. Itintroduces packets fragmentation and reassembly, headercompression and Link layer forwarding (in case of mesh undernetworks).RPL [6, 7]Lightweight distance vectorprotocol destined to WSN. Itbuilds a DODAG [8]representing the network.RPL performs a covering ofthe NDP functionalities(Messages : DIO, DIS, DAO).

FIGURE 4 : Example of RPL DODAG.


Introduction Notions

ContikiDescriptionReal time operating system [9], for embedded platforms. Contiki madeto use only one interface : introduction of a Packet Filter.What Contiki brings

uIP stack : small IPv6 (or IPv4) compliant stack, few RAM ;Protothreads : light threads stackless (blockable).

FIGURE 5 : Changes between standard IPv6 stack and 6LoWPAN stack.


Introduction CETIC prototype

Structure and modes

RPL

uIPv6

PacketFilter

ENC28J60 802.15.4

FIGURE 6 : CETIC prototypestructure.

1 Packet filter : differencebetween WSN and ethernetdata ;

2 Full bridge mode : switch,forward and translatingll-addresses ;

3 Hybrid bridge mode : switch,ND proxy and multi-hop (inroute-over) ;

4 Router : Prefix announcement,routing, forwarding (twoseparated subnets).



Structure and modes

RPL

uIPv6

PacketFilter

ENC28J60 802.15.4

DataTraffic

Translation

RPLTraffic








Structure and modes

RPL

uIPv6

PacketFilter

ENC28J60 802.15.4

RPLMessages

NDPMessages

DataTraffic

Translation

ND-ProxyMulti-hop








Structure and modes

RPL

uIPv6

PacketFilter

ENC28J60 802.15.4

RPLMessages

NDPMessages

DataTraffic

Translation

Multi-hopRoutingTable







Evaluation phase

Outline

1 Introduction

2 Evaluation phaseExample of basic scenarioThe restartSensors mobilityTransparent gateway

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesis

7 Conclusion

8 References


Evaluation phase

Organization of the evaluation phase

FIGURE 7 : Flowcharts of the evaluation phase.

During the phase1 Twelve scenarios defined and explained in documentation,

declined in the three modes of the border router ;2 When a issue was encountered, solutions were designed to

improve prototype.


Evaluation phase Example of basic scenario

Description

FIGURE 8 : Actors of the scenario.

In a one-sensor topology with border router in hybrid bridge andmanual configuration

1 Wait for the DODAG to be built (typically when a DAO is receivedby the border router) ;

2 Plug the computer to the border router ;3 Start sending pings to the sensor and wait for response.



Results

13sbefore

Ethernet

802.15.4BR SkyComputer(router)

User

Echo Request(seq=0)

NA

NS(bbbb::100)

DAD(bbbb::223:dffff:fe97:2492)

DAD(fe80::223:dfff:fe97:2492)RA(bbbb::/64)

Computer connection

DAO

DIO

NA

NS(aaaa::212:7400:1465:f55e)

DIO

DAD(aaaa::250:c2a8:cb76:d81b)

DAD(fe80::250:c2ff:fea8:ced0)


DAD(fe80::250:c2a8:cb76:d81b)

DAD(fe80::250:c2a8:cb76:d81b)

Echo Reply(Seq=0)

Ping to Sky

1

FIGURE 9 : Ping from Computer to Sensor (Sky) through the border router.



Results

13sbefore

Ethernet


User

Echo Request(seq=0)

NA

NS(bbbb::100)



Computer connection

DAO

DIO

NA

NS(aaaa::212:7400:1465:f55e)

DIO




DAD(fe80::250:c2a8:cb76:d81b)

DAD(fe80::250:c2a8:cb76:d81b)

Echo Reply(Seq=0)

Ping to Sky

2




Results

13sbefore

Ethernet


User

Echo Request(seq=0)

NA

NS(bbbb::100)



Computer connection

DAO

DIO

NA

NS(aaaa::212:7400:1465:f55e)

DIO




DAD(fe80::250:c2a8:cb76:d81b)

DAD(fe80::250:c2a8:cb76:d81b)

Echo Reply(Seq=0)

Ping to Sky

3



Evaluation phase The restart

Bridge in autoconf mode restarting in stable network

Issue encounteredWhen restarting, the border router requests a DODAG (using a DISmessage) and a prefix on the wired network. If it receives a DIO first, itbecomes leaf and root at the same time : loop.

FIGURE 10 : DODAG representation of the network before and afterrestarting.


Evaluation phase The restart

Solution

Changes to implementation

Increment the version number of the DODAG : the incrementednumber makes the network restarting ;Construct a prefixless DODAG (using link-local address asDODAG ID instead of global address) in autoconfiguration mode ;When a prefix is received from the wired network, add it to theDIO (in Prefix Information Option) and propagate it.

Changes to Contiki

The prefix treatment in a sensor already in a DODAG was defectiveand had to be modified to handle new prefix announced.


Evaluation phase Sensors mobility

Loss in wireless sensors networks

How can a loss occur ?Sensor problem, interferences, collisions ;Moving topology.

FIGURE 11 : DODAG representation of the network before and after a sensorloss.

Deal with lossesLosses in WSN can occur a lot of time : ETX metric used in RPL.


Evaluation phase Sensors mobility

Dealing with lost destinations

Before implementationThe lifetime attribute of the route is used. When lifetime expires, theassociated route is tested and can be removed from the table. Thismechanism prevent any kind of quick mobility among several subnets.

ProposalUse the ETX for descending routes, and remove routes when somecondition are encountered :

The ETX of the neighbor becomes greater than a threshold value ;No-ack penalties are encountered.


Evaluation phase Transparent gateway

Bridge mode to simplify subnets

FIGURE 12 : Several subnets visible as one subnet with bridge.

Issue encountered with full bridge

On-link prefix announced as off-link, and poorly propagated.


Implementation

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesis

7 Conclusion


Implementation

Features added

1 On-link prefix management and propagation (bit set and correctlymanaged by the sensor) ;

2 Incremented DODAG version number correctly managed by thesensors when restart ;

3 Prefix Information Option propagation and management by thesensors ;

4 Route Information Option management by the border router.


Implementation

Route Information Option management

Option of NDP’s RA message[10] used to set routes in routing tables.

Type Length Pref Len R RP

Route lifetime

Prefix (variable length)

FIGURE 13 : Route Information Option message format as specified in [10].

Before implementationBorder router managing RA but ignoring RIOs.

After implementationWhen a RIO is received from an IPv6 router, announced prefixes areadded to the routing table of the border router, and not spread to theWSN.


Using the testbed

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbedApplicationEvaluation

5 Contiki on Linux

6 Master thesis

7 Conclusion

8 References


Using the testbed Application

Scenario

Two applications1 UDP client running on the sensors, and sending to a server

frequent messages identifying them (each 15s) ;2 UDP server running on the border router, sending an

acknowledgment when receiving a message from a node.

FIGURE 14 : Testbed topology used for the scenario.


Using the testbed Evaluation

Metrics

What is measured ?PRR from testbed to server : the amount of messages (UDPpackets) sent is compared to the amount of messages received atthe UDP server (running on the border router) ;PRR from server to testbed : the amount of messagesAcknowledgment sent by the server compared to the amount ofmessages received on the sensors ;TCPIP forwarding : the amount of forwards done at each sensor ;CSMA : the amount of CSMA errors encountered at each sensorand through time.

How ?The packet trip is observable using traces all along the stacks (in theapplication, in the uIP stack and in CSMA).



Results

FIGURE 15 : Metrics.Maxime DENIS (UMONS) 6LoWPAN border router : Internship 6 December 2012 25 / 41


Results

FIGURE 15 : Metrics.



Analysis

PRRs

Metric Average valuePRRTB→S 99.75%PRRS→TB 98.01%

TABLE 1 : Average results of metrics.

RPL is optimized for collecting data (ascendant traffic).

TCPIP forwardingNodes T2 and T3 used for forwarding by T8 and sometimes by T5.



RPL routing

RPL is an asymmetric routing protocol which relies on a sink systemfor ascendant traffic and on routes for descendant traffic.

From sensor to border routerThe current implementationuses the default router toforward the packet.

From border router to sensorA lookup is performed to findthe best route to forward thepacket.

FIGURE 16 : Example of traffic on a RPLDODAG.


Contiki on Linux

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesis

7 Conclusion


Contiki on Linux

Successful portage of the Contiki’s app to Linux

PlatformBeaglebone using a 700Mhz ARM Cortex A8 [11], relying on theAngstrom distribution [12].

Linux Server

IP Tables

BR

SLIPTAP

RAWEth

RADVDRPL....

802.15.4 Raw or Ctrl (MAC, channel, Ack...)

Telos EthBeaglebone

FIGURE 17 : Linux portage and platform structure.


Master thesis

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesisSubjectConcrete applications

7 Conclusion

8 References


Master thesis Subject

Subject

What ?Multiple border router problematic : maintain a state betweenseveral border router ;Make border router more simple : using on an higher root(outside the RPL network, in WPAN).

Why ?Redundancy or Traffic engineering ;Run several QoS ;Invisible sink changes (mobility).


Master thesis Concrete applications

Redundancy paths and traffic engineering

Load balancing, robustness, etc.

FIGURE 18 : One QoS on same subnet : one instance and several DODAGs.



Several QoS

Collecting data, request data, energy-saving paths, etc., on samenetwork

FIGURE 19 : Two QoS on same subnet : several instances.



Invisible sink changes

Same QoS on two separated subnets.

FIGURE 20 : Invisible mobility.



Invisible sink changes

Same QoS on two separated subnets.

FIGURE 20 : Invisible mobility.Maxime DENIS (UMONS) 6LoWPAN border router : Internship 6 December 2012 34 / 41

Conclusion

Outline

1 Introduction

2 Evaluation phase

3 Implementation

4 Using the testbed

5 Contiki on Linux

6 Master thesis

7 Conclusion


Conclusion

Internship achievements1 Increased border router stability : some optimizations and

bugfixes ;2 Paper :

State of the art (the border router solutions) ;Complete description of the border router and scenarios detailed.

3 Features added :Border router more easily deployable ;Autoconfiguration ;Stability increased.

Master thesis perspectives1 RPL root outside WSN ;2 Mobility, redundancy, traffic engineering.


Conclusion

Questions ?


Conclusion

Demonstration

FIGURE 21 : Configuration.

SummaryBorder router web interface, pings, etc.


References

[1] “Redwire Econotag.”http://redwirellc.com/store/node/1 (last access :26/09/12).

[2] “ENC28J60.” http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889 (last access : 26/09/12).

[3] Crossbow, “Telos b.”http://www.xbow.jp/TelosbCatalog.pdf (last access :1/10/12).

[4] “6LoWPAN Backbone Router.” http://tools.ietf.org/html/draft-thubert-6lowpan-backbone-router-02(last access : 2/10/12).

[5] L. M. Ara, “Neighbor Discovery Proxy-Gateway for6LoWPAN-based Wireless Sensor Networks.” KTM Informationand Communication Technology.


http://redwirellc.com/store/node/1

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en022889

http://www.xbow.jp/TelosbCatalog.pdf

http://tools.ietf.org/html/draft-thubert-6lowpan-backbone-router-02

http://tools.ietf.org/html/draft-thubert-6lowpan-backbone-router-02

References

[6] “RFC 6550 : RPL : IPv6 Routing Protocol for Low-Power andLossy Networks.”https://datatracker.ietf.org/doc/rfc6550/ (lastaccess : 2/10/12).

[7] J.-P. Vasseur and A. Dunkels, Interconnecting smart objects withIP.Morgan Kauffman, 2012.

[8] S. Kuryla, “RPL : IPv6 Routing Protocol for Low power and LossyNetworks.” http://cnds.eecs.jacobs-university.de/courses/nds-2010/kuryla-rpl.pdf (last access :20/09/12), 2010.

[9] “Contiki 2.6 Doxygen.”http://contiki.sourceforge.net/docs/2.6/ (lastaccess : 17/09/12).


https://datatracker.ietf.org/doc/rfc6550/

http://cnds.eecs.jacobs-university.de/courses/nds-2010/kuryla-rpl.pdf

http://cnds.eecs.jacobs-university.de/courses/nds-2010/kuryla-rpl.pdf

http://contiki.sourceforge.net/docs/2.6/

References

[10] “RFC 4191 : Default Router Preferences and More-SpecificRoutes.” https://datatracker.ietf.org/doc/rfc4191/(last access : 11/10/12).

[11] “Beaglebone flyer.”http://beagleboard.org/static/flyer_latest.pdf(last access : 3/12/12).

[12] “Angstrom distribution.”http://linuxtogo.org/gowiki/AngstromManual (lastaccess : 3/12/12).


https://datatracker.ietf.org/doc/rfc4191/

http://beagleboard.org/static/flyer_latest.pdf

http://linuxtogo.org/gowiki/AngstromManual

Internship end

Technology

Transcript of Internship end