Routing Algorithmsfor

Wireless SensorNetworks

Artemis ParadisiJacques Tiberghien

- RPL: IPv6 Routing protocol for low power and lossy networks.

IPv6 on Low Power and Lossy Networks?

3

Applications

TCP/UDP

MAC&PHY

IPv6

Applications

TCP/UDP

IEEE 802.15.4

RPL

6LowPan

A

GFE

I J K

B CD

H

L M

The Internet

The LowPower network is just one subnetThe sink node plays the role of a router

6LowPan – Why ?

4

TCP/UDP

IEEE 802.15.4

RPL6LowPan

• Frame length : IPv6: <= 1280 bytes; IEEE 802.15.4: <= 81 bytes.Frame fragmentation & defragmentation

• Header length : IPv6 header >= 40 bytes; TCP header = 20 bytes, … No version field, no flow label, One subnet : 64 instead 128 bit addresses,Header compression

• Connectivity inside the subnet :• Single broadcast domain vs. multi-hop connectivityRoute-over architecture

001 resTLA SLANLA

3 13 8 24 18

INT

64IPv6 address :

6LowPan – Why ?

5

A

GFE

I J K

B CD

H

L M

The Internet

IPv6 : One subnet = one broadcast domain

This is not true in LowPans!Solutions :- Link level routing - Routing in the subnet !

“Route over”uses simplified versionsof IPv6 ND protocols.

Routing Protocol for Low Power and Lossy Networks

• RPL origin: “The Internet of things”.– IETF working group for IPv6 routing.– None of the existing protocols is adequate!– New design combining interesting ideas of all.

• RPL Basic Mechanisms– Routing based upon one or more Destination

Oriented Directed Acyclic Graphs (DODAGs)• Optimal routes between sink and all other nodes

for both the collect and distribute data traffics.• Redundant equivalent routes are kept for

reliability in case of link or node failure.– Multiple DODAGs if different optimisation criteria.

6

RPL: the DODAG

7

A

HF

C

G

EDB

I

NMLK

GroundedDODAG

Flo

atin

g D

AG

J

For node I,E is a parentG & H are siblings

1 1 1

1 1 1

For node G,D,H,L are neighborsD is preferred parent

Each link has a cost. (distance, latency, ETX, …)This cost can be augmented with node related data (battery state, …)1

The ETX cost function

8

ETX = Estimated number of transmissions from x to y. = Number of times a frame needs to be transmitted over a link before being acknowledged. = (dxy x dyx) -1 dxy = success rate from x to y.

Each node broadcasts precisely once per second a short message, each receiver counts during 10 seconds the number of broadcasts it receives from each neighbor.

dxy = (number of frames received from x by y) / 10

What about RDC ?

RPL: the RANK of nodes in a DODAG

9

A

HF

C

G

EDB

I

NMLK

GroundedDODAG

Flo

atin

g D

AG

J

Ran

k =

1.0

Ran

k =

2.0

For node I,E is a parentG & H are siblings

1 1 1

1 1 1

For node G,D,H,L are neighborsD is preferred parent

RPL: the RANK of nodes in a DODAG

10

A

H2

C1

G3

E1

D1

I2

NML

GroundedDODAG

For node I,E is a parentG & H are siblings

1 1 1

5 1 1

For node G,If route via a sibling (H) is “better” , then it should increase its rank.

1

RPL: Messages for routing

11

A

HF

C

G

EDB

I

NMLK

GroundedDODAG

Flo

atin

g D

AG

J

DA

O

1 1 1

1 1 1

DIODIS

RPL: Collect, Distribute and P2P routing

12

A

H

C

G

ED

I

NML

1 1 1

1 1 1

A

H

C

G

ED

I

NML

1 1 1

1 1 1

A

H

C

G

ED

I

NML

1 1 1

1 1 1

Collect Distribute P2P

13

Routing in sensor networks(1).

1

3

33

1

14

1

4

1

1

1 11

1

A0/0

GFE

I J K

B C

1

1

1

1

D

H

L M4 1

The Internet

For this example, links have a distance

as in DV and AODV.The Rank

calculations are made so that

Rank = hop count

14

Routing in sensor networks(2).

1

3

33

1

14

1

4

1

1

1 11

1

GFE1/1

I J K

B1/4 C

1

1

1

1

D

H

L M4 1

The Internet

A sends DIO to B and E. A becomes their preferred

parent.

A0/0

15

Routing in sensor networks(3).

1

3

33

1

14

1

4

1

1

1 11

1

G2/7

F2/5

E1/1

I J K2/8

B1/4

C2/5

1

1

1

1

D

H

L M4 1

The Internet

B sends DIO to A,C,F,G and K.

A ignores (rank). B becomes the parent of

all others.A0/0

16

Routing in sensor networks(4).

1

3

33

1

14

1

4

1

1

1 11

1

G2/7

F2/2

E1/1

I2/2

J2/2

K2/8

B1/4

C2/5

1

1

1

1

D

H

L M4 1

The Internet

E sends DIO to A,F,I and J.A ignores (rank).

E becomes the parent of F,I and J.

A0/0

17

Routing in sensor networks(5).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K2/8

B1/4

C2/5

1

1

1

1

D3/8

H

L M4 1

The Internet

C sends DIO to B,D and G.B ignores (rank).

C becomes the parent of D and G.

A0/0

18

Routing in sensor networks(6).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H

L M4 1

The Internet F sends DIO to B,E and K.

B and E ignore (rank), F becomes parent of K.

A0/0

19

Routing in sensor networks(7).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H

L M4 1

The Internet

A0/0

I sends DIO to E and J.E ignores (rank),

J ignores (distance)

20

Routing in sensor networks(8).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H

L M4 1

The Internet

A0/0

J sends DIO to E,I and K.E ignores (rank),

I and K ignore (distance)

21

Routing in sensor networks(9).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H4/9

L M4 1

The Internet

A0/0

D sends DIO to C and H.C ignores (rank),

D becomes parent of H

22

Routing in sensor networks(10).

1

3

331

14

1

4

1

1

1 11

1

G3/6

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H4/7

L M4 1

The Internet

A0/0

G sends DIO to B,C,H and K.B and C ignore (rank),K ignores (distance)

G becomes parent of H.

23

Routing in sensor networks(11).

1

3

331

14

1

4

1

1

1 11

1

G4/4

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H4/7

L4/6 M

4 1

The Internet

A0/0

K sends DIO to B,F,G,J and L.B,F and J ignore (rank),

K becomes parent of G and L.

24

Routing in sensor networks(12).

1

3

331

14

1

4

1

1

1 11

1

G4/4

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H5/5

L4/6 M

4 1

The Internet

A0/0

G sends DIO to B,C,H and K.B,C and K ignore (rank),

H adapts its rank and distance and keeps G as a parent

25

Routing in sensor networks(13).

1

3

331

14

1

4

1

1

1 11

1

G4/4

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H5/5

L4/6

M5/7

4 1

The Internet

A0/0

L sends DIO to K,H and M.K ignores (rank),

H ignores (distance)L becomes parent of M

26

Routing in sensor networks(14).

1

3

331

14

1

4

1

1

1 11

1

G4/4

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H5/5

L4/6

M6/6

4 1

The Internet

A0/0

H sends DIO to D,G,L and M.D,G and L ignore (rank),H becomes parent of M

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Routing in sensor networks(15).

1

3

331

14

1

4

1

1

1 11

1

G4/4

F2/2

E1/1

I2/2

J2/2

K3/3

B1/4

C2/5

1

1

1

1

D3/8

H5/5

L4/6

M6/6

4 1

The Internet

A0/0

Finally, the entire DODAGhas been constructed.

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Routing in sensor networks(1’).

1

3

33

1

14

1

4

1

1

1 11

1

GFE

I J K

B C

1

1

1

1

D

H

L M4 1

The Internet

For this example, links have a distance as in

DV and AODV.The Rank calculations

are made so that Rank = Distance to sink

A0

29

Routing in sensor networks(2’).

1

3

33

1

14

1

4

1

1

1 11

1

GFE1

I J K

B4

C

1

1

1

1

D

H

L M4 1

The Internet

A sends DIO to B and E. A becomes their preferred parent.

A0

30

Routing in sensor networks(3’).

1

3

33

1

14

1

4

1

1

1 11

1

GF2

E1

I2

J2

K

B4

C

1

1

1

1

D

H

L M4 1

The Internet

E sends DIO to A,F,I and J.A ignores (rank).

E becomes parentF,I and J.

A0

31

Routing in sensor networks(4’).

1

3

33

1

14

1

4

1

1

1 11

1

GF2

E1

I2

J2

K3

B3

C

1

1

1

1

D

H

L M4 1

The Internet

F sends DIO to B,E and K.E ignores (rank).

F becomes parent of B and K.

A0

32

Routing in sensor networks(5’).

1

3

33

1

14

1

4

1

1

1 11

1

G6

F2

E1

I2

J2

K3

B3

C4

1

1

1

1

D

H

L M4 1

The Internet B sends DIO to A,C,F,G and K.

A and F ignore (rank). B becomes parent of C and G.

K keeps its previous parent(distance).

A0

33

Routing in sensor networks(6’).

1

3

33

1

14

1

4

1

1

1 11

1

G4

F2

E1

I2

J2

K3

B3

C4

1

1

1

1

D

H

L6

M4 1

The Internet

K sends DIO to B,F,G,J and L.J ignores (rank),

B ignores (distance),K becomes parent of G and L.

A0

34

Routing in sensor networks(7’).

1

3

33

1

14

1

4

1

1

1 11

1

G4

F2

E1

I2

J2

K3

B3

C4

1

1

1

1

D7

H

L6

M4 1

The Internet

C sends DIO to B,D and G.B ignores (rank),

G ignores (distance),C becomes parent of D.

A0

35

Routing in sensor networks(8’).

1

3

33

1

14

1

4

1

1

1 11

1

G4

F2

E1

I2

J2

K3

B3

C4

1

1

1

1

D7

H5

L6

M4 1

The Internet

G sends DIO to B,C,H and K.B and K ignore (rank), C ignores (distance),

G becomes parent of H.

A0

36

Routing in sensor networks(9’).

1

3

33

1

14

1

4

1

1

1 11

1

G4

F2

E1

I2

J2

K3

B3

C4

1

1

1

1

D6

H5

L6

M6

4 1

The Internet

H sends DIO to D,G,L and M.G ignores (rank),

L ignores (distance),H becomes parent of D and M.

A0

RPL Conclusions

• When the network is started up, the DODAG is build.• The DODAG supports optimal routing, both for

collect and distribute protocols.• Protocols for detecting network changes and

subsequent DODAG repairs (local and global) are part of the RPL proposal (not explained here)

• An Objective Function, giving the rank of the nodes in function of the properties of the links and the nodes, can freely be chosen to influence the DODAG topology and prevent loops.

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