algorithms

1. Routing Algorithms
for
Wireless Sensor
Networks
Artemis Paradisi
Jacques Tiberghien

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

3. 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 C
D
H
L M
The Internet
The LowPower network is just one subnet
The sink node plays the role of a router

4. 6LowPan – Why ?
4
TCP/UDP
IEEE 802.15.4
RPL
6LowPan
• 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 connectivity
Route-over architecture
001 resTLA SLANLA
3 13 8 24 18
INT
64
IPv6 address :

5. 6LowPan – Why ?
5
A
GFE
I J K
B C
D
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 versions
of IPv6 ND protocols.

6. 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

7. RPL:
the DODAG
7
A
HF
C
G
EDB
I
NMLK
Grounded
DODAG
FloatingDAG
J
For node I,
E is a parent
G & H are siblings
1 1 1
1 1 1
For node G,
D,H,L are neighbors
D is preferred parent
Each link has a
cost. (distance,
latency, ETX, …)
This cost can be
augmented with
node related data
(battery state, …)1

8. 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 ?

9. RPL:
the RANK of nodes in a DODAG
9
A
HF
C
G
EDB
I
NMLK
Grounded
DODAG
FloatingDAG
J
Rank=1.0
Rank=2.0
For node I,
E is a parent
G & H are siblings
1 1 1
1 1 1
For node G,
D,H,L are neighbors
D is preferred parent

10. RPL:
the RANK of nodes in a DODAG
10
A
H
2
C
1
G
3
E
1
D
1
I
2
NML
Grounded
DODAG
For node I,
E is a parent
G & 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

11. RPL:
Messages for routing
11
A
HF
C
G
EDB
I
NMLK
Grounded
DODAG
FloatingDAG
J
DAO
1 1 1
1 1 1
DIO
DIS

12. 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. 13
Routing in sensor networks(1).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
A
0/0
GFE
I J K
B C
1
1
1
1
D
H
L M
4 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. 14
Routing in sensor networks(2).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
GF
E
1/1
I J K
B
1/4 C
1
1
1
1
D
H
L M
4 1
The Internet
A sends DIO to B and E.
A becomes their preferred
parent.
A
0/0

15. 15
Routing in sensor networks(3).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
2/7
F
2/5
E
1/1
I J
K
2/8
B
1/4
C
2/5
1
1
1
1
D
H
L M
4 1
The Internet
B sends DIO to A,C,F,G
and K.
A ignores (rank).
B becomes the parent of
all others.A
0/0

16. 16
Routing in sensor networks(4).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
2/7
F
2/2
E
1/1
I
2/2
J
2/2
K
2/8
B
1/4
C
2/5
1
1
1
1
D
H
L M
4 1
The Internet
E sends DIO to A,F,I and J.
A ignores (rank).
E becomes the parent of F,I
and J.
A
0/0

17. 17
Routing in sensor networks(5).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
2/8
B
1/4
C
2/5
1
1
1
1
D
3/8
H
L M
4 1
The Internet
C sends DIO to B,D and G.
B ignores (rank).
C becomes the parent of
D and G.
A
0/0

18. 18
Routing in sensor networks(6).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
L M
4 1
The Internet
F sends DIO to B,E and K.
B and E ignore (rank),
F becomes parent of K.
A
0/0

19. 19
Routing in sensor networks(7).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
L M
4 1
The Internet
A
0/0
I sends DIO to E and J.
E ignores (rank),
J ignores (distance)

20. 20
Routing in sensor networks(8).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
L M
4 1
The Internet
A
0/0
J sends DIO to E,I and K.
E ignores (rank),
I and K ignore (distance)

21. 21
Routing in sensor networks(9).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
4/9
L M
4 1
The Internet
A
0/0
D sends DIO to C and H.
C ignores (rank),
D becomes parent of H

22. 22
Routing in sensor networks(10).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
3/6
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
4/7
L M
4 1
The Internet
A
0/0
G sends DIO to B,C,H and K.
B and C ignore (rank),
K ignores (distance)
G becomes parent of H.

23. 23
Routing in sensor networks(11).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
4/4
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
4/7
L
4/6 M
4 1
The Internet
A
0/0
K sends DIO to B,F,G,J and L.
B,F and J ignore (rank),
K becomes parent of G and L.

24. 24
Routing in sensor networks(12).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
4/4
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
5/5
L
4/6 M
4 1
The Internet
A
0/0
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. 25
Routing in sensor networks(13).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
4/4
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
5/5
L
4/6
M
5/7
4 1
The Internet
A
0/0
L sends DIO to K,H and M.
K ignores (rank),
H ignores (distance)
L becomes parent of M

26. 26
Routing in sensor networks(14).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
4/4
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
5/5
L
4/6
M
6/6
4 1
The Internet
A
0/0
H sends DIO to D,G,L and M.
D,G and L ignore (rank),
H becomes parent of M

27. 27
Routing in sensor networks(15).
1
3
33
1
14
1
4
1
1
1 1
1
1
G
4/4
F
2/2
E
1/1
I
2/2
J
2/2
K
3/3
B
1/4
C
2/5
1
1
1
1
D
3/8
H
5/5
L
4/6
M
6/6
4 1
The Internet
A
0/0
Finally, the entire DODAG
has been constructed.

28. 28
Routing in sensor networks(1’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
GFE
I J K
B C
1
1
1
1
D
H
L M
4 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 sinkA
0

29. 29
Routing in sensor networks(2’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
GF
E
1
I J K
B
4
C
1
1
1
1
D
H
L M
4 1
The Internet
A sends DIO to B and E.
A becomes their
preferred parent.
A
0

30. 30
Routing in sensor networks(3’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
F
2
E
1
I
2
J
2
K
B
4
C
1
1
1
1
D
H
L M
4 1
The Internet
E sends DIO to A,F,I and J.
A ignores (rank).
E becomes parent
F,I and J.
A
0

31. 31
Routing in sensor networks(4’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
F
2
E
1
I
2
J
2
K
3
B
3
C
1
1
1
1
D
H
L M
4 1
The Internet
F sends DIO to B,E and K.
E ignores (rank).
F becomes parent of B
and K.
A
0

32. 32
Routing in sensor networks(5’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
6
F
2
E
1
I
2
J
2
K
3
B
3
C
4
1
1
1
1
D
H
L M
4 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).
A
0

33. 33
Routing in sensor networks(6’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
4
F
2
E
1
I
2
J
2
K
3
B
3
C
4
1
1
1
1
D
H
L
6
M
4 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.
A
0

34. 34
Routing in sensor networks(7’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
4
F
2
E
1
I
2
J
2
K
3
B
3
C
4
1
1
1
1
D
7
H
L
6
M
4 1
The Internet
C sends DIO to B,D and G.
B ignores (rank),
G ignores (distance),
C becomes parent of D.
A
0

35. 35
Routing in sensor networks(8’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
4
F
2
E
1
I
2
J
2
K
3
B
3
C
4
1
1
1
1
D
7
H
5
L
6
M
4 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.
A
0

36. 36
Routing in sensor networks(9’).
1
3
3
3
1
14
1
4
1
1
1 1
1
1
G
4
F
2
E
1
I
2
J
2
K
3
B
3
C
4
1
1
1
1
D
6
H
5
L
6
M
6
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.
A
0

37. 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.
37