Sensor Network Routing

1
Sensor Network Routing

• Romit Roy Choudhury
• and
• Pradeep Kyasanur
• (Some slides are based on Dr. Nitin Vaidyas
  tutorial)

2
A Review of Current Routing Protocols for Ad Hoc
Mobile Wireless Networks

• Elizabeth M Royer, Chai-Keong Toh

3
Mobile Ad Hoc Wireless Networks

• Unreliable wireless medium
• Mobile nodes
• No central authority
• Traffic patterns application specific
• Energy constraints

4
Example Ad Hoc Network
S
E
F
B
C
D
A
G
H
I
Nodes have unique identifiers Routing problem
find path between S and D
5
Classification of routing protocols

• Table-driven (proactive)
• Up-to-date routing information maintained
• Routing overhead independent of route usage
• Source-initiated (demand-driven / reactive)
• Routes maintained only for routes in use
• Explicit route discovery mechanism
• Hybrid Protocols
• Combination of proactive and reactive

6
Classification (cont.)
Ad Hoc Routing Protocols
Reactive
Hybrid
Proactive
Source-initiated on-demand
Table driven
Hybrid
ZRP
WRP
OSLR
DSDV
CGSR
DSR
AODV
TORA
ABR
SSR
7
Table-driven Routing Protocols

• Each node maintains a routing table
• Contains routes to all nodes in the network
• Changes to network topology is immediately
  propagated
• Protocols differ in mechanisms used to propagate
  topology information

8
Destination Sequenced Distance Vector (DSDV)

• Based on Bellman-Ford algorithm
• Enhanced with sequence number to avoid loops
• Fresher routes have higher sequence numbers
• Optimizations added to reduce routing overheads
  incremental data exchange, delayed exchange of
  updates

9
DSDV Example
Routing Table of Node A
A
B
C
D
Route information is exchanged periodically
10
Clusterhead Gateway Switch Routing (CGSR)

• Nodes organized into hierarchy of clusters.
• Each node has a clusterhead, selected using an
  election.
• Nodes send packet through clusterheads.
• Clusterheads communicate amongst themselves using
  DSDV.
• Two clusters are connected through a gateway node

11
Wireless Routing Protocol (WRP)

• Maintains multiple tables
• Distance, routing, link-cost, etc.
• Link change messages exchanged only between
  neighbors
• Loop freedom using novel algorithm
• Uses predecessor hop information

12
Other Table-Driven Protocols

• Optimized Link State Routing Protocol (OLSR)
  RFC 3626
• Optimization of link-state routing to wireless
• Topology Dissemination Based on Reverse Path
  Forwarding (TBRPF) - RFC 3684
• Also based on link-state routing

13
Source-Initiated On-Demand Routing

• Create routes only when needed
• Routes found using a route discovery process
• Route maintenance procedure used to repair routes

14
Ad Hoc On-Demand Distance Vector Routing (AODV)

• Now RFC 3561, based on DSDV
• Destination sequence numbers provide loop freedom
• Source sends Route Request Packet (RREQ) when a
  route has to be found
• Route Reply Packet (RREP) is sent back by
  destination
• Route Error messages update routes

15
Route Requests in AODV
S
E
F
B
C
D
A
G
H
I
Represents a node that has received RREQ for D
from S
16
Route Requests in AODV
Broadcast transmission
S
E
F
B
C
D
A
G
H
I
Represents transmission of RREQ
17
Route Requests in AODV
S
E
F
B
C
D
A
G
H
I
Represents links on Reverse Path
18
Reverse Path Setup in AODV
S
E
F
B
C
D
A
G
H
I

• Node C receives RREQ from G and H, but does not
  forward
• it again, because node C has already forwarded
  RREQ once

19
Route Reply in AODV
S
E
F
B
C
D
A
G
H
I
Represents links on path taken by RREP
20
Dynamic Source Routing (DSR)

• Similar to AODV in route discovery
• Full source-route is aggregated in RREQ, and sent
  back in RREP
• Each data packet has full source route
• Route table overhead only at source node
• However, each data packet has overhead

21
Route Requests in DSR
S
E
F
B
C
D
A
G
H
I
Represents a node that has received RREQ for D
from S
22
Route Requests in DSR
Broadcast transmission
S
E
F
B
C
D
A
G
H
I
Represents transmission of RREQ
23
Route Requests in DSR
S
E
F
B
C
D
A
G
H
I
RREQ keeps a list of nodes on the path from the
source
24
Route Reply in DSR
S
E
F
B
C
D
A
G
H
I
Represents links on path taken by RREP
25
Associativity-Based Routing

• Defines metric Degree of Association Stability
• This metric used instead of shortest hop
• Nodes with less mobility/better links have higher
  stability value
• DSR-like protocol is used for routing

26
Signal Stability Routing

• Signal strength of links is used as metric
• DSR-like routing is used
• RREQ is forwarded only if packet is received over
  a link with good signal strength

27
Other metrics

• Expected Transmission Time (ETT) metric
• Easier to compute, and more useful than signal
  strength
• Weighted Cumulative Expected Transmission Time
• Better for multi-radio, and asymmetric rate links

28
Temporally Ordered Routing Algorithm

• Directed Acyclic Graph (DAG) rooted at
  destination is used to route packets
• Link Reversal algorithm used to update DAG (along
  with notion of height)
• Algorithm is distributed and loop-free
• Recent result - Link reversal takes O(n2) time
  and message complexity to stabilize

29
TORA Example
A
F
B
C
E
G
Link (G,D) broke
D
Node G has no outgoing links
30
TORA Example
A
F
B
C
E
G
Represents a link that was reversed recently
D
Now nodes E and F have no outgoing links
31
TORA Example
A
F
B
C
E
G
Represents a link that was reversed recently
D
Nodes E and F do not reverse links from node
G Now node B has no outgoing links
32
TORA Example
A
F
B
C
E
G
Represents a link that was reversed recently
D
Now node A has no outgoing links
33
TORA Example
A
F
B
C
E
G
Represents a link that was reversed recently
D
Now all nodes (except destination D) have
outgoing links
34
TORA Example
A
F
B
C
E
G
D
DAG has been restored with only the destination
as a sink
35
Other routing protocols

• Geographic Routing Protocols
• Location Aided Routing (LAR)
• Distance Routing Effect Algorithm for Mobility
  (DREAM)
• Greedy Perimeter Stateless Routing (GPSR)
• Hybrid Routing Protocols
• Zone Routing Protocol (ZRP)

36
Discussion

• Proactive routing protocols suitable for high
  traffic load, low mobility
• On-demand routing protocols suitable for low
  traffic load and/or moderate mobility
• With high mobility, flooding of data packets may
  be the only option

37
Locating and Bypassing Routing Holes in Sensor
Networks

• Qing Fang, Jie Gao and Leonidas J. Guibas

38
GPSR

• Location of the destination node is assumed to be
  known
• Each node knows location of its neighbors
• Each node forwards a packet to its neighbor
  closest to the destination
• If routing holes are found, uses perimeter
  routing (right-hand rule)

39
Routing Holes
E
C
F
B
J
HOLE
D
S
G
A
I
H
40
Problem with GPSR Approach

• Maintaining perimeter graph expensive, especially
  in sensor networks
• Identifying holes (and boundary around holes)
  useful for routing around them
• Also useful for path migration, information
  storage
• Node where packets get stuck (due to a hole)
  define the boundary around holes

41
Definitions

• Weak stuck node P P is the closest node to node
  Q (among Ps neighbors), and Q is out of range of
  P
• Q is called black node

42
Definitions

• Strong stuck node P P is closest node to point
  Q, and Q is out of range of P
• Collection of Qs is called black region

43
Proposed Algorithms

• TENT rule enables detection of strongly stuck
  nodes

J
P
O
H
44
Proposed Algorithms

• BOUNDHOLE- identifies the boundary of a hole
• Start with a stuck node, and sweep
  counter-clockwise
• Move from stuck node to stuck node till the
  originating node is reached, completing loop

45
Discussion

• Identifying holes useful for many applications
• Hole identification assumes circular radio
  transmission pattern
• Can a similar algorithm be designed using
  connectivity properties alone?