Beacon Vector Routing: Scalable
Point-to-Point Routing in
Wireless Sensornets
R. Fonseca, Berkeley; S. Ratnasamy, Intel Research; J.
Zhao, ICI; C. T. Ee, D. Culler, S. Shenker, and I. Stoica,
Berkeley
NSDI 2005
The BVR Algorithm
• Algorithm in three distinct parts:
– Greedy forwarding
– Fallback Mode
– Scoped Flooding
The BVR Algorithm
• Define location based on number of hops to
the routing beacons
• Each node stores its location as a vector of
hop counts.
• P(q) = <q1,q2,q3,…qr>
• e.g. <5,1,6,4,3,5,7,9,3>
• Packets are routed based on these vectors
The BVR Algorithm
• Nodes retain the position of their
neighboring nodes.
• A nodes neighborhood is the collection
of nodes one hop away, for most nodes.
The BVR Algorithm
• The algorithm compares the difference
between the packet’s destination and
the current node’s neighbors.
Distance function
Main Rule: Minimize the
sum of the differences
for the beacons that are
closer
to the destination d than
to the current routing
node p
Ties in the Above are
broken by this rule:
Minimize the sum of the
distances to the farther
beacons
BVR Algorithm
Algorithm in operation
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 1:
- only one decision
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 2:
1:<0,2,6> = 8
3:<0,0,4> = 4
9 3
Choose node
b2
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 3:
2:<0,1,5> = 6
4:<0,1,4> = 5
7:<0,1,3> 9= 4
b2 node 7
Choose
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 4:
3:<0,0,4> = 4
5:<0,0,2> = 2
8:<0,0,2> 9= 2 -> tie!
b2
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
Reverse metrics:
5:<3,0,0> = 3
8:<3,2,0> = 5 <4,1,2>
10
Choose 5
Hop 4:
3:<0,0,4> = 4
5:<0,0,2> = 2
8:<0,0,2> 9= 2 -> tie!
b2
<5,3,2>
<5,2,1>
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 5:
4:<0,1,4> = 5
6:<0,1,2> = 3
7:<0,1,3> 9= 4
b2 node 6
Choose
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 6:
5: <0,0,2> = 2
15: <0,1,1> = 2 -> tie!
9
b2
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
2
<1,4,7>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
8
Reverse metrics:
5: <3,0,0> = 3
15: <1,0,0> = 1
<4,1,2>
Choose 15
Hop 6:
5: <0,0,2> = 2
15: <0,1,1> = 2 -> tie!
9
b2
10
14
<5,3,2>
<5,2,1>
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
Hop 7:
14: <0,0,0> = 0
Found node!
9
b2
10
12
13
b3
11
<5,2,3>
Beacon
Source
Destination
4
<2,5,8>
<1,4,6>
1
b1
2
<1,4,7>
<3,4,4>
5
<2,3,4>
6
3 <0,3,6>
<1,2,5>
7
15
<4,4,3>
<1,3,3>
14
8
<5,3,2>
<5,2,1>
<4,1,2>
10
9
12
13
b2
b3
11
<5,2,3>
Beacon
Source
Destination
BVR: Fallback Mode
• It is possible for greedy forwarding to
fail.
• This happens when no neighbor would
improve the minimum distance metric
• When this happens the protocol uses
fallback mode
BVR: Fallback Mode
• Forward packet towards the beacon
closest to the destination
• Parent goes back to forwarding
normally: first with greedy forwarding
and then fallback mode
BVR: Scoped Flooding
• When fallback mode fails the algorithm
resorts to scoped flooding
• In scoped flooding the node knows the
number of hops away the destination is, but
not the direction
• Floods only the number of hops needed
Example: non-ideal case
• Example where algorithm resorts to
flooding
b2
<3,0>
<2,1>
<0,3>
<3,1>
<2,2>
<1,3>
b1
<1,2>
<3,4>
<2,3>
Beacon
Source
Destination
b2
<3,0>
<2,1>
<0,3>
<3,1>
<2,2>
<1,3>
b1
<1,2>
Calculate forward:
<1-3,3-4> = <0,0>
<1-3,2-4> = <0,0>
Calculate reverse:
<3-1,4-3> = <2,1>
<3-1,4-2> = <2,2>
<3,4>
<2,3>
Beacon
Source
Destination
b2
<3,0>
<2,1>
<0,3>
<3,1>
<2,2>
<1,3>
b1
<1,2>
Calculate forward:
<1-3,3-4> = <0,0>
<1-3,2-4> = <0,0>
Calculate reverse:
<3-1,4-3> = <2,1>
<3-1,4-2> = <2,2>
<3,4>
<2,3>
Would forward to <1,3>, but not closer then where we’ve already been.
Initiate scoped flooding for 3 units away.
For such a small network, touches every node.
Beacon
Source
Destination
b2
<3,0>
<2,1>
<0,3>
<3,1>
<2,2>
<1,3>
b1
<1,2>
Calculate forward:
<1-3,3-4> = <0,0>
<1-3,2-4> = <0,0>
Calculate reverse:
<3-1,4-3> = <2,1>
<3-1,4-2> = <2,2>
<3,4>
<2,3>
Would forward to <1,3>, but not closer then where we’ve already been.
Initiate scoped flooding for 3 units away.
For such a small network, touches every node.
Beacon
Source
Destination
Adding another beacon fixes problem
b2
<3,0,3>
<2,1,2>
<0,3,2>
<3,1,4>
<2,2,4>
<1,3,3>
b3
b1
<2,3,0>
<1,2,1>
Calculate forward:
<3-3,1-4,4-1> = <0,0,3>
<1-3,3-4,3-1> = <0,0,2>
<3,4,1>
<2,3,2>
Beacon
Source
Destination
Adding another beacon fixes problem
b2
<3,0,3>
<2,1,2>
<0,3,2>
<3,1,4>
<2,2,4>
<1,3,3>
b3
b1
<2,3,0>
<1,2,1>
Calculate forward:
<2-3,2-4,4-1> = <0,0,3>
<0-3,3-4,2-1> = <0,0,1>
<3,4,1>
<2,3,2>
Beacon
Source
Destination
Adding another beacon fixes problem
b2
<3,0,3>
<2,1,2>
<0,3,2>
<3,1,4>
<2,2,4>
<1,3,3>
b3
b1
<2,3,0>
<1,2,1>
Calculate forward:
<1-3,3-4,3-1> = <0,0,2>
<1-3,2-4,1-1> = <0,0,0>
<3,4,1>
<2,3,2>
Beacon
Source
Destination
Adding another beacon fixes problem
b2
<3,0,3>
<2,1,2>
<0,3,2>
<3,1,4>
<2,2,4>
<1,3,3>
b3
b1
<2,3,0>
<1,2,1>
Calculate forward:
<0-3,3-4,2-1> = <0,0,1>
<2-3,3-4,2-1> = <0,0,1>
<2-3,3-4,0-1> = <0,0,0>
<3,4,1>
<2,3,2>
Beacon
Source
Destination
Adding another beacon fixes problem
b2
<3,0,3>
<2,1,2>
<0,3,2>
<3,1,4>
<2,2,4>
<1,3,3>
b3
b1
<2,3,0>
<1,2,1>
Calculate forward:
<1-3,2-4,1-1> = <0,0,0>
<3-3,4-4,1-1> = <0,0,0>
Tie! Calculate reverse:
<3-1,4-2,1-1> = <2,2,0>
<3-3,4-4,1-1> = <0,0,0>
-> forward to destination
<3,4,1>
<2,3,2>
Beacon
Source
Destination
Location Directory
• How does the sender get the
coordinates of the destination?
• Like a DNS service.
– Submits node ID
– Responds with location
• Hash function correlates nodes with
certain beacons
• Beacons must store all the
state data of the nodes
associated with it