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draft-cardenas-dff-05.txt
March 26, 2012
Ulrich Herberg (Fujitsu)
Background
 Advanced Metering Infrastructure (AMI) based on unreliable
wireless links
 Mesh topology
 Non-mobile nodes, but dynamic topology
 802.11 / 802.15.4 link layer
 Problems with relying completely on the control-plane to
update routes
 Control plane may not yet have converged
 High control overhead for fixing paths (reactive or proactive routing
protocol)
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Problem Statement
 Reactive Protocols
 If a link is unstable, RREQ may be required to repair the route
 The RREQ flood in the network in turn may lead to collisions and
further packet loss
 Repeating this process, the network may become unstable
 Proactive Protocols
 Invalid routes until protocol converges
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Solution Approach
 Instead of increasing repair / route update frequency in the
control plane, use data plane
 Find alternate paths
 Detect loops
 Update / poison routes
 No pre-computed alternative routes in control place
1. Exchange control traffic
2. Calculate routes
3. Forward packet
Control plane
3. Fill routing table
Data plane
2. Find route
Router operating system
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1. Receive packet
Mechanism
 General idea:
 If standard forwarding to next hop fails, try alternate neighbors in a DFS
fashion
 When all neighbors unsuccessfully tried, return packet to parent
 When loop detected (detected by storing sequence numbers), update
routing table (“poison route”)
source
e
a
b
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c
f
e⇒b
a⇒d
Example:
f
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loop
d
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Network topology
a
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destination
d
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Search Tree
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f
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Search Tree
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Headers
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Information Sets
 (P_orig_address, P_seq_number, P_prev_hop,
P_next_hop_neighbor_list, P_time)
 where




P_orig_address is the Originator Address of the received frame;
P_seq_number is the Sequence Number of the received frame;
P_prev_hop is the Source Address (i.e. the previous hop) of the frame;
P_next_hop_neighbor_list is a list of next hops to which the frame
has been sent previously;
 P_time specifies when this Tuple expires.
 Access required to list of bidirectional neighbors
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DUP Flag
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Approach Advantages
 Fewer control traffic messages
 Fewer collisions when flooding the network
 Increased reliability of the network
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0.9
0.8
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0.6
Standard DV
DV+DFF
WisReed
0.5
0.4
0.3
0.2
0.1
0
0
100
200
300
400
Nodes
Figure: Delivery ratio (from network simulation, source: [3])
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DFF Deployments
 US
 Field test on-going at KCEC (AMI + Internet service)
 Full scale will be 2,100 nodes
 Press release
http://www.kitcarson.com/index.php?option=com_content&view=article&i
d=45&Itemid=1
 Japan
 Large deployments
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References
Smart Meter
G
W
 [1] Depth-First Forwarding in Unreliable Networks
[Herberg, Cárdenas, Céspedes, Iwao. draft-dff-cardenas]
 [2] Dynamic Data Forwarding in Wireless Mesh Networks
[Iwao, et.al., IEEE SmartGridComm 2010]
 [3] Analysis of Data Forwarding Mechanisms in Unreliable
Networks
[Céspedes, Cárdenas, Iwao. IEEE Innovative Smart Grid
Technologies Conference 2012]
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