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MaxProp: Routing for Vehicle-BasedDisruption-Tolerant Networks
John Burgess, Brian Gallagher, David Jensen, �Brian Neil Levine
Department of Computer ScienceUniversity of Massachusetts Amherst
IEEE INFOCOM, April 2006 Supported by DARPA C-36-B82-S1, NSF-0519881, and NSF-0080199
© 2006
Networks in Challenged Environments �
§ Challenges� Sparse deployment� Short radio range� System suspension for power management� Unreliable/non-existent infrastructure� Node mobility
§ Example scenarios� Disasters� Countries with developing infrastructure� Underwater networking� Sparse sensor deployments
© 2006
Solution: Disruption Tolerant Networks (DTNs) �
§ DTNs lack end-to-end network paths for routing.§ Packets are stored, carried, and forwarded
� The mobility of nodes provides a path§ Replicating packets is effective for delivery
� Too much replication causes congestion
§ Our protocol for routing is motivated by our real DTN.� We wanted real mobility and radio propagation traces
© 2006
DieselNet�
• Deployed hardware on 40 buses.
• Each bus: Linux; two 802.11 radios; GPS 40GB hard drive
• Buses transfer data as they pass by each other and via available hot spots.
© 2006
Transfers Opportunities �
Bytes transferred
§ Red dots show bus-to-bus transfers§ Duration of transfer opportunities is the limiting resource.
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MaxProp Protocol Assumptions �
§ Vehicle-based DTN resources:� Plentiful power, storage, and CPU cycles� Limited bandwidth to peers
§ Unknown physical location§ Expectation of repeated contact with some
subset of all peers§ Nodes enter and exit network without warning
© 2006
Prioritized Packet Replication�
§ Problem: what is the order of transmitted packets during a transfer to a peer?
§ Sort outgoing packets by how well peer can deliver to destination (next slide).
§ New packets receive bump in priority� Unless device has a small buffer
§ Hop-lists prevent redundant transfers.§ Network-wide ACKs clear out old data.
© 2006
Deliverability Estimate �
1. Create a meeting graph of connection events.2. Assign to each edge between nodes i and j c(i,j)=“likelihood
that next peer i meets will be j”3. Apply Djikstra’s algorithm to find shortest path via B to D.
All packets to the same destination are assigned the same cost.
§ Peers exchange a running list of meeting frequencies with other peers.
§ When node A meets B:� A sorts its packets by the
estimated cost of routing the packet to its destination via B.
© 2006
Evaluation Goals �
1. Are all MaxProp protocol components complimentary?
2. How well does MaxProp perform?� High percentage of packets delivered� Low delivery latency
§ Comparison against:� Random� Dijkstra with a meeting oracle� Just our cost estimate (no acks, etc)
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Setup�
§ Trace-based simulation� DieselNet movements and data transfers� Node exits cause packet loss
§ In paper: � varied load� # of nodes� radio range
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Q1: Component Performance �
Max Prop (all)
Random+Lists Random+Acks
Random+ACKs+Lists
Random Cost Estimate
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Q2: Protocol performance �
§ 2-18 bundles /hr, 10k bundles, unlimited buffer
§ MaxProp has higher delivery rate than other protocols.
Dijkstra (/w meeting oracle)
Cost Estimate
MaxProp Random
© 2006
Related Work�DTN routing protocols:§ J. Davis, A. Fagg, and B.N. Levine, "Wearable Computers as Packet Transport
Mechanisms in Highly Partitioned Ad-Hoc Networks", in Proc. Intl Symp on Wearable Computers. October 2001
§ A. Lindgren, A. Doria, O. Schelen, “Probabilistic Routing in Intermittently Connected Networks”. In Proc. Intl Wrkshp on Service Assurance with Partial and Intermittent Resources (SAPIR 2004), August 2004.
§ S. Jain, K. Fall, and R. Patra, “Routing in a Delay Tolerant Network”. In Proc. ACM SIGCOMM, August 2004.
§ B. Burns, O. Brock, and B.N. Levine. “MV routing and capacity building in disruption tolerant networks”. In Proc. IEEE INFOCOM, March 2005.
§ T. Spyropoulos, K. Psounis, and C. Raghavendra, “Spray and Wait: An Efficient Routing Scheme for Intermittently Connected Mobile Networks”. ACM SIGCOMM WDTN 2005.
DTN platforms:§ P. Juang et al. “Energy-efficient computing for wildlife tracking: design tradeoffs and
early experiences with zebranet”. SIGOPS Oper. Syst. Rev., 36(5):96–107, 2002.§ A. Pentland, R. Fletcher, and A. Hasson. “Daknet: Rethinking connectivity in
developing nations”. IEEE Computer, 37(1):78–83, Jan 2004.
© 2006
Contributions �
§ DTNs provide networking in challenged environments§ We constructed DieselNet, a vehicle-based DTN testbed§ Transfer duration is the limiting resource§ MaxProp uses several mechanisms to route bundles
� Routing based on meeting history, age, acks, and hoplists§ Trace-based evaluation using DieselNet
§ Download the traces:http://prisms.cs.umass.edu/diesel/
© 2006
Setting the Threshold�
§ Average bytes per connection event = x§ Total onboard buffer size = b§ If x < b / 2 then p = x§ If b / 2 ≤ x < b then p = min (x, b - x)§ If x > b then p = 0
© 2006
Software Components �
§ Auto update� Update onboard software� Log operational status� Fault tolerant
§ Live IP� Neighbor discovery� Manage network connections
§ GPS update� Receive and log GPS information
§ DTN daemon� Store-and-forward DTN bundles
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Trace-based Simulators �
DTN Simulator DieselNet
Connection Events
Routing Protocol
Bundle Generation Parameters
Statistics
• Needed repeatable experiment
• Evaluated delivery rate and delay
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Synthesizing Traces �
Vehicle Simulator
GPS Location
logs
Radio Parameters
Bus Movement Parameters
Connection Events
• Needed to vary number of nodes and radio range
• Needed experiments with longer duration
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Virtual DTN Topology�
§ Connection events list generated as follows:� Connection number c chosen for each node pair from
an exponential distribution� All c below a threshold are set to 0 to reduce direct
peerings� Time between pair meetings chosen from a Poisson
distribution with mean s / c, where s is the is the duration of the simulation
© 2006
Simulation vs. Real Systems �
§ Radio model concerns � [Kotz et al]
§ Movement model concerns� [Yoon, Liu, Noble 2003]
§ Real systems provide sanity checks§ Advantages to an operational DTN
© 2006
Virtual DTN Topology Traces�
§ 18 bundles /hr, 10k bundles, unlimited buffer§ MaxProp best suited to vehicle-based networks