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Volcano Routing Scheme Routing in a Highly Dynamic Environment Yashar Ganjali Stanford University...
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Transcript of Volcano Routing Scheme Routing in a Highly Dynamic Environment Yashar Ganjali Stanford University...
Volcano Routing SchemeRouting in a Highly Dynamic Environment
Yashar GanjaliStanford University
Joint work with: Nick McKeownSECON 2005, Santa Clara, CA, Sep. 27, 2005
[email protected]://yuba.stanford.edu/~yganjali/
September 2005 Volcano Routing Scheme 2
Outline
Routing in MANETs Slowly changing topology Highly changing topology
Volcano Routing Scheme Single Flow Multiple Flows
Evaluation Mathematical Results Simulations
September 2005 Volcano Routing Scheme 3
Routing in Data Networks
Routing in data networks Phase 1: Route discovery
Proactive Reactive or on-demand
Phase 2: Packet forwarding Routing overhead is
reduced Discovery happens very
infrequently
sd
September 2005 Volcano Routing Scheme 4
Routing in MANETs
Changes in topology Node movements Wireless link issues
Route changes more frequent Temporary partitioning in
network Increased overhead of route
discovery phase Accelerate/defer the route
discovery process Use flooding to find routes as
quickly as possible Buffer when partitioned
September 2005 Volcano Routing Scheme 5
Highly Dynamic Topology
What if topology changes constantly?
Quickly moving nodes Highly dynamic environment Adversarial model
Route discovery failure two-phase routing doesn’t work
September 2005 Volcano Routing Scheme 6
One-Phase Routing
Eliminate explicit route discovery Assign a function to nodes that determines
the direction of packets Physical location of nodes:
Some variations of geographical routing Number of packets buffered in a node:
Volcano Routing Scheme (VRS)
September 2005 Volcano Routing Scheme 7
Outline
Routing in MANETs Slowly changing topology Highly changing topology
Volcano Routing Scheme Single Flow Multiple Flows
Evaluation Mathematical Results Simulations
September 2005 Volcano Routing Scheme 8
Volcano Routing Scheme (VRS) Lava flows towards the
sea (low altitude) Local balancing of load Obstacles do not stop
lava No explicit route
discovery Reordering layers
doesn’t disrupt the flow
September 2005 Volcano Routing Scheme 9
Volcano Routing Scheme
At the beginning of each time slot: Packets are generated at the source.
During the time slot: Each link (v,w) for which P(v) – P(w) >
transfers one packet from v to w. is called transfer threshold.
At the end of the time slot: Packets which arrive at destination are removed.
September 2005 Volcano Routing Scheme 10
Simple Example
Time slot 1 Packet generated
Time slot 2 Packet generated Two transfered One received
Time slot 3 Packet generated
Time slot 4 Packet generated One transfered One received
…
s d
m
September 2005 Volcano Routing Scheme 12
Pros and Cons
Advantages No explicit route discovery Completely distributed Low complexity Minimal amount of control
traffic Suitable for highly dynamic
environments System is proved to be
stable Path taken by packets is
near optimal
Limitations Requires continuous stream
of packets from source to destination
Packet reordering might happen
September 2005 Volcano Routing Scheme 13
Multi-Flow VRS
Time-Division VRS Divide time equally among K flows
Maximum-Pressure VRS For a link (v,w) serve the flow i which has the
maximum amount of pressure Pi(v)- Pi(w)
September 2005 Volcano Routing Scheme 15
Outline
Routing in MANETs Slowly changing topology Highly changing topology
Volcano Routing Scheme Single Flow Multiple Flows
Evaluation Mathematical Results Simulations
September 2005 Volcano Routing Scheme 16
Evaluation Method
Metrics Stability (packet loss ratio) Queue size distribution Routing path length
Factors Connectivity (communication range, number of
nodes, …) Number and amount of flows Mobility process Transfer threshold
September 2005 Volcano Routing Scheme 17
Stability
Strict Stability: total number of packets in the network is bounded.
F-Min-Provisioned: capacity of minimum cut is at least F.
Theorem. If the source injects at most F packets the system remains strictly stable if the network is F-min-provisioned. s d
September 2005 Volcano Routing Scheme 18
Packet Loss vs. Flow Demand 100 nodes distributed
uniformly in a 1x1 square
CR = 0.26 Velocity ~ [0.01..0.2] = 2 Average number of
neighbors = 20 Stability independent of
buffer size
September 2005 Volcano Routing Scheme 20
Packet Loss: Communication Range
Average No. of Neighbors = Flow Demand
September 2005 Volcano Routing Scheme 21
Packet Loss: Mobility Process No difference between
random walk and waypoint model
Stability independent of velocity
Extremely low velocity can cause instability
September 2005 Volcano Routing Scheme 23
Near-Optimal Paths
In a fixed topology packets take shortest paths.
If flow rate is D- we can choose such that Almost surely all packets
take the first D shortest paths.
Trade-ff between Number of outstanding
packets Routing path length
September 2005 Volcano Routing Scheme 25
Summary
Introduced Volcano Routing Scheme Distributed, fast, low complexity, … Need stream of packets
Variations of VRS: Time Division, Maximum Pressure
Stable under admissible traffic Short queuing delay Routing path near optimal
September 2005 Volcano Routing Scheme 28
Generalizing to More Flows
Flow 1 Source: node 1 Destination: node 4
Flow 2 Source: node 4 Destination: node 1