Routing Protocol Evaluation David Holmer [email protected].
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Transcript of Routing Protocol Evaluation David Holmer [email protected].
![Page 2: Routing Protocol Evaluation David Holmer dholmer@jhu.edu.](https://reader036.fdocuments.us/reader036/viewer/2022062314/56649e7f5503460f94b83cc1/html5/thumbnails/2.jpg)
Mobility Models
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Random Waypoint Mobility Two parameters
Pause Time (Pt) Max Speed (Vmax)
Each node starts at a random location
Executes loop Pause for Pt seconds Select a random
destination (waypoint) Move to that
destination at a random speed (0,Vmax)
Repeat upon arrival
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Random Waypoint Properties Advantages
Easy to implement Allows heterogeneous speeds and temporarily
stationary nodes Disadvantages
Non-uniform node distribution (tend towards center)
Un-stable instantaneous mobility (tends towards zero and oscillates)
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Random Waypoint Properties (cont)
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Random Waypoint Properties (cont)
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Modified Random Waypoint Narrow the random
speed range (.1 Vmax, .9 Vmax)
instead of ( 0, Vmax ) Pre-simulation
mobility Mobility properties
stabilize before routing and data commences
Doesn’t fix non-uniform node distribution
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Other Mobility Models Billiard Model
Node selects a random direction, speed, and time Moves in that direction at that speed for that time and then
repeats (may have pause time as well) Bounces off simulation boundary like a “billiard ball” Maintains uniform node distribution, and uniform average
speed (due to time selection) Group mobility patterns
Node mobility is sum of group mobility and individual mobility Used by clustering based routing protocols (well suited for
certain applications like the military) Trace based mobility patterns
Record real life people/vehicle/etc. motion patterns Requires location hardware such as GPS Difficult to try variations or change “parameters”
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Routing Performance
Metrics
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Routing Protocol Evaluation Metrics Four most common metrics
Delivery Ratio Latency Path Length Optimality Control Overhead
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Delivery Ratio Number of packets successfully received by the
destination / number sent by the source Evaluated by setting up a number of “test” flows
in the network Commonly a number of constant bit rate (CBR) flows
with a specified number of packets per second Uses UDP so every dropped packet results in a reduction
of the delivery ratio (no end-to-end retransmissions) Congestion Sensitive
A large enough test load will result in reduced delivery ratio for ANY protocol due to congestion
Mobility Sensitive If the routing protocol does not respond quickly to
topology change, then packets sent on links that no longer exist will be lost
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Delivery Ratio Examples
Delivery Ratio vs. Test Load Delivery Ratio vs. Mobility
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Latency The time between the creation of a packet and its
delivery to the destination Usually measured using the same setup as
delivery ratio Congestion sensitive
Latency will drastically increase as the congestion limit is reached (due to waiting in large buffers)
Retransmission sensitive Protocols that locally recover packets will achieve higher
delivery ratio but will increase latency On-demand sensitive
Protocols that setup routes after data is sent will have higher latency on the initial packets of a flow
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Latency Example
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Path Length Optimality The difference between the length of the path
used for sending packets in the protocol and the length of the best possible path
Measurement Protocol path length observed for each packet using test
flows Best possible path computed offline using same mobility
pattern Measure of protocol’s ability to track good routes
Extra hops from non-optimal routes will result in increased congestion and medium utilization
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Path Length Optimality Example
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Control Overhead Number/size of routing control packets
sent by the protocol Calculated using counters while simulating
with test flows Sometimes expressed as a ratio of control
to data Indication of how efficiently a routing
protocol operates High control overhead may adversely affect
delivery ratio and latency under higher loads
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Control Overhead Example