Asynchronous Ad-hoc Leader Election in Complete Networks
description
Transcript of Asynchronous Ad-hoc Leader Election in Complete Networks
![Page 1: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/1.jpg)
Asynchronous Ad-hoc Leader Election in Complete
NetworksNolan Irving
![Page 2: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/2.jpg)
Outline• Presentation of problem• Survey of current work• System description• Program description• Data collected• Conclusions
![Page 3: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/3.jpg)
Problem Statement• Ad-hoc network
• No existing backbone to network• Nodes are resource-poor
• Battery life• Processing power
![Page 4: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/4.jpg)
Problem Statement (cont.)• Leader election
• At any given time, there must be at most one leader
• Both links and nodes are unstable• Cannot safely assume reliable channels• Network must adapt to frequent changes
![Page 5: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/5.jpg)
Uses of Ad-hoc Networks• Rapid network deployment
• Combat situations• Search & rescue
![Page 6: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/6.jpg)
Why Elect?• The leader is used to control requests for
access to limited resources• Restoration of tokens• Grant resource requests
![Page 7: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/7.jpg)
Other Research• Multihop networks• Bidirectional links• Movement-based networks
![Page 8: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/8.jpg)
Flawed Assumptions• Algorithms assumed knowledge of number
of participating processors• Nearly all research assumed global ordering• Link representation inappropriate to
wireless networking
![Page 9: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/9.jpg)
Other Problems• Maintenance costs never addressed• Addition/removal of nodes ignored
• Problem increased by initialization requirement
![Page 10: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/10.jpg)
Problem Description• Asynchronous network• Unknown participants• No global ordering• Broadcast communication channel• CD enabled• Complete network
![Page 11: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/11.jpg)
Assumptions• Communications is a shared broadcast channel –
multiple simultaneous transmissions corrupt signal• Nodes can detect a collision – likewise, the sender
can detect a successful transmission• Network is single-hop – all processors can be
reached with a single broadcast• A successful broadcast will reach all participating
nodes
![Page 12: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/12.jpg)
Program Framework• Emulate asynchronous communications
using priority queue• Channel class keeps track of simultaneous
communications and status• Node class handles communications
requests
![Page 13: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/13.jpg)
Simulation Structure
N o d e 1 N o d e 2 N o d e 3 N o d e 4
E le c tio n O b je ct
C h a n n e l C la ss
C o m m un ica tio ns Q u e ue
![Page 14: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/14.jpg)
Program Framework (cont.)
• Leader election protocol• Global ordering• Adding/removing nodes
![Page 15: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/15.jpg)
Results• Times were an average of 1000 runs• Total time is listed in seconds
![Page 16: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/16.jpg)
Timing Results 1
0.00
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
5 10 15 20 25 50 100 150 250
0.05 sec
![Page 17: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/17.jpg)
Timing Results 2
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
5 10 15 20 25 50 100 150 250
0.10 sec
![Page 18: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/18.jpg)
Timing Results 3
0.00
0.50
1.00
1.50
2.00
2.50
3.00
5 10 15 20 25 50 100 150 250
0.02 sec
![Page 19: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/19.jpg)
Comparison of Results
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
5 10 15 20 25 50 100 150 250
0.10 sec0.05 sec0.02 sec
![Page 20: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/20.jpg)
Timing Results(0.05 second message duration)
0.00
5.00
10.00
15.00
20.00
25.00
5 10 15 20 25 50 100 150 250
AverageWorst
![Page 21: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/21.jpg)
Summary of Results• Linear relationship between message length
and election time• Polynomial growth of algorithm time and
message complexity with n
![Page 22: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/22.jpg)
Conclusions• Advantages
• System offered a simple asynchronous protocol for leader election
• Protocol allows for only one leader• Maintenance costs minimal• Handles new additions/dropped nodes easily• One of very few designs able to handle an
unknown number of nodes
![Page 23: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/23.jpg)
Conclusions• Disadvantages
• Time not strongly bounded• Delaying technique inefficient• Will not count participating processors• Unsuited to extremely large networks
![Page 24: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/24.jpg)
Sources• Fundamental Control Algorithms in Ad-hoc Networks.
Hatzis, et. Al. 1998.• Leader Election Algorithms for Mobile Ad-hoc Networks.
Malpani, et. Al. 2000.• Randomized Initialization Protocols for Ad-hoc Networks.
Nakano, Koji and Olariu, Stephan. 2000.• Randomized Leader Election Protocols for Ad-hoc
Networks. Nakano, Koji and Olariu, Stephan. 2000.
![Page 25: Asynchronous Ad-hoc Leader Election in Complete Networks](https://reader036.fdocuments.in/reader036/viewer/2022062814/568167d9550346895ddd35a4/html5/thumbnails/25.jpg)
Questions
???