Network Management

1
Network Management

• introduction
• motivation
• major components
• wired network management
• Internet management infrastructure
• tomography (using end-to-end measurement)
• wireless network management
• enterprise WLAN
• chaotic WLAN

2
Self-Managementin Chaotic Wireless Deployments

• Authors Aditya Akella, Glenn Judd,
• Srinivasan Seshan, Peter Steenkiste
• MobiCom 2005

3
Outline

• introduction
• characterizing current 802.11 deployments
• impact on end-user performance
• limiting the impact of interference
• power and rate selection algorithms
• conclusions

4
Introduction

• chaotic deployment
• unplanned
• highly variable AP densities
• unmanaged
• not configured to minimize interference
• questions
• impact of interference on end-user performance?
• how to improve end-user performance in chaotic
  deployments?

5
Related work

• management in wired networks IETF zeroconf,
  Thomson 1998, Droms 1997
• rate adaptation in ad-hoc networks Sadeghi 2002
• traffic scheduling in sensor networks and 802.11
  networks Qiao 2003, Kompella 2003
• power and rate control in ad-hoc routing
  protocols Kawadia2005, Draves 2004, Santhanam
  2003, Holland 2003
• commercial products

6
Outline

• introduction
• characterizing current 802.11 deployments
• impact on end-user performance
• limiting the impact of interference
• power and rate selection algorithms
• conclusions

7
Characterizing current 802.11 deployments

• measurement data sets
• Place Lab
• WifiMaps
• Pittsburgh Wardrive
• measurement observations
• 802.11 deployment density
• 802.11 channel usage
• 802.11b vs. 802.11g
• vendors and AP management support

8
802.11 deployment density
Data set Place Lab Degree of neighbor
APs (within 50m)
Deployment high density Degree3 (interference)
9
Measurement observations

• 802.11 channel usage
• 802.11b vs. 802.11g
• 20 are 802.11g
• vendors and AP management support

Channel usage
Popular AP vendors
10
Outline

• introduction
• characterizing current 802.11 deployments
• impact on end-user performance
• limiting the impact of interference
• power and rate selection algorithms
• conclusions

11
Simulation topology

• D clients with an AP
• Clients 1m away from AP
• APs on channel 6
• transmit power 15 dBm
• transmission rate 2Mbps
• RTS/CTS turned off
• two-ray path loss model
• Ricean fading model

Data set Pittsburgh Wardrive
12
Simulation set-up

• HTTP
• client run HTTP with AP
• two HTTP transfers separated by a think time
  (Poisson distribution)
• comb-ftpi
• i clients run long-lived FTP

13
Interference at low high client densities
One client per AP
Three clients per AP

• interference increases with client density
• more degradation when traffic load is high

14
Outline

• introduction
• characterizing current 802.11 deployments
• impact on end-user performance
• limiting the impact of interference
• power and rate selection algorithms
• conclusions

15
Limiting the impact of interference

• optimal static channel allocation
• transmit power control

16
Optimal static channel allocation
single channel
three channels

• optimal channel allocation helpful, but cannot
  eliminate interference

17
Transmit power control
power level 15dBm
power level 3dBm
optimal channel allocation transmit power
control
optimal channel allocation

• transmit power control improve application
  performance, and network capacity fairness

18
Outline

• introduction
• characterizing current 802.11 deployments
• impact on end-user performance
• limiting the impact of interference
• power and rate selection algorithms
• conclusions

19
Power and rate selection algorithms

• benefits of transmit power reduction
• fixed-power rate selection algorithms
• Auto Rate Fallback (ARF)
• Estimated Rate Fallback (ERF)
• power-controlled rate selection algorithms
• power-controlled Auto Rate Fallback (PARF)
• power-controlled Estimated Rate Fallback (PERF)
• performance evaluation

20
Benefits of transmit power reduction
distance between client and AP 10m

• lower transmit power supports higher AP density
• determine transmit power for a given AP density
  control to achieve a certain throughput

21
Fixed-power algorithm 1 Auto Rate Fallback (ARF)

• intuition a failed transmission indicates
  transmission rate too high
• a number of packets transmitted successfully gt
  select higher transmission rate
• a number of packets dropped gt decrease
  transmission rate
• idle for a certain amount of time gt use the
  highest possible transmission rate for next
  transmission

22
Fixed-power algorithm 2 Estimated Rate Fallback
(ERF)

• determines highest transmission rate based on SNR
• estimate SNR tag transmission power, path loss
  and noise estimate in packets
• SNR txPower pathloss noise
• accommodate uncertainty in SNR measurements

Rate (Mbps) Min. SNR (dB)
1 3
2 4
5.5 8
11 12
23
Power-controlled algorithms

• each AP acts socially
• reduce transmit power (interference to other APs)
  as long as not reduce its transmission rate
• power-controlled Auto Rate Fallback (PARF)
• at certain rate, reduce power level after a
  number of successful sends
• power-controlled Estimated Rate Fallback (PERF)
• reduce transmit power while maintain the required
  SNR for the transmission rate

24
Performance evaluation

• effect of power rate selection algorithms used
  by aggressor pair on victim pair

25
Performance evaluation
aggressor-pair rate limited
aggressor-pair rate unlimited

• PERF almost eliminates the interference on the
  victim pair

26
Conclusions

• chaotic networks
• unplanned
• unmanaged
• reduce interference while ensuring robust
  end-client performance
• PERF reduces transmission power as much as
  possible without reducing transmission rate

27
Wireless network management summary

• Reading list
• enterprise WLAN management a drastically
  different approach
• sensor network management
• Future research
• Management architecture?
• Tomography-based approach?