Title: Network Management
1Network Management
- introduction
- motivation
- major components
- wired network management
- Internet management infrastructure
- tomography (using end-to-end measurement)
- wireless network management
- enterprise WLAN
- chaotic WLAN
2Self-Managementin Chaotic Wireless Deployments
- Authors Aditya Akella, Glenn Judd,
- Srinivasan Seshan, Peter Steenkiste
- MobiCom 2005
3Outline
- introduction
- characterizing current 802.11 deployments
- impact on end-user performance
- limiting the impact of interference
- power and rate selection algorithms
- conclusions
4Introduction
- 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?
5Related 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
6Outline
- introduction
- characterizing current 802.11 deployments
- impact on end-user performance
- limiting the impact of interference
- power and rate selection algorithms
- conclusions
7Characterizing 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
8802.11 deployment density
Data set Place Lab Degree of neighbor
APs (within 50m)
Deployment high density Degree3 (interference)
9Measurement observations
- 802.11 channel usage
- 802.11b vs. 802.11g
- 20 are 802.11g
- vendors and AP management support
Channel usage
Popular AP vendors
10Outline
- introduction
- characterizing current 802.11 deployments
- impact on end-user performance
- limiting the impact of interference
- power and rate selection algorithms
- conclusions
11Simulation 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
12Simulation 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
13Interference 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
14Outline
- introduction
- characterizing current 802.11 deployments
- impact on end-user performance
- limiting the impact of interference
- power and rate selection algorithms
- conclusions
15Limiting the impact of interference
- optimal static channel allocation
- transmit power control
16Optimal static channel allocation
single channel
three channels
- optimal channel allocation helpful, but cannot
eliminate interference
17Transmit 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
18Outline
- introduction
- characterizing current 802.11 deployments
- impact on end-user performance
- limiting the impact of interference
- power and rate selection algorithms
- conclusions
19Power 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
20Benefits 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
21Fixed-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
22Fixed-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
23Power-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
24Performance evaluation
- effect of power rate selection algorithms used
by aggressor pair on victim pair
25Performance evaluation
aggressor-pair rate limited
aggressor-pair rate unlimited
- PERF almost eliminates the interference on the
victim pair
26Conclusions
- chaotic networks
- unplanned
- unmanaged
- reduce interference while ensuring robust
end-client performance - PERF reduces transmission power as much as
possible without reducing transmission rate
27Wireless network management summary
- Reading list
- enterprise WLAN management a drastically
different approach - sensor network management
- Future research
- Management architecture?
- Tomography-based approach?