IEEE PIMRC 2005 1

A Comparative Measurement A Comparative Measurement Study of the Workload of Wireless Study of the Workload of Wireless

Access Points in Campus Access Points in Campus NetworksNetworks

Maria PapadopouliMaria PapadopouliAssistant ProfessorAssistant Professor

Department of Computer ScienceDepartment of Computer ScienceUniversity of North Carolina at Chapel Hill University of North Carolina at Chapel Hill

(UNC)(UNC)

This work was partially supported by the IBM Corporation under an IBM Faculty Award 2004

2IEEE PIMRC 2005

Coauthor & collaboratorCoauthor & collaborator

Felix Hernandez-Felix Hernandez-CamposCampos

Department of Computer Department of Computer ScienceScience

University of North Carolina at University of North Carolina at Chapel Hill Chapel Hill

(UNC)(UNC)

3IEEE PIMRC 2005

RoadmapRoadmap

Motivation & Research ObjectivesMotivation & Research Objectives Main ContributionsMain Contributions Data AcquisitionData Acquisition Performance AnalysisPerformance Analysis Related workRelated work Future workFuture work

4IEEE PIMRC 2005

MotivationMotivation

Optimization of the performance of Optimization of the performance of wireless networkswireless networks

Better capacity planning & load Better capacity planning & load balancingbalancing

Support of applications with real-time Support of applications with real-time constraintsconstraints

Models for simulation studiesModels for simulation studies

5IEEE PIMRC 2005

Research ObjectivesResearch Objectives

Analyze traffic characteristics at each APAnalyze traffic characteristics at each AP Total number of bytes & packets (sent & Total number of bytes & packets (sent &

received)received) Different time scalesDifferent time scales Number of associations and roaming Number of associations and roaming

operationsoperations Impact of building typesImpact of building types

Contrast traffic models & distributions Contrast traffic models & distributions from large production wireless networks from large production wireless networks (UNC & Dartmouth)(UNC & Dartmouth)

6IEEE PIMRC 2005

Data AcquisitionData Acquisition 729-acre campus with 26,000 students, 3,000 729-acre campus with 26,000 students, 3,000

faculty, 9,000 staff faculty, 9,000 staff DiverseDiverse environment environment 14,712 unique MAC addresses14,712 unique MAC addresses 488 APs (Cisco 1200, 350, 340 Series)488 APs (Cisco 1200, 350, 340 Series) SNMP pollingSNMP polling every AP every 5minutes using every AP every 5minutes using

a non-blocking library calls a non-blocking library calls Tracing period of Tracing period of 63 days63 days

Data cleaning follows …

7IEEE PIMRC 2005

Aggregate Traffic Load Aggregate Traffic Load AnalysisAnalysis

8IEEE PIMRC 2005

Dichotomy among APs (1/2) Dichotomy among APs (1/2) APs with uploaders & APs APs with uploaders & APs

with downloaderswith downloaders

9IEEE PIMRC 2005

Dichotomy among APs Dichotomy among APs (2/2) (2/2)

APs with uploaders & APs with APs with uploaders & APs with downloadersdownloaders

10IEEE PIMRC 2005

Modeling Aggregate Sent & Modeling Aggregate Sent & Received TrafficReceived Traffic

Lognormal distribution

Significant heavier tail than lognormalTwo lognormals with different parameters

11IEEE PIMRC 2005

5-Minute Traffic Load5-Minute Traffic Load

Dartmouth APs receive has Dartmouth APs receive has

a lighter body (75% < 100KB)a lighter body (75% < 100KB)

UNC has two regions:UNC has two regions:

40% of intervals with very light 40% of intervals with very light traffic traffic

another close to sent distributionanother close to sent distribution

Similarity between Dartmouth & UNCSimilarity between Dartmouth & UNC [500KB, 2MB] during most active intervals[500KB, 2MB] during most active intervals

AP sent traffic load:

AP receive traffic load:

12IEEE PIMRC 2005

Total Number of Mcast/Bcast Total Number of Mcast/Bcast Packets Packets

Received vs. Sent by APReceived vs. Sent by AP

13IEEE PIMRC 2005

Total Number of Unicast Total Number of Unicast Packets Packets

Sent vs. Received by APSent vs. Received by AP

14IEEE PIMRC 2005

Summary of Summary of Contributions (1/2)Contributions (1/2)

Similarities between UNCSimilarities between UNC vs vs Dartmouth Dartmouth traces traces Log-normalityLog-normality is prevalent is prevalent Light traffic loadLight traffic load but with but with long tailslong tails Majority of APsMajority of APs send & receive packets of send & receive packets of

small sizesmall size Prominent Prominent dichotomy among APsdichotomy among APs

APs dominated by uploadersAPs dominated by uploaders AP dominated by downloadersAP dominated by downloaders APs with average large sent & small receive packetAPs with average large sent & small receive packet APs with small sent & large receive packetAPs with small sent & large receive packet

Substantial numberSubstantial number of of non-unicast packetsnon-unicast packets

15IEEE PIMRC 2005

Conclusions (2/2)Conclusions (2/2)

Heavy distribution of Heavy distribution of associations/roaming operationsassociations/roaming operations Daily averages between 170-4,310Daily averages between 170-4,310 Weak correlation with traffic loadWeak correlation with traffic load Need more efficient association Need more efficient association

mechanismsmechanisms

16IEEE PIMRC 2005

Future Research Plan Future Research Plan Analysis of packet headers for better Analysis of packet headers for better

understanding the understanding the uploading behavioruploading behavior Formal parametric models for traffic loadFormal parametric models for traffic load Spatial correlations of APs and classification of APs Spatial correlations of APs and classification of APs

based on various parameters (traffic based on various parameters (traffic characteristics, number of associations, distinct characteristics, number of associations, distinct clients)clients)

Topological propertiesTopological properties of wireless infrastructure of wireless infrastructure Analysis of traces from Analysis of traces from diverse set of testbedsdiverse set of testbeds & &

contrast of their traffic modelscontrast of their traffic models

UNC-FORTH data repository of traces & UNC-FORTH data repository of traces & benchmarksbenchmarks

17IEEE PIMRC 2005

More InfoMore Info

http://www.cs.unc.edu/~mariahttp://www.cs.unc.edu/~maria

http://www.ics.forth.gr/mobile/http://www.ics.forth.gr/mobile/

maria@cs.unc.edumaria@cs.unc.edu

Thank You!Thank You!