University of KansasA KTEC Center of Excellence 1
Soshant Bali*, Yasong Jin**, Victor S. Frost* and Tyrone Duncan**
Information and Telecommunication Technology Center*Electrical Engineering & Computer Science
**Department of Mathematics [email protected], 785-864-4833
A New Perspective on Internet Quality of Service: Measurement
and Predictions
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What is the perceived QoS for this end-to-end path?
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Outline• Develop end-to-end measurement
techniques• Develop prediction methodologies for fBM
traffic• A Few Words about our Graduate and
Research Programs at EECS@KU
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Premise• Voice networks had a very understandable QoS metric-
Blocking• Internet QoS metrics must correlate to end-user
experience. • Metrics such as delay and loss may have little direct
meaning to the end-user because knowledge of specific coding and/or adaptive techniques is required to translate delay and loss to the user-perceived performance.
• Detecting “observable impairments” must be independent of coding, adaptive playout or packet loss concealment techniques employed by the multimedia applications.
• Time between impairments and their duration are metrics that are easily understandable by network user.
• This research developed methods to detect these impairment events using end-to-end measurements.
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Network states• Noticeable impairments for Real-time
multi-media (RTM) services occur when the end-to-end connection is in one or more of the following states: • Burst loss, • High random loss, • Disconnected,• High Delay.
• Two other connection states are defined: • Congested,• Route change.
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Background• End-to-end argument
• end nodes: most functions implemented here including application specific functions
• core: important forwarding and routing functions are implemented here; not burdened by application specific functions, e.g., reliable delivery
• Anomalous events• failures: fiber cuts, power failures etc.• congestion• cause user-perceived impairments
• Inferring anomalous events from end-to-end observations• core nodes implement simple functions; do not inform end
nodes of anomalous events• need to infer anomalous events from end-to-end observations
• Several benefits if anomalous events are accurately inferred
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Significance• A new QoS metric for RTM applications
• ISPs can use impairments metric in service level agreements (SLAs)
• Fault diagnosis tools for ISPs• an alternative to traceroute for detecting layer 3 route
changes• method for detecting layer 2 failures
• Routing for overlay / content delivery networks• Increasing TCP throughput• Confidence interval for minimum RTT estimate
(byproduct)
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Goal• Given a set of active end-to-end network
measurements determine the network state and the temporal characteristics of impairment events
NetworkRound Trip TimePacket Loss Rate
TracerouteTime-to-live
NetworkState
Impairment Events:-Frequency -Duration
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Goal
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Route Change • Motivation
• Route changes can cause user perceived impairments• Need to divide observations into “homogenous” regions
• Layer 3 route changes• TTL• Traceroute• Not all route changes result in TTL change• Not all routers respond to ICMP massages for traceroute
• Layer 2 route changes are not visible end-to-end
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Route change state • RTT based route change detection
• TTL change: not all route changes result in TTL change• traceroute change: inefficient, not all routers respond to ICMP massages for traceroute • both layer 2 and layer 3 route changes can be detected using RTT based route change
detection• in figure below, minimum RTT changed but traceroute and TTL field of
IP header did not change; layer 2 route change
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Route Change Layer 2 Route Change
If – the time between changes >
ΔT– and the RTT difference across
the route change > ΔRTT– and variation in RTT<VRTT
– Then the proposed algorithm can detect
the changeRoute Change detected using the discussed procedure
(planetlab1.cambridge.intel-research.net and planet1.berkeley.intel-research.net, August 2004)
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Congested StateObserved from M/M/1
Queues
is an indicator of congestion
The end-to-end flow is in theCongested sate if:
Where
= Ave waiting time
= Packet loss rate
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Congested State
RTTs and a congestion event detected using the discussed procedure planetlab2.ashburn.equinix.planet-lab.org and planetlab1.comet.columbia.edu, 2/04
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Delay Impairment State• Given the RTT data,
an estimate is made of the minimum playout delay buffer size that is needed to avoid excessive packet losses.
• If minimum playout delay > Dplayout then a delay impairment has occurred.
Estimated one-way delays and minimum playout delay
planetlab2.ashburn.equinix.planet-lab.org and planetlab1.comet.columbia.edu
Feb, 2004
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Other Networks States• Disconnected state
• Period of consecutive packet losses > Ψ sec• Burst loss state
• ξsec < Period of consecutive packet losses < Ψ sec• High Random Loss State
• Insure enough observed losses, e.g., N, for “valid” loss probability estimate, RoT N > 10
• Observe N losses, if number of packets between the first and Nth loss < NL then network in high lose state
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Measurement data
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Congestion Events observed over a period of one week (DC1)
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Statistics of user-perceived impairments
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Other observations• Layer 2 route change
• 96 events were manually classified as layer 2 route changes
• ~71.8% layer 2 route changes were detected by the algorithm
• ~4% of the detected events were false positives.• ~8% of all layer 3 route changes were
preceded by burst or disconnect loss events.
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Summary of measurement results
• mean time between impairments: from 3.52hrs to 268hrs• mean duration of impairments: from 4.4mins to 92.5mins• on 2 paths congestion for 6-8 hrs during day (weekdays)
• burst loss, high random loss and high delay events were observed when connection was in congested state
• mean time between burst loss events that occurred during congestion = 14 min, mean duration = 22.64 sec
• mean time between layer 3 route changes = 7.23 hrs• 18% of all layer 3 route changes 1 sec apart, 15% 2 sec apart, 80%
less than 45 mins apart• 8% of all layer 3 route changes were preceeded by burst or
disconnect loss events• mean duration of burst loss events that precede layer 3 route
changes = 113.5 sec• mean time between layer 2 route changes = 58.22 hrs
• none of the layer 2 route changes were preceded by burst loss events
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Experimental Conclusions• Developed procedures to detect
impairment states for RTM services using end-to-end measurements.
• Developed techniques to detect layer two route changes and congestion
• The developed techniques consider multiple metrics at the same time to infer the presence of user perceived impairments.
Details in “Characterizing User-perceived Impairment Events Using End-to-End Measurements, Soshant Bali, Yasong Jin, V. S. Frost and T. Duncan, International Journal of Communication Systems.
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Predicting Properties of Congestion Events
Queu
e Si
ze in
Bits
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Predicting Properties of Congestion Events
Queu
e Si
ze in
Bits
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Predicting Properties of Congestion Events• Traffic Model fractional Brownian motion (fBm) • Qo(t) = Queue length at t• =Service rate• m=average input rate• a=variance of the input rate• BH(t)=standard fBm with parameter H• c=scaled surplus rate
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Sojourn Time
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Inter congestion event time
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Congestion duration
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Amplitude
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Conclusions• Developed methods to measure
impairments using end-to-end measurements
• Developed techniques to predict several properties of congestion events for fBM traffic:• Rate, • Duration, • Amplitude• For details see: “Predicting Properties of Congestion
Events for a Queueing System with fBM Traffic”, Yasong Jin, Soshant Bali. Tyrone Duncan, Victor S. Frost, accepted pending revisions for the IEEE Transactions on Networking.
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A Few Words about our Graduate Program at EECS@KU
• 37 faculty• 4 Fellows of the IEEE• Ex-Program Managers from DARPA, NSF, NASA• 10 new faculty in the past 3 years• Currently recruiting one more faculty member
• MS degrees in EE, CoE, CS• 150 MS students
• Ph.D. degrees in EE, CS• 75 Ph.D. students
• Two major research labs: ITTC and CReSIS• Research volume of over $20 million, with research
expenditures of $5.5 million in 2005• >50% of our graduate students are supported (over 140 in F’05)
• Almost all our Ph.D. students are supported
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EECS Research Space
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What Some of Our Recent Graduates Are Doing Now
• Cory Beard (PhD EE 1999) – Associate Professor UMKC• Jennifer Leopold (PhD CS 2000) - Professor of CS at Missouri, Rolla• Amit Kulkarni (PhD CS 2000) - GE Global Research Center• Daniel Cliburn (PhD CS 2001) - Professor of CS at Hanover College• Nathan Goodman (PhD EE 2002) - Professor of ECE at the University
of Arizona• Cindy Kong (PhD CS 2004) - Intel Corp.• Wesam Alanqar (PhD EE 2005) - Sprint Corp.• Jungwoo Ryoo (PhD CS 2005) - Professor at Arizona State University• David Janzen (PhD CS 2006) - Professor at Cal Poly, San Louis
Obispo
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Ph.D. Focus Areas• Communication Systems and Networking• Computer Systems Design• Interactive Intelligent Systems• Bioinformatics• Radar Systems and Remote Sensing
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Communication Systems and Networking• Advancing knowledge of systems
interconnected via radio and other technologies
• New methodologies to determine the performance and protection of Internet-based systems
• Theory and technologies that enable the delivery of reliable information in support of end-user applications independent of the access technology
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Computer Systems Design• Design of computing systems, ranging from
small, embedded elements to large, distributed computing environments
• All aspects of the system life cycle, including specification, verification, implementation and synthesis, and testing and evaluation of both hardware and software system components
• Principle application area of embedded and real-time systems with special emphasis on the interaction between hardware and software system components
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Interactive Intelligent Systems• Create intelligent and interactive systems with
sufficient intelligence to help humans accomplish important tasks
• Multi-modal interfaces to respond intelligently to user requests, process and present large quantities of information in many forms, and to perform tasks with minimal supervision
• Artificial intelligence, intelligent agents, information retrieval, data mining, human-computer interaction, modeling, visualization, multimedia systems, and robotics
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Bioinformatics• Information technology to process,
analyze, and present biological data in new, meaningful, and efficient ways
• Knowledge discovery and data mining and analysis as they relate to life sciences
• Making key advances in bioinformatics methods and tools for genomics and proteomics data analysis and other life-sciences-related problems
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Radar Systems and Remote Sensing• Radars, microwaves, communications,
and remote sensing technologies• New ways to use electromagnetic waves
in the remote sensing of the land (surface and subsurface), sea, polar ice, and the atmosphere
• Developing new remote sensing sensors (primarily radar), and new methods for solving electromagnetic problems
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FastTrack Ph.D.• Enter the Ph.D. program directly from the
B.S.• Finish in 5 years• 42 course credit hours past B.S.• Possible schedule:
Semester 1 3 coursesSemester 2 3 coursesSemester 3 2-3 courses +
researchSemesters 4-10 0-2 courses +
research
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Deadlines• The application deadline is March 1st, but
for full consideration for fellowships and research/teaching assistantships, applications should be received by January 1st.
• For more details about the application process please see our graduate admissions page.
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Websites• www.ittc.ku.edu• www.cresis.ku.edu• www.eecs.ku.edu• www.ku.edu
