bandwidth estimation workshop 2003 evaluating pathrate and pathload with realistic cross-traffic...
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Bandwidth Estimation Workshop 2003
Evaluating pathrate and pathload with realistic cross-
traffic
Ravi PrasadManish Jain
Constantinos Dovrolis (ravi, jain, [email protected])
College of ComputingGeorgia Institute of Technology
Bandwidth Estimation Workshop 2003
Background
PathrateEstimates path capacityBased on packet pair/train dispersion
Packet pair estimates: Set of possible capacity modes
Packet train estimates: ADR=Lower bound on capacity
Capacity = (Strongest and narrowest mode > ADR)
PathloadEstimates path available bandwidth (avail-bw)Based on one-way delay trend of periodic
streamsReports a range of avail-bw
Corresponds to variation in stream durationhttp://www.pathrate.org
Bandwidth Estimation Workshop 2003
Motivation
Recent studies pointed towards poor accuracy of these toolshttp://www.caida.org/outreach/presentations/2
003/bwest0308/doereview.pdfA measurement study of available bandwidth
estimation tools. Strauss et. al. IMC 2003Our objective: re-evaluate accuracy of
both toolsWide range of cross-traffic loadRealistic cross-traffic Completely monitored testbed (no guessing!)
Bandwidth Estimation Workshop 2003
Outline
Describe test methodologyTestbedCross-traffic type
Show accuracy results100Mbps path1Gbps pathWith Iperf cross-traffic
Explaining inaccuracies with Iperf cross-traffic
Conclusions
Bandwidth Estimation Workshop 2003
Testing methodology
Used local testbedComplete knowledge of path properties
Capacity Available bandwidth
Complete control of cross-traffic Rate Type (TCP vs UDP vs trace-driven)
Bandwidth Estimation Workshop 2003
Testbed
Narrow link capacity C = 100Mbps or 1Gbps
Bandwidth Estimation Workshop 2003
Cross traffic
Trace-driven cross-traffic generation: NLANR traces
OC-3, OC-12, OC-48 Trace information at the end of the talk
Packet size distributionUnmodified
Packet interarrivalsEither, scaled to achieve desired cross-traffic throughputOr, unmodified
Iperf-based cross-traffic Single TCP stream UDP stream
Bandwidth Estimation Workshop 2003
Results
Bandwidth Estimation Workshop 2003
FastEthernet: Traces with scaled interarrivals
Bandwidth Estimation Workshop 2003
FastEthernet:Traces with unmodified interarrivals
Bandwidth Estimation Workshop 2003
Gigabit path:Traces with scaled interarrivals
Bandwidth Estimation Workshop 2003
Gigabit Path:Iperf UDP Cross traffic
Bandwidth Estimation Workshop 2003
Gigabit path:Iperf single stream TCP
Bandwidth Estimation Workshop 2003
Unrealistic cross-traffic
Single stream TCP Entire window appears as
burst at beginning of RTT Minimum averaging
interval: RTT
L/C
TR
Tw
UDP periodic stream
Packet size: L Rate: R Dispersion: L/R Utilization = R/C
Bandwidth Estimation Workshop 2003
TR
TW TO
Seeks some “off” time periods of duration larger than L/C L: Probe size
TCP traffic Off period TO =TR - TW- L/C
Correct capacity estimate when TO > L/C
Pathrate under unrealistic traffic
L/C UDP periodic traffic If < 0.5then TO > L/C Else, underestimation
Bandwidth Estimation Workshop 2003
TRTW
Pathload under unrealistic traffic
Samples avail-bw in stream duration (TS)
TCP traffic Avail-bw averaging period TR
If TS << TR then:
Wide Avail-bw range estimate
UDP periodic traffic Avail-bw averaging period
L/R TS = 100 x L/C > L/R Correct avail-bw range
estimate
TSTS TS
L/C TS
Bandwidth Estimation Workshop 2003
Conclusions
Type of cross-traffic is important for bandwidth estimation tools
Pathrate and pathload perform well with realistic cross-traffic
Simulated traffic does not capture:Packet size distributionInterarrival distributionCorrelation structure
Bandwidth Estimation Workshop 2003
Trace identifiers
OC3 : MEM-1070464136-1, COS-1070488076-1, BWY-1063315231-1,
COS-1049166362-1OC12: MRA-1060885637-1OC48: IPLS-CLEV-20020814-093000-1