end-to-end asymmetric link capacity estimation
DESCRIPTION
End-to-end Asymmetric Link Capacity Estimation. Ling-Jyh Chen, Tony Sun, Guang Yang, M.Y. Sanadidi, Mario Gerla Dept. of Computer Science, University of California at Los Angeles. Definition. Capacity : maximum IP-layer throughput that a flow can get, without any cross traffic. - PowerPoint PPT PresentationTRANSCRIPT
End-to-end Asymmetric End-to-end Asymmetric Link Capacity EstimationLink Capacity Estimation
Ling-Jyh Chen, Tony Sun, Guang Yang, M.Y. Sanadidi, Mario GerlaLing-Jyh Chen, Tony Sun, Guang Yang, M.Y. Sanadidi, Mario GerlaDept. of Computer Science, University of California at Los AngelesDept. of Computer Science, University of California at Los Angeles
DefinitionDefinition CapacityCapacity: maximum IP-layer throughput that a flow can
get, without any cross traffic. Available BandwidthAvailable Bandwidth: maximum IP-layer throughput that
a flow can get, given (stationary) cross traffic.
Previous Work on Capacity EstimationPrevious Work on Capacity Estimation Per-hop based
pathchar: use different packet sizes to probe the per-hop link capacity
clink, pchar: variants of pathcharNettimer: use “packet tailgating” technique
End-to-end basedPathrate, Sprobe, CapProbe
These approaches are either one-way based or unable to estimate asymmetric link capacities.
Estimating Asymmetric LinksEstimating Asymmetric Links Asymmetric links are becoming popular (e.g.
DSL, cable modems, and satellite links). Knowing the capacity of BOTH direction links is
important for applications.
Related work: ALBP [Yu et al, ICC’03] employs a multi-packet delay
model to estimate “per-hop” capacity of asymmetric links.
Our ContributionOur Contribution We propose an end-to-end asymmetric link
capacity estimation technique, called AsymProbeAsymProbe.
AsymProbe is CapProbe based:round trip methodpacket pair basedsimple, fast, and accurate
Packet Pair DispersionPacket Pair DispersionT3
T2 T3
T3
T1
T3
Narrowest Link
20Mbps 10Mbps 5Mbps 10Mbps 20Mbps 8Mbps
Capacity = (Packet Size) / (Dispersion)
Issues: Compression and ExpansionIssues: Compression and Expansion
• Queueing delay on the first packet => compression
• Queueing delay on the second packet => expansion
CapProbe CapProbe (Rohit et al, SIGCOMM’04)(Rohit et al, SIGCOMM’04) Key insight: a packet pair that gets through with zero queueing
delay yields the exact estimate. CapProbe uses “Minimum Delay Sum” filter.
CapacityCapacity
Proposed Approach: AsymProbeProposed Approach: AsymProbe
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22
11
21
2
22
1
11
TPC
TPC
TTTCPT
CPT
AsymProbe: ExampleAsymProbe: ExampleC1 C2 P1 P2 T1 T2 C'1 C'2
1000kbps
500kbps
1500 bytes 100 bytes 12 ms 1.6 ms 1000.00 kbps 66.67 kbps
1500 bytes 300 bytes 12 ms 4.8 ms 1000.00 kbps 200.00 kbps
1500 bytes 500 bytes 12 ms 8 ms 1000.00 kbps 333.33 kbps
1500 bytes 700 bytes 12 ms 11.2 ms 1000.00 kbps 466.67 kbps
1500 bytes 900 bytes 12 ms 14.4 ms 833.33 kbps 500.00 kbps
1500 bytes 1100 bytes 12 ms 17.6 ms 681.82 kbps 500.00 kbps
1500 bytes 1300 bytes 12 ms 20.8 ms 576.92 kbps 500.00 kbps
1500 bytes 1500 bytes 12 ms 24 ms 500.00 kbps 500.00 kbps
500kbps
1000kbps
100 bytes 1500 bytes 1.6 ms 12 ms 66.67 kbps 1000.00 kbps
300 bytes 1500 bytes 4.8 ms 12 ms 200.00 kbps 1000.00 kbps
500 bytes 1500 bytes 8 ms 12 ms 333.33 kbps 1000.00 kbps
700 bytes 1500 bytes 11.2 ms 12 ms 466.67 kbps 1000.00 kbps
900 bytes 1500 bytes 14.4 ms 12 ms 500.00 kbps 833.33 kbps
1100 bytes 1500 bytes 17.6 ms 12 ms 500.00 kbps 681.82 kbps
1300 bytes 1500 bytes 20.8 ms 12 ms 500.00 kbps 576.92 kbps
1500 bytes 1500 bytes 24 ms 12 ms 500.00 kbps 500.00 kbps
C=P/TC=P/T
AsymProbe AlgorithmAsymProbe Algorithm AsymProbe has four phases:
Phase 1: the probing phase (P1=Pmax ; P2=Pmax ) (=> CapProbe)
Phase 2: the probing phase (P1=Pmax ; P2=Pmin)
Phase 3: the probing phase (P1=Pmin ; P2=Pmax )
Phase 4: the decision phase
AsymProbe AlgorithmAsymProbe Algorithm The decision phase:
IssuesIssues AsymProbe is able to estimate asymmetric link capacities when
the “asymmetric ratio” is larger than Pmin /Pmax and smaller than Pmax /Pmin.
AsymProbe can not estimate “extremely asymmetric” links.
Pmax is limited by MTU.
Pmin is limited by the supported system time resolution.
Packet SizeNarrow Link Capacity
100 Mbps 10 Mbps 1 Mbps
500 bytes 0.04 ms 0.4 ms 4 ms
1000 bytes 0.08 ms 0.8 ms 8 ms
1500 bytes 0.12 ms 1.2 ms 12 ms
SimulationSimulation AsymProbe: A <-> B; Cross Traffic: C <->B E->D: 1.5Mbps; D->E: 128kbps
Simulation ResultsSimulation Results Pmax=1500 bytes ; Pmin=100 bytes
EmulationEmulation
Pmax=1500 bytes ; Pmin=500 bytes
Emulation ResultsEmulation Results
Internet ExperimentsInternet Experiments P1=1500 bytes, P2=500 bytes Supported “asymmetric ratio” = 3:1
Application – TCP ProbeApplication – TCP Probe The concept of AsymProbe can be integrated
with other data transmission protocols, e.g. TCP. TCP packet size:
forward direction: TCP data 1500 bytes reverse direction: TCP ACK 40 bytes
According to AsymProbe algorithm: If , then T1>T2
TCP Probe estimates the capacity of the forward direction link If , then T1<T2
TCP Probe estimates the capacity of the reverse direction link
401500
Re
verse
forward
CC
401500
Re
verse
forward
CC
TCP ProbeTCP Probe
DelAck
TCP Probe:
CapProbe:
More details in [Anders et al, GI’05]
TCP Probe ApplicationTCP Probe Application
Vertical handoff usually results in a dramatic change in the path capacity.
Service agility using “Fast Rate Adaptation” (FRA) algorithm FRA forces TCP to enter Slow Start when detecting a handoff from
LOW to HIGH
Service Agility – TCP ProbeService Agility – TCP Probe
Unit: bps
TCP Probe with “fast rate adaptation” Vertical handoff from 10Mbps to 100Mbps
SummarySummary We propose an end-to-end asymmetric link
capacity estimation technique, called AsymProbe. We evaluate AsymProbe by simulation and
Internet experiments. The concept of AsymProbe can be integrated with
other data transmission protocols. We present a passive capacity estimation
technique, called TCP Probe, which integrates AsymProbe with TCP.
Thanks!Thanks!
CapProbe:CapProbe: http://nrl.cs.ucla.edu/CapProbe/