end-to-end asymmetric link capacity estimation ling-jyh chen, tony sun, guang yang, m.y. sanadidi,...

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 basedpathchar: use different packet sizes to probe

the per-hop link capacityclink, 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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11

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PC

T

PC

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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 500 bytes 12 ms 8 ms 1000.00 kbps 333.33 kbps






500kbps

1000kbps

100 bytes 1500 bytes 1.6 ms 12 ms 66.67 kbps 1000.00 kbps








C=P/TC=P/TC=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

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1500

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forward

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C

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1500

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verse

forward

C

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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/

end-to-end asymmetric link capacity estimation ling-jyh chen, tony sun, guang yang, m.y. sanadidi,...

Documents

capacity capacity slide

asymprobe slide

p max phase

probing phase p

decision phase slide

capacity of asymmetric

definition capacity

expansion slide