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Nanyang Technological University Zou ZiXuan

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1 Nanyang Technological University Zou ZiXuan
Packet Triplet: An Enhanced Packet Pair Probing for Path Capacity Estimation Good morning, welcome to my presentation—in which I will introduce an enhanced packet pair probing technique, called Packet Triplet for path capacity estimation. Nanyang Technological University Zou ZiXuan

2 OUTLINE The purpose of Packet Triplet
Previous Packet-Pair based techniques Packet Triplet probing Detailed approach Filtering scheme Experimental Results This is the outline of my presentation. First, I will introduce the purpose of Packet Triplet, then give the background knowledge of Packet-Pair based technique. After this, we proposed the detail of Packet Triplet technique, including Packet Triplet probing, detailed approach, the filtering scheme of packet triplet and our experimental results.

3 The purpose of Packet Triplet
Measuring the path capacity (bottleneck) Packet-Pair based Robust to cross traffic We developed Packet Triplet which is based on Packet-Pair scheme for the purpose of path capacity measurement, or say, the bottleneck measurement. We try to make the Packet Triplet robust to cross traffic, which means, with the existence of cross traffic among the measured path, we can also estimate the path capacity accurately.

4 Previous Packet-Pair based technique
Packet-Pair dispersion Originated by Keshav for congestion control Cross traffic effect—expression and extension Variants of Packet-Pair to deal with the effects of cross traffic. The principle of Packet-Pair dispersion is firstly proposed by Keshav in his TCP congestion control scheme. As the figure shows, two packets of same length L are sent back-to-back by the source. When these two packets arrive at the bottleneck link, they will be queued together in the buffer. After these packets are sent by the bottleneck link, they will be spread out in a time dispersion—delta=L/C, which is the transmission delay of the second packet at this link.

5 Previous Packet-Pair based technique
Statistical method Sending many packet pairs, using statistical approach Union and Intersection Kernel density Do not always lead to correct estimation Not a global modal but the local modal Observed by Paxson, investigated by Dovrolis

6 Previous Packet-Pair based technique
Model based detection Based on Multimodal distribution Packet-Train and Packet-Pair

7 Packet-Triplet probing
Deal with multimodal distribution Accurately estimate path capacity in different load traffic Different from model-based detection

8 Detailed approach Three back-to-back probing packets and dispersion pair

9 Detailed approach Packet Triplet probing Idea condition
No cross traffic The variation of Latency of probing packets Equivalent estimates

10 Detailed approach Cross traffic effect When
Narrow link capacity estimates (NLE)

11 Cont’d Post-narrow link estimates (PNLE) Equivalent noise (EN)
Occur in low frequency

12 Filtering scheme filter out the estimates in case of as the noises.
Of the remaining estimates, the estimate of lowest value and relatively high frequency of occurrence is selected as the set of NLE. The mean of the NLE estimates is considered as the bottleneck of measured path.

13 Experimental Results Simulation setup ns-2 Topology
P={50,20,10,30,25,40} Mps 1000 packet triplet experiments are done.

14 Cont’d Packet-Pair vs. Packet-Triplet
L=100bytes cross traffic load=20%, 50%, 80%

15 Cont’d L=700bytes CL=20%, 80%

16 Cont’d L=1000 bytes CL=20%, 80%

17 Conclusion The noise filtering and bottleneck detection are always efficient whenever the cross traffic is light or heavy when we choose the small probing packet size how to set is a remaining issue for our research on this topic

18 Thank You !!!!!!

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