An Investigation into Transport Protocols and Data Transport ...

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9.4. Summary 244 problems in being able to run these congestion control algorithms effectively as single high bandwidth flows. The problems arise primarily through the limited resources of hardware and implementation issues with software. The problems in particular are related to the large number of packets that need to be processed by both the sender and receiving TCP hosts. In particular, it was identified that the TCP receiver was not always sending acknowledgments for at least every other data packet. This results in ack stretching which increases the likelihood of buffer overflows due to larger bursts of data packets on the forward path. More evident, however, was that it causes Linux specific performance penalties due to the way in which cwnd and the number of packets in flight are calculated. A more serious problem, especially for larger values of cwnd required for higher speed, long distance networks, is that the processing of SACK packets was demonstrated to also be a bottleneck upon TCP transfer rates. As demonstrated, the former problem can be rectified with modifications to the Linux kernel. The latter problem can also be resolved with newer and faster hardware; however, a network-based solution was implemented to smooth the loss pattern and hence reduce the processing burden required. A limited study was conducted to show the interaction of multiple flows of New-TCP traffic. The results demonstrate and corroborate prior results (in Chapter 8) that ScalableTCP has problems with fair and equal sharing of network resources. It was also demonstrated that these New-TCP algorithms can have a serious negative impact upon existing network traffic flows, reducing the amount of traffic utilised by bulk Standard TCP flows by several orders of magnitude. However, as a direct consequence of the implementation problems aforementioned, this impact was reduced due to the inability for the New-TCP flows to be able to achieve high goodputs.
9.4. Summary 245 Nevertheless, a DiffServ demonstration was devised to show that with appropriate design and allocation of Best Effort and Assured Forwarding Per Hop Behaviours, the network bottleneck utilisation can be optimised to both provide high performance for the New-TCP flow, whilst protecting the traditional ‘existing’ traffic from the impact of sharing the bottleneck link. A separate study to inspect the performance of these New-TCP algorithms over the Internet was also conducted. It showed that for single flow experiments, FAST performed the best in terms of high goodput performance with high stability. BicTCP and H-TCP also performed well. Meanwhile, HSTCP and ScalableTCP were found to offer lower goodput (but still considerably higher than that of Standard TCP) due to the slow rate at which they grow cwnd when cwnd is small.
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An Investigation into Transport Pro
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Contents List of Figures . . . . .
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Contents 5 4.6 Summary . . . . . .
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Contents 7 8.2 Test Calibration . .
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Contents 9 10.3.5 Further Tests . .
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List of Figures 11 5.7 Effect on cw
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List of Figures 13 8.16 Unfairness
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List of Figures 15 8.32 Friendlines
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List of Figures 17 9.19 Dynamic swi
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List of Figures 19 D.1 Internet pat
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List of Tables 21 A.1 Hardware and
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Publications And Workshops Some of
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1.2. Research Scope 25 • Identifi
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1.4. Dissertation Outline 27 • Id
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Chapter 2 High Energy Particle Phys
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2.2. Analysis Methods 31 the data i
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2.3. Data Volumes and Regional Cent
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2.3. Data Volumes and Regional Cent
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2.4. Data Transfer Requirements 37
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2.5. Summary 39 data, the most impo
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3.1. Data Intercommunication 41 mov
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3.2. Network Monitoring 43 Whilst l
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3.2. Network Monitoring 45 Internet
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3.2. Network Monitoring 47 1 0.8 Bo
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Chapter 4 Transmission Control Prot
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4.1. Overview 51 Throughput Delay L
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4.2. Protocol Description 53 is dep
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4.2. Protocol Description 55 As a r
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4.3. Congestion Control 57 excessiv
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4.3. Congestion Control 59 probe fo
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4.4. Retransmission Timeout 61 tion
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4.5. TCP Variants 63 mechanisms are
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4.5. TCP Variants 65 connection ini
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4.5. TCP Variants 67 20 15 cwnd sst
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4.5. TCP Variants 69 no more acks t
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4.5. TCP Variants 71 [Hoe96]. In bo
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4.5. TCP Variants 73 TCP Timestamps
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4.6. Summary 75 traffic for a parti
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Chapter 5 TCP For High Performance
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5.1. TCP Hardware Requirements 79 G
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5.1. TCP Hardware Requirements 81 1
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5.1. TCP Hardware Requirements 83 C
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5.2. TCP Tuning & Performance Impro
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5.3. Network Aid in Congestion Dete
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5.3. Network Aid in Congestion Dete
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5.4. Analysis of AIMD Congestion Co
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5.5. Summary 109 5.5 Summary Even t
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6.1. Survey of New-TCP Algorithms 1
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6.2. Discussion and Deployment Cons
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6.3. Summary 133 6.3 Summary The re
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Chapter 7 Testing Framework for the
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7.1. Metrics 137 various New-TCP al
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7.1. Metrics 139 assuming equilibri
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7.2. Environment 141 of packets in
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7.2. Environment 143 T 0 B, T T 1 F
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Chapter 8 Systematic Tests of New-T
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8.1. Methodology 147 fed into the d
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8.1. Methodology 149 Various other
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8.2. Test Calibration 151 Goodput (
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8.2. Test Calibration 153 cwnd and
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8.2. Test Calibration 155 100 1 Agg
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8.2. Test Calibration 157 1000 FAST
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8.3. Results 159 10 100 Total Throu
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8.3. Results 161 14 12 HSTCP 1 α H
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8.3. Results 163 cwnd (packets) 120
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8.3. Results 165 Fraction Bytes Ret
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8.3. Results 167 1200 1000 HTCP 1 H
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8.3. Results 169 This is due to the
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8.3. Results 171 4000 3500 3000 HTC
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8.3. Results 173 800 700 600 Standa
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8.3. Results 175 1 1 Fairness Ratio
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8.3. Results 177 10 100 Total Throu
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8.3. Results 179 1000 Standard TCP
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8.3. Results 181 600 500 Standard T
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8.4. Discussion of Results 183 Asym
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8.4. Discussion of Results 185 New-
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8.4. Discussion of Results 187 Asym
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8.5. Summary 189 The importance of
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9.1. Transfer Tests Across Dedicate
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Page 243: 9.4. Summary 243 performance of sin
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Page 253 and 254: 10.3. Future Directions 253 low ove
Page 255 and 256: 10.3. Future Directions 255 porates
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Page 267 and 268: A.1. Data Storage 267 Read Speed (M
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Page 289 and 290: B.2. Wide Area Network Tests 289 Da
Page 291 and 292: C.3. DataTAG 291 Cisco 7606 Cisco 7
Page 293 and 294: Appendix D Network Paths of Interne
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295 ham02gva.datatag.org:192.91.239
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Bibliography 297 [All03] [AMA + 99]
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Bibliography 299 [BPSK96] H. Balakr
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Bibliography 301 [DC02] [ea02] [FF9
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Bibliography 303 [Flo03] [Flo04] S.
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Bibliography 305 [Hoe96] [IET] [Jac
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Bibliography 307 [KRB05] [Lah00] [L
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Bibliography 309 [MHR03] [MM96] M.
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Bibliography 311 [Pos81a] J. Postel
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Bibliography 313 [tePM] IEPM Intern
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