An Investigation into Transport Protocols and Data Transport ...

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9.2. Preferential Flow Handling Using DiffServ 222 cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh 0 0 50 100 150 200 250 300 Time (seconds) (a) With Congestion Moderation 0 0 50 100 150 200 250 300 Time (seconds) (b) Without Congestion Moderation Figure 9.22: Effect of Congestion Moderation on Standard TCP with 90% AF allocation. Scalable TCP is shown in Figure 9.21. It can be argued that the main difference between the three results was the high frequency with which ScalableTCP appears to re-enter its slow start-like phase, with HSTCP only occasionally also doing so. Similar to the previous single flow tests without DiffServ (See Figures 9.1), the cwnd histories showed that these drops in cwnd value were not associated with slow-starts, but with a large number of function calls of moderate_cwnd(). 9.2.4 Congestion Moderation An investigation into the performance of New-TCP algorithms with and without the facilitation of congestion moderation via the Linux moderate_cwnd() function was conducted. Note this is would be in violation of the TCP protocol specifications [Pos81b, Jac88], but would provide a simpler fix than rectifying the problems of Linux receivers imposing stretched acks. With Standard TCP, the difference with and without congestion moderation is shown in Figure 9.22. Standard TCP with congestion moderation turned off allows the cwnd to grow without the frequent reductions in cwnd
9.2. Preferential Flow Handling Using DiffServ 223 cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh 0 0 50 100 150 200 250 300 Time (seconds) (a) 70% AF with Congestion Moderation 0 0 50 100 150 200 250 300 Time (seconds) (b) 70% AF without Congestion Moderation cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh cwnd and ssthresh (packets) 30000 25000 20000 15000 10000 5000 cwnd ssthresh 0 0 50 100 150 200 250 300 Time (seconds) (c) 90% AF with Congestion Moderation 0 0 50 100 150 200 250 300 Time (seconds) (d) 90% AF without Congestion Moderation Figure 9.23: Effect of Congestion Moderation on HSTCP with 70% and 90% AF allocation. to very low relative values. Even without congestion moderation, it was also observed that there were a few drops in cwnd and goodput, which were briefly raised (not through slow start nor congestion avoidance) to their previous values before the drop. The cause of this action was found to be due to Linux undo’s [SK02] during which the ssthresh and cwnd values are reduced due to an indication of congestion. However, shortly afterwards, DSACK (See Section 4.5.5) and/or ack information infers that the congestion event was in fact not necessary and therefore the TCP cwnd and ssthresh values are readjusted to the previously recorded values. Without congestion moderation, HSTCP shows an appreciable difference
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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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Page 177 and 178: 8.3. Results 177 10 100 Total Throu
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Page 181 and 182: 8.3. Results 181 600 500 Standard T
Page 183 and 184: 8.4. Discussion of Results 183 Asym
Page 185 and 186: 8.4. Discussion of Results 185 New-
Page 187 and 188: 8.4. Discussion of Results 187 Asym
Page 189 and 190: 8.5. Summary 189 The importance of
Page 191 and 192: 9.1. Transfer Tests Across Dedicate
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Page 243 and 244: 9.4. Summary 243 performance of sin
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Page 247 and 248: 10.1. Summary 247 PCs. But at 1Gb/s
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Page 253 and 254: 10.3. Future Directions 253 low ove
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A.2. Network Interface Cards 273 la
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A.2. Network Interface Cards 275 de
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A.2. Network Interface Cards 277 of
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A.2. Network Interface Cards 279 PC
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A.2. Network Interface Cards 281 70
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A.2. Network Interface Cards 283 Th
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A.2. Network Interface Cards 285 20
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A.2. Network Interface Cards 287 ha
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B.2. Wide Area Network Tests 289 Da
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C.3. DataTAG 291 Cisco 7606 Cisco 7
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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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