DOWNLOAD MY Ph.D Thesis - UNAM

More documents

Recommendations

Info

Chapter 7Performance optimisation for the support of TCIS pIn order to provide service guarantees, a level of quantifiably reliable service may needto be supplemented with the ability to differentiate traffic and enable different servicelevels. Two types of QoS are proposed. They are complementary and designed for usein combination in different network contexts. These schemes are known as‘prioritisation’ and ‘reservation’. The analysis presented in the following twosubsections examines to what extent performance can be improved upon whenprioritisation and reservation mechanisms are used.7.3.1 Prioritisation in QoSOne approach to QoS is to use the Type of Service (ToS)-based relative priorities of theIPv4 header (or the 4-bit Priority field of the IPv6 header), which indicates in a simpleway the relative delay and drop sensitivity of a packet, as depicted in Figure 7.11. Thismethod gives TCIS streams higher priority than data packets, but does not provide aguarantee of bandwidth or latency.Although traffic prioritisation is not part of the DVB/DAVIC specification, a fastertransmission for the delivery of TCIS streams can be provided by mapping the ToS fieldwith 2-levels of priority at the DVB/DAVIC MAC layer, as explained below.The ToS indicates the desired usage of the packet. The field itself contains a 3-bitprecedence indicator for the priority of the packet and 3 flags (D, T and R) to showwhether delay, throughput or reliability are relevant for the transmission. Most routersin the Internet are as yet set to ignore the ToS field.0 3 7 15 31Ver IHL Type of service Total lengthIdentification Flags Fragment offsetTime to live ProtocolSource addressHeader checksumDestination addressOption + PaddingDataPrecedenceType of service3-bits 1-bits 1-bits 1-bits 2-bits111 Network control110 Internetwork control101 CRITIC/ECP100 Flash override011 Flash010 Immediate001 Priority000 RoutineDelay0 Normal1 LowThroughput0 Normal1 HighReliability0 Normal1 HighReservedFigure 7.11 – IP header structure.7-14
Chapter 7Performance optimisation for the support of TCIS pFor DVB/DAVIC cable networks, this field can be used to provide a faster delivery ofTCIS streams by assigning a higher priority to such streams. In this way, a packet thatarrives at the NIU can be classified according to its ToS requirement and placed in aqueue with two or more levels of prioritisation.In this section, a mixed traffic situation with 41.7 kbps (as described in Section 5.3.3)was used in order to provide a performance analysis when prioritisation for QoS isconsidered. For this analysis only the splitting tree algorithm was used because of itssuperior performance over the exponential backoff algorithm. Results presented here arefor the pure reservation access and the piggyback mechanisms.From Figure 7.12a, it can be seen that packet access delays produced by the PRAmechanism when prioritisation is not supported, were almost the same for both traffictypes. The maximum number of stations supported was 40 for VoIP traffic (with meanaccess delays of under 5 0ms) and 42 for Internet traffic (with mean access delays ofunder 500 ms). This is to be expected, since both traffic types were treated equally.However, from Figure 7.12b when prioritisation was supported, on high traffic loads orcongestion periods (above 44 stations or 59% of the cc), it was seen that packet accessdelays for VoIP traffic produced by the PRA and the PG mechanisms remained atMean Access Delay (ms)3002752502252001751501251007550250a) Without Prioritisation - PRA b) With Prioritisation - PRA & PGInternetTrafficVoIPTraffic34 36 38 40 42 44 46 48 50 52 54umber of Active Stations7-15PRAInternetTrafficPGVoIP TrafficPRA34 36 38 40 42 44 46 48 50 52 54 56 58umbe r of Active StationsFigure 7.12 – Mean access delay vs. No. of active stations for VoIP and Internet traffic.Splitting tree algorithm with and without prioritisation.
Page 6 and 7:
I would like to thank all the peopl
Page 10:
CHAPTER 6: OPTIMISATIO OF CRA ALGOR
Page 13 and 14:
FIGURE 5.17 - SYSTEM THROUGHPUT VS.
Page 15 and 16:
LIST OF TABLESTABLE 2.1 - NEXT GENE
Page 17 and 18:
Chapter 1Introduction pBecause of h
Page 19 and 20:
Chapter 1Introduction pA first step
Page 21 and 22:
Chapter 1Introduction passumption i
Page 23 and 24:
Chapter 1Introduction ppolynomial b
Page 25 and 26:
Chapter 1Introduction pIn general,
Page 27 and 28:
Chapter 1Introduction pminislots to
Page 29 and 30:
Chapter 1Introduction pThe authors
Page 31 and 32:
Chapter 1Introduction prate access
Page 33 and 34:
Chapter 1Introduction p1.4 Overview
Page 35 and 36:
Chapter 2OVERVIEW OF CURRENT CATVNE
Page 37 and 38:
Chapter 2Overview of current CATV n
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Chapter 3THE DVB/DAVIC PROTOCOL3.1
Page 57 and 58:
Chapter 3The DVB/DAVIC protocol pEu
Page 59 and 60:
Chapter 3The DVB/DAVIC protocol pMA
Page 61 and 62:
Chapter 3The DVB/DAVIC protocol pTh
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Chapter 3The DVB/DAVIC protocol p3.
Page 69 and 70:
Chapter 4Simulation and analytical
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Chapter 5Upstream channel capacity
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134: Chapter 5Upstream channel capacity
Page 143 and 144: Chapter 6Optimisation of CRA using
Page 171 and 172: Chapter 7PERFORMANCE OPTIMISATION F
Page 173 and 174: Chapter 7Performance optimisation f
Page 183: Chapter 7Performance optimisation f
Page 201 and 202: aChapter 7Performance optimisation
Page 209 and 210: Chapter 8Final conclusions p8.2 Gen
Page 211 and 212: Chapter 8Final conclusions pWe have
Page 213 and 214: Chapter 8Final conclusions pperform
Page 215 and 216: Chapter 8Final conclusions pslots i
Page 217 and 218: Chapter 8Final conclusions pfocused
Page 219 and 220: Chapter 8Final conclusions preserva
Page 221 and 222: Chapter 8Final conclusions pbandwid
Page 223 and 224: Chapter 8Final conclusions pThe opt
Page 225 and 226: Chapter 8Final conclusions p8.4 Fut
Page 227 and 228: Chapter 8Final conclusions pApplica
Page 229 and 230: Chapter 8Final conclusions pTCIS st
Page 231 and 232: Referencesp[17] I. Cidon, and M. Si
Page 233 and 234: Referencesp[50] N. F. Huang, C. A.
Page 235 and 236:
Referencesp[85] V. Rangel, R. Edwar
Page 237 and 238:
Referencesp[112] K. Sriram, “Meth
Page 239 and 240:
APPEDIX A: GLOSSARYAALABRADSLATMBCB
Page 241 and 242:
Appendix AGlossary pkbpsLANLLCMACMA
Page 243 and 244:
Appendix AGlossary pUSBUWVDSLVoDVoI
Page 245 and 246:
Appendix BProtocol stack and packet
Page 247 and 248:
Appendix BProtocol stack and packet
Page 249 and 250:
APPENDIX C: D VERIFICATION TEST FOR
Page 251 and 252:
Appendix D Verification test p209 2
Page 253 and 254:
Appendix EResults for a 6 Mbps upst
Page 255:
Appendix FGuide to CD-ROM p IEEE802
show all

DOWNLOAD MY Ph.D Thesis - UNAM

Create successful ePaper yourself

Delete template?

Save as template?