Network Algorithmics: An Interdisciplinary Approach to Designing Fast Networked Devices

596 Pages·2022·9.621 MB·English

by  George Varghese, Jun Xu

Network Algorithmics
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Network Algorithmics
An Interdisciplinary Approach to
Designing Fast Networked Devices
Second Edition
George Varghese
UCLA Department of Computer Science
Los Angeles, CA, United States
Jun Xu
School of Computer Science
Georgia Institute of Technology
Atlanta, GA, United States
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Contents
Prefacetothesecondedition .................................................. xvii
Preface .................................................................. xix
15principlesusedtoovercomenetworkbottlenecks ................................ xxv
PART 1 THE RULES OF THE GAME
CHAPTER1 Introducingnetworkalgorithmics ................................. 3
1.1 Theproblem:networkbottlenecks ................................. 3
1.1.1 Endnodebottlenecks ..................................... 4
1.1.2 Routerbottlenecks ...................................... 5
1.2 Thetechniques:networkalgorithmics .............................. 7
1.2.1 Warm-upexample:scentinganevilpacket..................... 8
1.2.2 Strawmansolution....................................... 8
1.2.3 Thinkingalgorithmically .................................. 9
1.2.4 Refiningthealgorithm:exploitinghardware ................... 10
1.2.5 Cleaningup............................................ 11
1.2.6 Characteristicsofnetworkalgorithmics ....................... 13
1.3 Exercise .................................................... 15
CHAPTER2 Networkimplementationmodels .................................. 17
2.1 Protocols .................................................... 18
2.1.1 Transportandroutingprotocols ............................. 18
2.1.2 Abstractprotocolmodel .................................. 18
2.1.3 Performanceenvironmentandmeasures ...................... 20
2.2 Hardware.................................................... 22
2.2.1 Combinatoriallogic...................................... 22
2.2.2 Timingandpower ....................................... 23
2.2.3 Raisingtheabstractionlevelofhardwaredesign ................ 24
2.2.4 Memories ............................................. 26
2.2.5 Memorysubsystemdesigntechniques ........................ 30
2.2.6 Component-leveldesign .................................. 31
2.2.7 Finalhardwarelessons ................................... 32
2.3 Networkdevicearchitectures ..................................... 33
2.3.1 Endnodearchitecture..................................... 33
2.3.2 Routerarchitecture ...................................... 35
2.4 Operatingsystems ............................................. 39
2.4.1 Uninterruptedcomputationviaprocesses ...................... 40
2.4.2 Infinitememoryviavirtualmemory ......................... 42
2.4.3 SimpleI/Oviasystemcalls ................................ 44
2.5 Summary .................................................... 45
2.6 Exercises .................................................... 45
vii
viii Contents
CHAPTER3 Fifteenimplementationprinciples ................................. 51
3.1 Motivatingtheuseofprinciples—updatingternarycontent-addressable
memories.................................................... 51
3.2 Algorithmsversusalgorithmics ................................... 55
3.3 Fifteenimplementationprinciples—categorizationanddescription ......... 57
3.3.1 Systemsprinciples ...................................... 58
3.3.2 Principlesformodularitywithefficiency ...................... 62
3.3.3 Principlesforspeedinguproutines .......................... 64
3.4 Designversusimplementationprinciples ............................ 66
3.5 Caveats ..................................................... 67
3.5.1 Eightcautionaryquestions................................. 69
3.6 Summary .................................................... 71
3.7 Exercises .................................................... 71
CHAPTER4 Principlesinaction ............................................ 75
4.1 Buffervalidationofapplicationdevicechannels ....................... 76
4.2 Schedulerforasynchronoustransfermodeflowcontrol ................. 78
4.3 RoutecomputationusingDijkstra’salgorithm ........................ 79
4.4 Ethernetmonitorusingbridgehardware ............................. 82
4.5 Demultiplexinginthex-kernel .................................... 84
4.6 Trieswithnodecompression ..................................... 85
4.7 Packetfilteringinrouters ........................................ 87
4.8 AvoidingfragmentationofLSPs .................................. 90
4.9 Policingtrafficpatterns ......................................... 92
4.10 Identifyingaresourcehog ....................................... 94
4.11 GettingridoftheTCPopenconnectionlist .......................... 96
4.12 Acknowledgmentwithholding .................................... 99
4.13 Incrementallyreadingalargedatabase .............................. 101
4.14 Binarysearchoflongidentifiers................................... 103
4.15 Videoconferencingviaasynchronoustransfermode ................... 105
PART 2 PLAYING WITH ENDNODES
CHAPTER5 Copyingdata ................................................. 111
5.1 Whydatacopies .............................................. 113
5.2 Reducingcopyingvialocalrestructuring ............................ 115
5.2.1 Exploitingadaptormemory ................................ 115
5.2.2 Usingcopy-on-write ..................................... 117
5.2.3 Fbufs:optimizingpageremapping ........................... 119
5.2.4 Transparentlyemulatingcopysemantics ...................... 123
5.2.5 Arezerocopiesusedtoday? ............................... 125
5.3 AvoidingcopyingusingremoteDMA .............................. 126
5.3.1 Avoidingcopyinginacluster .............................. 127
5.3.2 Modern-dayincarnationsofRDMA ......................... 128
Contents ix
5.4 Broadeningtofilesystems ....................................... 131
5.4.1 Sharedmemory ......................................... 131
5.4.2 IO-lite:aunifiedviewofbuffering........................... 132
5.4.3 AvoidingfilesystemcopiesviaI/Osplicing.................... 134
5.5 Broadeningbeyondcopies ....................................... 134
5.6 Broadeningbeyonddatamanipulations ............................. 137
5.6.1 Usingcacheseffectively .................................. 137
5.6.2 DirectmemoryaccessversusprogrammedI/O ................. 142
5.7 Conclusions .................................................. 142
5.8 Exercises .................................................... 143
CHAPTER6 Transferringcontrol ............................................ 145
6.1 Whycontroloverhead? ......................................... 147
6.2 Avoidingschedulingoverheadinnetworkingcode ..................... 149
6.2.1 Makinguser-levelprotocolimplementationsreal ................ 151
6.3 Avoidingcontext-switchingoverheadinapplications ................... 153
6.3.1 Processperclient ....................................... 154
6.3.2 Threadperclient ........................................ 155
6.3.3 Event-drivenscheduler ................................... 155
6.3.4 Event-drivenserverwithhelperprocesses ..................... 157
6.3.5 Task-basedstructuring.................................... 158
6.4 ScalableI/ONotification ........................................ 159
6.4.1 Aservermystery ........................................ 159
6.4.2 Problemswithimplementationsofselect()..................... 160
6.4.3 Analysisofselect() ...................................... 162
6.4.4 Speedingupselect()withoutchangingtheAPI ................. 163
6.4.5 Speedingupselect()bychangingtheAPI ..................... 164
6.5 AvoidingsystemcallsorKernelBypass ............................. 166
6.5.1 Thevirtualinterfacearchitectureproposal ..................... 169
6.5.2 DataPlaneDevelopmentKit(DPDK) ........................ 169
6.5.3 SingleRootI/OVirtualization(SR-IOV) ...................... 170
6.6 RadicalRestructuringofOperatingSystems.......................... 171
6.7 Reducinginterrupts ............................................ 172
6.7.1 Avoidingreceiverlivelock ................................. 173
6.8 Conclusions .................................................. 174
6.9 Exercises .................................................... 175
CHAPTER7 Maintainingtimers ............................................ 179
7.1 Whytimers? ................................................. 180
7.2 Modelandperformancemeasures ................................. 181
7.3 Simplesttimerschemes ......................................... 182
7.4 Timingwheels ................................................ 183
7.5 Hashedwheels................................................ 185
7.6 Hierarchicalwheels ............................................ 187
7.7 BSDimplementation ........................................... 189