Initial Block Synchronization
Patrick Strateman
patrick@strateman.ninja
46DF D7E7 BD50 F76A 2A0F 6FD7 77E8 0682 A83D B40E

What is Initial Block Synchronization?
Initial Block Synchronization(aka Initial Block Download)
1. Download blockchain
2. Validate blocks and transactions

Who does Initial Block Synchronization?
“[Bitcoin is] a solution to the double-spending problem using a peer-to-peer
distributed timestamp server to generate computational proof of the chronologicalorder of transactions.”
Initial Block Synchronization is how peers enter the bitcoin peer-to-peer network.
All bitcoin peers need to complete Initial Block Synchronization.

Runtime Complexity of Initial Block Synchronization
BSG(n) = Block Size Growth

Block Size Growth

Initial BlockSynchronization
TimeO(1)

O(n)

O(n)

O(n^2)

O(n^2)

O(n^3)O(2^n)O(2^n)IBS(n) = Integral[BSG[n], n]Real Data - Block Size

http://rusty.ozlabs.org/?p=498

Real Data -Initial Block Synchronizationi7-4700MQ 4c/8ht
32 GB memory
Samsung 840 EVO mSata
Connected to peer on 1Gbit/s LAN.

Real Data -Initial Block Synchronization
RaspberryPi 2ARMv7 4 cores
1GB memory
USB 3.0 external HDD
Connected to peer on 1Gbit/s LAN.
Note: node isn’t fully
synchronized yet!

Simulating Linear Blocksize Growth
20% annual capacity improvement
Year

Transactions Per Year2015

19,643,846.00

2016
2017

Transactions Total

Capacity Improvement

Adjusted Cost

Linear Relative Adjusted Cost

75,123,940.00

1.20

62,603,283.33

0.8333333333

39,287,692.00

69,504,375.00

1.44

48,266,927.08

0.6424972796

58,931,538.00

128,435,913.00

1.73

74,326,338.54

0.9893828591

2018

78,575,384.00

207,011,297.00

2.07

99,831,836.90

1.328895115

2019

98,219,230.00

305,230,527.00

2.49

122,665,303.10

1.632839054

2020

117,863,076.00

423,093,603.00

2.99

141,693,191.59

1.886125669

2021

137,506,922.00

560,600,525.00

3.58

156,453,317.96

2.082602669

2022

157,150,768.00

717,751,293.00

4.30

166,926,010.96

2.222008204

2023

176,794,614.00

894,545,907.00

5.16

173,368,989.76

2.307772859

2024

196,438,460.00

1,090,984,367.00

6.19

176,200,066.12

2.345458267

2025

216,082,306.00

1,307,066,673.00

7.43

175,915,470.75

2.341669922

2026

235,726,152.00

1,542,792,825.00

8.92

173,034,482.28

2.303320117

2027

255,369,998.00

1,798,162,823.00

10.70

168,063,272.49

2.237146674

2028

275,013,844.00

2,073,176,667.00

12.84

161,472,610.94

2.149416164

2029

294,657,690.00

2,367,834,357.00

15.41

153,685,405.42

2.045758056

2030

314,301,536.00

2,682,135,893.00

18.49

145,071,079.01

1.931089863

2031

333,945,382.00

3,016,081,275.00

22.19

135,944,567.561.809603804

2032

353,589,228.00

3,369,670,503.00

26.62

126,568,317.63

1.684793391

2033

373,233,074.00

3,742,903,577.00

31.95

117,156,115.70

1.55950441

Assumptions:●●

19,643,846 additionaltransactions per year
20% annual drop in theprice of bandwidth

Simulating 20% annual Blocksize Growth
20% annual bandwidth improvement
Year

Transactions Per Year2015

19,643,846.00

2016
2017

Transactions Total

Capacity Improvement

Adjusted Cost

Exponential Relative Adjusted
Cost

75,123,940.00

1.20

62,603,283.33

0.8333333333

45,129,707.17

75,346,390.17

1.44

52,323,882.06

0.6965007701

73,412,840.21

148,759,230.38

1.73

86,087,517.58

1.145939864

2018

103,680,840.78

252,440,071.16

2.07

121,740,003.45

1.620522079

2019

135,515,984.96

387,956,056.11

2.49

155,910,837.88

2.075381535

2020

168,658,417.56

556,614,473.67

2.99

186,409,061.02

2.481353627

2021

202,929,025.02

759,543,498.70

3.58

211,974,650.76

2.82166578

2022

238,196,022.50

997,739,521.19

4.30

232,042,324.24

3.088793323

2023

274,357,939.23

1,272,097,460.42

5.16

246,541,010.21

3.281790202

2024

311,333,977.99

1,583,431,438.41

6.19

255,733,017.43

3.404148097

2025

349,058,118.14

1,932,489,556.55

7.43

260,089,876.88

3.462143717

2026

387,475,293.62

2,319,964,850.17

8.92

260,199,496.81

3.463602905

2027

426,538,800.74

2,746,503,650.90

10.70

256,698,884.87

3.417005083

2028

466,208,474.45

3,212,712,125.35

12.84

250,227,114.42

3.330857173

2029

506,449,365.82

3,719,161,491.17

15.41

241,393,930.24

3.213275691

2030

547,230,758.42

4,266,392,249.59

18.49

230,760,167.20

3.0717261

2031

588,525,420.67

4,854,917,670.26

22.19

218,826,889.29

2.912878229

2032

630,309,026.94

5,485,226,697.20

26.62

206,030,801.60

2.742545207

2033

672,559,701.90

6,157,786,399.11

31.95

192,744,034.41

2.565680586

Assumptions:●●

19,643,846 additionaltransactions per year
20% annual drop in theprice of bandwidth

Simulating 20% annual Blocksize Growth
10% annual bandwidth improvement
Year

Transactions Per Year2015

19,643,846.00

2016
2017

Transactions Total

Capacity Improvement

Adjusted Cost

75,123,940.00

1.10

45,129,707.17

75,346,390.17

73,412,840.21

148,759,230.38

2018

103,680,840.78

2019

20% Exponential 10%
Improvement

68,294,490.91

0.9090909091

1.21

62,269,743.94

0.8288934785

1.33

111,765,011.55

1.487741611

252,440,071.16

1.46

172,419,965.27

2.295140075

135,515,984.96

387,956,056.11

1.61

240,890,187.65

3.206570205

2020

168,658,417.56

556,614,473.67

1.77

314,194,359.48

4.182346659

2021

202,929,025.02

759,543,498.70

1.95

389,765,912.51

5.188304986

2022

238,196,022.50

997,739,521.19

2.14

465,452,850.16

6.195799237

2023

274,357,939.23

1,272,097,460.42

2.36

539,493,503.30

7.181379242

2024

311,333,977.99

1,583,431,438.41

2.59

610,481,365.35

8.126322519

2025

349,058,118.14

1,932,489,556.55

2.85

677,325,800.38

9.016111247

2026

387,475,293.62

2,319,964,850.17

3.14

739,212,297.27

9.839903196

2027

426,538,800.74

2,746,503,650.90

3.45

795,564,276.48

10.590023322028

466,208,474.45

3,212,712,125.35

3.80

846,007,513.69

11.26149019

2029

506,449,365.82

3,719,161,491.17

4.18

890,337,691.31

11.85158408

2030

547,230,758.42

4,266,392,249.59

4.59

928,491,258.22

12.35945902

2031

588,525,420.67

4,854,917,670.26

5.05

960,519,579.01

12.78579876

2032

630,309,026.94

5,485,226,697.20

5.56

986,566,236.14

13.13251456

2033

672,559,701.90

6,157,786,399.11

6.12

1,006,847,282.06

13.40248238

Assumptions:●●

20% annual increase inblocksize
10% annual drop in theprice of bandwidth