Jolteon and Ditto �Network-Adaptive Efficient Consensus �with Asynchronous Fallback�

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FC 2022

Rati Gelashvili, Lefteris Kokoris-Kogias, Alberto Sonnino, Alexander Spiegelman, Zhuolun Xiang

1

UIUC

Mystenlabs

IST

Aptos

Aptos

Work done while all authors were working at Novi Research at Meta

Motivation

• State machine replication (SMR) builds permissioned blockchain

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• State-of-the-art of SMR:
• Efficient under good network, but no liveness under bad network
• Robust under bad network, but not efficient under good network
• Not adaptive to network conditions
• Q: Can we get the best of both worlds?

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2

Results

3

Adding async fallback path to psync protocol

Adding sync fast path to async protocol

Consensus on constant size messages. Crypto object size omitted in the cost.

HotStuff/DiemBFT: Optimistic Linear Path

4

propose

vote

propose

vote

propose

vote

L1

L2

L3

L4

block

QC = {2f+1 votes}

r

r

r+1

r+1

r+2

r+2

n=3f+1 nodes, f Byzantine faults

5

all-to-all �timeout

propose

vote

propose

vote

L1

L2

L3

L4

block

QC = {2f+1 votes}

r

r

r+2

r+2

propose

vote

TC = {2f+1 timeouts}

r+1

delayed

6

all-to-all �timeout

all-to-all �timeout

propose

vote

propose

vote

L1

L2

L3

L4

block

QC = {2f+1 votes}

r

r

TC = {2f+1 timeouts}

r+1

delayed

TC

r+2

No liveness

delayed

Meanwhile in Async World

• No assumed message delay bound => no timeouts
• Always live, but less efficient

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• Existing protocols: VABA, HBBFT, BEAT, Dumbo, …

7

VABA

8

Chained-VABA

9

n parallel HS

exchange last QC, wait for n-f QC, then elect leader

exchange latest QC of leader (similar to Pacemaker of HS)

continue from leader’s chain

Ditto: Combine HotStuff and Chained-VABA

10

sync chain same as HotStuff

Broadcast timeouts with high-QC

Build VABA chain extending high-QC

Chained-VABA finish, back to HotStuff

Ditto: Correctness Intuition

11

Ditto: Improved Latency

12

The 5-round HotStuff is called Jolteon

Implementation and Evaluation

• Ditto implementation in Rust (2k LOC) on top of HotStuff codebase (5k LOC)
• Use real cryptography (dalek), networking (tokio), and storage (rocksdb)
• Running across 5 different AWS regions

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• We want to show:
• Ditto is as good as HotStuff in common good case (sync, good leader)
• Ditto is as good as VABA in bad case (async, slow leader)

13

Evaluation: Good Case

14

Ditto is as good as HotStuff

VABA is worse than HotStuff/Ditto

Evaluation: Bad Case

15

Ditto is as good as VABA

HotStuff drops to 0

Summary

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