Multiple proposers choose locations to minimize network delays

On the Geographic Incentives of Multiple Concurrent Proposers

Computer Science and Game Theory

Summary

This paper looks at how multiple entities that propose new blocks in a network decide where to operate based on geography. Users pick which proposer to send their transactions to by considering how quickly their transactions will be included, which depends on both the physical distance to the proposer and the proposer's connection to other validators. The authors show that proposers try to position themselves to minimize the distance to their closest group of validators, which affects their reach and efficiency. When proposers also act as validators, they tend to group together, but if these roles are separate, they spread out geographically. Additional system features can reduce the impact of these distances and make proposer clustering less stable.

What this means in practice

A theory result. No direct application yet.

Authors

Kushal Babel, Jason Milionis, Eric Xue

Abstract

We study whether systems with multiple concurrent proposers (MCP) incentivize the geographic decentralization of proposers. In our model, concurrent proposers strategically choose their locations to maximize their captured market share of users, who decide where to send transactions by comparing each proposer's time to inclusion. The time to inclusion between a user and a proposer consists of two terms: the distance between them, and the distance between the proposer and her nearest quorum of attesters, the latter of which we term the quorum radius. We formally prove that proposers' quorum radii are the determinant of their incentives: proposers optimally choose where to locate in order to minimize their quorum radii. We obtain as a result co-location when proposers also serve as attesters, but geographic diversity when these roles are separate. We also examine pre-confirmations and faster intervalidator connections, showing that they attenuate the influence of the quorum radius and further destabilize co-location incentives.
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