On the Importance of Having an Identity or, is Consensus really Universal?

TL;DR

This paper investigates the role of Naming in consensus problems, revealing it as a crucial yet often overlooked assumption, and demonstrates that Naming is inherently more difficult than achieving consensus in shared memory models.

Contribution

It uncovers the necessity of Naming for Herlihy's consensus universality and clarifies the complexity differences between Naming and Consensus in shared memory systems.

Findings

Naming is a necessary assumption for Herlihy's universality result.

Naming is shown to be harder than Consensus in a precise formal sense.

Differences between shared memory models are highlighted and analyzed.

Abstract

We show that Naming-- the existence of distinct IDs known to all-- is a hidden but necessary assumption of Herlihy's universality result for Consensus. We then show in a very precise sense that Naming is harder than Consensus and bring to the surface some important differences existing between popular shared memory models.