PIP 38 - Phased expansion of Validator Slots on Polygon PoS

Authors

Vasanti Rode
Parvez Shaikh

Type: Contracts

Table of Contents:

  • Abstract
  • Motivation
  • Specification
  • Rationale
  • Backward Compatibility
  • Security Considerations
  • Copyright

Abstract

Expanding the number of validators within the Polygon PoS network is a crucial step toward enhancing decentralization. By increasing the number of validators, validation responsibilities are distributed more widely, which reduces the risk of centralization and strengthens the network’s security and resilience. This proposal outlines the considerations for expanding the number of validator slots to ensure robust network performance.

Motivation

The primary motivation for increasing the number of validator slots within the Polygon PoS network is to improve decentralization which can be observed via the following metrics:

  • Geographical Distribution of Nodes: Expanding the number of validator slots allows for a wider geographical distribution of nodes. By having validators in diverse locations globally, the risk of localized disruptions is reduced, and the network’s health is enhanced to prevent regional failures.
  • Decrease Stake Centralisation: More validator slots means that voting power and block production can be more evenly distributed across a larger number of validators.
  • Improve Nakamoto Coefficient: The Nakamoto Coefficient, which measures the minimum number of validators required to compromise a network, should improve with an increase in validator nodes. A higher coefficient indicates a more secure and decentralized network, as it becomes harder for any group to disrupt the network’s consensus.

Specification

The proposed expansion involves a phased increase in the number of validator slots, starting from the current 105 slots to 110, then to 115, further to 120 and finally to 125. This incremental approach, with ongoing community review and feedback, allows for careful monitoring and management of each expansion stage. The specific steps include:

  1. Assessing the current infrastructure and ensuring it can support the additional validators.
  2. Implementing the first phase by adding 5 validator slots and monitoring the network’s performance and stability.
  3. Gradually increasing the slots in subsequent phases (as noted above) based on performance metrics and network impact.
  4. Conducting thorough monitoring at each stage to ensure seamless integration and functionality.
  5. In the event that the expansion from 105 to 110 validators negatively impacts the network’s health, the community may consider taking corrective action to offboard the last 5 validators who were onboarded.

Rationale

Increasing the number of validator slots in phases offers several advantages:

  • It helps the network grow gradually, lowering the risks that come with adding many new validators all at once.
  • Each phase can be evaluated for performance, ensuring that any issues are identified and addressed promptly.
  • It ensures that the network infrastructure and support mechanisms are adequately scaled to handle the increased load, thereby maintaining overall network health and performance.

Backwards Compatibility

The expansion of validator slots is designed to be fully backwards compatible. Existing validators and network operations should not be affected by the increase in slots. The system architecture should ensure that the integration of new validators occurs smoothly, without disrupting ongoing operations or diminishing the performance of current validators.

Test Cases

To ensure the success of the validator slot expansion, the following test cases will be conducted:

  • Performance Testing: Evaluate the network’s ability to handle the increased number of validators, focusing on transaction processing times, block generation, and overall output.
  • Stability Testing: Monitor the network for any signs of instability or degradation in performance following the addition of new validators.

Security Considerations

Security remains a top priority during the expansion process. Security measures will include:

  • Enhanced monitoring and alerting systems to detect and respond to any abnormal activity.
  • Suggested implementation of best practices for validator operations.

Copyright

All copyrights and related rights in this work are waived under CC0 1.0 Universal.

1 Like

hi Vasanti, Thanks for making the post about the expansion.

While Smart Stake is all for an increased validator set in general, the motivations of the proposal on stake centralization and nakamoto coefficient aspects aren’t really going to be improved by simply increasing the validator set.

If you refer to Stake Heat Map or Validator Stake Distribution at https://analytics.smartstake.io/polygon/stats/vp , you will see that the bottom 70 validators control less than 10% stake collectively. The bottom 40 control only 1% voting power.

If you compare the VP Curve Changes in the last 18 months, there is hardly any stake redistribution.

While Stake Centralization and Nakamoto Coefficient both indicate that significant improvements are needed, I am not sure expanding the validator set is the way to achieve it. Even the additional geographical distribution is not going to provide significant benefits given how low the VP of newly added validators is going to be.

The only exception to the above is any VC or exchanges that you want to onboard via this increase. For regular validators, it is an uphill battle in Polygon to acquire Voting Power.

Many of the validators have been around since 2020/early 2021 and their VP is still very low. I think the network will be well served with other initiatives that encourage community/VCs/Project team to distribute their stake better than how it has been for many years now.

4 Likes

Exactly.

Stake (de)centralization is not a function of N number of nodes. It is a distribution within the N set. Increasing N would actually actually increase the amount of effort/work to decentralize stake, as it now has to be evenly distributed among more validators. It seems that the proposers have this logic inverted. As is, it’s akin to saying right now we can’t evenly feed 100 ppl, but if we try to evenly feed 200 ppl we should be able to get it done.

Similarly, increasing N does not help improve the Nakamoto Cx at all. The coefficient is purely a function which reflects stake decentralization in face of the consensus rules, so see the paragraph above.

In other words, it makes no sense to try to improve decentralization via an expanded set. If those aspects are truly a concern, they should be first addressed within the current validator set.

As for the 1st point, Geographical Distribution of Nodes, an increased N would yield even more low income validators joining the set, since stake decentralization isn’t being efficiently or directly addressed. These low income validators for the most part run nodes in two setups: at one of the large cheaper providers of lower quality (e.g. Hetzner/OVH/Contabo), or at home. While the former setup actually decreases geographical decentralization, the latter would indeed improve it. But the question then becomes, does the network benefit from nodes running in consumer HW in people’s basements, on likely a single uplink and no power redundancy?

2 Likes

We totally agree with SmartStake, 100%. We’d prefer to see a tax on the larger validators and their delegators to encourage more equal stake. That tax could go into the community pool and used for quite a few different things.

1 Like

Thank you, Vasanti and Parvez, for this proposal.

We completely agree with our colleagues above. While we’re open to expanding the set, we’re not entirely certain it will address the decentralization of the network stake.

It would be beneficial if, alongside the potential expansion, an official and transparent delegation program from the Foundation (with potential involvement from VCs or exchanges) could be introduced. Such a program could reward validators based on their performance, thereby encouraging top-performing and reliable participants to accumulate voting power. This approach wouldn’t just enhance stake distribution within the current set and motivate all validators to perform at their best, thus improving network performance, but also instill confidence in the positive outcomes of expanding the set if the proposal is approved.

Hi Vasanti

Thank you for addressing the issue and we totally agree there is a decentralization issue. We support the other comments too. Expanding the nr of validators can be feasible once the concentration of stake is regulated and equalized. Most of the validators are at an operational net loss.

The issue has been addressed before too. Please lookup PIP5.
Atlas-Staking

I agree that maintaining the current slots is crucial and that we should seek other ways to improve the system. Expanding the number of validators can further complicate the equitable distribution of stake.