Technical Proposal: Transaction Relay for Enhanced Block Building

BNB Smart Chain
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Technical Proposal: Transaction Relay for Enhanced Block Building

Overview

Current block building systems, particularly in the context of Proposer-Builder Separation (PBS), often suffer from limitations in validator selection and transaction inclusion speed. The current model, where builders are restricted to sending bids only to pre-registered validators, creates a bottleneck. This proposal outlines a system where a proxy layer can broadcast transactions to a broader network, fostering competition and reducing transaction latency.

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Problem Statement

  • Increased Transaction Latency: Transactions must wait for specific, pre-selected validators to propose blocks, especially the registered validators are not incumbent validators that propose blocks to the network. This can lead to significant delays, especially if the builder has few validators registered.
  • Consensus block production: The delay can be deteriorated if the number of blocks that each validator can propose consecutively. The current setting is 4, but can be increased in the future.
  • Reduced Competition: Limited validator selection reduces competition among builders and validators, potentially leading to less efficient fee markets and suboptimal block construction.

Proposed Solution: Open Transaction Relay Proxy (OTRP)

The core of this proposal is the creation of an Open Transaction Relay Proxy (OTRP). This role acts as a parallel, permissionless layer alongside the existing validator set. It enables proxy to disseminate transactions more widely, increasing the likelihood of inclusion in a block, regardless of pre-registration.

Workflow

  1. Transaction Submission: A user submits a transaction to a proxy.
  2. OTRP Broadcast: The proxy broadcasts the transaction to all registered builders.
  3. Builders will pick up the transactions, build blocks and send bids to validators.

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Advantages

  • Increased Validator Competition: Opens up block building to a wider range of validators(through the whole network of builders), fostering competition and potentially leading to lower fees and better transaction inclusion.
  • Faster Transaction Inclusion: Transactions are broadcast to a larger network, increasing the probability of being included in a block quickly, even if specific pre-registered validators are unavailable or slow.
  • Improved Censorship Resistance: Makes it more difficult for individual validators to censor specific transactions, as there are more avenues for inclusion.
  • Enable the possibility to increase the consecutive block production when block time is reduced to subsecond(see details from BNBChain 2025 roadmap).

Conclusion

The Open Transaction Relay Network presents a viable path towards a more open, competitive, and efficient block building ecosystem. By allowing builders to broadcast transactions to a wider network, it addresses the limitations of current systems and promotes faster transaction inclusion, and greater validator participation.