This week, the Leios team continued working on various aspects of the protocol and its simulation capabilities. They made progress in implementing and testing the Haskell and Rust simulators, focusing on protocol behavior under different network conditions.

Simulation progress​

• Haskell simulation

  • Moved configuration and topology parsers to the leios-trace-hs package for reuse in formal methods
  • Investigated differences in IBs referenced with Rust simulation: identified that inconsistencies were caused by the same sequence of random samples being used across different runs
  • Simplified sortition code by using an external statistics package
  • Tested Full Leios, resolving tension between r_EB/eb-max-age-slots and praos-chain-quality/η
  • Fixed cabal run ols -- generate-topology close-and-random, listing producers properly and decreasing variance in upstream peers.

• Rust simulation

  • Investigated anomalies in simulation results: identified that earlier IB production failures were caused by low connectivity and lower CPU usage compared to the Haskell simulation
  • Refined Full Leios implementation
  • Added Full Leios support to the visualizer
  • Migrated the visualizer from Next.js to Vite.

Analysis of simulations​

• Tag leios-2025w13: simulated 198 Short Leios scenarios, varying IB production rate, IB size, network topology, CPU limits, and protocol flags
• CPU limits: analyzed the impact of CPU constraints on IB propagation, finding that diffusion can be affected under stress conditions
• Vote propagation: compared freshest-first and oldest-first vote propagation, with freshest-first potentially improving IB delivery reliability
• Extended voting period: compared an extended voting period to a limited one in the Haskell simulation, observing minimal differences except for occasional improvements in reliable vote delivery.

Ongoing investigations​

• Investigating qualitative discrepancies between Haskell and Rust simulation results to determine whether they stem from differences in simulator resolution or simulation infidelities.

Additional resources​

• Monthly review meeting – March 2025.

This week, the Leios team made significant progress in protocol development, focusing on improving simulation capabilities and analyzing protocol behavior under various network conditions. A comparison of Haskell and Rust simulations across 18 scenarios demonstrated that the Leios protocol scales effectively to mainnet-sized networks. However, congestion occurs when the input block rate reaches 30 IB/s.

Simulation comparison​

• Compared 18 scenarios between Haskell and Rust simulations at tag leios-2025w12
• Recent fixes and adjustments enabled meaningful comparison between simulations
• Identified differences when comparing the Haskell and Rust results, which are under active investigation.

Analysis of simulations​

• Completed the first simulation of Short Leios, evaluating IB production rate, IB size, and network topology
• Demonstrated that the Leios protocol scales effectively to mainnet-sized networks
• Identified congestion occurring when the input block rate exceeds 30 IB/s
• Suggested that allowing IBs larger than current Praos RBs may have advantages in TCP efficiency, network usage, and adapting to fluctuating transaction loads.

Peak CPU	Mean CPU

Haskell simulation​

• Implemented expiration of blocks:
  • Blocks are removed from the relay buffer once diffusion stops and cleared from other states as specified
• Developed an initial Full Leios implementation:
  • Currently in early testing
  • Added the praos-chain-quality configuration parameter for the \eta parameter from the specification.

Rust simulation​

• Developed an initial Full Leios implementation using estimated values for some parameters.

Formal methods​

• Short Leios trace verification: modeling local state evolution of a node
• Developed an initial trace verifier for Short Leios simulation traces in leios-trace-verifier.

This week, the Leios team made significant progress in simulation capabilities, with a successful comparison of Rust and Haskell simulations across 90 scenarios. A mainnet-scale analysis of Leios on a realistic 3,000-node network revealed unexpected performance benefits from network topology. Insights from sharding performance analysis provided important optimization strategies. Finally, the team refined both simulation implementations for greater realism and comparability, while the formal methods team developed initial trace verification tools for Short Leios.

Simulation comparison​

• Compared 90 scenarios between Rust and Haskell simulations at tag leios-2025w11
• Recent fixes and adjustments enabled meaningful comparison between simulations
• Identified issues requiring further investigation.

Analysis of mainnet-scale simulation​

• Completed the first analysis of Leios on a mainnet-scale network simulation using the Rust simulator
• Discovered that a 3,000-node mainnet-scale network transports IBs faster than an artificial 100-node network
• Identified 'shortcut' edges in larger networks as a likely factor in the improved transport speed.

Performance analysis of sharding​

• Created computational models to analyze the relationship between the fraction of shards without an IB and the expected number of extra IBs
• Evaluated performance characteristics of the simplest sharding scheme.

Haskell simulation​

• Fixed a bug in the relay protocol that prevented full diffusion of votes
• Adjusted the priority of certified EBs for inclusion in RBs
• Added support for an output log format that shares a common subset with the Rust simulator
• Analyzed TCP realism in comparison to idealized diffusion:
  • Discovered that higher IB rates and sizes improve diffusion times
  • Identified ledger state access as a significant source of latency.

Rust simulation​

• Expanded logs to include total IB size and parent ID of RBs
• Implemented the same EB selection strategy as in the Haskell simulation
• Added validation of IB headers before propagation to neighbors
• Investigating lower congestion in the Rust simulation compared to Haskell.

Formal methods​

• Developed the initial trace verifier for Short Leios simulation traces in leios-trace-verifier.

Research​

• Progressing on ledger design by exploring options and trade-offs
• Analyzing how concurrent input blocks in Leios create unique ledger-level challenges not present in Praos
• Evaluating approaches that balance multiple properties, including:
  • Conflict avoidance in the blockchain
  • Guaranteed fee payment for block producers
  • Transaction eligibility and inclusion speed
  • User experience regarding fee payment
• Investigating sharding-based solutions with various optimization strategies
• Planning to share more detailed findings at Leios public meeting by the end of March
• Targeting a comprehensive recommendation for implementors by the end of April.

From Short Leios to Full Leios​

• Planning the simulation roadmap for transitioning from Short Leios (currently implemented) to Full Leios
• Developing implementation guidelines for simulators to incorporate the pipeline referencing scheme specified in the papers
• Identifying key components needed to simulate the complete ledger inclusion guarantees of Full Leios.

This week in Leios development, the team focused on simulation analysis, formal methods, and documentation updates. Key accomplishments include in-depth analysis of simulations at tag leios-2025w10, advancements in formal methods through a working trace verifier, and the development of technical reports.

Cross-simulation analysis​

• Completed a comprehensive analysis of simulations at tag leios-2025w10:
  • Analyzed Haskell simulation performance with and without CPU usage considerations
  • Varying key protocol parameters:
    • IB production rate
    • IB size
    • Length of Leios stages
  • Identified the following aspects of Leios:
    • Delay between IB generation and receipt at nodes
    • Peak and mean CPU usage over time
    • Breakdown of CPU usage by task type
    • Sizes of IBs, EBs, and RBs
    • Duplicate IB references in EBs
    • Reference to EBs from RBs
    • Resource utilization in network traffic.

Protocol and formal methods​

• Began developing a trace verifier in Agda:
  • Implemented event trace parsing using the Haskell module leios-trace-hs.

Documentation and research​

• Completed the full draft of the Leios technical report #1
• Created a skeletal draft of the Leios CIP
• Aligned with the latest CIP template
• Developed a detailed simulation analysis for the 100-node Leios network.

Programming and testing​

• Resolved several simulation issues:
  • #235: RB size does not reflect the presence of a certificate
  • #234: Fast transmission of large blocks at moderate IB rate
  • #232: Monotonicity of EB inclusion in RBs
  • #230: EBs are not large enough to include their IBs
  • #229: Rust simulations panics from overflow
• Enabled the visualization of network traffic and logging messages for multiple predefined 'scenarios' instead of a single hard-coded trace
• Updated the visualization to display resource utilization in network traffic.

Rust simulation visualization​

• Improved visualization capabilities:
  • Added support for multiple predefined 'scenarios' instead of single hard-coded trace
  • Moved the visualization logic to the client-side web worker for better performance
  • Added the visualization of per-node network traffic breakdown by message type
• Fixed critical simulation bugs:
  • Resolved issue #229 causing time travel and crashes in high-traffic high-latency scenarios.

This week in Leios development, the team focused on simulation analysis and formal methods. Key accomplishments include detailed analyses of both Haskell and Rust simulations, initial work on a protocol dashboard, and advancements in formal methods through trace verification in Agda.

Cross-simulation analysis​

• Completed a comprehensive analysis of simulations at tag leios-2025w09:
  • Refactored the ELT workflow to improve simulation data processing
  • Modified the Rust simulator to generate fixed-size input blocks (IBs) for comparison with Haskell
  • Partially resolved discrepancies in congestion metrics between simulators
  • Developed detailed analyses of:
    • IB generation to receipt elapsed time
    • Time-in-flight over node-to-node links
  • Identified the dual role of network bandwidth and CPU bottlenecks in high throughput congestion.

Protocol dashboard initiative​

• Initiated the design of an interactive protocol dashboard with planned features:
  • Protocol parameter configuration
  • Stake distribution settings
  • Performance visualization:
    • Block arrival efficiency
    • Transaction duplication
    • Leios operation rewards
    • Resource utilization
  • Security metrics visualization:
    • Quorum failure analysis
    • Certificate forgery detection
    • Adversarial block tracking.

Rust simulation​

• Enhanced parallel message handling capabilities:
  • Implemented parallel mini-protocol message transmission
  • Added even bandwidth distribution between mini-protocols
  • Introduced the simulate-transactions configuration option
  • Updated simulation output for better Haskell compatibility
  • Improved block visualization for scenarios with high IB counts.

Formal methods​

• Commenced trace verifier development in Agda:
  • Added decidability to Short Leios protocol relational specification
  • Implemented a proof-by-computation approach for execution traces
  • Applied the successful methodology from Streamlet formalization.

This week in Leios development, CPS-0018 for transaction throughput was approved, along with improved Docker support for simulations and analysis of cross-simulation results. The team also examined input block (IB) production rates and their impact on network performance.

Protocol development​

• CPS-0018 'Greater transaction throughput' officially approved:
  • Merged into Cardano Foundation's CIP/CPS repository
  • Documents urgency of higher transaction throughput
  • Defines goals for the Leios initiative
  • Identifies key open questions and use cases.

Cross-simulation analysis​

• Conducted a comprehensive analysis of IB production rates ranging from 1 IB/s to 100 IB/s:
  • Developed an ELT workflow for data processing via MongoDB
  • Created an R Jupyter notebook for analysis and visualization
  • Identified and addressed three significant bugs (#207, #208, #209)
• Key findings from the Haskell simulation:
  • Network congestion emerges at high IB production rates
  • Both average propagation time and slow propagation tail increase
  • A critical threshold of ~40 IBs/s was identified, beyond which network congestion severely impacts block reception
• Comparison of PeerNet and Haskell simulations:
  • Both exhibit qualitatively similar block propagation distributions
  • Both demonstrate protocol breakdown under high block production rates
  • Differences in resolution and configuration prevent exact comparison.

Infrastructure improvements​

• Added comprehensive Docker support for both simulations:
  • Optimized multi-stage Docker files for Haskell and Rust
  • Simplified deployment process
  • Enabled easy configuration via volume mounts and parameters
  • Documented usage in README.md.

Rust simulation​

• Enhanced Rust simulation capabilities:
  • Implemented bandwidth usage tracking
  • Added configurable bandwidth limits per connection
  • Fixed issues identified in cross-simulation comparisons
  • Started updating visualizations for improved clarity.

Haskell simulation​

• Enhanced IB sortition handling for IB/slot < 1
• Began integrating block expiration and diffusion-halt proposal
• Implemented ideal timing calculations for diffusion:
  • Added uniform block behavior configuration
  • Identified relay mini-protocol complexities:
    • Variable latency (3-4) for block transfer
    • Latency depends on traffic conditions and request handling.

Formal methods​

• Moved formal specification to a dedicated repository
• Established a conformance testing framework:
  • Enabled testing between Short Leios implementations
  • Documented the test suite execution process
• Initiated a survey of network models across IO consensus projects.

This week, the Leios team made significant progress across multiple areas. Major developments included detailed DeltaQ analysis of network topologies, extensive BLS cryptography benchmarking, and improvements to both simulations. The team also explored succinct schemes for BLS key registration and conducted a detailed certificate performance analysis. Both Haskell and Rust simulations received substantial updates to improve visualization and support more realistic testing conditions.

DeltaQ analysis​

• Enhanced the topology-checker with ΔQSD analysis capabilities:
  • Extracts inter-node latencies from given topologies
  • Classifies latencies into near/far components
  • Builds parameterized ΔQ models
  • Outputs fitted models in delta_q web app syntax
• Key findings from topology analysis:
  • Clear distinction between near/far components in examined topologies
  • Unexpectedly high hop counts in latency-weighted Dijkstra paths:
    • Min 4-5, max 8 for topology - 100
    • Min 8, max 20 for 'realistic' topology
  • Model fitting achieved rough shape matching but showed significant deviations at low latencies
  • Resource usage tracking goals remain unmet due to complexity in understanding load multiplication factors.

BLS cryptography​

• Completed comprehensive benchmarking of certificate operations:
  • Detailed performance analysis across committee sizes (500-1000 seats)
  • Certificate generation: 63.4ms - 92.5ms
  • Certificate verification: 104.8ms - 144.9ms
  • Certificate weighing: ~12ms consistently
• Explored succinct schemes for key registration:
  • Proposed 90-day key evolution with 124-byte KZG commitments
  • Analyzed message sizes for key opening (316 bytes per pool)
  • Investigated SNARK-based alternatives for proof of possession
• Added BLS crypto to the CI pipeline with automated testing
• Documented parallelization strategies for certificate operations.

Formal methods​

• Added a conformance testing client for the executable Short Leios specification
• Successfully merged the executable specification for Simplified Leios into main.

Haskell simulation​

• Updated configuration defaults for block sizes and timings
• Added support for idealized simulation conditions:
  • Single-peer block body requests
  • TCP congestion window modeling
  • Mini-protocol multiplexing
  • Unlimited bandwidth links support
• Enhanced simulation output and analysis:
  • Added raw field for accumulated data
  • Implemented block diffusion CDF extraction
  • Created multi-CDF plotting capabilities.

Rust simulation​

• Enhanced visualization capabilities:
  • Added block size breakdown display
  • Implemented total bytes sent/received tracking
  • Added total TX count and CPU time metrics
• Improved event handling:
  • Updated to standard timestamp format (seconds)
  • Enhanced CPU task event structure
  • Added CBOR output support
• Added support for multiple strategies:
  • Implemented ib-diffusion-strategy (freshest-first, oldest-first, peer-order)
  • Added relay-strategy affecting TXs, IBs, EBs, votes, and RBs
  • Enabled unlimited EB and vote bundle downloads from peers.

This week, the Leios team worked on cryptography benchmarking and cost calculator improvements. The team completed a reference implementation for Leios cryptography and enhanced the online cost calculator with user-requested features. They also updated both Haskell and Rust simulations to improve visualization and network modeling capabilities.

Haskell simulation​

• Added support for Send and Receive voting stages, providing:
  • A new leios-vote-send-recv-stages configuration option
  • A configurable stage length via leios-stage-active-voting-slots
• Implemented multiple diffusion strategies:
  • Added oldest-first strategy
  • Added configurable strategies for IBs, EBs, and votes via *-diffusion-strategy configurations
• Created a new small scenario for 100 nodes with 2,000 kB links
  • Tuned IB parameters to utilize one-third of link capacity
  • Added configurations for both single-stage and send-recv voting
• Fixed several simulation behaviors:
  • Improved block generation logic
  • Prevented duplicate EB inclusion in the base chain
  • Confirmed proper EB inclusion timing relative to vote diffusion
• The main difference observed between single-stage and send-recv is that the former shows a longer tail in the CPU usage CDF when the simulation is run with unlimited cores.

Cryptography implementation​

The Rust benchmarks for Leios cryptography were redesigned as a reference implementation:

• Implemented the Fait Accompli sortition
• Enhanced sortition to use rational arithmetic instead of quad-precision floats
• Added Quickcheck tests for all capabilities
• Added benchmarks for serialization
• Optimized vote and certificate size.

Cost calculator improvements​

The team enhanced the online Leios cost calculator:

• Added support for both hyperscale and discount cloud providers
• Made discount providers the default option
• Added option to amortize storage costs perpetually
• Updated defaults:
  • Single relay deployment
  • More conservative 50% disk compression
  • Perpetual storage cost amortization.

Throughput simulator​

The team updated the Cardano throughput simulator with:

• The latest cloud-computing cost model
• Synchronized assumptions with an online cost calculator.

Rust simulation​

• Made minor fixes to the new graph generation strategy
• Planned out a roadmap for visualization work focusing on the Leios transaction lifecycle.

The Leios team continued refining Haskell and Rust simulations, standardizing inputs, outputs, and event logging for better comparability. The team defined standard formats for configuration parameters and network topology for running the Leios protocol. They also worked on logging identical simulation events to compare and feed them into the DeltaQ model and, consequently, the executable specification, ensuring alignment with formal methods.

Haskell simulation updates​

• The short-leios simulation now outputs diffusion latency data
• Added support for different input block (IB) diffusion strategies:
  • freshest-first: higher slot numbers requested first
  • peer-order: requested in order of peer announcement
• Added support for Vote (Send) and Vote (Recv) stages.

Rust simulation progress​

• Added an 'organic' topology generator that better matches mainnet topology
• The generator creates clusters of colocated stake pools and relays
• The simulation uses stake to determine relay connectivity
• Topology insights gathered from stake pool owners:
  • Most pools have multiple relays (2,312 relays across 1,278 pools)
  • Pool operators often run multiple colocated pools sharing relays
  • Relays typically maintain ~25 active outgoing connections
  • Incoming connections scale with stake weight (10-400+ connections).

DeltaQ update​

• Wrote a comprehensive 2025-01 report covering work since September 2024.

Formal methods​

• Finalizing executable specifications for simplified and short Leios
• Extracted short Leios specification to Haskell for conformance testing.

Simulation progress​

Haskell implementation​

• Enhanced parameter handling with support for reading configurations and topologies from disk
• Added a new generate-topology command for random topology generation
• Aligned Leios sortition with algorithms from sortition benchmarks and the technical report
• Completed analysis comparing the Praos simulation with the benchmark cluster
  • Adoption times within 10% of measured values
  • Review of simulation parameters pending
• Next steps identified:
  • Generate topologies with block producers behind relays
  • Begin comparison with the idealized diffusion model
  • Configure and run simulations for higher throughput.

Rust implementation​

• Completed the first pass of block-level visualization
• Updated topology files to include baked-in latencies
• Improved output with human-readable names from the shared topology format
• Enhanced simulation output comparability across different simulations.

Analysis and research​

Sortition analysis​

• Completed a detailed analysis of the 'Fiat Accompli' sortition scheme using mainnet stake distribution (Epoch 535)
• Key findings for 500-vote committees:
  • 406 largest stake block-producers would be deterministic voters
  • ~88 voters would be randomly selected
  • Significant certificate size reduction achieved through deterministic voter selection.

Downstream impact assessment​

Started comprehensive analysis of Leios's impact on the ecosystem:

• Identified impacts on indexers, explorers, SDKs, and APIs resulting from ledger and node changes
• Transaction construction and memory-pool sharding effects on DApps and wallets
• Physical layer visibility considerations for sophisticated use cases
• High throughput implications for event filtering efficiency
• Transaction journey time considerations from memory pool to Praos block reference.

DeltaQ analysis​

• Successfully matched ΔQ model for IB diffusion across both simulations and implementations
• Identified key differences in simulation approaches:
  • Haskell simulation includes bandwidth effects (328ms network delay per hop at 1MB/s)
  • Rust simulation currently excludes bandwidth effects
• Enabled cross-simulation topology sharing for consistent testing.