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· 2 min read
Marcin Szamotulski

High level summary

We have been working towards cardano-node-1.35.5 release. QA & benchmarking teams gave a green light for the release, and we made decent progress with some CI problem which we encountered on the way (PR #4612). We are also working on peer sharing, making improvements in our testing infrastructure, reducing technical debt and making progress towards io-sim- Galois is making progress on Handshake improvements.

Low level summary

Our diffusion simulation network now includes a mixed network of initiator only and initiator and responder nodes. issue #4222

We are now reviewing the peer sharing pull request.

We are also reviewing pull request which introduces handshake query flag. PR #4256

We fixed a bug in our network simulator. The bug was triggered when a node died when performing a simultaneous TCP open (a corner case of a corner case!). PR #4265

We also refactored Snocket interface and removed the bearer construction from its methods. PR #4260

We are working towards releasing io-sim- on Hackage, which includes reviewing two PRs: PR #57 and PR #60 as well as writing an announcement blog post.

· One min read
Marcin Szamotulski

High level summary

In last sprint the team focused on preparations for the conference talk at OPODIS 2022. We also worked on preparations to publish io-sim and related packages on Hackage (PR #57, PR #60).

We also started reviewing:

  • ouroboros-network
  • cardano-node
  • cardano-ledger repositories for open-source readiness (PR #4128).

We prepared a PR which changes how node-to-node and node-to-client protocol versiones are serialised in cardano-node log (PR #4691).

· 4 min read
Marcin Szamotulski

Stake-Driven Data Diffusion Release for Relays

IOG networking team decided to release the Stake-Driven Data Diffusion with Robust Optimised Peer Selection also more commonly known as P2P. In the last update, we informed about a performance regression, but it turns out it only affects block producers, and thus we highly advise against running it on such nodes. Further investigation is required to find the cause of it.

On IOG's benchmarking cluster we have seen quite a good performance improvement on block propagation itself. The cluster is running a static topology with valency 6 (each node is connected to 6 other nodes). In which every of the 50 nodes are block producers. The setup of this network is the same as mainnet. We've seen 40-50% performance improvement on block propagation comparing to the same cluster deployed with the same topology but using non-P2P nodes. We think this performance improvement is caused by using full duplex connections. Quite likely the transaction traffic floating in both directions on the same TCP connection helps to keep the TCP window open. Note that in a cluster of 50 nodes with valency 6 the probability of having at least one duplex connection is more than 50%. We don't expect the same improvement on mainnet because the network is much wider and the transaction traffic is not as large.

Just before the release we squashed two small bugs:

  • issue #4163 - top level integration bug in keep-alive;
  • issue #4177 - a bug in outbound-governor;
  • PR #4165 - a fix cardano-ping support of NodeToNodeV_10.

Peer Sharing

We were carrying a review of peer sharing PR.


Neil Davies was invited to give a guest lecture entitled Avoiding System Catastrophes at UCLouvain.

What have we achieve last sprint

  • issue #4163: we found out that a control message is not passed to the keep-alive mini-protocol, this results in every demotion executing demotion timeout rather than a graceful termination. With the fix the node will no longer log:

    { "kind": "PeerStatusChangeFailure"
    , "peerStatusChangeType": "WarmToCold (ConnectionId {localAddress =, remoteAddress =})"
    , "reason": "TimeoutError"
  • issue #4177: we fixed an assertion failure in the outbound-governor; now we don't try demoted peers which are being demoted already.

  • PR #4155: we refactored ouroboros-network packages. There's a top level ouroboros-consensus-diffusion package which integrates network & consensus code. We also introduced:

    • ouroboros-network-api package which contains the API shared between network & conensus;
    • ouroboros-network-mock package which contains mock API used for testing (e.g. a mock chain & chain producer, etc.)
    • ouroboros-network-protocols package which contains implementation of all (but handshake) mini-protocols, exposes a testlib and contains test and cddl components.

    This made the dependency tree of network & consensus packages much cleaner.

  • PR #4169: we described the usage of release branches in doc.

  • PR #4165: we fixed cardano-ping support of NodeToNodeV_10 protocol.


The abstract of the talk:

An essential step to ensuring that distributed systems are fit for purpose.

Distributed systems have become an integral part of our society and daily lives. We are, both implicitly and explicitly, individually as well as collectively, placing ever more trust in them.

Are they worthy of this trust? Our need for them to be ‘fit-for-purpose’ goes well beyond notions of functional correctness (i.e. never getting the wrong answer). We need them to deliver the desired outcomes in a timely, robust, reliable, resilient fashion, at scale and in a sustainable way (both economically and environmentally).

This all sounds like a worthy aspiration, but what would be a practical approach to capturing and reasoning about these issues? How can we ensure that systems can meet their fit-for-purpose objectives, not just in their design but as they are deployed, encounter the imperfect world, are scaled to become economic, and proceed into ongoing maintenance?

This talk will illustrate how the notions of Outcomes and Quality Attenuation (as captured by ‘∆Q’) are being used to both frame the necessary notions and provide a basis for assuring the refinement and reification of such systems, from initial concept to operational infrastructure.

You can download the slides from here.

· 2 min read
Marcin Szamotulski

High-level summary

In last sprint we got a performance report of P2P performance testing cluster (which consists of 50 nodes). There is a performance regression in the header notification metric. The P2P cluster is constructed with the same topology as the non-p2p reference one this indicates some regression which needs to be further investigated. This poses a risk for releasing P2P.

We also continued to work on peer sharing: pull #4019.

We continued working on dynamic block production which is required for P2P release for BP nodes: pull #3159.

We simplified the P2P topology format: issue #4559, pull #3888.

We added a new trace point for asynchronous demotions of local peers with Warning severity. This trace is important for SPOs.

Detail description

Performance regression

Below we include a graph which shows the performance regression of the P2P code base vs non P2P.

On the x axis is time in seconds which measures the delay from the start of the slot to when a header was received. The y axis is the percentile of nodes that received a header. We are currently investigating possible causes of the regression.

New P2P topology form

The new topology file format is described in this issue #4559.

Tracing improvements

  • We improved a handshake error reporting, pull #4136
  • We added TraceDemoteLocalAsynchronous rendered as DemoteLocalAsynchronous in json format, pull #4127. Such demotions should be investigated by the pool operator. They can indicate a problem in the deployed system, but also they could indicate a remote problem in arranged connections with other SPOs.

Open Source Improvements

We improved documentation of io-sim and typed-protocols for open-source contributors and/or maintenance tasks: pull #22, pull #45, pull #48.

· 3 min read
Marcin Szamotulski

High-level summary

The team has focused on debuging & fixing bugs for the P2P single relay release, which included

  • diagnosing, fixing and writing tests for a bug in peer-state-actions which fortunately hasn't been released;
  • diagnosing & preventing misconfiguration of DNS

We also focused on developing peer sharing. We also held a session with the scientists on eclipse evasion.

Detailed description

P2P Network Stack

During the past two weeks the team focused on p2p single relay release and peer sharing. We found and fixed an important bug recently introduced in one of the components of p2p networking stack (fortunately never released). Together with a fix, we designed a unit test diffusion simulation as well as quickcheck property test (both could reproduce it). We also changed the code in a way that if such a bug is reintroduced in the future, it will be obvious to diagnose. For more see:

Initial benchmarking run of the P2P code was executed. The results where unlike what we see on the mainnet. We found a possible misconfiguration of the cluster (caused by 0 TTL on domain names), which could be the direct cause of it. We wrote a PR which rules out such misconfiguration. We are awaiting on the next benchmarking results. See more at:


We also started working on P2P single relay release. The PR ouroboros-network#4120 includes 108 patches cherry-picked from the master branch. We started working toward integration these changes against the release branch of cardano-node. Early next week we ought to be able to have an early version of cardano-node with non experimental P2P support!

For more detailed release plan please see P2P - Single Relay issue.


We identified and fixed missing error reporting in consensus initialisation phase. See more at ouroboros-network#4015

Cardano Node

We also made changes in cardano-node in order to give better experience for node operators. This includes updating severities of some of the traces as well as implementing new format of the p2p topology file. For more see:

Peer Sharing

We continued working on implementation of peer sharing. We have an early implementation which will be reviewed and analysed in next weeks. We started working on cardano-node integration. We need PR #4392 to be merged before such integration will be able to land in cardano-node, although this is not blocking us currently. See more at:

Eclipse Evasion

We held a session which included Alexander Russel, Sandro Coretti-Drayton and Nick Frisby from the consensus team. We discussed high lever design of the eclipse evasion scheme, which is important for the design and implementation of ouroboros-genesis. We got a positive feedback from the researchers.


In this period we made little progress towards releasing IO-Sim on Hackage. A single PR which added a few missing instances of the STM monad.

Open Source

We made sure the CI runs for PRs which comes from forks (which is important to accept contributions from 3rd parties).

Mithril Cardano Integration

We held initial discussions with Arnaud Bailly about possible path to integrate mithril to cardano-node and take advantage of the ouroboros-network diffusion layer.