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This is more of a clarification than as a question. Since I didn't have the rep to post a comment in this question, I'm putting this itself as a question.

Sources I've referred till now:

A fundamental problem in distributed computing and multi-agent systems is to achieve overall system reliability in the presence of a number of faulty processes. -Wikipedia

It explicitly indicates that consensus is a fundamental problem in Distributed Systems.

However,

"Consensus" means when everyone is on the same page. -Bitcoin SE.

My understanding till now is that if every node had one vote, then for the whole network of nodes to agree on a decision, use of consensus is required. If the system at hand is not distributed, then the environment reduces to just one node which doesn't need consensus mechanism at all to come to a decision. So my confusion is, are there any situations where consensus is required even when the system is not distributed?

If yes, please explain what's the difference between the terms "Consensus" and "Distributed Consensus". If possible, present an example.

If no, does that mean the terms are the same?

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  • This is more of a clarification than as a question. Since I didn't had the rep to post a comment in this question, I'm putting this itself as a question Weird
    – user103136
    Dec 29, 2020 at 0:03
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    I was referring to how Stackexchange works is weird. I don't have any issues with your question. Sorry I am not the best person to answer it though and other people might know better about consensus.
    – user103136
    Dec 29, 2020 at 3:49
  • I actually put that line because I didn't want my question to get dismissed or downvoted because it seemed to be a small & silly question to me. However, it was a gap in my knowledge. So, I had to ask anyway.
    – schegu
    Dec 29, 2020 at 4:26
  • Consensus is a concept used by bitcoin, however exists in other computer systems as well. I recommend you look at the computer science stack exchange.
    – qxotk
    Jan 21, 2021 at 17:12

1 Answer 1

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A consensus is an agreement between several agents. So it's always distributed in that sense. But here it is about the process of how to achieve such consensus. It's not dictated by one master. But agreed on by distributed voting.

Due to temporal logic being a nasty beast, you can't assume everyone to be on the same page at a specific point of time. But eventually everyone will reach a certain state of consensus.

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  • So, Are you conveying that the answer to the final question is "No, they're both the same terms" ?
    – schegu
    Dec 30, 2020 at 13:22
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    I think this is correct. Consensus is more a generic non-technical term, that doesn't even need to apply to computers or networks. Distributed consensus is a more specific term referring to the sort of solutions that are used in distributed computing systems to reach consensus.
    – Pieter Wuille
    Dec 30, 2020 at 19:05
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    Nope nroot, I don't! In addition to what Pieter wrote, I see a huge difference. Consensus is referring to a result. While distributed consensus is also about processes to achieve such a result.
    – pisjatblin
    Dec 31, 2020 at 17:10

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