In the question "How does the system sustain regular low-effort "splitting attacks"?" a scenario about the ability to disrupt the network by spamming double-spends and having the network work to resolve these incompatibilities is drawn. The question tries to evaluate the possibility to shut the network down by having it resolve so many double-spends that it's basically unable to confirm anything anymore since it has to discard so many half confirmed parts of the tangle that it doesn't get to grow a confirmed part anymore.

Within my answer and the following chat discussion it crystallized itself that we have two different assumptions of how quickly the network determines double-spends.

That is my question, is there a way to determine how fast a double spend is detected by a IOTA network?

I'm saying a IOTA network because I assume it to be vastly different depending on the amount of nodes, their connection pattern and the load the network has to process. The IOTA whitepaper already makes an important distinction between a high load and a low load regime (v1.3, p.10). I figure it makes quite an important difference how the network topology is made up. Imagine a line of a thousand nodes with only one left and right neighbor each versus a thousand nodes with nine neighbors in a random distribution. Or imagine that distribution being optimized for a low hop count?

How quickly is a double-spend detected and what are the most important parameters to evaluate that speed?

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    How quickly it is detected is in fact an important question. However, maybe even more important is the related question how quickly it can be resolved. If one node detects a double spend, it can't prevent others from building on one branch (either because they haven't detected the conflict or they assume they are strengthening the 'winning' branch). – lex82 Dec 13 '17 at 14:35
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    Huge question. I don't think it is possible to write a complete and motivated answer within the limit allowed on stackexchange. It may requires a complete book to cover all topologies, tip selection algorithms (and the impact of different tip selection algorithm on different node), bad neighbors ban strategy, ... – ben75 Dec 16 '17 at 20:23
  • The question is not really well presented. What matters is not detection of doublespends but rather preventing parts of the network from coming to a different conclusion about consensus and thereby excluding any spend from being honored and later reversed. Currently the Coo allows all nodes to agree on a set of transcations and that can never be reversed. WIth regards to double spends shutting down the network, we have seen that floods of reattaches (which are double spends) are just ignored by the new tipsel in 1.5. – Spamalot Jul 2 '18 at 10:39
  • @Spamalot, what you're describing is a different question. I'm specifically not asking about the network but about the influence of topology on the detection speed. As Lex & Ben already noted resolution might be more important and the number of topologies might be too manyfold to be properly answered here. Declaring in a comment that another issue might be more important doesn't make the initial question less worthy of analysis. – Helmar Jul 2 '18 at 15:45

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