Note that the 4MB number comes from a single network metric.

Quotes directly from the paper in question: http://fc16.ifca.ai/bitcoin/papers/CDE+16.pdf

>Our results hinge on the key metric of effective throughput in the overlay network, which we define here as which blocks propagate within an average block interval period the percentage of nodes to.
...
>Note that as we consider only a subset of possible metrics (due to difficulty in accurately measuring others), our results on reparametrization may be viewed as upper bounds: additional metrics could reveal even stricter limits.

It says nothing about any mining centralization pressure, DoS attacks, etc. A single metric among many we have to contend with.






On Fri, Jan 27, 2017 at 3:34 PM, Russell O'Connor via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:


On Jan 27, 2017 03:03, "Andrew Johnson via bitcoin-dev" <bitcoin-dev@lists.linuxfoundation.org> wrote:

Other researchers have come to the conservative conclusion that we could handle 4MB blocks today.

I believe this is a mischaracterization of the research conclusions.  The actual conclusion was that the maximum value for the blocksize that the network can safely handle (at that time) is some value that is (conservatively) no more than 4MB.  This is because the research only studies one aspect of the effect of blocksize on the network at a time and the true safe value is the minimum of all aspects.  For example, the 4MB doesn't cover the aspect of quadratic hashing for large transactions in large blocks.

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