Measuring minrelaytxfee across the Bitcoin network

The observation regarding a significant portion of IPv4 nodes not sending a FEEFILTER message raises questions about their nature and purpose. Peter Todd's suggestion that these might be spy nodes adds a layer of intrigue to the analysis. Upon further inspection, it was found that many of these nodes are clustered within the same subnet, with groupings of approximately 50 nodes each. This pattern could indicate a deliberate arrangement, possibly for monitoring or other specific functions within the network.

Further scrutiny revealed that some of these nodes might be operating on software versions predating the year 2016. This is significant because the capability to send feefilter messages was only introduced in the Bitcoin protocol as per a GitHub pull request from 2016. Therefore, nodes running on older versions would inherently lack the functionality to send feefilter messages. Additionally, there exists the possibility that some nodes have intentionally disabled the feefilter option. This could be achieved by using a software version older than 2021 and applying the -feefilter configuration option, as detailed in another GitHub pull request from 2021. This deliberate disabling of the feefilter feature could serve various purposes, including but not limited to privacy preservation, experimentation, or other operational strategies within the Bitcoin network.