Also, invalid transactions seem important to understand. I want to know what kind of reprocussions it causes in the ecosystem, if any, or do they just eventually filter into non-existance?
They almost immediately filter into non-existence.
Every node on the network verifies every transaction it receives before it adds the transaction to it's own mempool, or relays the transaction to any other connected peers.
Therefore, if anyone tries to connect to any nodes and broadcast an invalid transaction, every one of those connected peers will reject the invalid transaction. It won't be accepted into their own mempools, AND it won't be relayed to ANY other nodes.
Furthermore, if a node is found to be repeatedly sending invalid data, then the nodes that it is connected to will close that connection so that they don't need to repeatedly check invalid data.
Excellent- thanks!
Taking this a bit further to rejected transactions...on another altcoin I was mining (not bitcoin, as individual users no longer can mine), apparently I mined my first block ever ( super excited) and got paid, it showed the number of coins I had in my wallet. But then apparently the crypto "forked". I had to upgrade my software to continue mining. However, after the upgrade, my payment for my newly mined block disappeared! I inquired to the sysop about it, he responded that likely my new mined block was mined during a "fork", thereby rejected by all the nodes I was attempting to connect to.
If this is inappropriate to ask about in a bitcoin thread, by all means just tell me I wont bring it up again. But I'm thinking perhaps the same thing could have occurred in the past with Bitcoin itself during a fork? Mined blocks would not be valid?
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So, after a couple weeks of testing, ie. having my wallet and the entire chain offline on a removable drive, than plugging in and starting the resync all over again, happy to report ( I know I know I'm preaching to the choir) that everything works perfectly! Both times Bitcoin Core has synced back up to the network and brought the chain up to date even after being offline for a week. So---I can happily say that: It is
NOT impossible to download now, but still is definitely too slow and too big!
