Bitcoin core full node: should I choose my peers or is it okay to use the coded ones?

If you use connect, You'll only connect to those specific nodes.

addnode On the other hand, try to connect to the specified nodes, but keep connecting to others too (unless you add more nodes than outgoing connections, I suppose).

It may be useful with respect to privacy to connect only to the nodes you trust; How to find them is another question.

Also, as far as I know, there are no coded pairs in the official bitcoin binaries.

You can find the sample file bitcoin.conf here for more information.

Bitcoin Core is frozen trying to synchronize and / or connect to peers

I downloaded Bitcoin Core directly to my laptop and sent BTC to what I think is my wallet. The BTC is no longer in my sender's wallet and I do not see it in my bitcoin core wallet. It was working slowly but now it is frozen at 12 percent.

Did the Bitcoin Core relay blocks run sequentially or in parallel with their peers before the compact blocks?

It is not as simple as "send sequentially" or "send in parallel". Each connection is its own socket and the kernel performs package programming. The Bitcoin protocol does not have any recognition. When a node sends a message, it delivers it to the TCP stack, which often simply accepts the entire message immediately. Then it's up to the kernel to send it.

So, in a sense, it's not even really possible to send it sequentially & # 39; without some type of massive redesign, but neither would it be generally desirable to do so: TCP will not send more than the current reception window without obtaining an acknowledgment. So, if I had to wait until TCP had sent all the data to one pair before starting to send the next one, it would be waiting for it not to send any time. It would also increase exposure to tarpit attacks, where a malicious pair intentionally delays reception to delay propagation to all others.

Therefore, Bitcoin has always reviewed the list of pairs and delivered everything that had to be sent to each of them, leaving it in the kernel to program the packages. In the past, it was proposed to hand it over to only a few and then wait for it to be obtained before they reach the rest, but it is not obvious how to prevent tarpits in a robust way, and BIP152 largely raises the issue.