17. More in the Transaction Pool, Networking Broadcast, and Coding Details

17

More on the TransactionPool, NetworkingBroadcast, andCoding Details

IN THE FIRST SECTION BELOW, Satoshi expands on the transaction pool. He then describes his experiment on the networking broadcast mechanism where nodes request items from their neighbors. Lastly, Satoshi mentions that he has been working on the code for the last 18 months.

Re: Bitcoin P2P e-cash paper

Satoshi Nakamoto Mon, 17 Nov 2008 13:33:040800

James A. Donald wrote:

Satoshi wrote: Fortunately, it’s only necessary to keep a pendingtransaction pool for the current best branch.

This requires that we know, that is to say an honest well behaved peer whose communications and data storage is working well knows, what the current best branch is

I mean a node only needs the pending-tx pool for the best branch it has. The branch that it currently thinks is the best branch. That’s the branch it’ll be trying to make a block out of, which is all it needs the pool for.

Broadcasts will probably be almost completely reliable.

Rather than assuming that each message arrives at least once, we have to make a mechanism such that the information arrives even though conveyed by messages that frequently fail to arrive.

I think I’ve got the peer networking broadcast mechanism covered.

Each node sends its neighbours an inventory list of hashes of the new blocks and transactions it has. The neighbours request the items they don’t have yet. If the item never comes through after a timeout, they request it from another neighbour that had it. Since all or most of the neighbours should eventually have each item, even if the coms get fumbled up with one, they can get it from any of the others, trying one at a time.

The inventory-request-data scheme introduces a little latency, butit ultimately helps speed more by keeping extra data blocks off the transmit queues and conserving bandwidth.

You have an outline and proposal for such a design, which is a big step forward, but the devil is in the little details.

I believe I’ve worked through all those little details over the last year and a half while coding it, and there were a lot of them. The functional details are not covered in the paper, but the sourcecode is coming soon. I sent you the main files. (available by request at the moment, full release soon)

Satoshi Nakamoto

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