When a transaction is broadcast to the network, what is actually being sent?

Client creates a new transaction, adds it to its memory pool
Client broadcasts an inv frame, which indicates that it has something in its memory pool, by giving the hash of the transaction to one or more connected peers
Peer receives inv frame, checks its own memory pool, it's not in there, so it sends a getdata frame back
Client receives a getdata frame for the transaction it just created, so it sends a tx with the entire transaction
Peer receives the tx, hashes it and puts it in the memory pool
Peer now has something new in the memory pool, and broadcasts an inv to all connected peers
Client gets an inv frame, notices that it's already in the memory pool, and ignores it
Another client gets the inv frame as well, getdata's it, stores the tx, sends inv, and repeat that until the entire network has the transaction.

References :

Tom van der Woerdt

Posted 2013-04-16T20:54:28.970

Reputation: 2 397

Correct me if I'm wrong, but doesn't bitcoin only send the transaction to one peer if it originated the transaction? – Nick ODell – 2013-04-16T21:01:36.660

1@NickODell Perhaps, but that's implementation related, and not a network rule. – Tom van der Woerdt – 2013-04-16T21:02:29.510

Thank you Tom, very clear explanation. However, I still have a question. Based on Satoshi paper http://bitcoin.org/bitcoin.pdf, the hash consists of the public key of the receiver too. I suppose that the public key is added in order to have different hashes?

– anapaso – 2013-04-16T21:27:33.650

(Disclaimer: I've never read the paper, I've only built a client.) The hash of a transaction is simply the entire transaction (tx) hashed (unlike blocks, which only have their headers hashed). This includes all the inputs and outputs. – Tom van der Woerdt – 2013-04-16T22:15:44.583

how fast or how long does it take to broadcast the information to all peers? i mean when i'm mining, and somebody has already found a new block, how long would it take till i receive the information and start mining again on new block? – ulkas – 2013-04-17T07:11:55.813

Reaching all peers can take a long time (maybe even up to an hour), as there are always a few edges on the network where it takes a lot longer. However, for most nodes it's a matter of seconds to maybe two minutes. – Tom van der Woerdt – 2013-04-17T09:04:52.033

When a transaction is broadcast to the network, what is actually being sent?

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