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Date: Sun, 31 May 2015 09:31:45 +0800
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From: Chun Wang <1240902@gmail.com>
To: bitcoin-development@lists.sourceforge.net
Content-Type: text/plain; charset=UTF-8
Subject: [Bitcoin-development] Fwd:  Block Size Increase Requirements
Precedence: list

On Sat, May 30, 2015 at 9:57 PM, Gavin Andresen <gavinandresen@gmail.com> wrote:
>> Bad miners could attack us and the network with artificial
>> big blocks.
>
>
> How?
>
> I ran some simulations, and I could not find a network topology where a big
> miner producing big blocks could cause a loss of profit to another miner
> (big or small) producing smaller blocks:
>
> http://gavinandresen.ninja/are-bigger-blocks-better-for-bigger-miners
>
> (the 0.3% advantage I DID find was for the situation where EVERYBODY was
> producing big blocks).

If someone propagate a 20MB block, it will take at best 6 seconds for
us to receive to verify it at current configuration, result of one
percent orphan rate increase. Or, we can mine the next block only on
the previous block's header, in this case, the network would see many
more transaction-less blocks.

Our orphan rate is about 0.5% over the past few months. If the network
floods 20MB blocks, it can be well above 2%. Besides bandwidth, A 20MB
block could contain an average of 50000 transactions, hundred of
thousands of sigops, Do you have an estimate how long it takes on the
submitblock rpccall?

For references, our 30Mbps bandwidth in Beijing costs us 1350 dollars
per month. We also use Aliyun and Linode cloud services for block
propagation. As of May 2015, the price is 0.13 U.S. dollars per GB for
100Mbps connectivity at Aliyun. For a single cross-border TCP
connection, it would be certainly far slower than 12.5 MB/s.

I think we can accept 5MB block at most.

(sorry forgot to cc to the mailing list)