Subject: Re: [bitcoin-dev] The increase of max block size should be determined by block height instead of block time

From: Jorge Timón <[email-masked]>
Date: Fri, 18 Dec 2015 21:10:02 +0100

Well, if it's not going to be height, I think median time of the previous
block is better than the time of the current one, and would also solve Chun
Wang's concerns.
But as said I prefer to use heights that correspond to diff recalculation
(because that's the window that bip9 will use for the later 95%
confirmation anyway).
On Dec 18, 2015 9:02 PM, "Jeff Garzik" <[email-masked]> wrote:

> From a code standpoint, based off height is easy.
>
> My first internal version triggered on block 406,800 (~May 5), and each
> block increased by 20 bytes thereafter.
>
> It was changed to time, because time was the standard used in years past
> for other changes; MTP flag day is more stable than block height.
>
> It is preferred to have a single flag trigger (height or time), rather
> than the more complex trigger-on-time, increment-on-height, but any
> combination of those will work.
>
> Easy to change code back to height-based...
>
>
>
> On Fri, Dec 18, 2015 at 2:52 PM, Jorge Timón <
> [email-masked]> wrote:
>
>> I agree that nHeight is the simplest option and is my preference.
>> Another option is to use the median time from the previous block (thus
>> you know whether or not the next block should start the miner confirmation
>> or not). In fact, if we're going to use bip9  for 95% miner upgrade
>> confirmation, it would be nice to always pick a difficulty retarget block
>> (ie block.nHeight % DifficultyAdjustmentInterval == 0).
>> Actually I would always have an initial height in bip9, for softforks too.
>> I would also use the sign bit as the "hardfork bit" that gets activated
>> for the next diff interval after 95% is reached and a hardfork becomes
>> active (that way even SPV nodes will notice when a softfork  or hardfork
>> happens and also be able to tell which one is it).
>> I should update bip99 with all this. And if the 2 mb bump is
>> uncontroversial, maybe I can add that to the timewarp fix and th recovery
>> of the other 2 bits in block.nVersion (given that bip102 doesn't seem to
>> follow bip99's recommendations and doesn't want to give 6 full months as
>> the pre activation grace period).
>> On Dec 18, 2015 8:17 PM, "Chun Wang via bitcoin-dev" <
>> [email-masked]> wrote:
>>
>>> In many BIPs we have seen, include the latest BIP202, it is the block
>>> time that determine the max block size. From from pool's point of
>>> view, it cannot issue a job with a fixed ntime due to the existence of
>>> ntime roll. It is hard to issue a job with the max block size unknown.
>>> For developers, it is also easier to implement if max block size is a
>>> function of block height instead of time. Block height is also much
>>> more simple and elegant than time.
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>>
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>