I am so confused. First came Bitcoin XT which tried to solve Bitcoin's block size cap (and apparently it failed) but now there is something new called Bitcoin Unlimited? I just read a few things about it and as far as I understood you can choose any block size right? What is this? Another alt coin or a fork?
There are two parameters that a node running BU can set. The first one is the "excessive block size".
Blocks larger than that size will not be accepted, at least not right away.
Which brings us to the other setting, "accept depth". Say you set that at 5, then if you see
the block that you marked previously as excessive in the longest chain at depth 5 from the tip,
then you will accept that block. So you will always end up on the longest chain.
In practice, the block settings will tend to be conservative and reflect the actual limit of the
nodes processing power. It is unlikely that there will be wild fluctuations of block values with
the honest nodes, as it is in their interest not to fall behind. It is futile to have a select group imposing
a block limit on the network, instead it will be found via communication and negotiation among different
user groups.
There will be enhancements in the client to assist users to arrive at suitable settings and
to distinguish between honest and bad actors. What will probably be next is signaling of
user settings to the network like pictured here (a BU node I'm currently running):
This announces to the network that my node will not accept blocks larger than 2.4MB unless 3 blocks
have been mined after it in the longest chain.
Hope this clears some of the confusion.
