Where we are on the block size question?
The block size debate has been going on for months now. It has been protracted, unpleasant and at points seemingly impossible to solve, but the broad strokes are clear: the bitcoin network has finite capacity and the increasing volume of transactions means it has just about reached its limits. Without an upgrade to allow for larger blocks, new transactions will be badly delayed, or else higher fees will be required to ensure a transaction is included in the next block.
There have been endless proposals to solve the problem, but so far none have attracted the support required to implement them. Back in the summer it looked like there was consensus around 8 MB blocks (up from the present 1 MB) with Gavin Andresenâs Bitcoin XT. Block size would then double every two years, to a maximum of 32 GB. Unfortunately, there was fierce opposition to this so-called unilateral attempt to fix the problem, with the effect that the big mining pools held back, hoping for a solution that would keep everyone happy, including the core developers who had not had any say in it. More recently, Bitcoin Classic has attracted some supportâââat the time of writing, more than a fifth of the network is running it, some 1,350 nodes. However, these nodes represent a minority of overall hashrate, and there is no chance of Classic being activated as things stand.
More promisingly, a recent meeting between key bitcoin stakeholders in Hong Kong seems to have thrashed out a deal. Come April, a new release will enable support for Segregated Witness or SegWitâââessentially a clever sleight-of-hand that will allow more transactions to be squeezed into 1 MB blocks without the disruption of a hard fork. In July, a further release will raise total block capacity to 4 MB, with 2 MB for ânon-witnessâ dataâââa substantial increase overall. Assuming enough miners get behind this, the hard fork will activate in July 2017.
Whilst consensus of any kind represents progress, critics have claimed it is âtoo little, too lateâ. The need for greater block size is now: transactions are already being delayed, forcing senders to pay higher fees if their transfers are urgent. Bitcoin businesses are hamstrung by this problem, which reduces the quality of the service they are able to offer and undermines two of the key benefits of bitcoin in the first placeâââfast, low-cost transactions. At times of peak use, transactions that might have been accepted in a few minutes a year ago can now take hours.
There is also the question of sustainability. The changes proposed multiply the capacity of the bitcoin network by perhaps 3 or 4 times, but itâs entirely possible we will find ourselves back at deadlock in another couple of years if adoption continues to increase at the present rate, or faster.
Hopefully, by then we will have learned some important lessons about reaching consensus. It is critically important that bitcoin retains the advantages that have attracted so many businesses, users and investors if it is to grow and thrive as a means of global payment.












