Geth, which is the standalone client version (with a command line interface) of Go Ethereum (one of the three original implementations of the Ethereum protocol), has already been updated (v1.18.20) such that it supports the changes needed for the Constantinople upgrade (hard fork) planned by Ethereum core developers to take place in January 2019.
Back in October, Ari Paul, the Chief Investment Officer at cryptoasset investment firm BlockTower Capital, explained via a series of tweets the important distinction in cryptocurrency networks between the "cryptographic protocol", the "consensus rules", and the "client implementation":
3/ For all cryptocurrency networks, you have the cryptographic protocol - the way everyone has to interact with the network at the most basic level including submitting and verifying transactions. This is often only loosely documented, and these cryptographic computations— Ari Paul (@AriDavidPaul) October 18, 2018
4/ can be done in many different programming languages. Then you have the consensus rules (like Bitcoin's nakamoto consensus of having all nodes adopt the longest chain with valid rules as the valid chain.) Again, the specifics here are often only loosely documented.— Ari Paul (@AriDavidPaul) October 18, 2018
5/ Then you have the client implementation - the software users and miners/validators use to implement the cryptography and consensus rules. In Bitcoin there are several competing clients with meaningful usage, but Core has a strong majority and is treated as "canonical".— Ari Paul (@AriDavidPaul) October 18, 2018
He then pointed out that for Ethereum, the situation is "somewhat similar, but there's less of a clear canonical implementation," even though Geth is currently the most popular client. The other two main Ethereum clients are "Parity Ethereum" and Aleth.
Ethereum's Constantinople upgrade, one of the effects of which will be to reduce the mining reward per block from 3 ETH to 2 ETH, was originally set to take place in November. However, since the upgrade in October on the Ropsten testnet did not go so well, the core developers decided to postpone the activation of the Constantinople code changes on the mainnet to sometime in January 2019.
Last Friday, the 7th of December, during a core developers meeting, it was agreed that the activation point for Constantinople would be block 7,080,000 on the Ethereum blockchain, with the update going live once this block has been mined. According to Afri Schoedon, the release manager for Partity Ethereum, this upgrade is expected to take place between January 14th and 18th.
The Geth developers call their latest release on GitHub, v1.18.20, which occurred on Tuesday (December 11th), "a bit of a special release."
"On one hand it's the release that finally enables the Constantinople hard fork on mainnet at block 7080000 (and Rinkeby at block 3660663). It's also our last planned release of the 1.8 family (we'll still do hotfixes if need be), meaning that we'll start merging backwards incompatible changes onto master in preparation of Geth 1.9.0 (we don't have an ETA for it, but January the earliest)."
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