The Ethereum network is set for a planned upgrade at block number 13,773,000, anticipated to happen on Wednesday, December 8, 2021. Please note that the exact timing may change due to fluctuations in block times and different time zones. Make sure to upgrade your node by Sunday, December 5, 2021, to accommodate potential variations in block times.
What is Arrow Glacier?
Similar to Muir Glacier, the Arrow Glacier network upgrade modifies the parameters of the Ice Age/Difficulty Bomb, delaying it by several months. This approach has been adopted in previous upgrades, including Byzantium, Constantinople, and London, without introducing any additional changes.
The difficulty bomb impacts only Proof of Work networks, and therefore, it is relevant exclusively to the Ethereum mainnet and the Ropsten test network. As Ethereum progresses towards a Proof of Stake model, the decision has been made to delay the bomb on the mainnet for the time being while aiming to execute the Proof of Stake transition on Ropsten before the bomb is triggered there.
For further details on Arrow Glacier and the background of the difficulty bomb, please check out the Ethereum Cat Herders’ explainer blog post.
Client Versions
Node operators must upgrade to one of the listed client versions below to remain compatible with the Arrow Glacier upgrade:
Note: OpenEthereum, which was announced as deprecated earlier this year, has provided support for Arrow Glacier under version number 3.3.0-rc.14, available for download here.
However, we recommend adhering to prior deprecation notices and opting for alternative client software. If you decide to use OE for the Arrow Glacier upgrade, please proceed with caution and thoroughly review the changes to the codebase before deploying it in production.
Upgrade Specification and EIPs
You can find the complete specification for the upgrade in the execution-specs repository here.
One EIP is included in this upgrade: EIP-4345: Difficulty Bomb Delay to June 2022.
As an Ethereum user or ether holder, is there anything I need to do?
If you are using an exchange, web wallet service, mobile wallet service, or hardware wallet, you do not need to take any action unless instructed otherwise by your exchange or wallet service.
As a node operator or miner, what do I need to do?
Ensure you download the latest version of your Ethereum client from the table provided above.
What happens if I am a miner or node operator and I do not participate in the upgrade?
If you run an Ethereum client that isn’t updated to the latest version (as listed above), your client will sync to the pre-fork blockchain when the upgrade goes live. You will find yourself on an incompatible chain continuing to follow the old rules, thus unable to send Ether or engage with the post-upgrade Ethereum network.
What is a network upgrade in Ethereum-land?
A network upgrade denotes a modification to the fundamental Ethereum protocol, establishing new rules aimed at enhancing the system. The decentralized characteristic of blockchain technology complicates network upgrades, requiring collaboration and communication with the community and developers of various Ethereum clients to ensure a seamless transition.
What occurs during a network upgrade?
Following a consensus within the community on the changes that will be incorporated in the upgrade, modifications to the protocol are implemented into the different Ethereum clients like geth, Erigon, Besu, and Nethermind. These protocol modifications are activated at a designated block number. Nodes that have not updated to the new rules will be left on the old chain adhering to the previous regulations.
Why “Arrow Glacier”?
Previously, we utilized Devcon names for network upgrades, but when we encountered an upgrade aimed solely at delaying the bomb, we shifted our naming convention. To emphasize the nature of this upgrade (pushing back the “Ice Age”), we adopted a glacier-themed name, as seen with Muir Glacier.
This upgrade continues in the same spirit. With the transition to Proof of Stake approaching, a retreating glacier was chosen, thus named Arrow Glacier 
!
Thank You!
A heartfelt thank you to the Ethereum community and all developers across different clients and platforms for their input, insights, and contributions. This may well be the final network upgrade on Ethereum prior to the shift to Proof of Stake. Let’s make it count!
Special thanks to Harshil Gudka for the cover image.
This field is rapidly changing and inherently complex. If you opt to follow the guidance in this post and continue your participation, ensure you understand the implications. Keep in mind that risks exist, including unforeseen bugs. By choosing to act on these recommendations, you alone accept the resultant risks. This post and its suggestions do not constitute a sale or specific warranties regarding the Ethereum network or related clients mentioned herein.
Dutch
English
French
German
Greek
Italian
Portuguese
Russian
Spanish