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Subnet types

Concept

Overview​

A subnet on ICP is a collection of interacting replicas that run their own, separate instance of the ICP consensus mechanism, effectively creating their own blockchain on which a set of canisters can run. Each subnet can communicate with other subnets and is controlled by a root subnet. The root subnet uses chain-key cryptography to delegate its authority to the various subnets.

You can learn more about subnets and how they work here.

There are three primary types of subnets: system, application, and the European subnet.

Application subnets​

Application subnets are the most common type of subnet on ICP. Almost all canisters run on an application subnet. Application subnets can be individually configured to have different features enabled or disabled, for example the Bitcoin integration subnet.

System subnets​

System subnets are reserved for running canisters that provide a system functionality to ICP, such as the NNS canisters. System subnets have special configurations, such as not charging cycles to any of the canisters running on the subnet since system canisters need to be available at all times. System subnets also have a more generous per-call instruction limit and a more generous Wasm module size limit.

Fiduciary subnets​

A fiduciary subnet is a subnet larger than 13 nodes. Canisters running on this larger subnet will pay more cycles compared to canisters running on 13 node subnets, but in return they will have a higher level of security due to the bigger subnet size. The cycle costs scale linearly to the number of nodes. The fiduciary subnet type was created to enable safer deployment of DeFi applications which need even stronger guarantees than the ones that a 13-node subnet can provide.

You can deploy to a fiduciary subnet using the command dfx ledger create-canister --subnet-type fiduciary.

The European subnet​

The 'European' type subnet indicates that the subnet is comprised of only node machines located in the European geographic region. This type of subnet allows for developers and enterprises to build applications that require a GDPR-aligned infrastructure and leverage blockchain decentralization with regional data sovereignty needs.

The European subnet enables applications to be GDPR-compliant, but developers and enterprises must take further measures to ensure that their applications meet all GDPR requirements.

Using a European subnet​

To find a list of all subnet types using dfx, the dfx ledger command can be used with the show-subnet-types argument:

dfx ledger --network ic show-subnet-types

This should return the output:

["european", "fiduciary"]

Creating developer identity for the European subnet​

This is an optional step; it is not required to create a new separate identity in order to use the European subnet.

To create a new identity, use the dfx identity new command:

dfx identity new ic-european

Then, to use this identity, run the dfx identity use command:

dfx identity use ic-european

Using a developer identity on the European subnet​

To use this identity as a controller of a canister, get the identity's principal with the command:

dfx identity get-principal

Save this principal ID to be used as the CONTROLLER value in a future step.

You can check the current balance for that principal by running the command:

dfx ledger --network=ic balance

To top up your principal's balance, you can send cycles to the principal using the NNS dapp, or learn how to convert ICP tokens into cycles.

Creating a cycles wallet​

If you'd like to create a new wallet on the European subnet, run the following dfx ledger command:

dfx ledger --network ic create-canister --amount 0.5 --subnet-type european CONTROLLER

Please note that the cycles wallet will be removed from dfx in a future release.

It is recommended to use the cycles ledger instead, which does not require any specific flags for different subnet types.

Replace CONTROLLER with the principal ID that you took note of earlier after running the dfx identity get-principal command.

Adjust the --amount 0.5 to the number of ICP tokens that you want to send the new canister. More information can be found in the documentation.

This command will return a canister ID. Using that canister ID, you can deploy the wallet canister code to the new canister with the command:

dfx identity --network ic deploy-wallet <WALLET_CANISTER_ID>

For example:

❯ dfx identity --network ic deploy-wallet nanx4-baaaa-aaaap-qb4sq-cai
Creating a wallet canister on the ic network.
The wallet canister on the "ic" network for user "ic-european" is "nanx4-baaaa-aaaap-qb4sq-cai"

Then, whenever you create new canisters using that WALLET_CANISTER_ID, the new canisters will be created on the same European subnet.

You can check the wallet balance of the wallet canister with the command:

dfx wallet --network=ic balance

The current wallet settings are stored in your local file system in the file $HOME/.config/dfx/identity/<identity_name>/wallets.json. The file's contents will resemble the following:

{
    "identities": {
        "ic-european": {
            "ic": "nanx4-baaaa-aaaap-qb4sq-cai"
        }
    }
}

Important notes about deploying to the European subnet​

When deploying a project to the mainnet using dfx:

  • If your canisters have already been created, dfx will continue to deploy the canisters on the same subnet that they are already located on.

  • If your canisters do not exist yet, when they are created dfx will create them on the same subnet as your wallet canister. It is recommended to consistently use the same wallet on the European subnet.

  • If your canisters do not exist yet, you can specify the wallet canister that should be used to create them by using the dfx deploy --wallet <WALLET_CANISTER_ID>. This will create the new canisters on the same subnet where the specified <WALLET_CANISTER_ID> is located.