Ethereum Networks

There exist a variety of Ethereum-based networks that largely conform to the formal specification defined in the Ethereum Yellow Paper, but which may or may not interoperate with each other.

Among these Ethereum-based networks are Ethereum, Ethereum Classic, Ella, Expanse, Ubiq, Musicoin, and many others. While mostly compatible at the protocol level, these networks often have features or attributes that require maintainers of Ethereum client software to make small changes in order to support each network. Because of this, not every version of Ethereum client software runs every Ethereum-based blockchain.

Currently, there are six main implementations of the Ethereum protocol, written in six different languages:

• Parity, written in Rust

• Geth, written in Go

• cpp-ethereum, written in C++

• pyethereum, written in Python

• Mantis, written in Scala

• Harmony, written in Java

In this section, we will look at the two most common clients, Parity and Geth. We’ll show how to set up a node using each client, and explore some of their command-line options and application programming interfaces (APIs).

Should I Run a Full Node?

The health, resilience, and censorship resistance of blockchains depend on them having many independently operated and geographically dispersed full nodes. Each full node can help other new nodes obtain the block data to bootstrap their operation, as well as offering the operator an authoritative and independent verification of all transactions and contracts.

However, running a full node will incur a cost in hardware resources and bandwidth. A full node must download 80–300 GB of data (as of January 2020, depending on the client configuration) and store it on a local hard drive. This data burden increases quite rapidly every day as new transactions and blocks are added. We discuss this topic in greater detail in Hardware Requirements for a Full Node.

A full node running on a live mainnet network is not necessary for Ethereum development. You can do almost everything you need to do with a testnet node (which connects you to one of the smaller public test blockchains), with a local private blockchain like Ganache, or with a cloud-based Ethereum client offered by a service provider like Infura.

You also have the option of running a remote client, which does not store a local copy of the blockchain or validate blocks and transactions. These clients offer the functionality of a wallet and can create and broadcast transactions. Remote clients can be used to connect to existing networks, such as your own full node, a public blockchain, a public or permissioned (proof-of-authority) testnet, or a private local blockchain. In practice, you will likely use a remote client such as MetaMask, Emerald Wallet, MyEtherWallet, or MyCrypto as a convenient way to switch between all of the different node options.

The terms “remote client” and “wallet” are used interchangeably, though there are some differences. Usually, a remote client offers an API (such as the web3.js API) in addition to the transaction functionality of a wallet.

Do not confuse the concept of a remote wallet in Ethereum with that of a light client (which is analogous to a Simplified Payment Verification client in Bitcoin). Light clients validate block headers and use Merkle proofs to validate the inclusion of transactions in the blockchain and determine their effects, giving them a similar level of security to a full node. Conversely, Ethereum remote clients do not validate block headers or transactions. They entirely trust a full client to give them access to the blockchain, and hence lose significant security and anonymity guarantees. You can mitigate these problems by using a full client you run yourself.

Full Node Advantages and Disadvantages

Choosing to run a full node helps with the operation of the networks you connect it to, but also incurs some mild to moderate costs for you. Let’s look at some of the advantages and disadvantages.

Advantages:

• Supports the resilience and censorship resistance of Ethereum-based networks

• Authoritatively validates all transactions

• Can interact with any contract on the public blockchain without an intermediary

• Can directly deploy contracts into the public blockchain without an intermediary

• Can query (read-only) the blockchain status (accounts, contracts, etc.) offline

• Can query the blockchain without letting a third party know the information you’re reading

Disadvantages:

• Requires significant and growing hardware and bandwidth resources

• May require several days to fully sync when first started

• Must be maintained, upgraded, and kept online to remain synced

Public Testnet Advantages and Disadvantages

Whether or not you choose to run a full node, you will probably want to run a public testnet node. Let’s look at some of the advantages and disadvantages of using a public testnet.

Advantages:

• A testnet node needs to sync and store much less data—about 45 GB depending on the network.

• A testnet node can sync fully in a few hours.

• Deploying contracts or making transactions requires test ether, which has no value and can be acquired for free from several “faucets.”

• Testnets are public blockchains with many other users and contracts, running “live.”

Disadvantages:

• You can’t use “real” money on a testnet; it runs on test ether. Consequently, you can’t test security against real adversaries, as there is nothing at stake.

• There are some aspects of a public blockchain that you cannot test realistically on a testnet. For example, transaction fees, although necessary to send transactions, are not a consideration on a testnet, since gas is free. Further, the testnets do not experience network congestion like the public mainnet sometimes does.

Local Blockchain Simulation Advantages and Disadvantages

For many testing purposes, the best option is to launch a single-instance private blockchain. Ganache (formerly named testrpc) is one of the most popular local blockchain simulations that you can interact with, without any other participants. It shares many of the advantages and disadvantages of the public testnet, but also has some differences.

Advantages:

• No syncing and almost no data on disk; you mine the first block yourself

• No need to obtain test ether; Ganache is initialized with accounts that already hold ether for testing

• No other users, just you

• No other contracts, just the ones you deploy after you launch it unless you use the option of forking off an existing Ethereum node

Disadvantages:

• Having no other users means that it doesn’t behave the same as a public blockchain. There’s no competition for transaction space or sequencing of transactions.

• No miners other than you means that mining is more predictable; therefore, you can’t test some scenarios that occur on a public blockchain.

• If you are forking off an existing Ethereum node, it will need to be an archival node for you to interact with state from blocks that may have been pruned otherwise