Why Portal Needs To Be Its Own Network

Piper Merriam,projectEthereump2pstorage

We commonly get asked why we don't use one of the various general purpose distributed storage networks (like Filecoin/IPFS or Bittorrent). Baked into this question is an assumption that general purpose storage networks would solve the problem that Portal is aiming to solve.

Problem 1: Content Addressing

One issue that arises with general purpose storage networks is around content addressing. We are not able to use just any arbitrary content addressing scheme. Portal Network requires that all data be verifiable as canonical chain data. The way Ethereum data is verified is baked into the Ethereum protocol. A simple example of this is verification of a block header. This involves taking the keccak hash of the RLP encoded block header. A more complex example of this is anchoring state data using a Hexary Merkle Patricia Trie proof to the Header.state_root.

Each piece of Ethereum's data has some form of anchoring proof which guarantees it is canonical chain data. These anchoring proofs ensure that extra data cannot be added to the Portal Network, and thus, ensure that the network cannot be abused or spammed with superfluous data.

In order for a general purpose storage network to work for Ethereum's data, it would require its content addressing scheme to support every method of cryptographic anchoring used for Ethereum data. For most networks this isn't possible.

Problem 2: Competition for Storage

Another property of storage networks is whether they are incentivised. Networks like Filecoin require payment for durable storage. Networks like bittorrent's DHT do not have any incentives and simply house the most recent and most popular data.

In the Portal Network model, we aim to provide free access to the data, and thus, networks that require payment are not suitable for our use case. However, using a general purpose storage network that lacks incentives would mean that all of the Ethereum data would be competing for storage space with all of the other data stored in the network. And at the level of the clients for the protocol, this would mean that individual users would likely be storing some mixture of Ethereum data and other data.

In order for Portal Network to be useful, it must provide reliable access to the data its users want. Since the Ethereum data is all canonically anchored, that means at any given time there is a finite quantity of data that needs to be stored, and thus there is a finite amount of capacity that must be sourced from the network to store it.

In a general purpose network, increased usage by other applications storing other types of non-Ethereum data would result in more contention and possibly the eviction of Ethereum specific data. Thus, using a general purpose storage network would reduce our ability to provide strong guarantees that Ethereum's data can be reliably retrieved from the network.

Problem 3: Resource Constrained Devices

The Portal Network aims to be acccessible for resource constrained devices. This means that participation in our protocol must be sufficiently simple that low resource devices are able to participate and contribute to the protocol in a meaningful way. In the general case, we lose these controls by using a general purpose protocol.

Protocols like IPFS/Filecoin are built on top of LibP2P, which is based on long lived connections between nodes. This ends up discriminating against nodes that are not able to reliably stay online and maintain these long lived connections.

Even in the case where a general purpose storage network was friendly towards a low resource device, it is unclear how such a network would allow that device to contribute back to the Portal Network in a meaningful way. Such a node's contribution to the network would naturally be split between all of the data stored on the network. We want our users to know that their contribution is going directly towards supporting Ethereum's data.

Problem 4: Freedom of movement

The current designs for Portal Network range from quite simple to mildly complex.

The History network is quite simple. It works out to a key/value store with reasonably simple validation logic for ensuring data is canonical.

The Beacon network is more complex. It implements more complex validation logic and more complex data types from the Beacon chain light client protocol. Additionally, it requires some out-of-band information to be able to properly anchor to the canonical chain.

The State network is also quite complex. It implements complex data types and validation logic for handling and distributing state data. It implements a model where the payloads for data being Gossip'd are different from the payloads for when data is being retrieved. The network requires complex logic for how data is gossip'd into the network.

Each of these networks required implementing complex validation logic in the clients that would not be feasible in most general purpose storage networks. Going forward, we only expect these requirements to increase. As our network grows, so will our requirements for client behavior. Because of this, we need direct control over the low levels of the protocol and the clients to that protocol, making general purpose networks not suitable for our use case.


Hopefully this sheds some light on why the Portal Network has chosen to build its own storage network. General purpose storage networks are an exciting and new space. Projects like IPLD (opens in a new tab) are promising in solving some of these problems. There is so much room for innovation in this area.

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