Architecture

Hyperledger Fabric is a unique implementation of distributed ledger technology (DLT) that ensures data integrity and consistency while delivering accountability, transparency, and efficiencies unmatched by other blockchain or DLT technology.

Hyperledger Fabric implements a specific type of permissioned blockchain network on which members can track, exchange and interact with digitized assets using transactions that are governed by smart contracts - what we call chaincode - in a secure and robust manner while enabling participants in the network to interact in a manner that ensures that their transactions and data can be restricted to an identified subset of network participants - something we call a channel.

The blockchain network supports the ability for members to establish shared ledgers that contain the source of truth about those digitized assets, and recorded transactions, that is replicated in a secure manner only to the set of nodes participating in that channel.

The Hyperledger Fabric architecture is comprised of the following components: peer nodes, ordering nodes and the clients applications that are likely leveraging one of the language-specific Fabric SDKs. These components have identities derived from certificate authorities. Hyperledger Fabric also offers a certificate authority service, fabric-ca but, you may substitute that with your own.

All peer nodes maintain the ledger/state by committing transactions. In that role, the peer is called a committer. Some peers are also responsible for simulating transactions by executing chaincodes (smart contracts) and endorsing the result. In that role the peer is called an endorser. A peer may be an endorser for certain types of transactions and just a ledger maintainer (committer) for others.

The orderers consent on the order of transactions in a block to be committed to the ledger. In common blockchain architectures (including earlier versions of the Hyperledger Fabric) the roles played by the peer and orderer nodes were unified (cf. validating peer in Hyperledger Fabric v0.6). The orderers also play a fundamental role in the creation and management of channels.

Two or more participants may create and join a channel, and begin to interact. Among other things, the policies governing the channel membership and chaincode lifecycle are specified at the time of channel creation. Initially, the members in a channel agree on the terms of the chaincode that will govern the transactions. When consensus is reached on the proposal to deploy a given chaincode (as governed by the life cycle policy for the channel), it is committed to the ledger.

Once the chaincode is deployed to the peer nodes in the channel, end users with the right privileges can propose transactions on the channel by using one of the language-specific client SDKs to invoke functions on the deployed chaincode.

The proposed transactions are sent to endorsers that execute the chaincode (also called “simulated the transaction”). On successful execution, endorse the result using the peer’s identity and return the result to the client that initiated the proposal.

The client application ensures that the results from the endorsers are consistent and signed by the appropriate endorsers, according to the endorsement policy for that chaincode and, if so, the application then sends the transaction, comprised of the result and endorsements, to the ordering service.

Ordering nodes order the transactions - the result and endorsements received from the clients - into a block which is then sent to the peer nodes to be committed to the ledger. The peers then validate the transaction using the endorsement policy for the transaction’s chaincode and against the ledger for consistency of result.

Some key capabilities of Hyperledger Fabric include:

• Allows for complex query for applications that need ability to handle complex data structures.
• Implements a permissioned network, also known as a consortia network, where all members are known to each other.
• Incorporates a modular approach to various capabilities, enabling network designers to plug in their preferred implementations for various capabilities such as consensus (ordering), identity management, and encryption.
• Provides a flexible approach for specifying policies and pluggable mechanisms to enforce them.
• Ability to have multiple channels, isolated from one another, that allows for multi-lateral transactions amongst select peer nodes, thereby ensuring high degrees of privacy and confidentiality required by competing businesses and highly regulated industries on a common network.
• Network scalability and performance are achieved through separation of chaincode execution from transaction ordering, which limits the required levels of trust and verification across nodes for optimization.

For a deeper dive into the details, please visit this document.