# Validation

## What are nodes?&#x20;

Nodes are Umbrella’s “boots on the ground”. They are the physical computer hardware that runs our software. They serve several critical functions:&#x20;

1. They vote on and validate blocks of transactions They communicate with other nodes to agree on the state of the blockchain&#x20;
2. They store the history (state) of the blockchain as a universal source of truth&#x20;
3. They are the network's endpoints that enable users to access and interact with applications built on the network.&#x20;

Different classes of them perform different functions. The categories are not mutually exclusive. Some validator nodes are light nodes while others are archival nodes, but a few distinctions are common:&#x20;

1. Validator nodes participate in consensus to finalize transactions and agree on the state of the blockchain&#x20;
2. Archival nodes typically store the entire state of the blockchain&#x20;
3. Light nodes only store a small portion of the state of the blockchain

## HDAG - ABFT&#x20;

Transactions are validated by the node that provides the most efficient path to finalization. This would typically be the geographically closest supernode, but to prevent predictability and reduce attacks on leaders there is a randomization algorithm to prevent all transactions from flowing through a single or a few nodes. This incentivizes new nodes in untapped geographical locations because it would mean lower costs of operation which in turn pushes decentralization positively for the network.&#x20;

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