Blockchain is an append-only, sequential, chained, data structure replicated over a peer-to-peer network, where transactions are stored and grouped to form new blocks. Participants to the networks (peers) achieve distributed consensus on the validity of the transaction and on the ordering. Blocks are data structure comprising transactions and header that includes a link to the previous block through a hash. More generally nowadays blockchain networks are part of a wider family named Distributed Ledger Network or DLT. There are several implementations of DTLs and some of them share the same consensus mechanism, the engine that allows such solutions to be temper-resistant. In this white paper we want to give a high level but complete overview of the various consensus mechanisms running within DLTs and of the advantages/disadvantages of each of them, without anyway the aim to provide a ranking.