Thread by @NaitsabesMue

There is growing recent interest in DAG-based protocols for reliable broadcasting, e.g. @Aleph__Zero @aptos. There are striking similarities between these protocols and the @IOTA 2.0 solution, however, also fundamental differences.
Let me explain some of them. (1/n)

The DAG can be seen as a shared mempool. Before transactions can be added to the ledger they have to be broadcasted from the users to the block producing nodes. In traditional blockchains this is done via a shared memory-pool and only some leader is allowed to add blocks. (2/n)

Protocols like Hashgraph, Aleph, Nahrwal, are changing this. Let s take a closer look at the most recent Nahrwal.

Every validator is allowed to add blocks. However, they can not add blocks as they please. First, they send the blocks content to all others validators, (3/n)

These nodes sign that the content of the block is available to them. When a node receives a (super-)majority of signature it adds these signature to its block that then becomes part of the DAG.
On top of this there is another mechanism to increase the reliability: (4/n)

The protocol works in rounds.
Each node can issue only one block per round. For data-availability and also security aspects, every block of the current round has to refer a (super-)majority of the blocks of the previous round. In a nutshell, this is the DAG-based mempool. (5/n)

So let’s take a look at #IOTA 2.0 and its DAG, the so-called Tangle. Here, not only validators can add blocks, but every node can. Hence, we obtain real DAG-based mempool on the node and not only on the validator level. (6/n)

The "signing-off the blocks" in Narhwal, which happens on an additional all-to-all communication, is replaced by an “On-Tangle” signing that is called Witness Weight. (7/n)

Without the additional communication overhead, we obtain the result that blocks have been seen by a (super-)majority of the other nodes. (8/n)

The design that every node can issue blocks whenever it wants, so no-round-based sychronization, demands some sort of congestion control see the blog post for more details. blog.iota.org/explaining-the… (9/n)

This is important for #fairness properties, as we want that every honest node has a fair chance to participate in the protocol.
This kind of feature is not yet present in Nahrwal and even mentioned as an open problem. (10/n)

However the proposed garbage collection mechanism ensures a reasonable degree of fairness, at least in the non-malicious setting. (11/n)

Conclusion: the #IOTA Tangle is a distributed mempool on the node level and needs no additional communication between the nodes. It reduces the communciation overhead to a minimum and enables everybody to write on the ledger. (n/n)