AllConcur: Leaderless Concurrent Atomic Broadcast

arxiv.org

25 pointssteeve6 comments

Paper's network assumptions:

"We assume a model of reliable communication—messages cannot be lost (only delayed). This is a reasonable assumption if we consider a reliable protocol, such as TCP."

Paxos network assumptions:

"Messages can take arbitrarily long to be delivered, can be duplicated, and can be lost, but they are not corrupted." - http://research.microsoft.com/en-us/um/people/lamport/pubs/p...

Sounds like Paxos could be implemented on top of UDP whereas AllConcur requires TCP?

Duplicated and lost messages will happen in practice - TCP attempts to build reliable communication on an unreliable medium. Not clear from the paper if this matters.

I think the larger misunderstanding of the paper is the requirement that paxos have a leader - lamport's synod algorithm does not require a leader, the leader is an optimization!

Without a long-lived leader, the performance would be so bad that I doubt there is a single production implementation that doesn't use that optimization.

Not really fair to compare to Paxos if the network assumption is different.

How does this differ from RAFT?

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