poanetwork
/
hbbft
mirror of https://github.com/poanetwork/hbbft.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Improve formatting and add comments for broadcast docs.

This commit is contained in:
pawanjay176 2019-05-28 18:24:38 +05:30
parent 429642a680
commit 9281f406b0
1 changed files with 11 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
src/broadcast/mod.rs
View File

@ -45,13 +45,14 @@
//! optimisitic case, a node only needs _N - 2 f_ chunks to decode a value and every additional
//! `Echo` message over that is wasteful.
//! The modified algorithm introduces two new message types:
//! * `CanDecode(h)` - Indicates node has enough shards to recover message with merkle root `h`.
//! * `CanDecode(h)` - Indicates node has enough chunks to recover message with merkle root `h`.
//! * `EchoHash(h)` - Indicates node can send an `Echo(p[i])` message upon request.
//!
//! Let `g` be the `fault_estimate` i.e. the estimate of number of faulty nodes in the network
//! that we want to optimize for.
//! Note that the algorithm is still correct when more than `g` nodes are faulty.
//!
//! Define the `left` nodes for any node `i` as the `N - 2f + g` nodes to the left side of `i` after
//! Define the left nodes for any node `i` as the _N - 2 f + g_ nodes to the left side of `i` after
//! arranging all nodes in a circular list.
//!
//! With the new message types and definitions, the modified algorithm works as follows:
@ -67,7 +68,6 @@
//! * A node that has received _2 f + 1_ `Ready`s **and** _N - 2 f_ `Echo`s with root hash `h`
//! decodes and outputs the value, and then terminates.
//!
//!
//! Only the first valid `Value` from the proposer, and the first valid `Echo` and `EchoHash` message from every
//! validator, is handled as above. Invalid messages (where the proof isn't correct), `Values`
//! received from other nodes, and any further `Value`s, `Echo`s and `EchoHash`s are ignored, and the sender is
@ -97,7 +97,7 @@
//! A validator sends `Ready(h)` as soon as it knows that everyone will eventually be able to
//! decode the value with root hash `h`. Either of the two conditions in the third point above is
//! sufficient for that:
//! * If it has received _N - f_ `Echo`s or `EchoHash` with `h`, it knows that at least _N - 2 f_
//! * If it has received _N - f_ `Echo`s or `EchoHash`s with `h`, it knows that at least _N - 2 f_
//! **correct** validators have multicast an `Echo` or `EchoHash` with `h`, and therefore everyone will
//! eventually receive at least _N - 2 f_ valid ones. So it knows that everyone will be able to
//! decode, and can send `Ready(h)`.
@ -119,6 +119,13 @@
//! _2 f + 1_ `Ready`s **and** _N - 2 f_ `Echo`s with root hash `h`), we know that
//! everyone else will eventually satisfy it, too. So at that point, we can output and terminate.
//!
//! In the improved algorithm, with _f = 0_ and _g = 0_, we can get almost 66% savings in bandwith.
//! With `f` faulty nodes and _g = f_, we can get almost 33% reduction in bandwith.
//! With `f` faulty nodes and _g = 2 f_, it is essentially the original algorithm plus the `CanDecode`
//! messages. Note that the bandwith savings numbers are only upper bounds and can happen only in an ideal
//! network where every node receives every `CanDecode` message before sending `Ready`. The practical
//! savings in bandwith are much smaller but still significant.
//!
//!
//! ## Example
//!