Module polkadot_node_network_protocol::grid_topology

Grid topology support module Grid topology support implementation The basic operation of the 2D grid topology is that:

• A validator producing a message sends it to its row-neighbors and its column-neighbors
• A validator receiving a message originating from one of its row-neighbors sends it to its column-neighbors
• A validator receiving a message originating from one of its column-neighbors sends it to its row-neighbors

This grid approach defines 2 unique paths for every validator to reach every other validator in at most 2 hops.

However, we also supplement this with some degree of random propagation: every validator, upon seeing a message for the first time, propagates it to 8 random peers. This inserts some redundancy in case the grid topology isn’t working or is being attacked - an adversary doesn’t know which peers a validator will send to. This is combined with the property that the adversary doesn’t know which validators will elect to check a block.

Structs

• GridNeighbors
  Information about the grid neighbors for a particular node in the topology.
• RandomRouting
  A representation of routing based on sample
• SessionBoundGridTopologyStorage
  A storage for the current and maybe previous topology
• SessionGridTopologies
  A set of topologies indexed by session
• SessionGridTopology
  Topology representation for a session.
• SessionGridTopologyEntry
  An entry tracking a session grid topology and some cached local neighbors.
• TopologyPeerInfo
  Information about a peer in the gossip topology for a session.

Enums

• RequiredRouting
  Routing mode

Constants

• DEFAULT_RANDOM_CIRCULATION
  The number of peers to randomly propagate messages to.
• DEFAULT_RANDOM_SAMPLE_RATE
  The sample rate for randomly propagating messages. This reduces the left tail of the binomial distribution but also introduces a bias towards peers who we sample before others (i.e. those who get a block before others).