diff --git a/book/src/SUMMARY.md b/book/src/SUMMARY.md index d27b99f8ba..a655b58146 100644 --- a/book/src/SUMMARY.md +++ b/book/src/SUMMARY.md @@ -15,6 +15,7 @@ - [Synchronization](synchronization.md) - [Leader Rotation](leader-rotation.md) - [Fork Generation](fork-generation.md) + - [Data Plane Fanout](data-plane-fanout.md) - [Anatomy of a Fullnode](fullnode.md) - [TPU](tpu.md) @@ -34,7 +35,6 @@ - [Secure Vote Signing](vote-signer.md) - [Staking Rewards](staking-rewards.md) - [Fork Selection](fork-selection.md) - - [Data Plane Fanout](data-plane-fanout.md) - [Reliable Vote Transmission](reliable-vote-transmission.md) - [Bank Forks](bank-forks.md) - [Cluster Economics](ed_overview.md) diff --git a/book/src/data-plane-fanout.md b/book/src/data-plane-fanout.md index 5c6ac9c075..a66d0973d7 100644 --- a/book/src/data-plane-fanout.md +++ b/book/src/data-plane-fanout.md @@ -1,48 +1,11 @@ # Data Plane Fanout -This article describes the current single-layer broadcast and retransmit -mechanisms as well as proposed changes to add a multi-layer retransmit via an -Avalanche mechanism. - -## Current Design - -There's two basic parts to the current data plane's fanout design. - -#### Broadcast Service - -In this service, the leader distributes its data across the Layer-1 nodes. -Currently, Layer-1 nodes are all known "TVU peers" (`ClusterInfo::tvu_peers`). -The leader performs a round-robin broadcast where it sends each blob of data to -only one validator at a time. That way each Layer-1 node only receives partial -data from the leader and the Retransmit Stage in each Layer-1 node's TVU will -ensure all data is shared between its Layer-1 peers and a complete window is -received. - -#### Retransmit Stage - -The Retransmit stage *forwards* data from a Layer-1 node to all of _its_ -"retransmit peers" (list of TVU peers excluding the leader). So as nodes start -seeing complete windows they can send their votes back to the leader. -Validators know to only forward blobs that came from the leader by checking the -signatures against the current leader. - -**Cluster_info -> retransmit** = Used by TVUs to retransmit. Currently Layer-1 -sends this to all TVU peers, leader is automatically excluded. - -**Cluster_info -> broadcast** = Used by leader to broadcast to layer-1 nodes. - -**BroadcastService -> run** = Used by leader (TPU) to broadcast to all -validators. Currently all TVU Peers are considered layer-1. But blobs are -transmitted sort of round robin. See Cluster_info->Broadcast. - -## Proposed Design - -The new design organizes the network by stake and divides it into a collection +The the cluster organizes itself by stake and divides into a collection of nodes, called `neighborhoods`. The leader broadcasts its blobs to the layer-1 (neighborhood 0) nodes exactly like it does without this mechanism. The main difference being the number of nodes in layer-1 is capped via the configurable `DATA_PLANE_FANOUT`. If the fanout is smaller than the nodes in -the network then the mechanism will add layers below layer-1. Subsequent layers +the cluster then the mechanism will add layers below layer-1. Subsequent layers (beyond layer-1) follow the following constraints to determine layer-capacity. Each neighborhood has `NEIGHBORHOOD_SIZE` nodes and `fanout/2` neighborhoods are allowed per layer. @@ -54,21 +17,21 @@ peers). This means any node has to only send its data to its neighbors and each neighborhood in the layer below instead of every single TVU peer it has. The retransmit mechanism also supports a second, `grow`, mode of operation that squares the number of neighborhoods allowed per layer which dramatically -reduces the number of layers needed to support a large network but can also +reduces the number of layers needed to support a large cluster but can also have a negative impact on the network pressure each node in the lower layers has to deal with. A good way to think of the default mode (when `grow` is disabled) is to imagine it as `chain` of layers where the leader sends blobs to layer-1 and then layer-1 to layer-2 and so on, but instead of growing layer-3 to the square of number of nodes in layer-2, we keep the `layer capacities` constant, so all layers past layer-2 will have the same number of nodes until -the whole network is covered. When `grow` is enabled, this quickly turns into a +the whole cluster is covered. When `grow` is enabled, this quickly turns into a traditional fanout where layer-3 will have the square of the number of nodes in layer-2 and so on. -Below is an example of a two layer network. Note - this example doesn't +Below is an example of a two layer cluster. Note - this example doesn't describe the same `fanout/2` limit for lower layer neighborhoods. -Two layer network +Two layer cluster #### Neighborhoods @@ -87,7 +50,7 @@ src="img/data-plane-neighborhood.svg" class="center"/> #### A Weighted Selection Mechanism To support this mechanism, there needs to be a agreed upon way of dividing the -network amongst the nodes. To achieve this the `tvu_peers` are sorted by stake +cluster amongst the nodes. To achieve this the `tvu_peers` are sorted by stake and stored in a list. This list can then be indexed in different ways to figure out neighborhood boundaries and retransmit peers. For example, the leader will simply select the first `DATA_PLANE_FANOUT` nodes as its layer 1 nodes. These @@ -113,7 +76,7 @@ lower layer neighborhood. Each node can receive blobs froms its peer in the layer above as well as its neighbors. As long as the failure rate is less than the number of erasure -codes, blobs can be repaired without the network failing. +codes, blobs can be repaired without the cluster failing. #### Constraints @@ -130,5 +93,5 @@ capacities. When this mode is disabled (default) all layers after layer 1 have the same capacity to keep the network pressure on all nodes equal. Future work would involve moving these parameters to on chain configuration -since it might be beneficial tune these on the fly as the network sizes change. +since it might be beneficial tune these on the fly as the cluster sizes change.