Merge pull request #111 from lazyledger/adlerjohn-node_types

Define node types and configuration parameters

README.md

@@ -13,3 +13,4 @@ LazyLedger Specifications
 - [Block Proposer](specs/block_proposer.md)
 - [Networking](specs/networking.md)
 - [Light client](specs/light_client.md)
+- [Node types](specs/node_types.md)

rationale/distributing_rewards.md

@@ -17,7 +17,7 @@ This forms the primary motivation of the scheme discussed here: a mechanism for
 
 ## Distribution Scheme
 
-The scheme presented here is an incarnation of Cosmos' [F1 fee distribution scheme](https://github.com/cosmos/cosmos-sdk/blob/master/docs/spec/_proposals/f1-fee-distribution/f1_fee_distr.pdf). F1 has the nice property of being approximation-free and, with proper implementation details, can be highly efficient with state usage and completely iteration-free in all cases.
+The scheme presented here is an incarnation of Cosmos' [F1 fee distribution scheme](https://github.com/cosmos/cosmos-sdk/blob/master/docs/spec/fee_distribution/f1_fee_distr.pdf). F1 has the nice property of being approximation-free and, with proper implementation details, can be highly efficient with state usage and completely iteration-free in all cases.
 
 Naively, when considering a single block, the reward that should be given to a delegator with stake $x$, who's delegating to a validator with total voting power $n$, whose reward in that block is $T$, is:
 

specs/node_types.md

@@ -0,0 +1,105 @@
+Node Types
+===
+
+- [Node Parameters](#node-parameters)
+    - [Block Headers](#block-headers)
+        - [Compact Block Headers](#compact-block-headers)
+        - [Extended Block Headers](#extended-block-headers)
+    - [Block Bodies](#block-bodies)
+        - [No Bodies](#no-bodies)
+        - [Sampled Bodies](#sampled-bodies)
+        - [Partial Bodies](#partial-bodies)
+        - [Full Bodies](#full-bodies)
+    - [Transactions](#transactions)
+        - [No Transactions](#no-transactions)
+        - [Full Transactions](#full-transactions)
+- [Node Types](#node-types)
+
+## Node Parameters
+
+Nodes that run the [LazyLedger protocol](./consensus.md) have a number of parameters that can be tweaked with regards to which parts of the data is downloaded, validated, and/or stored. All nodes process the `header` and `lastCommit` fields of each [block](./data_structures.md#block), but can handle the `availableDataHeader` and `availableData` fields differently.
+
+We define security assumptions as assumptions under which a given node is guaranteed accountable consensus safety (i.e. that finalized blocks will remain in the prefix of all future sequences of blocks accepted by the node, unless a supermajority (> 2/3) of validator voting power performs an attributable—and thus [penalizable](./consensus.md#blockavailabledataevidencedata)—malicious action) and state safety (i.e. that an invalid state transition will not be included in the chain accepted by the node).
+
+### Block Headers
+
+#### Compact Block Headers
+
+Nodes that only process compact block headers will download and validate the [block header](./data_structures.md#header) _without_ downloading or validating the `availableDataHeader` [block](./data_structures.md#block) field that is committed to in the block header. These nodes cannot perform Data Availability Sampling on [block bodies](#block-bodies).
+
+Secure under an honest supermajority of validator voting power and a weak subjectivity assumption.
+
+#### Extended Block Headers
+
+Nodes that process extended block headers will download and validate both the [compact block header](#compact-block-headers) and the 
+[`availabledataheader`](./data_structures.md##availabledataheader) [block](./data_structures.md#block) field. These nodes can perform Data Availability Sampling on [block bodies](#block-bodies), and their security assumptions depend on how block bodies are handled.
+
+### Block Bodies
+
+Block bodies (the `availableData` [block](./data_structures.md#block) field) can be downloaded and optionally stored and/or served. Storing and serving block body data has no effect on node security assumptions.
+
+#### No Bodies
+
+Nodes that only process [compact block headers](#compact-block-headers) have no need for block bodies and simply do not process block bodies.
+
+Secure under an honest supermajority majority of validator voting power and a weak subjectivity assumption.
+
+#### Sampled Bodies
+
+These nodes perform Data Availability Sampling on block bodies.
+
+Secure under an honest minority of nodes and a weak subjectivity assumption.
+
+#### Partial Bodies
+
+These nodes fully download and validate [the erasure coding](./data_structures.md#2d-reed-solomon-encoding-scheme) of a random subset of block bodies (configurable locally). Since the erasure coding of each block is stateless, nodes that perform validation of partial bodies contribute to the overall security of the network by being able to produce [fraud proofs of invalid erasure coding](./data_structures.md#invalid-erasure-coding).
+
+Secure under an honest minority of nodes and a weak subjectivity assumption.
+
+#### Full Bodies
+
+These nodes fully download and validate [the erasure coding](./data_structures.md#2d-reed-solomon-encoding-scheme) of all block bodies.
+
+If [transactions are not processed](#no-transactions), secure under an honest minority of nodes and a weak subjectivity assumption. If [transactions are processed](#full-transactions), secure under a weak subjectivity assumption.
+
+### Transactions
+
+#### No Transactions
+
+These nodes process do not process requests [with a reserved namespace ID](./data_structures.md#arranging-available-data-into-shares) and thus to not know the chain state without relying on a third party.
+
+At most secure under an honest minority of nodes and a weak subjectivity assumption.
+
+#### Full Transactions
+
+Nodes that wish to produce new blocks must know the [chain state](./data_structures.md#state). Processing all block bodies is actually not needed to know the LazyLedger state, as [transactions that pay for message inclusion commit to messages](./../rationale/message_block_layout.md). These nodes process all requests [with a reserved namespace ID](./data_structures.md#arranging-available-data-into-shares) from block bodies and perform Data Availability Sampling for the remaining (message) data.
+
+At most secure under a weak subjectivity assumption.
+
+## Node Types
+
+For convenience, we will define several common parameter configurations:
+1. [Full nodes](https://en.bitcoin.it/wiki/Full_node) provide the strongest security guarantees. Block bodies do not need to be stored.
+    - Block headers: [Extended Block Headers](#extended-block-headers)
+    - Block bodies: [Full Bodies](#full-bodies)
+    - Transactions: [Full Transactions](#full-transactions)
+1. Partial nodes are capable of producing fraud proofs of invalid transactions and contribute to validating the erasure coding of random blocks.
+    - Block headers: [Extended Block Headers](#extended-block-headers)
+    - Block bodies: [Partial Bodies](#partial-bodies)
+    - Transactions: [Full Transactions](#full-transactions)
+1. Light nodes perform Data Availability Sampling (DAS) and are secure under an honest minority.
+    - Block headers: [Extended Block Headers](#extended-block-headers)
+    - Block bodies: [Sampled Bodies](#sampled-bodies)
+    - Transactions: [No Transactions](#no-transactions)
+1. Superlight nodes do not perform DAS and are secure under an honest majority.
+    - Block headers: [Compact Block Headers](#compact-block-headers)
+    - Block bodies: [No Bodies](#no-bodies)
+    - Transactions: [No Transactions](#no-transactions)
+1. Light validator nodes can produce new blocks with strong security guarantees and light resource requirements.
+    - Block headers: [Extended Block Headers](#extended-block-headers)
+    - Block bodies: [Sampled Bodies](#sampled-bodies)
+    - Transactions: [Full Transactions](#full-transactions)
+1. Storage nodes provide the same security guarantees as full nodes. Block bodies (in [erasure-coded form](./data_structures.md#2d-reed-solomon-encoding-scheme)) are stored and served to the network.
+    - Block headers: [Extended Block Headers](#extended-block-headers)
+    - Block bodies: [Full Bodies](#full-bodies)
+    - Transactions: [Full Transactions](#full-transactions)