Teku networking

Network endpoints

Localhost net interface:

• JSON API
• Metrics
• Validator

External net interface:

• Libp2p: TCP :9000 : Spec, JVM implementation (Kotlin)
• Discovery: UDP :9000 : Spec, JVM implementation (Java)

Libp2p

Main Libp2p essenses

• Connection: secured, multiplexed (Connection.kt, Spec)
• Stream: Raw binary duplex channels atop of Connection (Stream.kt)
• Protocol binding: client protocol handler (ProtocolBinding.kt)

Basic Libp2p Pipeline Sample

TCP Socket
   ^
Multistream: /noise
   ^ 
Noise (Negotiator then Cipher)
   ^   (secured connection)
Multistream: /mplex/6.7.0 or /yamux (not supported yet)
   ^ 
Mplex stream multiplexer
   ^  ^  ^  ^  ^   (Streams)
Multistream: /ipfs/id/1.0.0, 
             /ipfs/ping/1.0.0, 
             /meshsub/1.1.0,  (Gossip 1.1)
             /eth2/beacon_chain/req/<method>/<ver> (Eth2 RPC)
   ^  ^  ^  ^  ^ 
Negotiated Protocol Handler

Implementation overview

https://github.com/libp2p/jvm-libp2p

Architecture

• built with Netty
• expose a lot of Netty API: Channel, ChannelPipeline, ChannelHandler, ByteBuf
• Libp2p Connection, Stream are essntially Netty Channels
• All libp2p components like security handlers, multiplexers, protocol selectros, protocl bindings are essentially Netty ChannelHandlers

Components

Minimal Libp2p spec subset required for implementing Eth2 node

• Transport:
  – TCP
  – WebSocket (disabled in Teku now)
• Security:
  – Plain (for tesing only)
  – Secio (disabled in Teku now)
  – Noise-XX-25519-ChaChaPoly-SHA256 (Spec)
• Stream multiplexing: only mplex (Spec)
• Protocols bindings:
  –Gossip 1.1: Generic pubsub spec, Gossip (v1.0 + v1.1) spec
  –Ping
  –Identity
• No Connection manager
• No Libp2p discovery (Just MDns which is kind of standalone service now)

Maturity

The JVM library can still be assumed as beta-version:

• The first version was implemented in just 2.5 months with minimal testing and without any compatibility tests: aka Alpha version
• While adoping it in Teku many compatibility and reliablity issues were fixed, a number of unit tests were added (though still far from acceptable coverage): aka Beta version

Teku integration

Overview

networking:p2p module: Eth2 agnostic Libp2p binding. Contains generic classes for RPC, subscriptions
networking:eth module: Extends p2p classes for Eth2 specific functions

Configuration of Libp2p host: LibP2PNetwork.java

• Eth2 RPC methods (Spec, BeaconChainMethods.java): raw Libp2p Streams
  – /eth2/beacon_chain/req/status
  – /eth2/beacon_chain/req/ping
  – /eth2/beacon_chain/req/metadata
  – /eth2/beacon_chain/req/beacon_blocks_by_root
  – /eth2/beacon_chain/req/beacon_blocks_by_range
• Eth2 pubsub topics (Spec, tech.pegasys.teku.networking.eth2.gossip package): Gossip 1.1 topics:
  – beacon_block: new blocks broadcasting (BlockTopicHandler.java)
  – beacon_attestation_{subnet_id}: unaggregated attestations broadcasting to the subnet subnet_id
  – beacon_aggregate_and_proof aggregated attestations broadcasting to be included in future blocks
  – voluntary_exit, proposer_slashing, attester_slashing

Eth2 RPC

• /eth2/beacon_chain/req/* protocol ID
• A new Stream per each request/response (RpcHandler.java)
• [snappy[ssz[request|response]]] (Snappy framing variant)
• Response may contain several chunks. Each chunk may be fragmented to several snappy frames. (IMO good place for hacking)
  Response sample respCode len1 [chunk-1-1] len2 [chunk-2-1][chunk-2-2]

Eth2 pubsub

• beacon_attestation_{subnet_id} topics subscriptions are volatile. A validator node needs to change subnet subscriptions on per epoch basis.
• [snappy[ssz[message]]] (Snappy block variant)
• Specific Gossip parameters (LibP2PNetwork.createGossip()) for Eth2 network (Gossip 1.1 parameters are yet to be defined)

Discovery

Spec: https://github.com/ethereum/devp2p/blob/master/discv5/discv5.md
JVM Implementation: https://github.com/PegaSysEng/discovery

• Netty UDP
• RLP encoding
• Contains ENR field with peer attestation subnet subscriptions to better handle frequently changed beacon_attestation_{subnet_id} Gossip subscriptions

Maturity may also be considered as Beta

Blst library