Add Transport and lower-level libp2p specifications

specs/networking/libp2p-standardization.md

@@ -9,6 +9,57 @@ configuration and messaging formats.
 
 # Libp2p Protocols
 
+## Transport
+
+This section details the libp2p transport layer that underlies the
+[protocols](#protocols) that are listed in this document.
+
+Libp2p allows composition of multiple transports. Eth2.0 clients should support
+TCP/IP and optionally websockets. Websockets are useful for implementations
+running in the browser and therefore native clients would ideally support these implementations 
+by supporting websockets.
+
+An ideal libp2p transport would therefore be TCP/IP with a fallback to
+websockets.
+
+### Encryption
+
+Libp2p currently offers [Secio](https://github.com/libp2p/specs/pull/106) which
+can upgrade a transport which will then encrypt all future communication. Secio
+generates a symmetric ephemeral key which peers use to encrypt their
+communication. It can support a range of ciphers and currently supports key
+derivation for elliptic curve-based public keys.
+
+Current defaults are:
+- Key agreement: `ECDH-P256` (also supports `ECDH-P384`)
+- Cipher: `AES-128` (also supports `AES-256`, `TwofishCTR`)
+- Digests: `SHA256` (also supports `SHA512`)
+
+
+## Protocols
+
+This section lists the necessary libp2p protocols required by Ethereum 2.0
+running a libp2p network stack.
+
+## Multistream-select
+
+#### Protocol id: `/multistream/1.0.0`
+
+Clients running libp2p should support the [multistream-select](https://github.com/multiformats/multistream-select/)
+protocol which allows clients to negotiate libp2p protocols establish streams
+per protocol.
+
+## Multiplexing
+
+Libp2p allows clients to compose multiple multiplexing methods. Clients should
+support [mplex](https://github.com/libp2p/specs/tree/master/mplex) and
+optionally [yamux](https://github.com/hashicorp/yamux/blob/master/spec.md)
+(these can be composed).
+
+**Mplex protocol id: `/mplex/6.7.0`**
+
+**Yamux protocol id: `/yamux/1.0.0`**
+
 ## Gossipsub
 
 #### Protocol id: `/meshsub/1.0.0`
@@ -70,11 +121,14 @@ number of shard subnets will be defined via `SHARD_SUBNET_COUNT` and the shard
 
 ### Messages
 
-Messages sent across gossipsub are fixed-size length-prefixed byte arrays.
-Each message has a maximum size of 512KB (estimated from expected largest uncompressed
-block size).
+#### Libp2p Specification
 
-The byte array is prefixed with a unsigned 64 bit length number encoded as an
+*This section simply outlines the data sent across the wire as specified by
+libp2p - this section is aimed at gossipsub implementers to standardize their implementation of this protocol*
+
+Libp2p raw gossipsub messages are sent across the wire as fixed-size length-prefixed byte arrays.
+
+The byte array is prefixed with an unsigned 64 bit length number encoded as an
 `unsigned varint` (https://github.com/multiformats/unsigned-varint). Gossipsub messages therefore take the form:
 ```
 +--------------------------+
@@ -86,7 +140,17 @@ The byte array is prefixed with a unsigned 64 bit length number encoded as an
 +--------------------------+
 ```
 
-The body of the message is an SSZ-encoded object. For the `beacon_block` topic,
+The body represents a protobuf-encoded [Message](https://github.com/libp2p/go-libp2p-pubsub/blob/master/pb/rpc.proto#L17-L24). 
+
+In the following section we discuss the data being sent in the `data` field of
+the protobuf gossipsub `Message`.
+
+#### Eth2.0 Specifics
+
+Each message has a maximum size of 512KB (estimated from expected largest uncompressed
+block size).
+
+The `data` that is sent in a Gossipsub message is an SSZ-encoded object. For the `beacon_block` topic,
 this will be a `beacon_block`. For the `beacon_attestation` topic, this will be
 an `attestation`.
 
@@ -100,6 +164,9 @@ The [RPC Interface](./rpc-interface.md) is specified in this repository.
 
 #### Protocol Id: `/ipfs/id/1.0.0` (to be updated to `/p2p/id/1.0.0`)
 
+*To be updated to incorporate discv5*
+
+
 The Identify protocol (defined in go - [identify-go](https://github.com/ipfs/go-ipfs/blob/master/core/commands/id.go) and rust [rust-identify](https://github.com/libp2p/rust-libp2p/blob/master/protocols/identify/src/lib.rs))
 allows a node A to query another node B which information B knows about A. This also includes the addresses B is listening on.
 
@@ -120,4 +187,6 @@ type of connecting node. Suggested format:
 
 #### Protocol Id: `/eth/serenity/disc/1.0.0`
 
+*To be updated to incorporate discv5*
+
 The discovery protocol to be determined.