- The value MUST be a list of binary encoded multiaddr prefixed by their size.
- The size of the multiaddr MUST be encoded in a Big Endian unsigned 16-bit integer.
- The size of the multiaddr MUST be encoded in 2 bytes.
- The `secp256k1` value MUST be present on the record;
`secp256k1` is defined in [EIP-778](https://eips.ethereum.org/EIPS/eip-778) and contains the compressed secp256k1 public key.
- The node's peer id SHOULD be deduced from the `secp256k1` value.
- The multiaddresses SHOULD NOT contain a peer id.
- For raw TCP & UDP connections details, [EIP-778](https://eips.ethereum.org/EIPS/eip-778) pre-defined keys SHOULD be used;
The keys `tcp`, `udp`, `ip` (and `tcp6`, `udp6`, `ip6` for IPv6) are enough to convey all necessary information;
- To save space, `multiaddrs` key SHOULD only be used for connection details that cannot be represented using the [EIP-778](https://eips.ethereum.org/EIPS/eip-778) pre-defined keys.
- The 300 bytes size limit as defined by [EIP-778](https://eips.ethereum.org/EIPS/eip-778) still applies;
In practice, it is possible to encode 3 multiaddresses in ENR, more or less could be encoded depending on the size of each multiaddress.
## Usage
### Many connection types
Alice is a node operator, she runs a node that supports inbound connection for the following protocols:
- TCP 10101 on `1.2.3.4`
- UDP 20202 on `1.2.3.4`
- TCP 30303 on `1234:5600:101:1::142`
- UDP 40404 on `1234:5600:101:1::142`
- Secure Websocket on `wss://example.com:443/`
- QUIC on `quic://quic.example.com:443/`
Alice SHOULD structure the ENR for her node as follows:
- In the scheme above, the flags `lightpush`, `filter`, `store` and `relay` correlates with support for protocols with the same name.
If a protocol is not supported, the corresponding field MUST be set to `false`.
Indicating positive support for any specific protocol is OPTIONAL,
though it MAY be required by the relevant application or discovery process.
- Flags marked as `undef` is not yet defined.
These SHOULD be set to `false` by default.
## Usage
- A Waku v2 node MAY choose to populate the `waku2` field for enhanced discovery capabilities,
such as indicating supported protocols.
Such a node MAY indicate support for any specific protocol by setting the corresponding flag to `true`.
- Waku v2 nodes that want to participate in [Node Discovery Protocol v5](https://github.com/ethereum/devp2p/blob/master/discv5/discv5.md) [[4]](#references), however,
MUST implement the `waku2` key with at least one flag set to `true`.
- Waku v2 nodes that discovered other participants using Discovery v5,
MUST filter out participant records that do not implement this field or do not have at least one flag set to `true`.
- In addition, such nodes MAY choose to filter participants on specific flags (such as supported protocols),
or further interpret the `waku2` field as required by the application.
