# Preamble

    EIP: 868
    Title: Node Discovery v4 ENR Extension
    Author: Felix Lange <fjl@ethereum.org>
    Type: Standard Track
    Category: Networking
    Status: Draft
    Created: 2018-02-02
    Requires: EIP-8, EIP-778

# Abstract

This EIP defines an extension to Node Discovery Protocol v4 to enable authoritative
resolution of Ethereum Node Records (ENR).

# Motivation

To bridge current and future discovery networks and to aid the implementation of other
relay mechanisms for ENR such as DNS, we need a way to request the most up-to-date version
of a node record.

# Specification

Implementations of Node Discovery Protocol v4 should support two new packet types, a request
and reply of the node record. The new packets are:

### enrRequest (0x05)

RLP: `[ expiration ]`

When a packet of this type is received, the node should reply with an enrResponse packet
containing the current version of its record.

To guard against amplification attacks, the sender of enrRequest should have replied to a
ping packet recently. The expiration field, a UNIX timestamp, should be handled as for all
other existing packets, i.e. no reply should be sent if it refers to a time in the past.

### enrResponse (0x06)

RLP: `[ requestHash, ENR ]`

This packet is the response to enrRequest. 

- `requestHash` is the hash of the entire enrRequest packet being replied to.
- `ENR` is the node record.

The recipient of the packet should verify that the node record is signed by node who
sent enrResponse.

# Copyright

Copyright and related rights waived via CC0.