Which two protocols apply to both IPv4 and IPv6?

Two protocols that apply to both IPv4 and IPv6 are:

SNMP: This stands for Simple Network Management Protocol, which is a protocol that allows network administrators to monitor and manage network devices such as routers, switches, servers, printers, etc. SNMP uses a client-server model, where an SNMP manager (client) can query or configure an SNMP agent (server) on a network device using SNMP messages. SNMP can operate over both IPv4 and IPv6 networks56.

DNS: This stands for Domain Name System, which is a protocol that translates human-readable domain names (such as www.example.com) into numerical IP addresses (such as 192.0.2.1 or 2001:db8::1) that identify network devices. DNS uses a hierarchical distributed database of name servers that store and resolve domain names and IP addresses. DNS can support both IPv4 and IPv6 addresses78.

References: Simple Network Management Protocol - Wikipedia, SNMP over IPv6 - Cisco, Domain Name System - Wikipedia, DNS for IPv6 - Cisco