Tanenbaum's Computer Networks says:
5.6 THE NETWORK LAYER IN THE INTERNET
5.6.4 Internet Control Protocols
In addition to IP, which is used for data transfer, the Internet has several companion control protocols that aIn re used in the network layer. They include ICMP, ARP, and DHCP. In this section, we will look at each of these in turn, describing the versions that correspond to IPv4 because they are the protocols that are in common use. ICMP and DHCP have similar versions for IPv6; the equivalent of ARP is called NDP (Neighbor Discovery Protocol) for IPv6.
Does it mean that the companion control protocols of the Internet, e.g. ICMP, ARP/NDP, and DHCP, are in the network layer?
https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol lists ICMP and NDP in the Internet layer (i.e. the network layer?), and DHCP in the application layer.
Is DHCP in the application layer or the network layer? If the former, why are ICMP and NDP in the Internet layer (i.e. the network layer?)?