The document discusses address mapping, error reporting, and multicasting at the network layer. It describes how Address Resolution Protocol (ARP) is used to map between logical IP addresses and physical MAC addresses on a local network. It also explains how Reverse ARP (RARP), Bootstrap Protocol (BOOTP), and Dynamic Host Configuration Protocol (DHCP) can be used to map physical addresses to logical addresses. Additionally, it outlines how Internet Control Message Protocol (ICMP) provides error reporting for IP without a built-in mechanism. Finally, it states that Internet Group Management Protocol (IGMP) is involved in IP multicasting.