Final answer:
The domain of a DNS lookup is contained within the payload of a network frame, which carries the actual data including the DNS query.
Step-by-step explanation:
The domain of a DNS lookup is contained within the payload of a network frame. The payload is the part of the packet where the actual data is contained, and for a DNS query, this includes the domain name that the request is looking to resolve into an IP address. The header of a network frame contains control information such as source and destination addresses, error-checking data, and sequencing information.
The trailer contains error checking and other transmission-related details. The data-link layer is responsible for the node-to-node transfer of the frame and its handling on the physical network, but it does not contain the actual DNS lookup data.