In a DNS Proxy configuration, which command outcome corresponds to creating a DNS Response with the TC bit set and rcode NOERROR?

• A. Create a DNS Request with TC bit set and rcode NOERROR
• B. Create a DNS Response with TC bit set and rcode NOERROR
• C. Set TC bit and rcode NOERROR in the DNS Request from Client
• D. Set TC bit and rcode NOERROR in the DNS Response from DNS server

Answer: (B)

In DNS, the Truncated (TC) bit in a response signals that the answer won’t fit in a single UDP packet and the client should retry over TCP to obtain the full data. The rcode NOERROR indicates the query was processed successfully without errors; it’s not signaling a problem, just that the data was too large for one UDP response.

In a DNS Proxy scenario, when the full answer can’t be sent in one UDP response, the proxy crafts a response back to the client with the TC bit set and NOERROR as the response code. This clearly communicates: the answer is valid and there is more data to fetch over TCP, not that something went wrong. That’s why creating a DNS Response with the TC bit set and rcode NOERROR is the appropriate outcome.

The other options aren’t correct because the TC bit and rcode belong in responses, not requests, and a request can’t carry an rcode. While a DNS server’s response might also include TC, the action described—what the proxy explicitly returns to the client—centers on constructing a response with TC set and NOERROR.