FUNDAMENTALS OF COMPUTER

Detailed explanation-1: -A DNS server uses well-known port 53 for all its UDP activities and as its server port for TCP. It uses a random port above 1023 for TCP requests. A DNS client uses a random port above 1023 for both UDP and TCP.

Detailed explanation-2: -The answer is DNS is mostly UDP Port 53, but as time progresses, DNS will rely on TCP Port 53 more heavily.

Detailed explanation-3: -DNS uses TCP for Zone transfer and UDP for name, and queries either regular (primary) or reverse. UDP can be used to exchange small information whereas TCP must be used to exchange information larger than 512 bytes.

Detailed explanation-4: -The DNS uses TCP Port 53 for zone transfers, for maintaining coherence between the DNS database and the server. The UDP protocol is used when a client sends a query to the DNS server. The TCP protocol should not be used for queries as it gives a lot of information, which is useful to attackers.

Detailed explanation-5: -Port 53 is the well-known port number for DNS. Many years ago it was common for certain DNS implementations to send queries from source port 53.