COMPUTER NETWORKS AND COMMUNICATIONS
NETWORK SECURITY AND CYBERSECURITY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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udp/tcp 53
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tcp 21
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udp 21
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udp/tcp 427
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Detailed explanation-1: -The answer is DNS is mostly UDP Port 53, but as time progresses, DNS will rely on TCP Port 53 more heavily.
Detailed explanation-2: -DNS uses Port 53 which is nearly always open on systems, firewalls, and clients to transmit DNS queries. Rather than the more familiar Transmission Control Protocol (TCP) these queries use User Datagram Protocol (UDP) because of its low-latency, bandwidth and resource usage compared TCP-equivalent queries.
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: -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. These days, it is good practice to use non-privileged source ports (i.e., 1024 or greater) and to use a different, random source port for each query.