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Strictly speaking, the question is invalid, as DNS uses both UDP and TCP for its transport.
The expected use is for DNS to run on top of UDP, with a fall-back to TCP for data packages that can't fit into a single 8K UDP packet. Large replies and zone transfers will fall in to this category. DNS can also be configured to work exclusively over TCP, but this isn't recommended.
Early MS Windows systems used DNS over TCP exclusively. Fortunately the more recent editions (XP onwards) use DNS over UDP by default, falling back to TCP only when necessary.
Why UDP rather than TCP? It's simply a matter of efficiency. To start a TCP connection a minimum of three packets are required (SYN out, SYN+ACK back, ACK out). By the time you add a data packet into that and close the session off correctly you will have sent several packets. In contrast, UDP can get away with a minimum of two packets (one question, one reply).
DNSSec adds a layer of complexity to this, but with caching the extra resource required can usually be mitigated against a number of queries.
What else can I help you with?
What port dns use?
Port 53
What port is the Web Server listening on for a DNS request?
A web server typically listens for DNS requests on port 53, which is the standard port for DNS (Domain Name System) communication. However, web servers themselves do not respond to DNS queries; instead, DNS servers handle those requests. Web servers generally listen for incoming HTTP requests on port 80 (for HTTP) and port 443 (for HTTPS).
What is port 53 used for?
DNS
What is the default port number DNS?
DNS uses port 53. DNS queries are generally performed via UDP, and zone transfers are normally done via TCP.
What is the difference between a DNS port and UDP?
There are a lot of differences between a DNS port and UDP. An example would be DNS is for translation while UDP actually relays the host communication.
What is the dns port number and dhcp port number?
DHCP listens for incoming on UDP 67 and send out on UDP 68 For 'well known' and 'registered' ports, you can check http://www.iana.org/assignments/port-numbers too. by gerson.freire@terra.com.br
Where can one get information on a Comcast DNS server?
One can get more information on a Comcast DNS server from the following sources: What's My DNS, Comcast, DNS Knowledge, ZDNet, DSL Reports, Port Forward, Open DNS, Mac Medics, to name a few.
How does Open DNS rank compared to other internet security providers?
The appreciable difference of Open DNS is not in performance over other DNS. The advantage of Open DNS over other DNS products is the added features of typo correction and fishing philter, and how unintrusively those features operate.
What are the port numbers of domain name system?
The Domain Name System (DNS) primarily uses two port numbers: UDP port 53 and TCP port 53. UDP is typically used for standard DNS queries due to its lower overhead, while TCP is employed for tasks that require reliable communication, such as zone transfers and larger query responses. Both ports are essential for the functioning of DNS services on the internet.
What is default port for ip?
TCP has no default port. Individual applications - such as FTP, DNS, or Telnet - do have default ports.
What service is used to resolve host or domain names to addresses?
DNS (port 53)
What Protocol and Port is used by DNS for responses larger than 512 bytes?
TCP 53
