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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 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 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
What three protocols operate at the application layer of the OSI model?
There are many more than three protocols which can operate at the application layer. Some of these are; Telnet FTP TFTP SMTP IMAP POP DNS RARP BOOTP SNMP CMOT
What is the connection between dns and collision domain?
There really isn't a connection; collision domains operate on LANs and DNS is a translation service between symbolic names and IP addresses. They aren't related.
