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Does DNS query use TCP or UDP?
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. For example, a domain client finding a domain controller using DNS.
Why DNS uses UDP and not TCP?
1) UDP is much faster. TCP is slow as it requires 3-way handshake. DNS servers (since they use UDP) don’t have to keep connections. 2) DNS requests are generally very small and fit well within UDP segments.
Does DNS request use UDP?
DNS has always been designed to use both UDP and TCP port 53 from the start 1 , with UDP being the default, and fall back to using TCP when it is unable to communicate on UDP, typically when the packet size is too large to push through in a single UDP packet.
Does nslookup use TCP or UDP?
By default when you run the NSLOOKUP queries, it is using the UDP protocol.
Why does DNS use UDP for queries?
DNS uses the User Datagram Protocol (UDP) on port 53 to serve DNS queries. UDP is preferred because it is fast and has low overhead. A DNS query is a single UDP request from the DNS client followed by a single UDP reply from the server.
When to use TCP or UDP for DNS?
UDP can be used to exchange small information whereas TCP must be used to exchange information larger than 512 bytes. If a client doesn’t get response from DNS, it must retransmit the data using TCP after 3-5 seconds of interval. There should be consistency in DNS Zone database.
When to use UDP or TCP for EDNS?
When the length of the answer exceeds 512 bytes and both client and server support EDNS, larger UDP packets are used. Otherwise, the query is sent again using the Transmission Control Protocol (TCP).
Which is faster, UDP or TCP on the transport layer?
There are following interesting facts about TCP and UDP on the transport layer that justify the above. 1) UDP is much faster. TCP is slow as it requires 3-way handshake. The load on DNS servers is also an important factor. DNS servers (since they use UDP) don’t have to keep connections.
Why does DNS transfer zone data to TCP?
To make this, DNS always transfers Zone data using TCP because TCP is reliable and make sure zone data is consistent by transferring the full zone to other DNS servers who has requested the data. The problem occurs when Windows 2000 server and Advanced Server products uses Dynamic ports for all above 1023.