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Is DNS query UDP or TCP?
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.
What happens if a DNS query over UDP gets lost?
From the network side, a lost DNS-over-UDP request is just lost. The client may try again but that is the application side. DNS can also use TCP, although this is uncommon for a normal client request.
What happens if DNS packet is lost?
DNS primarily uses UDP (User Datagram Protocol) as its transport protocol and thus a non-connection-oriented protocol. Even one lost packet leads to massive delays. 2.120 only sends a new request to the DNS server after a five second delay.
Which is UDP port does a DNS query use?
Normal DNS queries use UDP port 53, but longer queries (> 512 octets) will receive a ‘truncated’ reply, that results in a TCP 53 conversation to facilitate sending/receiving the entire query. Also, the DNS server binds to port 53, but the query itself originates on a random high-numbered port (49152 or above) sent to port 53.
Why do I get a deny inbound UDP message?
Explanation This is a connection-related message. This message is displayed if a UDP packet containing a DNS query or response is denied. Recommended Action If the inside port number is 53, the inside host probably is set up as a caching name server.
Where does the DNS server send the response to?
Also, the DNS server binds to port 53, but the query itself originates on a random high-numbered port (49152 or above) sent to port 53. The response will be returned to this same port from port 53. So, if you’re planning on doing some security snooping on DNS queries from your network, you’ll need to take the above into account.
Can a UDP reply of more than 512 bytes be seen?
A UDP reply of greater than 512 bytes may be seen if the client used EDNS (0) to advertise a larger payload, and the receiving server supports it. This will only happen if hardware sitting between the two does not interfere and result in a dropped or mangled packet.