2020-5-27 · All I keep hearing is "if the answer is too long, DNS will use TCP". This does not explain how it happens though. So here's the situation: DNS client asks for resolution of a record using UDP. The record is too long for UDP: server answers with specific opcode, to have client switch to TCP; server doesn't answer at all, and client re-tries over TCP

This is the IP of the UDP DNS server that we will connect whenever we get a DNS-over-TCP request. The way we perform DNS over TCP is as follows: The resolver or end user connects via TCP to the zoneserver daemon. The resolver sends a DNS query over TCP. The zoneserver program converts the query in to a UDP query. Why does DNS use UDP? As you just read, the UDP is unreliable but a lot faster than TCP, but don’t panic just yet. DNS requests are very tiny, so they have no problems fitting into the UDP segments. It doesn’t use a time-consuming three-way hand-shake procedure to start the data transfer like TCP does. Unknown TCP or UDP Traffic Identifies the percentage of the network traffic that is using TCP or UDP, and the responsible app is not recognized by the firewall. Metric Details Jul 06, 2017 · The Role of TCP in DNS. TCP is still a second-class citizen in the DNS protocol. The standard defines DNS on both the UDP and TCP transport layer, but the overwhelming majority of DNS traffic happens over UDP. From what we can observe, TCP counts just for about 3% of normal DNS queries. Oct 16, 2019 · The reality is that DNS queries can also use TCP port 53 if UDP port 53 is not accepted. Now with the impending deployment of DNSSEC and the eventual addition of IPv6 we will need to allow our firewalls for forward both TCP and UDP port 53 packets.

The most commonly used UDP protocol is Domain Name System (DNS) and we use it constantly to translate between names and IP addresses and vice versus (other uses are there, just less common). Now, we can today run DNS over TCP and a number of people advocate for that, but I'm not personally one of them.

What are the pros/cons with TCP vs UDP? | NordVPN … UDP is mainly used for online streaming and downloading. TCP is more reliable but a little slower than UDP and usually used for web browsing. You can watch our video for a more detailed explanation: NSLookup, how to set to TCP from UDP? 2016-8-19 · The Transmission Control Protocol (TCP) is used when the response data size exceeds 512 bytes, or for tasks such as zone transfers. Some resolver implementations use TCP for all queries. I suggest you trust NSLookup and other applications to be smart enough to know how they should behave.

The most commonly used UDP protocol is Domain Name System (DNS) and we use it constantly to translate between names and IP addresses and vice versus (other uses are there, just less common). Now, we can today run DNS over TCP and a number of people advocate for …

How To Set NSLookup to Use TCP – 250 Hello