Why does DNS use UDP and not TCP? - GeeksforGeeks

What is User Datagram Protocol (UDP/IP)? UDP is a communication protocol used across the Internet for especially time-sensitive transmissions such as video playback or DNS lookups. It speeds up communications by not requiring what’s known as a “handshake”, allowing data to be transferred before the receiving party agrees to the communication. RFC 7766 DNS over TCP March 2016 1.Introduction Most DNS [] transactions take place over UDP [].TCP [] is always used for full zone transfers (using AXFR) and is often used for messages whose sizes exceed the DNS protocol's original 512-byte limit. 53/TCP,UDP: DNS (Domain Name System - Sistema de nome de domínio) Oficial 57/TCP: MTP, Mail Transfer Protocol (Protocolo de transferência de e-mail) 67/UDP: Feb 28, 2013 · Consider the subsequent TCP SYN packet sent by your host. Does the destination IP address of the SYN packet correspond to any of the IP addresses provided in the DNS response message? The destination of the SYN packet is, the same address that was provided in the DNS response message as the type “A” address of the webpage. 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. Jul 23, 2020 · The ways in which the DNS uses UDP: DNS server uses connectionless messaging. UDP is a connectionless protocol. DNS server uses UDP for segment or short message transfer as DNS do not have to keep connection. DNS request is very small in size. So, it can fit well within UDP segments. DNS uses UDP as it has only 8 bytes of header overhead

A part of the DNS service is that it uses UDP, and Azure Firewall uses SNAT for address translation from every internal source, resulting in every UDP request from one IP to an external provider (,, etc.) will use one port out of the 65.000 available in the TCP protocol for that unique destination.

It’s not always this simple DNS thing such as “single query – single answer, both via UDP”. Sometimes you have some more options or bigger messages that look and behave differently on the network. For example: IP fragmentation for larger DNS answers that do not fit into a single UDP datagram (hopefully not after the DNS flag day 2020 anymore ), or DNS via TCP, or some newer options within the EDNS … Why is UDP used for DNS instead of TCP? Isn't TCP supposed Mar 02, 2011 domain name system - Do DNS queries always travel over UDP

Apr 22, 2018 · Utility applications like DNS, DHCP, RIP and others use UDP. The use of UDP is expected to increase with IOT as sensor type data is ideal for sending via UDP vs TCP. For more details there is a very useful side by side TCP/UDP comparison. TCP and UDP Headers. The UDP header (8 bytes) is considerably much smaller than the TCP header (20 bytes).

DNS n'est pas un protocole de transmision et DNS n'utilise pas UDP ou TCP. DNS permet a des protocoles UDP ou TCP d'utiliser DNS ou si tu prefere UDP ou TCP passent au travers d'une DNS qui n'est autre qu'une resolution de nom de domaine et non pas une couche de transmission de protocole. Du reste des paquets de type ARP par exemples sont Preparing for DNSSEC: Best Practices, Recommendations, and DNS can use either the User Datagram Protocol (UDP) or Transmission Control Protocol (TCP); historically, it uses a destination port of 53. When the DNS protocol uses UDP as the transport, it has the ability to deal with UDP retransmission and sequencing. DNS - TCP or UDP Mar 31, 2007 Why does DNS use UDP? - Quora Nov 29, 2011