TCP与UDP区别 - 纯情的小公鸡 - 博客园
TFTP uses UDP because of point 1, it was designed to be implemented in very limited environments. DNS uses UDP because of points 2,4 and 5. The small request and response doesn't justify the resource use of TCP. Low latency realtime stuff like games, VOIP etc uses UDP because of point 3. TCP is a connection-based protocol, and UDP is a connectionless-based protocol. So if it's TCP, we call it the TCP segment, and if it's UDP, we call it the UDP datagram. Now, let's go ahead and Apr 16, 2019 · However, unlike Transmission Control Protocol (TCP), the User Datagram Protocol (UDP) does not provide any guarantee or reassurance of the delivery of datagrams across a network. Not all protocols at the Application Layer uses TCP, there are many Layer 7 protocols which uses the User Datagram Protocol (UDP). Aug 19, 2016 · 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.
tcp - Why DNS uses UDP as the transport layer protocol
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.
TCP and UDP. These services can also realy on TCP instead of UDP because TCP is a connection-oriented protocol whereas UDP is connection-less! then why use UDP? For example, DNS uses both TCP and UDP for valid reasons described below. Note that UDP messages are not larger than 512 Bytes and are trucncted when greater than this size. So DNS uses
2017-11-1 · DNS uses TCP instead of UDP for transmitting data when the data size exceeds 512 bytes. DNS also uses TCP for transferring entire DNS zones between zones. In either case, port 53 is used. RFC 7766 - DNS Transport over TCP - Implementation 2020-7-19 · 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.The growing deployment of DNS Security (DNSSEC) and IPv6 has increased response sizes and therefore the use of TCP. What’s the Difference Between TCP and UDP? 2017-7-3 · RELATED: How to Use Wireshark to Capture, Filter and Inspect Packets. Whether an application uses TCP or UDP is up to its developer, and the choice depends on what an application needs. Most apps need the error-correction and robustness of TCP, but some applications need the speed and reduced overhead of UDP.