Does dns use tcp or udp

Does DNS use TCP or UDP or both? TCP is a connection-oriented protocol and it requires data to be consistent at the destination and UDP is connection-less protocol and doesn’t require data to be consistent or don’t need a connection to be established with host for consistency of data. UDP packets are smaller in size. Can’t be greater then 512 bytes. So any application needs data to be transffered greater than 512 bytes uses TCP We often discuss why services use both the protocols i.e. 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 truncated when greater than this size. So DNS uses TCP for Zone transfer and UDP for name 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. If a client doesn’t get response from DNS it must retransmit the data using TCP after 3-5 seconds of interval. Check: To get updates follow us on Subscribe to get free blog content to your Inbox Search for: Recent Posts • • • • • Categories • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Archives • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • ...

There are quite is few services which may use both DNS, lets have a quick run through TCP and UDP protocols. What is TCP? TCP is a connection-oriented protocol where the devices in communication should establish a connection before they can start with data transmission. The same stands true for termination of connection . Notable is that TCP is reliable and it guarantees delivery of data to the destination device. What is UDP? UDP is a connectionless protocol where there is no establishment of connection before data transmission. Further, there is no overhead related to opening, maintaining and terminating a connection. A key aspect of UDP is that delivery of data to the destination is not guaranteed. While considering between Example Scenario: When does DNS use TCP or UDP? Lets take scenario of UDP protocol requirement in DNS – A Client queries for a record from DNS server. Even if the DNS server response is lost or becomes corrupt, its not a major challenge since client can ask for it again. Considering such use case, it is rational to use UDP when communicating with DNS for translation of domain name. So, when does DNS use TCP? In order to maintain a consistent DNS database between DNS Servers. Hence, a transfer of DNS records (Zone transfer) between Primary and secondary DNS Servers is required which uses TCP protocol. The requirement here is that TCP, due to its reliability makes sure zone data is consistent across DNS servers. When a client doesn’t receive a response...

In this post, I explain why some services use both the protocols TCP and UDP. DNS which is one such service stands for Domain Name System. It is a decentralized naming system for computers, services, or any resource connected to the internet or a private network. DNS translates a human-readable domain name such as Does DNS use TCP and UDP? On the question of whether DNS uses TCP and UDP. The answer is yes, DNS work on both TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). The DNS (Domain Name System) is one such example. Other services that work on both TCP and UDP include DHCP (Dynamic Host Configuration Protocol), SNMP (Simple Network Management Protocol), and TFTP (Trivial File Transfer Protocol). Please see The domain name to IP address mappings is kept up to date in a distributed database by DNS. A user’s web browser sends a DNS query to a DNS server when they input a domain name to get the IP address connected to the domain name. The IP address is provided to the browser so that it can connect to the server hosting the website if the DNS server has the mapping stored in its database. Read DNS is a critical component of the internet infrastructure. It is responsible for ensuring that users can access websites and other internet resources using human-readable domain names. The How DNS Works on TCP and UDP? When a client sends a DNS query to a DNS server, it can use either TCP or UDP as the transport protocol. The choice of transport protocol depends...

I know that when we first type an address on the URL and enter. The DNS query starts. I don't who initiates, but my guess is application will only initiate the DNS query. The DNS query already knows which IP to contact to get the information ( DNS server is preset). SO, the application will put the Domain name in the payload, the Transport layer will put as UDP or TCP ( I don't know , i.e.also the question), the src and destination IP will be put by Network layer. In DNS we already know the DNS server IP ( this is destination IP), a response will come back. This will be the destination IP. Now, the rest of the communication can happen. As we know that http is TCP. But, I don't know is DNS query a tcp or udp? Please correct my understanding also if you find something wrong here. As many things, it depends. DNS queries are generally handled over UDP. If you do an A record lookup for "www.google.com" (which is what happens when you go to www.google.com in your browser) the answer that comes back will be in a UDP packet. If the query is for a large record (>512 bytes), like a big DKIM key, then the DNS request will use TCP. How ISP can offer me an IP address, when I got connected for the first time? In my opinion, I would have done DHCPDISCOVER, and then things would have fallen at place. But, the question is at what address will I broadcast? This is also not known. Please throw some light on it. I am new to networking, please bear with me. Thanks for contributing an answer to...

Well I know that might sound a stupid question and I believe that the most proper answer will be like I will be able to tell as my experience builds up and I learn more and more about the protocols. However I am a student and I am not having much hands on experience in the field. Though I can google for any given protocol, I want to know if there is any rule of thumb. I still feel asking for "rule of thumb" is stupid, but still I am looking for one. I encountered 23-TCP-UDP. What does this mean? Telnet can operate on both TCP port 23 and UDP port 23? Also I found that in my textbook, it says TFTP uses UDP, but if we look in the above table, TFTP line is 69-TCP-UDP. So just guessing whats going on in the above table. You asked a good question. Don't let anyone tell you otherwise. Regrettably, there is no rule of thumb for the types of protocols that use TCP verses the types of protocols that use UDP. The decision whether a protocol uses one or the other come down to whomever wrote/created the protocol to begin with. If they didn't want to bother with writing their own "reliable delivery" system, then they can simply use TCP which provides all the reliability innately. If they thought (knowing their own protocol innately) that they could write a better or more appropriate "reliable delivery" system, then they can build that into the protocol itself and simply use UDP as their transport. As an example, take a look at a UDP Whereas FTP, which runs over TCP, does not have a bui...

Before anyone asks: I've seen 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 • server opens TCP connection to client (stupid, if you count NAT, but who knows?) • client somehow (?) 'knows' that given query should be run over TCP so it doesn't bother with UDP in the first place • DNS pixies magically turn UDP into TCP when needed I've been looking all over the internet for the answer, but there's lot of noise (see above), and I can't seem to write proper Google query for that (nor can I find the info in RFCs, for that matter). All I could find was in RFC5966: "A resolver SHOULD send a UDP query first, but MAY elect to send a TCP query instead if it has good reason to expect the response would be truncated if it were sent over UDP (with or without EDNS0) or for other operational reasons, in particular, if it already has an open TCP connection to the server.". When should resolver "expect" that the response will be truncated? The client does not know in advance that the response will be too large, so it will query the server via UDP. The server will respond via UDP and will include as much as possible and set the truncated header bit ("TC" The client can then resend the req...

Hybrid Workplace Speed your transition to a secure, multi-cloud organization to support your hybrid workforce SaaS-Enabled Enterprise Secure cloud-managed, cloud-native network services for distributed enterprises On-Premises + Cloud-Managed Networking Uniting enterprise grade and cloud native core networking services for the hybrid enterprise Accelerate Office 365 performance Ensure fast, reliable user experiences Secure IoT Protect devices across IoT environments Deploy IPv6 Set your network foundation up for success Optimize SD-WAN Use cloud-managed DNS, DHCP and IPAM for better ROI Support Encrypted DNS Offer DoT/DoH services while maintaining security and performance The answer is DNS is mostly UDP Port 53, but as time progresses, DNS will rely on TCP Port 53 more heavily. 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. When Does DNS Switch to TCP? The next natural question is: when will DNS messages exceed 512 bytes? Actually, this happens quite often in today’s environment. When DNS was first implemented, the only thing that would be so large that it exceeded the 512-byte limit was a zone transfer, in which one DNS server sends every single resource record in the zone to another machine, usually another DNS server. In modern DNS systems though, we are increa...

• Courses • Summer Skill Up • • • Data Structures and Algorithms • • • • • • • For Working Professionals • • • • • • For Students • • • • • • • • Programming Languages • • • • Web Development • • • • • Machine Learning and Data Science • • • New Courses • • • • School Courses • • • • Tutorials • DSA • • • • • Data Structures • • • • Linked List • • • • • • • Tree • • • • • • • • • • • • • • • • Algorithms • Analysis of Algorithms • • • • • • • • • • • • • • Searching Algorithms • • • • Sorting Algorithms • • • • • • • • • • • • • • • • • • • • • • • • System Design • System Design Tutorial • • • • • • • • • • • • Software Design Patterns • • • • • • • • • • • Interview Corner • • • • • • • • • • Languages • • • • • • • • • • • • • Web Development • • • • • CSS Frameworks • • • • • • • • • • JavaScript Frameworks • • • • • • JavaScript Libraries • • • • • • • • • • • • • • • • • • • • • • School Learning • • • Mathematics • • • • • • • • • CBSE Syllabus • • • • • • Maths Notes (Class 8-12) • • • • • • Maths Formulas (Class 8 -11) • • • • • NCERT Solutions • • • • • • RD Sharma Solutions • • • • • • Science Notes • • • • Physics Notes (Class 8-12) • • • • • • Chemistry Notes (Class 8-12) • • • • • • Biology Notes • • • • • Social Science Syllabus • • • • • Social Science Notes • SS Notes (Class 7-12) • • • • • CBSE History Notes (Class 7-10) • • • • CBSE Geography Notes (Class 7-10) • • • • CBSE Civics Notes (Class 7-10) • • • Commerce • • • • • • • CBSE Previous Year Papers...

In this article This article explains why some services use both the protocols TCP and UDP. Applies to: Windows Server 2003 Original KB number: 556000 SUMMARY DNS and some other services work on both the protocols. We'll take an example of DNS Service. Two protocols are different from each other. TCP is a connection-oriented protocol and it requires data to be consistent at the destination and UDP is connection-less protocol and doesn't require data to be consistent or don't need a connection to be established with host for consistency of data. UDP packets are smaller in size. UDP packets can't be greater than 512 bytes. So any application needs data to be transferred greater than 512 bytes require TCP in place. For example, DNS uses both TCP and UDP for valid reasons described below. UDP messages aren't larger than 512 Bytes and are truncated when greater than this size. 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. 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. 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 s...

I know that when we first type an address on the URL and enter. The DNS query starts. I don't who initiates, but my guess is application will only initiate the DNS query. The DNS query already knows which IP to contact to get the information ( DNS server is preset). SO, the application will put the Domain name in the payload, the Transport layer will put as UDP or TCP ( I don't know , i.e.also the question), the src and destination IP will be put by Network layer. In DNS we already know the DNS server IP ( this is destination IP), a response will come back. This will be the destination IP. Now, the rest of the communication can happen. As we know that http is TCP. But, I don't know is DNS query a tcp or udp? Please correct my understanding also if you find something wrong here. As many things, it depends. DNS queries are generally handled over UDP. If you do an A record lookup for "www.google.com" (which is what happens when you go to www.google.com in your browser) the answer that comes back will be in a UDP packet. If the query is for a large record (>512 bytes), like a big DKIM key, then the DNS request will use TCP. How ISP can offer me an IP address, when I got connected for the first time? In my opinion, I would have done DHCPDISCOVER, and then things would have fallen at place. But, the question is at what address will I broadcast? This is also not known. Please throw some light on it. I am new to networking, please bear with me. Thanks for contributing an answer to...