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 server and Advanced Server products uses Dynamic ports for all above 1023. In this case, your DNS server should not be internet facing that is, doing all standard queries for client machines on the network. The router (ACL) must permitted all UDP inbound traffic to access any high UDP ports for it to work.
LDAP always uses TCP - this is true and why not UDP because a secure connection is established between client and server to send the data and this can be done only using TCP not UDP. UDP is only used when finding a domain controller (Kerberos) for authentication. For example, a domain client finding a domain controller using DNS.
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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.
The standard port for DNS is port 53. DNS client applications use the DNS protocol to query and request information from DNS servers, and the server returns the results to the client using the same port. Port 53 is used for both TCP and UDP communication.
The unique DNA binding mode allows the TCP domains to display broad specificity for a range of DNA sequences even shorter than 11 bp, adding further complexity to the regulatory network of plant TCP transcription factors.
The answer to the question: Which of the following protocols uses both TCP and UDP? is option D, i.e., DNS. The application layer protocol Domain Name Server, abbreviated as DNS, uses both TCP and UDP at the transport layer.
Simplicity - UDP is a lot simpler than TCP. TCP is optimized for long data transfers and has a bunch of complex mechanisms such as flow control and congestion control for optimizing the rate of data flow. DNS doesn't need any of these mechanisms for simple queries since the typical amount of sent data is tiny.
The DHCP employs a connectionless service model, using the User Datagram Protocol (UDP). It is implemented with two UDP port numbers for its operations which are the same as for the bootstrap protocol (BOOTP). The server listens on UDP port number 67, and the client listens on UDP port number 68.
DNS is an Application-layer protocol. The Application layer is the top-most layer on the TCP/IP Model. Just like every application layer protocol, DNS uses the User Datagram Protocol (UDP) on the Transport layer of the TCP/IP model to transport data.
A DNS server that supports DNS over TLS listens for and accepts TCP connections on Port 853, unless it has a mutual agreement with its server to use a different port for DoT.
Among the two most common transport protocols on the Internet, TCP is reliable and UDP isn't. HTTP therefore relies on the TCP standard, which is connection-based. Before a client and server can exchange an HTTP request/response pair, they must establish a TCP connection, a process which requires several round-trips.
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.
Yes, TCP and UDP can be integrated in the same application. This can be done through the use of sockets, which allow for communication between two computers. Socket programming allows for the exchange of data between a server and a client, regardless of the protocol being used.
Layer 4 of the OSI Model Handles Transport Protocols Like TCP and UDP. Layer 4 of the OSI model, also known as the transport layer, manages network traffic between hosts and end systems to ensure complete data transfers.
At a high level, the DNS protocol operates (using OSI model terminology) at the application level, also known as Layer 7. This layer is shared by HTTP, POP3, SMTP, and a host of other protocols used to communicate across an IP network.
The DHCP employs a connectionless service model, using the User Datagram Protocol (UDP). It is implemented with two UDP port numbers for its operations which are the same as for the bootstrap protocol (BOOTP). The server listens on UDP port number 67, and the client listens on UDP port number 68.
Since DNS uses UDP instead of TCP, if a packet is lost, there is no automatic recovery. Does this cause a problem? Yes, when DNS packets are lost, or a DNS server is unable to respond, this can cause problems with applications. DNS handles the resolution of host names to IP addresses.
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