IP желісінде деректерді жіберу протоколы: UDP

Principal protocol used for transmission of datagrams across an IP network

In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network. Within an IP network, UDP does not require prior communication to set up communication channels or data paths. UDP uses a simple connectionless communication model with a minimum of protocol mechanisms. UDP provides checksums for data integrity, and port numbers for addressing different functions at the source and destination of the datagram. It has no handshaking dialogues and thus exposes the user's program to any unreliability of the underlying network; there is no guarantee of delivery, ordering, or duplicate protection. If error correction facilities are needed at the network interface level, an application may instead use Transmission Control Protocol (TCP) or Stream Control Transmission Protocol (SCTP) which are designed for this purpose. UDP is suitable for purposes where error checking and correction are either not necessary or are performed in the application; UDP avoids the overhead of such processing in the protocol stack. Time sensitive applications often use UDP because dropping packets is preferable to waiting for packets delayed due to retransmission, which may not be an option in a real time system. The protocol was designed by David P. Reed in 1980 and formally defined in .

UDP is a simple message oriented transport layer protocol that is documented in Although UDP provides integrity verification (via checksum) of the header and payload, it provides no guarantees to the upper layer protocol for message delivery and the UDP layer retains no state of UDP messages once sent. For this reason, UDP sometimes is referred to as Unreliable Datagram Protocol. If transmission reliability is desired, it must be implemented in the user's application. A number of UDP's attributes make it especially suited for certain applications. It is transaction oriented, suitable for simple query response protocols such as the Domain Name System or the Network Time Protocol. It provides datagrams, suitable for modeling other protocols such as IP tunneling or remote procedure call and the Network File System. It is simple, suitable for bootstrapping or other purposes without a full protocol stack, such as the DHCP and Trivial File Transfer Protocol. It is stateless, suitable for very large numbers of clients, such as in streaming media applications like IPTV. The lack of retransmission delays makes it suitable for real time applications such as Voice over IP, online games, and many protocols using Real Time Streaming Protocol. Because it supports multicast, it is suitable for broadcast information such as in many kinds of service discovery and shared information such as Precision Time Protocol and Routing Information Protocol.

Lacking reliability, UDP applications may encounter some packet loss, reordering, errors or duplication. If using UDP, the end user applications must provide any necessary handshaking such as real time confirmation that the message has been received. Applications, such as TFTP, may add rudimentary reliability mechanisms into the application layer as needed. Some VPN systems such as OpenVPN may use UDP and perform error checking at the application level while implementing reliable connections. QUIC is a transport protocol built on top of UDP. QUIC provides a reliable and secure connection. HTTP/3 uses QUIC as opposed to earlier versions of HTTPS which use a combination of TCP and TLS to ensure reliability and security respectively. This means that HTTP/3 uses a single handshake to set up a connection, rather than having two separate handshakes for TCP and TLS, meaning the overall time to establish a connection is reduced.

Transmission Control Protocol is a connection oriented protocol and requires handshaking to set up end to end communications. Once a connection is set up, user data may be sent bi directionally over the connection. Reliable – TCP manages message acknowledgment, retransmission and timeouts. Multiple attempts to deliver the message are made. If data gets lost along the way, data will be re sent. In TCP, there's either no missing data, or, in case of multiple timeouts, the connection is dropped. Ordered – If two messages are sent over a connection in sequence, the first message will reach the receiving application first. When data segments arrive in the wrong order, TCP buffers the out of order data until all data can be properly re ordered and delivered to the application. Heavyweight – TCP requires three packets to set up a socket connection before any user data can be sent. TCP handles reliability and congestion control. Streaming – Data is read as a byte stream, no distinguishing indications are transmitted to signal message (segment) boundaries. User Datagram Protocol is a simpler message based connectionless protocol. Connectionless protocols do not set up a dedicated end to end connection. Communication is achieved by transmitting information in one direction from source to destination without verifying the readiness or state of the receiver. Unreliable – When a UDP message is sent, it cannot be known if it will reach its destination; it could get lost along the way. There is no concept of acknowledgment, retransmission, or timeout. Not ordered – If two messages are sent to the same recipient, the order in which they arrive cannot be guaranteed. Lightweight – There is no ordering of messages, no tracking connections, etc. It is a very simple transport layer designed on top of IP. Datagrams – Packets are sent individually and are checked for integrity on arrival. Packets have definite boundaries which are honored upon receipt; a read operation at the receiver socket will yield an entire message as it was originally sent. No congestion control – UDP itself does not avoid congestion. Congestion control measures must be implemented at the application level or in the network. Broadcasts – being connectionless, UDP can broadcast sent packets can be addressed to be receivable by all devices on the subnet. Multicast – a multicast mode of operation is supported whereby a single datagram packet can be automatically routed without duplication to a group of subscribers.