Datagram is a combination of the words data and telegram. Therefore, it is a message containing data that is sent from location to another. A datagram is similar to a packet, but does not require confirmation that it has been received. This makes datagrams ideal for streaming services, where the constant flow of data is more important than 100% accuracy.
Datagrams are also called "IP datagrams" since they are used by the Internet protocol (IP). This protocol defines how information is sent between systems over the Internet. For example, each device connected to the Internet must have an IP address, which serves as a unique identifier. Whenever data is transmitted via the Internet protocol, it is broken up into packets or datagrams, which each contain a header plus the actual data transmitted.
A datagram header defines the source and destination of the data as well as other information, such as the total length (or size) of the datagram, time to live (TTL), and the specific protocol used to transfer the data. Generally, datagrams are sent via the UDP protocol, which is used for media streaming and other services that do not require confirmation that the data has been received. Packets, on the other hand, are typically sent via TCP, which guarantees all the data sent has been received.