Editing Datagram (section)

== Definition ==
The term ''datagram'' is defined as follows:{{Ref RFC|1594}}
{{Quote|"A self-contained, independent entity of data carrying sufficient information to be routed from the source to the destination computer without reliance on earlier exchanges between this source and destination computer and the transporting network."|RFC 1594}}

A datagram needs to be self-contained without reliance on earlier exchanges because there is no connection of fixed duration between the two communicating points as there is, for example, in most voice telephone conversations.<ref>{{cite book|last1=Tanenbaum|last2=Wetherall|first1=Andrew S.|first2=David J.|title=''Computer networks, fifth edition''|year=2011|page=59|publisher=Pearson |isbn=978-0-13-255317-9}}</ref>

Datagram service is often compared to a mail delivery service; the user only provides the destination address but receives no guarantee of delivery, and no confirmation upon successful receipt. Datagram service is therefore considered [[Reliability (computer networking)|unreliable]]. Datagram service routes datagrams without first creating a predetermined path. Datagram service is therefore considered [[connectionless]]. There is also no consideration given to the order in which it and other datagrams are sent or received. In fact, many datagrams in the same group can travel along different paths before reaching the same destination in a [[Out-of-order delivery|different order]].<ref>{{cite IETF |rfc=4737 |title=Packet Reordering Metrics |date=November 2006}}</ref>