A datagram is a self-contained, independent data unit that is sent between two endpoints ( peer to peer ) without further securing the connection . This data unit contains information that is to be transported over a network by means of a datagram service . A datagram is characterized by its low protocol overhead and essentially contains the receiving and sending addresses as well as the user data. The route that the datagram takes through the network is determined by it and is completely independent of any route selection made beforehand.
OSI model (layer structure)
The OSI terminology distinguishes datagrams with regard to the OSI layer. Datagrams of the data link layer are called data frames and the network layer is called data packets.
|OSI layer||Datagram label|
|Layer 1||Chip (data transmission)|
|Layer 2||Data frame ( 802.3 and 802.11 ),
data cell ( ATM )
|Layer 3||Data packet|
|Layer 4||Data segment|
The datagrams are transmitted by a router using TCP based on the packet switching principle . However, a datagram differs in its properties from a network-transmitting data unit based on packet switching, in that a datagram is provided with control information in the header and possibly with error-checking measures in the trailer (protocol element).
Datagrams must contain full sender and recipient addresses (overhead). Of application programs is usually required that the data will actually arrive in the correct order. However, compliance with the sequence is not guaranteed by a datagram network, which is why there is no guarantee that the datagram will arrive (correctly) at the recipient. Therefore, a sequence control must be implemented in the end systems. Often it is not even certain that the recipient actually exists.
The process is conceptually very simple, which is why it can be implemented on mini and microcomputers with little effort . Datagrams can also be sent to several endpoints (broadcast or multicast) at the same time. Datagrams are often used on servers that serve many clients. There is no overhead for connection management and can take place quite efficiently at the application level on low-error transmission media (e.g. in a LAN ). This procedure is also better protected against data misuse, as only parts of the actual communication can be intercepted at any point inside the network.
A modern application of the datagram is the SMS (Short Message) in mobile communications.
- Manfred Burke: Computer Networks. Concepts and techniques of data transmission in computer networks. BG Teubner Verlag, Stuttgart 1994, ISBN 3-519-02141-2 , p. 18.
- Christoph Meinel, Harald Sack: Internetworking. Technical basics and applications. Springer-Verlag, Berlin / Heidelberg 2012, ISBN 978-3-540-92940-6 .
- Mark A. Dye, Rick McDonald, Antoon W. Rufi: Networking Basics. CCNA exploration companion guide, Addison-Wesley Verlag, Munich 2008, ISBN 978-3-8273-2685-0 .
- Reinhold Franck: Computer networks and data communication. Springer Verlag, Berlin / Heidelberg 1986, ISBN 978-3-642-70267-9 .
- Jörg Rech: Ethernet. Technologies and protocols for computer networking, 3rd updated edition, Heise Zeitschriften Verlag GmbH & Co KG, Hanover 2014, ISBN 978-3-944099-04-0 .
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- ↑ Douglas Comer: TCP-IP: Concepts, Protocols, Architectures. mitp Verlag, 2011, ISBN 978-3-8266-9111-9 .
- ^ Walter E. Proebster: Computer networks: technology, protocols, systems, applications. Oldenbourg Verlag, 2002, ISBN 3-486-25777-3 .