As per Relevance of the word datagram, we have this rfc below:
RFC 768 J.
28 August 1980
User Datagram
----------------------
------------
This User Datagram Protocol (UDP) is defined to make available
datagram mode of packet-switched computer communication in
environment of an interconnected set of computer networks.
protocol assumes that the Internet Protocol (IP) [1] is used as
underlying protocol
This protocol provides a procedure for application programs to
messages to other programs with a minimum of protocol mechanism.
protocol is transaction oriented, and delivery and duplicate
are not guaranteed. Applications requiring ordered reliable delivery
streams of data should use the Transmission Control Protocol (TCP) [2].
------
0 7 8 15 16 23 24 31
+--------+--------+--------+--------+
| Source | Destination |
| Port | Port |
+--------+--------+--------+--------+
| | |
| Length | Checksum |
+--------+--------+--------+--------+
|
| data octets ...
+---------------- ...
User Datagram Header
------
Source Port is an optional field, when meaningful, it indicates the
of the sending process, and may be assumed to be the port to which
reply should be addressed in the absence of any other information.
not used, a value of zero is inserted
Postel [page 1]
28 Aug 1980
User Datagram Protocol RFC 768
Destination Port has a meaning within the context of a
internet destination address
Length is the length in octets of this user datagram including
header and the data. (This means the minimum value of the length
eight.)
Checksum is the 16-bit one's complement of the one's complement sum of
pseudo header of information from the IP header, the UDP header, and
data, padded with zero octets at the end (if necessary) to make
multiple of two octets
The pseudo header conceptually prefixed to the UDP header contains
source address, the destination address, the protocol, and the
length. This information gives protection against misrouted datagrams
This checksum procedure is the same as is used in TCP
0 7 8 15 16 23 24 31
+--------+--------+--------+--------+
| source address |
+--------+--------+--------+--------+
| destination address |
+--------+--------+--------+--------+
| zero |protocol| UDP length |
+--------+--------+--------+--------+
If the computed checksum is zero, it is transmitted as all ones (
equivalent in one's complement arithmetic). An all zero
checksum value means that the transmitter generated no checksum (
debugging or for higher level protocols that don't care).
User
--------------
A user interface should
the creation of new receive ports
receive operations on the receive ports that return the data
and an indication of source port and source address
and an operation that allows a datagram to be sent, specifying
data, source and destination ports and addresses to be sent
[page 2]
28 Aug 1980
RFC 768 User Datagram
IP
IP
-------------
The UDP module must be able to determine the source and
internet addresses and the protocol field from the internet header.
possible UDP/IP interface would return the whole internet
including all of the internet header in response to a receive operation
Such an interface would also allow the UDP to pass a full
datagram complete with header to the IP to send. The IP would
certain fields for consistency and compute the internet header checksum
Protocol
--------------------
The major uses of this protocol is the Internet Name Server [3], and
Trivial File Transfer [4].
Protocol
---------------
This is protocol 17 (21 octal) when used in the Internet Protocol
Other protocol numbers are listed in [5].
----------
[1] Postel, J., "Internet Protocol," RFC 760, USC/
Sciences Institute, January 1980.
[2] Postel, J., "Transmission Control Protocol," RFC 761,
USC/Information Sciences Institute, January 1980.
[3] Postel, J., "Internet Name Server," USC/Information
Institute, IEN 116, August 1979.
[4] Sollins, K., "The TFTP Protocol," Massachusetts Institute
Technology, IEN 133, January 1980.
[5] Postel, J., "Assigned Numbers," USC/Information
Institute, RFC 762, January 1980.
Postel [page 3]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
RFC documents can be found at I.E.T.F.
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