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User Datagram Protocol (RFC0768)

IP.com Disclosure Number: IPCOM000003816D
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2019-Feb-14
Document File: 3 page(s) / 4K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR

Related Documents

10.17487/RFC0768: DOI

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 73% of the total text.

RFC 768 J. Postel ISI 28 August 1980

User Datagram Protocol ----------------------

Introduction ------------

This User Datagram Protocol (UDP) is defined to make available a datagram mode of packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol (IP) [1] is used as the underlying protocol.

This protocol provides a procedure for application programs to send messages to other programs with a minimum of protocol mechanism. The protocol is transaction oriented, and delivery and duplicate protection are not guaranteed. Applications requiring ordered reliable delivery of streams of data should use the Transmission Control Protocol (TCP) [2].

Format ------

0 7 8 15 16 23 24 31 +--------+--------+--------+--------+ | Source | Destination | | Port | Port | +--------+--------+--------+--------+ | | | | Length | Checksum | +--------+--------+--------+--------+ | | data octets ... +---------------- ...

User Datagram Header Format

Fields ------

Source Port is an optional field, when meaningful, it indicates the port of the sending process, and may be assumed to be the port to which a reply should be addressed in the absence of any other information. If not used, a value of zero is inserted.

Postel [page 1]

28 Aug 1980 User Datagram Protocol RFC 768 Fields

Destination Port has a meaning within the context of a particular internet destination address.

Length is the length in octets of this user datagram including this header and the data. (This means the minimum value of the length is eight.)

Checksum is the 16-bit one’s complement of the one’s complement sum of a pseudo header of information from the IP header, the UDP header, and the data, padded with zero octets at the end (if necessary) to make a multiple of two octets.

The pseudo header conceptually prefixed to the UDP header contains the source address, the destination address, the protocol, and the UDP 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 (the equivalent in one’s complement arithmetic). An all zero transmitted checksum value means that the transmitter generated no checksum (for debugging or for higher level protocols that don’t care).

User Interface --------------

A user interface should allow

the creation of new receive ports,

receive operations on the receive ports that return the data octets and an indication of source port and source address,

and an operation that allows a datagram to be sent, specifying the data, source and destination ports and addresses to be sent.

[page 2] Postel

28 Aug 1980 RFC 768 Use...

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