University of Glasgow

School of Computing Science Glasgow G12 8QQ UK sm@smcquistin.uk

University of Glasgow

School of Computing Science Glasgow G12 8QQ UK vivianband0@gmail.com

University of Glasgow

School of Computing Science Glasgow G12 8QQ UK d.jacob.1@research.gla.ac.uk

University of Glasgow

School of Computing Science Glasgow G12 8QQ UK csp@csperkins.org

This document describes UDP using Augmented Packet Header Diagrams. This document is an example of the Augmented Packet Header Diagram language: it is not intended as a contribution to any ongoing or future work on maintaining or extending UDP.

Introduction This document uses Augmented Packet Header Diagrams to describe UDP , and is intended to further discussion about the design and implementation of the Augmented Packet Header Diagram language and tooling. Given this purpose, this document is not intended as a contribution to any ongoing or future work on maintaining or extending UDP. Further, this document does not necessarily reflect UDP, and its extensions, as presently standardised.

UDP Header This document describes the UDP protocol. The UDP protocol uses UDP Headers. A UDP Header is formatted as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source port | Destination port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | : : Payload : : | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where:

Source port (Src): 2 bytes.

Sending port.

Destination port (Dest): 2 bytes.

Destination port.

Length (L): 2 bytes; L >= 8.

Length of the header and payload in bytes.

Checksum: 2 bytes.

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.

Payload: L-8 bytes.

The payload of the UDP datagram, which is the whose size is the value of the Length field, less 8 bytes for the header.

IANA Considerations This document contains no actions for IANA.

Security Considerations The security implications of the Augmented Packet Header Diagrams format are considered in .

Acknowledgements This work has received funding from the UK Engineering and Physical Sciences Research Council under grant EP/R04144X/1.

Informative References

Source code repository The source code for tooling that can be used to parse this document, and generate parser code for the protocol it describes, is available from .