Zero Text Length EOF Message
Vint Cerf's 1969 proposal to use a zero-length message to mark the end of a file.
Cerf, V., "Zero Text Length EOF Message", RFC 13, DOI 10.17487/RFC0013, August 1969, <https://www.rfc-editor.org/info/rfc13>.
@misc{rfc13,
series = {Request for Comments},
number = 13,
howpublished = {RFC 13},
publisher = {RFC Editor},
doi = {10.17487/RFC0013},
url = {https://www.rfc-editor.org/info/rfc13},
author = {V. Cerf},
title = {{Zero Text Length EOF Message}},
pagetotal = 1,
year = 1969,
month = aug,
} RFC text
Network Working Group Vint Cerf
Request for Comments: 13 UCLA
20 August 1969
Referring to NWG/RFC: 11, it appears that file transmissions over
auxiliary connections will require some mechanism to specify "END-OF-
FILE." It is proposed that a length 0 (zero) message be used for this
purpose. Figure 1 shows the format:
|<---32 bits--->|<---32 bits--->|<----16 bits---->|<------?------>|
+---------------+---------------+-----------------+---------------+
| leader | marking | checksum | padding |
+---------------+---------------+-----------------+---------------+
Figure 1
Zero Text Length EOF Message
[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by Michael Brunnbauer 1/97 ]
AI ELI5
On this page
§1Why an End-of-File Signal
The proposal is written by Vint Cerf at UCLA, dated 20 August 1969, and refers to RFC 11. The author notes that file transmissions over auxiliary connections will need a mechanism to say END-OF-FILE.
The suggestion is that a message of length 0 (zero) be used for the purpose. Because every message already carries a length, a message with no text is easy to tell apart from data.
When the last page has been sent, send a blank page to say the book is finished.
§2The Zero Text Length Message
Figure 1 shows the layout of the zero text length EOF message as four fields in order: a 32-bit leader, a 32-bit marking, a 16-bit checksum and padding. The figure labels the padding width with a question mark, so it is not fixed in the text.
The RFC does not explain the individual fields. It gives only the figure and the proposal.
The empty envelope still has an address part, a spacer, a check number and some filler, but nothing inside.
§3What the Note Leaves Open
RFC 13 is a single page. It says nothing about acknowledgements, error handling or what a receiver should do on seeing the message, and it refers only to RFC 11 for the surrounding context.
It is only a first idea. The author does not say what the receiver does next.