Mail Box Protocol
A network drop box for files to be printed or processed.
Watson, R.W., "Mail Box Protocol", RFC 196, DOI 10.17487/RFC0196, July 1971, <https://www.rfc-editor.org/info/rfc196>.
@misc{rfc196,
series = {Request for Comments},
number = 196,
howpublished = {RFC 196},
publisher = {RFC Editor},
doi = {10.17487/RFC0196},
url = {https://www.rfc-editor.org/info/rfc196},
author = {R.W. Watson},
title = {{Mail Box Protocol}},
pagetotal = 4,
year = 1971,
month = jul,
} RFC text
NETWORK WORKING GROUP Richard W. Watson
Request for Comments #196 SRI-ARC
NIC 7141 July 20, 1971
Categories: A.5, D.7
Obsoletes: none
Updates: none
A MAIL BOX PROTOCOL
The purpose of this protocol is to provide at each site a
standard mechanism to receive sequential files for immediate or
deferred printing or other uses. The files for deferred printing
would probably be stored on intermediate disk files, although
details of how a file is handled, stored, manipulated, or printed
at a site are not the concern of this protocol.
It is also assumed that there would be a program at the sending
site which sends the file in the format given below with the
optional control codes when appropriate. This program could
probably be accessed as a subcommand of the Telnet program.
The motivation for developing this protocol is the Network
Information Center's (NIC) need to be able to deliver messages
and documents to remote sites, and to be able to receive
documents for cataloging, redistribution, and other purposes from
remote site without having to know the details of path name
conventions and file system commands at each site. Multiple mail
boxes (128) are allowed at each site and are identified as
described below. The default is mail box number 0 for use with
the standard mail printer defined below.
A mail box, as we see it, is simply a sequential file to which
messages and documents are appended, separated by an appropriate
site dependent code.
Although this protocol will enable people to transmit messages
directly without going through the NIC, we want to encourage
people to use the NIC as much as possible, so that dialogue will
be recorded, cataloged and available for viewing online at NIC,
using the powerful facilities of the ARC on Line System (NLS).
The Mail Box Protocol will use established network conventions,
specifically the Network Control Program, Initial Connection
Protocol, and Data Transfer Protocol, NIC 7104.
The normal transmission is to be full 7-bit ASCII in 8-bit bytes,
the high order bit set to zero.
A MAIL BOX PROTOCOL RFC 196 NIC 7141
The standard receiving mail printer for mail box number 0 is
assumed to have a print line 72 characters wide, and a page of 66
lines. The new line convention will be carriage return (X'OD')
followed by line feed (X'OA') as per the Telnet Protocol RFC 158,
NIC 6768. The standard printer will accept form feed (X'OC') as
meaning move paper to the top of a new page.
It is the senders responsibility to control the length of the
print line and page. If more than 72 characters per line are sent
or if more than 66 lines are sent without a form feed, than the
receiving site can handle these situations as appropriate for
them. These conventions can be changed by control codes as
described below.
A message or document being sent to any mail box is a string of 8
bit bytes.
At the head of the message or document sent to mail box number 0
there is to be an initial address string terminated by a form
feed. This address string is to contain the sender's name and
address, and the receiver's name and address formatted in some
reasonable, easy-to-read form for a clerk to read and distribute.
Comments could also be included in the address string.
The format of information in mail boxes other than mail box
number 0 is not explicitly defined by this protocol.
Initial Connection
Initial Connection will be as per the Official Initial
Connection Protocol, Documents #2, NIC 7101, to a standard
socket not yet assigned. A candidate socket number would be
socket #5.
Data Transmission
Data Transmission will be as per the Data Transfer Protocol,
RFC 171, NIC 6793. That is, there will be a Modes Available
handshake, and then transmission of special control
information and data. A message or document is defined to be a
block of data. Control information is to be global. That is,
once a control mode is set it is assumed to apply during the
A MAIL BOX PROTOCOL RFC 196 NIC 7141
life of the connection unless explicitly changed. More than
one document may be sent during the life of the connection
unless the infinite bit stream mode is used. In the latter
case there will be one message or document per connection. A
reasonable convention for control information sent using the
infinite bit stream mode seems to be to assume that is applies
only to the next data stream connection from the host which
sent the control stream.
Control Information
The sending process should be capable of allowing the user to
indicate the control codes associated with the transmission of
a mail item. The control codes can be used with any mail box
number.
Mail Box Number
A site may find, as is the case at NIC, that it is useful
to have more than one receiving mail box, each to be
associated with a different process.
The mail box number for material to be printed by the
standard mail printer is mail box number 0 and is used by
default.
Code X'DO'
Meaning: A seven bit binary number in an eight bit field
with the high order bit set to zero is to follow
indicating the receiving mail box number.
Transmission Code Type
The default code type is 7-bit ASCII in an 8 bit field,
high order bit to zero.
'Code X'AO'
Meaning: A Data Type signal indicating that the
transmission code is 7-bit ASCII in an 8-bit field, high
order set to zero.
A MAIL BOX PROTOCOL RFC 196 NIC 7141
Code X'A1'
Meaning: Transparency, i.e. a stream of 8 bit bytes.
Code X'A2'
Meaning: EBCDIC
Other character codes could be added in the future.
Printer Control Codes
The default settings are a print line of 72 characters and
a print page of 66 lines.
Code X'D1
Meaning: Set line width to 72 characters.
Code X'D2'
Meaning: Use the full width of your printer.
Code X'D3'
Meaning: Set page size to 66 lines.
Code X'D4'
Meaning: Set page size to infinite.
Other virtual printer control codes can be added in the
future.
Other classes of control codes can be added as the need
arises.
[ This RFC was put into machine readable form for entry ]
[ into the online RFC archives by BBN Corp. under the ]
[ direction of Alex McKenzie. 12/96 ]
AI ELI5
On this page
§1Mail Boxes for Network Document Delivery
RFC 196 proposes a Mail Box Protocol as a standard mechanism for remote sites to send sequential files to each other. Each site maintains one or more numbered mail boxes (up to 128 per site). Senders deposit files into a mail box, and the receiving site handles them according to that site's policy—typically printing them, storing them for later retrieval, or redistributing them.
The protocol was motivated by the Network Information Center's (NIC) need to deliver documents to remote sites and to receive documents for cataloging and redistribution. Rather than requiring the NIC to know each site's unique file system and naming conventions, the mail box protocol provides a standard interface.
Instead of learning how to use each computer's file system, you just drop a file in its mailbox, and it handles it from there.
§2Format and Control Codes
Mail boxes use a simple format: messages are strings of 8-bit bytes, normally 7-bit ASCII with the high bit zero. The standard mail box (number 0) assumes a printer with a 72-character line and 66-line page, using carriage return and line feed (CR LF) for newlines and form feed (FF) to move to a new page.
Senders can use optional control codes to specify the mail box number, transmission code type (ASCII, transparent 8-bit, or EBCDIC), and printer settings such as line width and page size. At the head of a message to mail box 0, an address string identifies the sender and receiver, formatted for a clerk to read and distribute by hand.
You format your file like a normal text document, optionally add instructions about how to print it, then send it. The receiving computer figures out the rest.
§3Network Layering and Simplicity
The Mail Box Protocol builds on established network conventions: the Network Control Program (NCP), the Initial Connection Protocol (ICP), and the Data Transfer Protocol. A sender initiates a connection to a standard socket (candidate: socket 5) and follows the Modes Available handshake before transmitting control information and data.
The protocol's strength is its simplicity. It delegates the details of file handling, storage, and printing to each site, avoiding the complexity of specifying how every host should organize its files or what file systems it uses. This makes it practical across the diverse computers of the early ARPA Network.
It uses the standard network setup (NCP, ICP, Data Transfer), then just sends your file with a few hints about formatting. Simple and it works.