SMTP Service Extensions for Transmission of Large and Binary MIME Messages (RFC1830)
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
This memo defines two extensions to the SMTP service. The first service enables a SMTP client and server to negotiate the use of an alternate DATA command "BDAT" for efficiently sending large MIME messages. The second extension takes advantage of the BDAT command to permit the negotiated sending of unencoded binary data. This memo defines an Experimental Protocol for the Internet community.
Network Working Group G. Vaudreuil Request for Comments: 1830 Octel Network Services Category: Experimental August 1995
SMTP Service Extensions for Transmission of Large and Binary MIME Messages
Status of this Memo
This memo defines an Experimental Protocol for the Internet community. This memo does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.
This memo defines two extensions to the SMTP service. The first service enables a SMTP client and server to negotiate the use of an alternate DATA command "BDAT" for efficiently sending large MIME messages. The second extension takes advantage of the BDAT command to permit the negotiated sending of unencoded binary data.
The MIME extensions to the Internet message protocol provides for the transmission of many kinds of data which were previously unsupported in Internet mail. Anticipating the need to more efficiently transport the new media made possible with MIME, the SMTP protocol has been extended to provide transport for new message types. RFC 1426 defines one such extension for the transmission of unencoded 8 bit MIME messages [8BIT]. This service extension permits the receiver SMTP to declare support for 8 bit body parts and the sender to request 8 bit transmission of a particular message.
One expected result of the use of MIME is that the Internet mail system will be expected to carry very large mail messages. In such transactions, there is a need to eliminate the requirement that the message be scanned for "CR LF . CR LF" sequences upon sending and receiving to detect the end of message.
Independent of the need to send large messages, Internet mail is increasingly multi-media there is a need to avoid the overhead of base64 and quoted-printable encoding of binary objects sent using the MIME message format over SMTP between hosts which support binary message processing.
Vaudreuil Experimental [Page 1]
RFC 1830 Binary and Large Message Transport August 1995
This memo uses the mechanism defined in [ESMTP] to define two extensions to the SMTP service whereby a client ("sender-SMTP") may declare support for the message chunking transmission mode using the BDAT command and support for the sending of Binary messages.
3. Framework for the Large Message Extensions
The following service extension is hereby defined:
1) The name of the data chunking service extension is "CHUNKING".
2) The EHLO keyword value associated with this extension is "CHUNKING".
3) A new SMTP verb is defined "BDAT" as an alternative to the "DATA" command of [RFC821]. The BDAT verb takes two arguments. The first argument indicates the length of the binary data packet. The second optional argument indicates that the data packet is the last.
bdat-cmd ::= "BDAT" SP chunk-size [ SP end-marker ] CR LF chunk-size ::= 1*DIGIT end-marker ::= "LAST"
The CHUNKING service extension enables the use of the BDAT alternative t...