Network Working Group Greg Vaudreuil Internet Draft Tigon Corporation Expires: 4/18/94 October 18, 1993 SMTP Service Extensions for Command Streaming 1.Status of this Memo This document is an Internet Draft. Internet Drafts are working documents of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute working documents as Internet Drafts. Internet Drafts are valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet Drafts as reference material or to cite them other than as a "work in progress". 2.Abstract This memo defines an extension to the SMTP service whereby an SMTP client and server may negotiate the use of a command streaming implementation model for SMTP. This model enables the batching of the all commands between the EHLO and DATA command. This extension significantly reduces the number of packets and round trips to send a message. Batching the MAIL FROM and RCPT TO commands for multiple receipients significantly decreases the protocol processing overhead when sending messsages to multiple receipients. 3.Introduction One source of inefficiency in the use of SMTP, especially when used in in a central mail hub, is the implicit requirement to send the full SMTP command stream, including each RCPT TO command sychronously, that is, to wait for a response to the previous command before sending the next. This stop and wait interaction often adds minutes to the length of a SMTP session, partly when validation of addresses may require non-local table lookup. This memo uses the mechanism defined in [4] to define extensions to the SMTP service whereby a client ("sender-SMTP") may declare support for a atreaming command mode. 4.Framework for the Binary Extensions The following service extension is hereby defined: 1) The name of the service extension is "Stream" 2) The EHLO keyword value associated with this extension is "STREAM" Internet Draft Expires 4/18/94 3) No parameter is used with the STREAM keyword 5.The Stream service extension When a client SMTP wishes to submit (using the MAIL command) a content body consisting of a MIME message containing arbitrary octet-aligned material, it first issues the EHLO command to the server SMTP. If the server SMTP responds with code 250 to the EHLO command, and the response includes the EHLO keyword value STREAM, then the server SMTP is indicating that it supports the command streaming implementation model and will the batching of all commands between the EHLO and the accept MIME messages containing arbitrary octet-aligned material. After receiving the 250 response to the EHLO command with the STREAM keyword, the MAIL FROM and RCPT TO commands can optionally be sent as a block. If the MAIL FROM address is invalid or otherwise unavailable, the following RCPT TO commands should be answered with the 503 command out of sequence error. Note: While SMTP does not explicitly require the stop and wait behavior, and while the protocol as defined will work in a streaming model, the examples have led implementors to build SMTP servers in such a manner as to require this behavior. This service extension recognizes the desire to use a streaming implementation model and explicitly encourages its use. Vaudreuil [Page 2] Internet Draft Expires 4/18/94 6.Usage Examples The following dialogue illustrates the use of the stream service extension to send a 7BIT object to three recipients without the stop and wait for an explicit 250 for each recipient: S: C: S: 220 cnri.reston.va.us SMTP service ready C: EHLO ymir.claremont.edu S: 250-cnri.reston.va.us says hello S: 250 STREAM C: MAIL FROM: C: RCPT TO: C: RCPT TO: C: RCPT TO: S: 250 ... Sender ok S: 250 ... Recipient ok S: 250 ... Recipient ok S: 250 ... Recipient ok C: DATA S: 354 Send message, terminated by a dot. ... . S: 250 OK C: QUIT S: 250 Goodbye 7.Security Considerations This RFC does not discuss security issues and is not believed to raise any security issues not already endemic in electronic mail and present in fully conforming implementations of [1]. 8.Acknowledgements This document is the result of numerous discussions in the IETF SMTP Extensions Working Group. Text for this document was liberally copied from RFC 1426 by John Klensin, Marshall Rose, Need Freed, Dave Crocker, and Einar Stefferud. Vaudreuil [Page 3] Internet Draft Expires 4/18/94 9.References [1] Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821, USC/Information Sciences Institute, August 1982. [2] Crocker, D., "Standard for the Format of ARPA Internet Text Messages", STD 11, RFC 822, UDEL, August 1982. [3] Borenstein, N., and N. Freed, "Multipurpose Internet Mail Extensions", RFC 1341, Bellcore, Innosoft, June 1992. [4] Klensin, J., WG Chair, Freed, N., Editor, Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extensions" RFC 1425, [5] Klensin, J., WG Chair, Freed, N., Editor, Rose, M., Stefferud, E., and D. Crocker, "SMTP Service Extension for 8bit- MIMEtransport" RFC 1426, United Nations University, Innosoft International, Inc., Dover Beach Consulting, Inc., Network Management Associates, Inc., The Branch Office, February 1993. 10. Author's Address Gregory M. Vaudreuil The Tigon Corporation 17080 Dallas Parkway Dallas, TX 75248-1905 214-733-2722 Gvaudre@cnri.reston.va.us Vaudreuil [Page 4]