RFC 1845 (rfc1845) - Page 1 of 7

SMTP Service Extension for Checkpoint/Restart

Network Working Group                                         D. Crocker
Request For Comments: 1845                        Brandenburg Consulting
Category: Experimental                                          N. Freed
                                            Innosoft International, Inc.
                                                   A. Cargille, WG Chair
                                                          September 1995


                         SMTP Service Extension
                         for Checkpoint/Restart

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.

Abstract

   This memo defines an extension to the SMTP service whereby an
   interrupted SMTP transaction can be restarted at a later time without
   having to repeat all of the commands and message content sent prior
   to the interruption.

1.  Introduction

   Although SMTP is widely and robustly deployed, various extensions
   have been requested by parts of the Internet community. In
   particular, when dealing with very large messages over less reliable
   connections it is possible for substantial resources to be consumed
   by repeated unsuccessful attempts to transmit the message in its
   entirety. The original SMTP specification [1] does not provide any
   means to pick up a partially completed transaction after the
   underlying TCP connection has been broken and reestablished.

   This memo provides a facility by which a client can uniquely identify
   a particular SMTP transaction. The server then stores this
   identifying information along with all the information it receives as
   the transaction proceeds. If the transaction is interrupted during
   the data transfer phase the SMTP client may establish a new SMTP
   session at a later time and ask the server to continue the
   transaction from the point where the server lost its connection with
   the client. The server then reestablishes the transaction context and
   tells the client where to resume operations. If this is acceptable
   the client resumes operations at this point.





Crocker, Freed & Cargille     Experimental