RFC 2920 (rfc2920) - Page 1 of 9

SMTP Service Extension for Command Pipelining

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Network Working Group                                          N. Freed
Request for Comments: 2920                                     Innosoft
STD: 60                                                  September 2000
Obsoletes: 2197
Category: Standards Track


             SMTP Service Extension for Command Pipelining

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   This memo defines an extension to the Simple Mail Transfer Protocol
   (SMTP) service whereby a server can indicate the extent of its
   ability to accept multiple commands in a single Transmission Control
   Protocol (TCP) send operation. Using a single TCP send operation for
   multiple commands can improve SMTP performance significantly.

1.  Introduction

   Although SMTP is widely and robustly deployed, certain extensions may
   nevertheless prove useful. In particular, many parts of the Internet
   make use of high latency network links.  SMTP's intrinsic one
   command-one response structure is significantly penalized by high
   latency links, often to the point where the factors contributing to
   overall connection time are dominated by the time spent waiting for
   responses to individual commands (turnaround time).

   In the best of all worlds it would be possible to simply deploy SMTP
   client software that makes use of command pipelining: batching up
   multiple commands into single TCP send operations. Unfortunately, the
   original SMTP specification [RFC-821] did not explicitly state that
   SMTP servers must support this. As a result a non-trivial number of
   Internet SMTP servers cannot adequately handle command pipelining.
   Flaws known to exist in deployed servers include:





Freed                       Standards Track
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