RFC 1854 (rfc1854) - Page 1 of 7
SMTP Service Extension for Command Pipelining
Alternative Format: Original Text Document
Network Working Group N. Freed
Request For Comments: 1854 Innosoft International, Inc.
Category: Standards Track A. Cargille, WG Chair
October 1995
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.
Abstract
This memo defines an extension to the SMTP service whereby a server
can indicate the extent of its ability to accept multiple commands in
a single TCP send operation. Using a single TCP send operation for
multiple commands can improve SMTP performance significantly.
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 [1] 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:
(1) Connection handoff and buffer flushes in the middle of
the SMTP dialogue. Creation of server processes for
incoming SMTP connections is a useful, obvious, and
harmless implementation technique. However, some SMTP
servers defer process forking and connection handoff
Freed & Cargille Standards Track