RFC 3783 (rfc3783) - Page 1 of 14
Small Computer Systems Interface (SCSI) Command Ordering Considerations with iSCSI
Alternative Format: Original Text Document
Network Working Group M. Chadalapaka
Request for Comments: 3783 R. Elliott
Category: Informational Hewlett-Packard Co.
May 2004
Small Computer Systems Interface (SCSI)
Command Ordering Considerations with iSCSI
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
Internet Small Computer Systems Interface (iSCSI) is a Small Computer
Systems Interface (SCSI) transport protocol designed to run on top of
TCP. The iSCSI session abstraction is equivalent to the classic SCSI
"I_T nexus", which represents the logical relationship between an
Initiator and a Target (I and T) required in order to communicate via
the SCSI family of protocols. The iSCSI session provides an ordered
command delivery from the SCSI initiator to the SCSI target. This
document goes into the design considerations that led to the iSCSI
session model as it is defined today, relates the SCSI command
ordering features defined in T10 specifications to the iSCSI
concepts, and finally provides guidance to system designers on how
true command ordering solutions can be built based on iSCSI.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions and Acronyms . . . . . . . . . . . . . . . . . . . 3
2.1. Definitions. . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of the iSCSI Protocol . . . . . . . . . . . . . . . . 4
3.1. Protocol Mapping Description . . . . . . . . . . . . . . 4
3.2. The I_T Nexus Model. . . . . . . . . . . . . . . . . . . 5
3.3. Ordered Command Delivery . . . . . . . . . . . . . . . . 6
3.3.1. Questions. . . . . . . . . . . . . . . . . . . . 6
3.3.2. The Session Guarantee. . . . . . . . . . . . . . 6
3.3.3. Ordering Onus. . . . . . . . . . . . . . . . . . 7
3.3.4. Design Intent. . . . . . . . . . . . . . . . . . 7
Chadalapaka & Elliott Informational