Network Working Group J. Satran
Request for Comments: 3720 K. Meth
Category: Standards Track IBM
C. Sapuntzakis
Cisco Systems
M. Chadalapaka
Hewlett-Packard Co.
E. Zeidner
IBM
April 2004
Internet Small Computer Systems Interface (iSCSI)
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 (2003). All Rights Reserved.
Abstract
This document describes a transport protocol for Internet Small
Computer Systems Interface (iSCSI) that works on top of TCP. The
iSCSI protocol aims to be fully compliant with the standardized SCSI
architecture model.
SCSI is a popular family of protocols that enable systems to
communicate with I/O devices, especially storage devices. SCSI
protocols are request/response application protocols with a common
standardized architecture model and basic command set, as well as
standardized command sets for different device classes (disks, tapes,
media-changers etc.).
As system interconnects move from the classical bus structure to a
network structure, SCSI has to be mapped to network transport
protocols. IP networks now meet the performance requirements of fast
system interconnects and as such are good candidates to "carry" SCSI.
Satran, et al. Standards Track [Page 1]
RFC 3720 iSCSI April 2004
Table of Contents
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 9
2. Definitions and Acronyms. . . . . . . . . . . . . . . . . . . 10
2.1. Definitions. . . . . . . . . . . . . . . . . . . . . . 10
2.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . 14
2.3. Conventions. . . . . . . . . . . . . . . . . . . . . . 16
2.3.1. Word Rule. . . . . . . . . . . . . . . . . . 16
2.3.2. Half-Word Rule . . . . . . . . . . . . . . . 17
2.3.3. Byte Rule. . . . . . . . . . . . . . . . . . 17
3. Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1. SCSI Concepts. . . . . . . . . . . . . . . . . . . . . 17
3.2. iSCSI Concepts and Functional Overview . . . . . . . . 18
3.2.1. Layers and Sessions. . . . . . . . . . . . . 19
3.2.2. Ordering and iSCSI Numbering . . . . . . . . 19
3.2.2.1. Command Numbering and
Acknowledging . . . . . . . . . . 20
3.2.2.2. Response/Status Numbering and
Acknowledging . . . . . . . . . . 23
3.2.2.3. Data Sequencing . . . . . . . . 24
3.2.3. iSCSI Login. . . . . . . . . . . . . . . . . 24
3.2.4. iSCSI Full Feature Phase . . . . . . . . . . 25
3.2.4.1. Command Connection Allegiance . . 26
3.2.4.2. Data Transfer Overview. . . . . . 27
3.2.4.3. Tags and Integrity Checks . . . . 28
3.2.4.4. Task Management . . . . . . . . . 28
3.2.5. iSCSI Connection Termination . . . . . . . . 29
3.2.6. iSCSI Names. . . . . . . . . . . . . . . . . 29
3.2.6.1. iSCSI Name Properties . . . . . . 30
3.2.6.2. iSCSI Name Encoding . . . . . . . 31
3.2.6.3. iSCSI Name Structure. . . . . . . 32
3.2.6.3.1. Type "iqn." (iSCSI
Qualified Name) . . . 32
3.2.6.3.2. Type "eui." (IEEE
EUI-64 format). . . . 34
3.2.7. Persistent State . . . . . . . . . . . . . . 34
3.2.8. Message Synchronization and Steering . . . . 35
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