A Conceptual Overview of iSCSI

Executive Summary

This White Paper provides a conceptual overview of iSCSI emphasizing the relationship of the

iSCSI protocol to other computer subsystems. A basic understanding of mass storage and

networking technologies is assumed. Concepts presented in this document include:

• iSCSI relationship with SCSI and TCP/IP

• iSCSI co-existence with current network traffic

• iSCSI utilization of mass storage and networking concepts

• iSCSI definition in terms of current network model

• iSCSI definition in terms of current mass storage model

1. Introduction

The Internet Small Computer Systems Interface (iSCSI) is a SCSI mass storage transport that

operates between the Transport Control Protocol (TCP) and the SCSI Protocol Layers. The iSCSI

protocol is defined in RFC 3720 [iSCSI], which was finalized by the Internet Engineering Task Force

(IETF) in April, 2004. A mandate of the iSCSI protocol design required no modifications to the

existing SCSI or TCP/IP protocols.

Figure 1. SCSI Transport Protocols

The Small Computer Systems Interface (SCSI) Architectural Model [SAM] is a family of protocols

defining a communication protocol with SCSI I/O devices. SCSI is a client-server architecture. The

phrase “SCSI Client” is synonymous with “SCSI initiator” and “SCSI server” is synonymous with

Parallel SCSI

Transport

Ethernet

FCP and

Fibre Channel

Transport

SCSI Protocol Layer

TCP

Networking

Upper

Level

Protocols

iSCSI

Transport

Applications

File Systems

Volume Management