Intro to Iscsi

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IMPACT modules consist of focused, in-depth training content that can be consumed in about 1-2 hours

Welcome to Introduction to iSCSI - IMPACT

2004 EMC Corporation. All rights reserved. These materials may not be copied without EMC's written consent.

EMC Global Education IMPACT

For questions or support please contact Global Education

! Complete Course Directions on how to

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complete status for this course.

! Course Description

! Student Resource Guide Training slides with notes

! Assessment Must be completed online

(Note: Completed Assessments will be reflected online within 24-48 hrs.)

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EMC Global Education

Introduction to iSCSIIMPACT

Course Description

e-Learning

This course presents the student with the necessaryinformation to understand the basics of the iSCSIprotocol, iSCSI PDU format, address and naming, andiSCSI logins in an IP storage network.

Course

Number:MR-5WP-ISCSI

Method: Impact Duration: 2hours

Audience

This course is intended for any person responsible for prospecting, architecting, deploying, operating, ormaintaining a SAN or NAS environment in which iSCSI technology is used.

Prerequisites

The prerequisites listed are helpful to understanding the course content and should be completed priorto registering for this course. The prerequisites for this course include:

None

Assumed knowledge for successful completion includes:

Basic understanding of networking

TCP/IP knowledge

Course Objectives

Upon successful completion of this course, participants should be able to:

Explain the basic concepts of the iSCSI protocol

List the iSCSI login processes

Explain how data is carried between the initiator and the target

Modules Covered

These modules are designed to support the course objectives. The following modules are includedin this course:

SCSI Concepts

iSCSI Concepts

iSCSI Layers

iSCSI Addresses and Names

iSCSI Login

iSCSI Discovery

iSCSI Communication

Labs


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iSCSI Overview, 1

EMC Global Education 2004 EMC Corporation. All rights reserved.

iSCSI Overview IMPACT

Copyright 2004 EMC Corporation. All rights reserved.

These materials may not be copied without EMC's written consent.

EMC believes the information in this publication is accurate as of its publication date. The information is

subject to change without notice.

THE INFORMATION IN THIS PUBLICATION IS PROVIDED AS IS. EMC CORPORATION MAKES NO

REPRESENTATIONS OR WARRANTIES OF ANY KIND WITH RESPECT TO THE INFORMATION IN THIS

PUBLICATION, AND SPECIFICALLY DISCLAIMS IMPLIED WARRANTIES OF MERCHANTABILITY OR

FITNESS FOR A PARTICULAR PURPOSE.

Use, copying, and distribution of any EMC software described in this publication requires an applicable

software license.

EMC is a registered trademark


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iSCSI Overview

After completing this course, you will be able to:

! Explain the basic concepts of the iSCSI protocol

! List the iSCSI login processes

! Explain how data is carried between the initiator and

the target


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iSCSI Overview, 3


SCSI Concepts

Lesson

As a result of completing this lesson, students should be able to do the following:

List the basic components of the SCSI environment

Explain the differences between a Logical Unit and a Logical Unit Number Define a SCSI task


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iSCSI Overview, 4


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Target and Initiator

The basic components of the SCSI environment are target, initiator, logical units, and logical unit number.

SCSI is a client-server architecture. Clients of a SCSI interface are called "initiators". Initiators issue SCSI

"commands" to request services from components, logical units, of a server known as a "target". The "device

server" on the logical unit accepts SCSI commands and processes them.


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Nodes

! A single Initiator or Target

! Names are assigned to allNodes

! Independent of IP addressand independent of MACaddress

Within iSCSI a Node is defined as a single Initiator or Target. These definitions map to the traditional SCSI

Target/ Initiator model. iSCSI Names are assigned to all Nodes and are independent of the associated

address.


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Logical Unit Number

Target

LUNs

1 2 3 4

At the highest level, SCSI is a family of interfaces for requesting services from I/O devices, including hard

drives, tape drives, CD and DVD drives, printers, and scanners. In SCSI terminology, an individual I/O device

is called a "logical unit" (LU).

A "SCSI transport" maps the client-server SCSI protocol to a specific interconnect. Initiators are one endpoint

of a SCSI transport. The "target" is the other endpoint. A target can contain multiple Logical Units (LUs). Each

Logical Unit has an address within a target called a Logical Unit Number (LUN).

A Logical Unit Number (LUN) is the logical unit address. A single address will be used to identify individual

logical units.


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SCSI Tasks

Target

LUNs

1 2 3 4

A SCSI task is a SCSI command or possibly a linked set of SCSI commands. Some LUs support multiple

pending (queued) tasks, but the queue of tasks is managed by the logical unit. The target uses an initiator

provided "task tag" to distinguish between tasks. Only one command in a task can be outstanding at any

given time.

Each SCSI command results in an optional data phase and a required response phase. In the data phase,

information can travel from the initiator to target (e.g., WRITE), target to initiator (e.g., READ), or in both

directions. In the response phase, the target returns the final status of the operation, including any errors.


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iSCSI Concepts

Lesson


Define iSCSI

Identify the advantages and disadvantages of iSCSI Explain the three protocols used in a IP Storage Network

Identify the IP Storage Deployment Models


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What is iSCSI?

! A method to transfer blocks of data using the TCP/IPnetwork

! Serialized service delivery subsystem

! SCSI protocol over IP (Internet Protocol)

TCP is a reliable transport that retransmits dropped packets IP is an unreliable transport mechanism (packet dropping

allowed)

Ethernet (10/100/1G/10G) is a popular Physical Transportlayer

The Internet Small Computer Systems Interface (iSCSI) protocol provides a means of transporting SCSI

packets over TCP/IP. iSCSI works by wrapping SCSI commands into TCP and transporting them over an IP

network. Since iSCSI is IP based traffic, it can be routed or switched on standard Ethernet equipment.


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iSCSIs still SCSI

! iSCSI architecture follows the typical SCSI model

LUTargetInitiatorOS

TCP / IP

Network

With the invention of fiber channel the SCSI cables between the initiator and target have been replaced with

fiber cables. Now with the invention of iSCSI the fiber cables are being replaced with less expensive network

cables and existing TCP/ IP networks.


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Advantages of iSCSI

! Many customers are moving from distributed to

centralized data storage.

! SCSI is already installed for storage connections.

!

TCP/IP is already installed for LANcommunications.

! LAN switching is currently cheaper than FC

switching.

dd

iSCSI also leverages IP knowledge and infrastructure. iSCSI leverages SCSI knowledge and standards.

IP knowledge is more widespread than FC knowledge.


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Protocols used in a IP Storage Network

iSCSI

FC

iSCSI/FC

Gateway

FC

FCIP

Router

FCIP

Router

FC

FC

iFCP

Switch

iFCP

Switch

FC

IPNetwork

IPNetwork

IPNetwork

IPNetwork

iFCPFCIP

protocols used in a IP Storage Network

Today, there are three protocols used in block storage over IP approaches in development:

iSCSI Native TCP/IP protocol. An IP-based protocol for establishing and managing Connections

between IP-based storage devices, hosts, and clients. No Fibre Channel content, but bridging between

iSCSI and FC is possible.

FCIP TCP/IP based tunneling/encapsulating protocol for connecting/extending Fibre Channel SANS.

More IP content, little Fibre Channel content. FCIP is a protocol used to merge two or more SANS

together using IP.

iFCP Gateway to gateway protocol for FC over IP. Mapping natively in IP across Fibre Channel and

IP. An IP-based tunneling protocol for interconnecting Fibre Channel devices together in place of Fibre

Channel switches. iFCP allows fabrics to remain independent.


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IP Storage Deployment Models

= IP

= FCNative! All Ethernet (No Fibre Channel)

! iSCSI Protocol

! Ethernet Switches & Routers

Bridging! Servers Ethernet Attached

! Storage FC Attached (SAN or DAS)

! iSCSI Protocol

Extension! Servers & Storage SAN Attached

! FCIP or iFCP Protocol

! SRDF

Native iSCSI allows for all communications using Ethernet. Initiators may be directly attached to iSCSI

Targets or may be connected using standard Ethernet routers and switches.

Bridging architectures allow for the Initiators to exist in an Ethernet environment while the storage remains in

a Fibre Channel SAN.

Extension architectures are most often used to provide connectivity across large distances. Either FCIP or

iFCP bring the long distance benefits of IP to Fibre Channel.


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Can we bridge FC to iSCSI?

Host still sees LUNs

whether FC or iSCSI

Symm still arbitrates access

via Volume Logix;

switch zoning still applies

Router can determine

which IP portals are seen

by hosts

IP FC

Yes, with qualified bridges see the latest EMC support Matrix.

Restrictions on the environment:

The network must be a local layer 2 network dedicated solely to the iSCSI configuration.

The network must be engineered with no packet loss or duplication.

iSCSI sessions may need to be manually re-established.

A PSQ (Pre-site Qualification) is required for each implementation.

Network design is key to making sure iSCSI works.

Real-world implementations require Gigabit Ethernet.

Consider iSCSI a local-area technology.

Segregate iSCSI traffic from general traffic. Layer 2 VLANs are particularly good for this type of design.

Oversubscription is OK for general user LANs, but not for iSCSI.


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Specifications

! www.ietf.org

The IP Storage workgroupmaintains current drafts

! www.t10.org

The Internet Engineering Task Force (IETF) is a community of network designers, operators, vendors, and

researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet.

The actual technical work of the IETF is done in its working groups, which are organized by topic into several

areas (e.g., routing, transport, security, etc.). The current draft specifications for iSCSI are in the RFCprocess and can be located at http://ietf.org

T10 is a Technical Committee of the Internationals Committee on Information Technology Standards

(INCITS). INCITS is accredited by, and operates under rules that are approved by, the American National

Standards Institute (ANSI). These rules are designed to insure that voluntary standards are developed by the

consensus of industry groups. INCITS develops Information Processing System standards, while ANSI

approves the process under which they are developed and publishes them. Related specifications on the

SCSI architectural model are located at http://www.t10.org


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Protocol Mapping

EthernetHeader

Ethernet

Header

IP

Header

TCP

Header

iSCSI

Header

SCSI Commands

& Data

CR

C

The iSCSI protocol is a mapping of the SCSI remote procedure invocation model over the TCP protocol.

SCSI commands are carried by iSCSI requests and SCSI responses and status are carried by iSCSI

responses. iSCSI also uses the request response mechanism for iSCSI protocol mechanisms.


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iSCSI PDU

Expected Data Transfer Length or Opcode Specific Fields

Initiator Task Tag or Opcode specific

Logical Unit Number (LUN)

DataSegmentLengthTotalAHSLength

Opcode Specific Fields.|I| Opcode

Basic

Header

Segment

Basic

Header

Segment

Additional

Header

Segment

Additional

Header

Segment

Header

Digest

Header

DigestSCSI

Command & Data

SCSI

Command & Data

Header

Data

Digest

Header

Data

Digest

In keeping with similar protocols, the initiator and target divide their communications into messages. This

message is the iSCSI protocol data unit (iSCSI PDU).


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Architectural Model

iSCSINode

TargetIP Network

Network

Portal

10.1.2.1TCP port

3250

NetworkPortal

10.1.2.2TCP port

3260

iSCSINode

Initiator

Network

Portal

10.1.1.1

Network

Portal

10.1.1.2

Network Entity

iSCSI Client

Network Entity

iSCSI Server

There are two major network components associated with iSCSI. The first is the Network Entity, the specific

device or gateway accessible to the IP network. This device must have one or more Network Portals

available for use. The second network component is the Network Portal. This component of the Network

Entity has an assigned IP address and a listening TCP port.


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iSCSI Portal Groups

iSCSINode

TargetIP Network

Network

Portal

10.1.2.1TCP port

3250

NetworkPortal

10.1.2.2TCP port

3260

iSCSINode

Initiator

Network

Portal

10.1.1.1

Network

Portal

10.1.1.2

Network Entity

iSCSI Client

Network Entity

iSCSI Server

iSCSI supports multiple connections within the same session; some implementations will have the ability to

combine connections in a session across multiple Network Portals. A Portal Group defines a set of Network

Portals within an iSCSI Node that collectively supports the capability of coordinating a session with

connections that span these portals. Portal Groups are identified within an iSCSI Node by a portal group tag,a simple unsigned-integer between 0 and 65535. Both iSCSI Initiators and iSCSI Targets have portal groups,

though only the iSCSI Target Portal Groups are used directly in the iSCSI protocol.


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iSCSI Layers

Lesson


List the layers of the iSCSI architectural model

Explain the concept of TOE and how it is used to increase performance

Describe the iSCSI frame composition


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iSCSI Layers

Ethernet

Command Descriptor Blocks

Builds/receives iSCSI PDUs

Control messages, SCSI commands,

parameters, data

Packet transmission protocol

Optical and Electrical Interfaces, Cables,

Connectors, etc.

Volume managers, File systems, applications

IP

TCP

iSCSI

SCSI Device Driver

Application

The iSCSI protocol is broken up into logical layers.


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Ethernet

Ethernet




parameters, data


Optical and Electrical Interfaces, Cables,

Connectors, etc.


IP

TCP

iSCSI

SCSI Device Driver

Application

Ethernet is the most widely-installed local area network (LAN) technology. Specified in a standard, IEEE

802.3, Ethernet was originally developed by Xerox and then developed further by Xerox, DEC, and Intel. An

Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet systems provide

transmission speeds up to 1 Gbps throughput and may use traditional copper or fiber optic cable. Devices areconnected to the cable and compete for access using a Carrier Sense Multiple Access with Collision

Detection (CSMA/CD) protocol.

Fast Ethernet or 100BASE-T provides transmission speeds up to 100 megabits per second and is typically

used for LAN backbone systems, supporting workstations with 10BASE-T cards. Gigabit Ethernet provides an

even higher level of backbone support at 1000 megabits per second (1 gigabit or 1 billion bits per second).

10-Gigabit Ethernet provides up to 10 billion bits per second.


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NIC & TOE

! Checksum offload

Fragmentation, out of orderpackets handled by host

Could hurt systemperformance

! Full TCP/IP offload

Fragmentation, out of orderpackets handled by TOE

Increasedmemory/processingrequirements

iSCSI & SCSI handled byhost

! Full TCP/IP+iSCSI/SCSI

Completes storageconnection

Runs all layers on TOE

Traditional Ethernet adapters (NIC) are designed to transfer packetized file level data among PCs, servers

and storage devices, such as NAS appliances. However, NICs do not traditionally transfer block level data,

which is handled by a storage host bus adapter, such as Fibre Channel or parallel SCSI. In order for a NIC to

process block level data the data needs to be placed into a TCP/IP packet before being sent over the IPnetwork. Through the use of iSCSI drivers on the host or server, a NIC can transmit packets of block level

data over an IP network. When using a NIC, the server handles the packet creation of block level data and

performs all of the TCP/IP processing. This is extremely CPU intensive and lowers the overall server

performance. The TCP/IP processing performance bottleneck has been the driving force behind the

development of TCP/IP offload engines (TOE) on adapter cards. A TOE removes the TCP/IP processing from

the host CPU and completes TCP/IP processing and packet creation on the HBA. Thus a TCP/IP offload

storage NIC operates more like a storage HBA rather than a standard NIC.


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IP

Ethernet




parameters, data


Optical and Electrical Interfaces, Cables,Connectors, etc.


IP

TCP

iSCSI

SCSI Device Driver

Application

The Internet Protocol (IP) is the method or protocol by which data is sent from one computer to another. Each

host on the network has at least one IP address that uniquely identifies it from all other computers on the

Internet. When you send or receive data, the message gets divided into chunks called packets. Each of these

packets contains both the sender's address and the receiver's address.

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Packets

iSCSI PDU

IP Packet

TCP Segment

Basic

Header

Segment

Additional

Header

Segment

Data

Header

Data

Digest

Header

Digest

TCP

Header

IP

Header

Because a message is divided into a number of packets, each packet can, if necessary, be sent by a different

route across the network. Packets can arrive in a different order than the order they were sent in. The Internet

Protocol just delivers them. It's up to another protocol, the Transmission Control Protocol (TCP) to put them

back in the right order.

An "iSCSI packet" contains SCSI data and the iSCSI header, which is created by the iSCSI initiator, and is

then wrapped in other protocol layers to facilitate its transport.

The Ethernet Header is used to provide the physical network capability (CAT5, MAC, FDX, etc).

The IP Header provides packet routing information used for moving the information across the network and

the TCP Header contains the information needed to guarantee delivery to the target destination.

The iSCSI Header explains how to extract SCSI commands and data.

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SCSI to iSCSI Mapping

SCSI Command and DataSCSI Command and Data

Header DataHeader Data

PDU PDU


PDU


PDU


IP packetIP packet

IP packetIP packet

IP packetIP packet

IP packetIP packet

IP packetIP packet

IP packetIP packet

IP packetIP packet

IP packetIP packet

As in most networking protocols the data is broken up and encapsulated within packets for transmission. In

iSCSI the SCSI commands are issued and broken into iSCSI PDUs. These in turn are broken into IP packets

and transmitted across the physical level. The receiving node must then reassemble the data and pass it up

the network stack until a SCSI command is extracted.

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TCP

Ethernet




parameters, data




IP

TCP

iSCSI

SCSI Device Driver

Application

Communication between the initiator and target occurs over one or more TCP connections. The TCP

connections carry control messages, SCSI commands, parameters, and data within iSCSI Protocol Data

Units. The group of TCP connections that link an initiator with a target form a session (loosely equivalent to a

SCSI I_T nexus).

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iSCSI Session ID

TSIH

ISID

The two principal Session Ids in iSCSI are the ISID and the TSIH. The Initiator Session ID (ISID) is generated

by the initiator during session login. There is one ISID for each session between a Target and Initiator pair

and is used for all additional logins during that session. The Target Session Identifying Handle (TSIH) is an

assigned tag by the Target for a session with a specific Initiator.

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iSCSI

Ethernet




parameters, data




IP

TCP

iSCSI

SCSI Device Driver

Application

The iSCSI layer builds/receives iSCSI PDUs and relays/ receives them to/from one or more TCP

connections.

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PDU Template

Data Digest (Optional)

DataSegment, Command Data (Optional)

AHS (Optional)

Header Digest (Optional)

SCSI Command Descriptor Block (CDB)

ExpStatSN

CmdSN

z

y

x

48

32

28

24Expected Data Transfer Length or Opcode Specific Fields20

Initiator Task Tag or Opcode specific

8

16

4

0

Byte 3Byte 2Byte 1Byte 0




7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

iSCSI Protocol Data Units (PDUs) are used to carry messages between the Target and the Initiator. It is

within the PDU that the actual mapping of SCSI data, commands and responses to iSCSI take place. PDUs

are padded to the closest integer number of four byte words. The padding bytes should be sent as 0. Each of

the segments within the PDU

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Basic Header Segment

48

44

40

36

32

28

24

Expected Data Transfer Length or Opcode Specific Fields20Initiator Task Tag or Opcode specific16

12

8

4

0





7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

The Basic Header Segment (BHS) is 48 bytes long. The Opcode and DataSegmentLength fields appear in

all iSCSI PDUs. In addition, when used, the Initiator Task Tag and Logical Unit Number always appear in the

same location in the header. The Immediate Delivery (I) bit is to mark a request for immediate execution,

however the operations involved (all or part of them) may be postponed to allow the target to receive all

relevant tasks.

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Opcodes

! Initiator opcodes

NOP-Out

SCSI Command

SCSI Task Managementrequest

Login Request

Text Request SCSI Data-out for write

operations

Logout Request

SNACK Request

Vendor specific codes

! Target opcodes

NOP-In

SCSI Response

SCSI Task Managementresponse

Login Response

Text Response SCSI Data-in for read

operations

Logout Response

Ready To Transfer (R2T)

Asynchronous Message

Vendor specific codes

Reject

The Opcode indicates the type of iSCSI PDU the header encapsulates. The Opcodes are divided into two

categories: initiator opcodes and target opcodes. Initiator opcodes are in PDUs sent by the initiator (request

PDUs). Target opcodes are in PDUs sent by the target (response PDUs).

Examples include the Login commands and Text Requests which assist in the discovery process.

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Additional Header Segment

Data-Digest (optional)mData Segment (optional)l

Header Digest (optional)k

Additional Header Segment (AHS) (optional)+

48

0


Basic Header Segment (BHS)

7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

The Additional Header Segments (AHS) are optional and when present follow the BHS. The AHS is used for

extended CDB information and bi-directional Read-Data requests.

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Data Segment




48

0



7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

The (optional) Data Segment contains PDU associated data. Its payload effective length is provided in the

BHS field - DataSegmentLength. The Data Segment is also padded to an integer number of 4 byte words.

Some SCSI commands require additional parameter data to accompany the SCSI command. This data may

be placed beyond the boundary of the iSCSI header in a data segment. Alternatively, user data (e.g., from aWRITE operation) can be placed in the data segment (both cases are referred to as immediate data).

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Header and Data Digest




48

0



7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

Optional header and data digests protect the integrity of the header and data, respectively. The digests, if

present, are located after the header and PDU-specific data, and cover the data and the padding bytes. The

decision as to whether there will be digests is negotiated during the Login Phase.

The separation of the header and data digests is useful in iSCSI routing applications, where only the headerchanges when a message is forwarded. In this case, only the header digest would be recalculated. Digests

are not included in data or header length fields.

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SCSI

Ethernet




parameters, data




IP

TCP

iSCSI

SCSI Device Driver

Application

The SCSI layer builds/receives SCSI Command Descriptor Blocks (CDB) and passes/receives them with the

remaining command execute parameters to/from the iSCSI layer.

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Reserved0x01

x

4

0


ExtendedCDB...+padding

AHSLength (CDBLength-15)

7 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 07 6 5 4 3 2 1 0

Command Descriptor Blocks (CDB) are the data structures used to contain the command parameters that an

initiator sends to a target. The CDB content and structure is defined by and device-type specific SCSI

standards.

There are 16 bytes in the CDB field to accommodate the commonly used CDBs. Whenever the CDB is largerthan 16 bytes, an Extended CDB AHS MUST be used to contain the CDB spillover.

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iSCSI Address & Names

Lesson


Identify the parts of the iSCSI name

List the parts of the iSCSI address

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iSCSI Names

! iSCSI names contain three parts Type designator

Naming Authority

String determined by naming authority

! iqn. iSCSI Qualified Name

iqn.2003-04.com.emc.symmetrix.0093 iqn.2003-04.com.emc.symmetrix.0093:diskarray.1

! eui. Extended Unique Identifier eui.50060482AEA5574E

Names enable iSCSI storage resources to be managed regardless of address. An iSCSI node name is also

the SCSI device name of an iSCSI device. The iSCSI name of a SCSI device is the principal object used in

authentication of targets to initiators and initiators to targets. It is also used to identify and manage iSCSI

storage resources. They are associated with iSCSI nodes, and not iSCSI network adapter cards, so the

replacement of network adapter cards does not require reconfiguration of all SCSI and iSCSI resourceallocation information.

iSCSI names must be unique within the operational domain of the end user. However, because the

operational domain of an IP network is potentially worldwide, the iSCSI name formats are worldwide unique.

To assist naming authorities in the construction of worldwide unique names, iSCSI provides two name

formats for different types of naming authorities.

iSCSI Qualified Name

To generate names of this type, the person or organization generating the name must own a registered

domain name. This domain name does not have to be active, and does not have to resolve to an address; it

just needs to be reserved to prevent others from generating iSCSI names using the same domain name.

Since a domain name can expire, be acquired by another entity, or may be used to generate iSCSI names by

both owners, the domain name must be additionally qualified by a date during which the naming authority

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iSCSI Addresses

! Address is the path to end point (iSCSI node) which isa combination of IP address (v4 or v6)

TCP Port

iSCSI name

! The address usually corresponds to the NetworkPortal

! Can be changed at any time except for the target TCPPort (3260)

An iSCSI address is comprised of the iSCSI Name and its Location. The Location is a combination of the

Host name, the IP address and, in the case of a Target, the TCP port number.

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iSCSI Login

Lesson


List the steps of the iSCSI login process

Explain the purposes of the iSCSI login process

Identify the types of iSCSI security

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Overview

! Login Validate User

Validate access rights

! Negotiate parameters for that session PDU size

Immediate data support

! Initiator (Host) Sends CMD as OPCODE encapsulatedin an iSCSI PDU

! Target (Storage) receives command, replies with R2T

! For a Write/Data Out (Read/Data In), Host (Target)sends data encapsulated in an iSCSI PDU

! Target sends encapsulated Status back to Initiator

The iSCSI login process includes several stages. During the login the user is authenticated and security

parameters are exchanged. Once the session is established the Initiator is able to send SCSI commands to

the Target. Normal SCSI command procedures are followed including Status replies.

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accept

login

Purpose of Login

! Enable a TCP connection

! Authentication

! Negotiate sessionparameters

! Marking the connection

The purpose of the iSCSI login is to enable a TCP connection for iSCSI use, authentication of the parties,

negotiation of the session's parameters and marking of the connection as belonging to an iSCSI session. A

session is used to identify to a target all the connections with a given initiator that belong to the same I_T

nexus. The targets listen on a well-known TCP port or other TCP port for incoming connections. The initiator

begins the login process by connecting to one of these TCP ports.

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Login Stages

Security

Negotiation

Operational

Parameter

Negotiation

The Login process proceeds in two stages - the security negotiation stage and the operational parameter

negotiation stage. Both stages are optional but at least one of them has to be present to enable setting some

mandatory parameters.

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Login

Login Response

Login Request

The iSCSI Login Phase is carried through Login requests and responses. Once suitable authentication has

occurred and operational parameters have been set, the session transitions to Full Feature Phase and the

initiator may start to send SCSI commands.

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Login Phase Start

Protocol version

iSCSI names

Negotiation state

The Login Phase starts with a login request from the initiator to the target. The initial login request includes:

Protocol version supported by the initiator.

iSCSI Initiator Name and iSCSI Target Name

Negotiation stage that the initiator is ready to enter.A login may create a new session or it may add a connection to an existing session. Between a given iSCSI

Initiator Node selected by an InitiatorName and a given iSCSI target defined by an iSCSI TargetName and a

Target Portal Group Tag.

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Login Security Negotiations

Security Login

Key Value

Parameters

The security exchange sets the security mechanism and authenticates the initiator user and the target to each

other. The exchange proceeds according to the authentication method chosen in the negotiation phase and is

conducted using the login requests' and responses' key=value parameters.

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Types of iSCSI Security

! iSCSI supports several different types of security:

Encryption

IPSec

IKE

Authentication

Kerberos v5 SRP (Secure Remote Password)

SPKM1 / 2

CHAP (possibly using RADIUS servers but not the protocol itself)

CHAP is the only must-support protocol in the current iSCSI spec, and its the only one EMC supports at

this time.

iSCSI Security CHAP basics. CHAP verifies identity using a hashed transmission.Secret key is known by both parties. Periodic re-challenges guard against replay attacks.

The target (not necessarily the iSCSI target, but the security requestor) initiates the challenge.

CHAP is a one-way protocol but may be implemented in two directions to provide security for both ends.

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iSCSI Security CHAP process

Challenge

Target compares hashes;

If they match, passwords

must be the same.

Hash

CHAP target sends out arandom challenge message

& hashes it with the

locally-stored key.

Requestor builds hash

with its locally-stored

key and sends it back.

Keyfhash

Challenge fhash Key Hash

Hash Hash

=

=

(Transmit)

(Transmit)

Key is never sent over the link. Hash function is one way; key cannot be mathematically derived from hash.

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Session Establishment

ISID

TSIH

The login PDU includes the ISID part of the session ID (SSID). The target portal group that services the login

is implied by the selection of the connection endpoint. For a new session, the TSIH is zero. As part of the

response, the target generates a TSIH.

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Full Feature Phase

SCSI

commands

Once the initiator is authorized to do so, the iSCSI session is in the iSCSI Full Feature Phase. A session is in

Full Feature Phase after successfully finishing the Login Phase on the first (leading) connection of a session.

A connection is in Full Feature Phase if the session is in Full Feature Phase and the connection login has

completed successfully. An iSCSI connection is not in Full Feature Phase when it does not have an

established transport connection or when it has a valid transport connection, but a successful login was notperformed or the connection is currently logged out.

In a normal Full Feature Phase, the initiator may send SCSI commands and data to the various LUNs on the

target by encapsulating them in iSCSI PDUs that go over the established iSCSI session.

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Operational Parameter Negotiation

! HeaderDigest andDataDigest (CRC32)

! MaxConnections,

! SendTargets,

! TargetName,

! InitiatorName,

!

TargetAlias,! InitiatorAlias,

! TargetAddress

! TargetPortalGroupTag

! R2T

! ImmediateData

! MaxRecvDataSegmentLength (PDU data size)

! MaxBurstSize

! FirstBurstSize

! DefaultTime2Wait

! DefaultTime2Retain

!

MaxOutstandingR2T! DataPDUInOrder

! DataSequenceInOrder

! ErrorRecoveryLevel

! SessionType

! Vendor Specific Key Format

Operational parameter negotiation during the login may occur in two situations. The first is starting with the

first Login request if the initiator does not propose any security/ integrity option. The other situation is

immediately after the security negotiation if the initiator and target perform such a negotiation.

Operational parameter negotiation may involve several Login request-response exchanges started and

terminated by the initiator. The initiator MUST indicate its intent to terminate the negotiation by setting the Tbit to 1; the target sets the T bit to 1 on the last response.

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iSCSI Connection Termination

TCP FIN

Graceful TCP connection shutdowns are done by sending TCP FINs. A graceful transport connection

shutdown should only be initiated by either party when the connection is not in iSCSI Full Feature Phase. A

target may terminate a Full Feature Phase connection on internal exception events, but it should announce

the fact through an Asynchronous Message PDU.

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iSCSI Discovery

Lesson


List the iSCSI Discovery methods

Explain the purposes of the iSNS service

Describe Discovery using Service Location Protocol

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iSCSI Discovery

! Defines how the Initiator finds the Target

! Methods of discovery Manual Configuration (SendTarget)

The initiator queries an iSNS

The initiator use SLP

iSCSI Discovery is the process where the Initiator finds the Target. This process is required before discovery

of Logical Units and LUNs.

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Manual Configuration

! Initiator is configured with the iSCSI address of theTarget Up to 255 characters long

iSCSI addresses (IP,TCP port)

! Initiator connects to an iSCSI server and initiates an

iSCSI discovery session! Upon successful login, the initiator issues

SendTargets command

! The Target returns a list of targets with the address,names and aliases

The ability to define a Target manually places the control into the administrators hands. Each Target must be

identified by its iSCSI name to each Initiator. This method could be difficult to manage since it requires direct

changes to each Initiator within the storage network. Additionally the iSCSI name can be up to 255 characters

long opening the potential to mistypes.


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iSCSI Overview, 59

St N S O i


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Storage Name Server Overview

! iSNS is a client/server model

! The iSNS server is passive May send state change notifications to the registered clients

in response to an action by an iSNS client

! iSNS clients register & manipulate the objects in the

iSNS server initiators, targets, management stations, switches

! An iSNS server can be hosted on a target, switch,initiator, or stand-alone server with specified IPaddress

The iSNS database is the information repository for the iSNS server(s). It maintains information about iSNS

client attributes. A directory-enabled implementation of iSNS may store client attributes in an LDAP directory

infrastructure.

There are four main functions of the iSNS:

1) A Name Service Providing Storage Resource Discovery

2) Discovery Domain (DD) and Login Control Service

3) State Change Notification Service

4) Open Mapping of Fibre Channel and iSCSI Devices

iSCSI Overview, 60

iSNS D i Di


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iSNS Domain Discovery

Discovery

Domains

Device B

Host B

Host A

Host C

Device A

Discovery Domains (DD) are a security and management mechanism used to partition storage resources.

Discovery Domains limit the discovery process to the administrator-configured subset of relevant storage

devices, preventing initiators from attempting login to devices that they shouldn't have access to.

When queried, the iSNS server will provide information only for storage entities that share at least one

common DD. Initiators will not be able to "see" devices that they do not have at least one common DD.

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iSNS Example


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iSNS Example

Security

Keys

Management Platform

iSNS

Device B

Host B

Host A

Host C

Device A

iSNS Protocol registration and query messages are sent by iSNS clients to servers, while notification

messages are sent by iSNS servers to iSNS clients. Messages originating at the client are sent to the iSNS

server at the well-known iSNS TCP or UDP port number.

The iSNS provides a registration function to allow all entities in a storage network to register and query the

iSNS database. Both targets and initiators can register in the iSNS database, as well as query for informationabout other initiators and targets. This allows, for example, a client initiator to obtain information about target

devices from the iSNS server. This service is modeled on the Fibre Channel Generic Services Name Server

described in FC-GS-3, with extensions, operating within the context of an IP network.

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State Change


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State Change

iSNS

Device B

Host B

Host A

Host C

Device A

Host

logs

out

SCN

service

The State Change Notification (SCN) service allows the iSNS to issue notifications about network events that

affect the operational state of iSNS clients. The iSNS client has the ability to register for these notifications of

events detected by the iSNS. The types of events for which SCNs can be sent include change in Discovery

Domain membership and device registration updates.

The State Change Notification service utilizes the Discovery Domain Service to control the distribution ofnotification messages. Notifications about changes within a DD are limited to members of that DD.

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Service Location Protocol (SLP)


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Service Location Protocol (SLP)

! A discovery mechanism with minimal configuration A good choice for small or medium networks

! The Service Agent advertises the iSCSI address asURL: iSCSI://[:]/

= IP address = optional and can be the IANA assigned (3260)

= target iSCSI name

! This address is primarily used for discovery

The Service Locator Protocol (SLP) was standardized in the IETF. It provides automatic client configuration

for applications and advertisement for network services. The Service Location Protocol eliminates the need

for a user to know the name of a network host supporting a service. Rather, the user names the service and

supplies a set of attributes which describe the service. The Service Location Protocol (SLP) allows the user to

bind this description to the network address of the service. The SLP is comprised of a process working on theclient's behalf to establish contact with some service. The User Agent (UA) retrieves service information from

the Service Agents or Directory Agents. The Service Agent (SA) is a process working on behalf of one or

more services to advertise the services and their capabilities. The process that collects service

advertisements is called the Directory Agent (DA) . There can only be one DA present per given host.

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SLP Example


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SLP Example

SLP

UA

iSCSI

Initiator

TCP/IP

Management Code

SLP

UA

iSCSI

Initiator

TCP/IP

Management CodeIP Network

SLP

Directory

Agent

For SLP to work the target would advertise its name:IP address:port either to a DA in the network or on its

own via its SA. The initiator contacts the DA directly, using its UA, looking for targets or could multicast

looking for an SA to request targets. All normal login processes follow from here.

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iSCSI Communications

Topic


Explain the data flow model of iSCSI

List the error correction methods of iSCSI

iSCSI Overview, 66

Ordering & Numbering


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O de g & u be g

! Every iSCSI PDU message is numbered

! Commands are numbered by CmdSN and are unique per iSCSIsession

! Status is numbered by StatSN and are unique per TCPconnection

! Data are numbered by DataSN and are unique per command

CmdSN

StatSN

CmdSN

StatSN StatSN

PDU #1 PDU #1

PDU #2

PDU #3

PDU #1

PDU #2

PDU #3

PDU #4

Similar to Fibre Channel and other network protocols, iSCSI uses a numbering system to manage the

breakup of data into smaller packets. At the highest level the CmdSN (Command Sequence Number) is

unique within an iSCSI session. The CmdSN is similar in operation to the OXID in Fibre Channel. At the TCP

connection level, the StatSN is the unique numbering identifier. The StatSN is equivalent to the SEQ_ID. The

DataSN field is also sequenced per command and is similar to the SEQ_CNT. Unlike command and status,data PDUs and R2Ts are not acknowledged by a field in regular outgoing PDUs.

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Data Flow


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! Data transfer on the same path as command andstatus

! Data out may be unsolicited or solicited

! Unsolicited data can be Sent as part of the command message or

Separate data messages (as in WRITE command)! Solicited data is sent

Only in response to a target initiated Ready-to-Transfer(R2T) message

Connection Allegiances when there are multiple connections are distributed for a single session. Data Out

means that data in the direction from the initiator to the target.

iSCSI Overview, 68

Example of iSCSI Data Flow


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68

p

192.168.0.58 192.168.0.100 TCP 1039 > 3260 [SYN] Seq=1771272578 Ack=0192.168.0.100 192.168.0.58 TCP 3260 > 1039 [SYN,ACK] Seq=2980037053 Ack=1771272579192.168.0.58 192.168.0.100 TCP 1039 > 3260 [ACK] Seq=1771272579 Ack=2980037054192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037054 Ack=1771272779192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037118 Ack=1771272827192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037166 Ack=1771272875192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI SCSI: Inquiry192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037238 Ack=1771272923192.168.0.100 192.168.0.58 iSCSI SCSI Data In192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)192.168.0.58 192.168.0.100 TCP 1039 > 3260 [ACK] Seq=1771272923 Ack=2980037338192.168.0.58 192.168.0.100 iSCSI SCSI: Inquiry192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037338 Ack=1771272971192.168.0.100 192.168.0.58 iSCSI SCSI Data In192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)192.168.0.58 192.168.0.100 TCP 1039 > 3260 [ACK] Seq=1771272971 Ack=2980037438192.168.0.58 192.168.0.100 iSCSI SCSI: Inquiry192.168.0.100 192.168.0.58 TCP 3260 > 1039 [ACK] Seq=2980037438 Ack=1771273019192.168.0.100 192.168.0.58 iSCSI SCSI Data In

192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)192.168.0.58 192.168.0.100 TCP 1039 > 3260 [ACK] Seq=1771273019 Ack=2980037538

TCP

iSCSI

Login

SCSI

Inquiry

In this example we see the establishment of the TCP session and then the transition to the iSCSI Login

sequence. For each successful login there is a Login Response issued. After the Full feature phase login, the

SCSI Inquiry phase begins and we are operating under normal SCSI 3 rules of discovery.

iSCSI Overview, 69

iSCSI CmdSN


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69

iSCSI (SCSI Command)Opcode: SCSI Command (0x01).0.. .... = I: Queued deliveryFlags: 0xc0

1... .... = F: Final PDU in sequence.1.. .... = R: Data will be read from target..0. .... = W: No data will be written to target.... .000 = Attr: Untagged (0x00)

TotalAHSLength: 0x00DataSegmentLength: 0x00000000LUN: 0000000000000000

InitiatorTaskTag: 0x48346681ExpectedDataTransferLength: 0x00001000

CmdSN: 0x0000015d

ExpStatSN: 0x00000003SCSI CDB

Opcode: Read(10) (0x28)DPO = 0, FUA = 0, RelAddr = 0Logical Block Address (LBA): 4572840Transfer Length: 8Vendor Unique = 0, NACA = 0, Link = 0

Command Sequence Number

The CmdSN (Command Sequence Number) enables ordered delivery across multiple connections in a single

session. For task sets, the CmdSN of the Task Management function request helps identify the tasks upon

which to act, namely all tasks associated with a LUN and having a CmdSN preceding the Task Management

function request CmdSN.

For Task Management, the coordination between responses to the tasks affected and the Task Managementfunction response is done by the target.

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iSCSI StatSN


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iSCSI (SCSI Command)Opcode: SCSI Command (0x01).0.. .... = I: Queued deliveryFlags: 0xa1

1... .... = F: Final PDU in sequence.0.. .... = R: No data will be read from target..1. .... = W: Data will be written to target.... .001 = Attr: Simple (0x01)

TotalAHSLength: 0x00DataSegmentLength: 0x00000000LUN: 0038000000000000

InitiatorTaskTag: 0x00000c21ExpectedDataTransferLength: 0x00000800CmdSN: 0x00000c21

ExpStatSN: 0x00000c25

HeaderDigest: 0xdc7346d9 (Good CRC32)SCSI CDB

Opcode: Write(10) (0x2a)DPO = 0, FUA = 0, RelAddr = 0Logical Block Address (LBA): 1254559Transfer Length: 4Vendor Unique = 0, NACA = 0, Link = 0

Status Sequence Number

Responses in transit from the target to the initiator are numbered. The StatSN (Status Sequence Number) is

used for this purpose. StatSN is a counter maintained per connection. StatSN is a Sequence Number that the

target iSCSI layer generates per connection and that in turn, enables the initiator to acknowledge status

reception. StatSN is incremented by 1 for every response/status sent on a connection except for responses

sent as a result of a retry or SNACK. In the case of responses sent due to a retransmission request, theStatSN MUST be the same as the first time the PDU was sent unless the connection has since been

restarted.

Status numbering starts with the Login response to the first Login request of the connection. The Login

response includes an initial value for status numbering (any initial value is valid).

iSCSI Overview, 71

iSCSI R2T


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iSCSI (Ready To Transfer)Opcode: Ready To Transfer (0x31)TotalAHSLength: 0x00DataSegmentLength: 0x00000000LUN: 0038000000000000InitiatorTaskTag: 0x00000c21TargetTransferTag: 0x0000001cStatSN: 0x00000c25ExpCmdSN: 0x00000c22MaxCmdSN: 0x00000d22R2TSN: 0x00000000

BufferOffset: 0x00000000DesiredDataLength: 0x00000800HeaderDigest: 0xb44fe89f (Good CRC32)

Ready to Transfer

R2T is the mechanism by which the SCSI target "requests" the initiator for output data. R2T specifies to the

initiator the offset of the requested data relative to the buffer address from the execute command procedure

call and the length of the solicited data.

To help the SCSI target associate the resulting Data-out with an R2T, the R2T carries a Target Transfer Tag

that will be copied by the initiator in the solicited SCSI Data-out PDUs. There are no protocol specificrequirements with regard to the value of these tags, but it is assumed that together with the LUN, they will

enable the target to associate data with an R2T.

iSCSI Overview, 72

SCSI Read Transaction


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72

192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981054 Ack=1787967638192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981118 Ack=1787967686192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981166 Ack=1787967734192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787967734 Ack=2774981238192.168.0.58 192.168.0.100 iSCSI SCSI: Read(10)(LBA: 0x0045c6a8, Len: 8)192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981238 Ack=1787967782192.168.0.100 192.168.0.58 iSCSI SCSI Data In

192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774982698 Ack=1787967782192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787967782 Ack=2774982698192.168.0.100 192.168.0.58 TCP 3260 > 1041 [PSH,ACK] Seq=2774984158 Ack=178796192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787967782 Ack=2774985382192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787967782 Ack=2774985430

iSCSILogin

SCSIREAD

SCSI

Dataand

Status

If an initiator issues a READ command, the target must send the requested data followed by the status to the

initiator over the same TCP connection that was used to deliver the SCSI command.

iSCSI Overview, 73

SCSI Write Transaction


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73

192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981054 Ack=1787967638192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981118 Ack=1787967686192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 iSCSI Login Command192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774981166 Ack=1787967734192.168.0.100 192.168.0.58 iSCSI Login Response (Success)192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787967734 Ack=2774981238192.168.0.58 192.168.0.100 iSCSI SCSI: Write(10)(LBA: 0x01117480, Len: 8)192.168.0.58 192.168.0.100 TCP 1041 > 3260 [ACK] Seq=1787969242 Ack=2774985430192.168.0.58 192.168.0.100 iSCSI NOP Out, NOP Out, NOP Out

192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774985430 Ack=1787970702192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774985430 Ack=1787971926192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)192.168.0.58 192.168.0.100 iSCSI SCSI: Write(10)(LBA: 0x01117428, Len: 8)192.168.0.58 192.168.0.100 iSCSI SCSI: Write(10)(LBA: 0x01117428, Len: 8)192.168.0.58 192.168.0.100 iSCSI NOP Out, NOP Out, NOP Out, NOP Out, NOP Out,192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774985478 Ack=1787974846192.168.0.100 192.168.0.58 TCP 3260 > 1041 [ACK] Seq=2774985478 Ack=1787976070192.168.0.100 192.168.0.58 iSCSI SCSI Response (Good)

iSCSILogin

SCSI

WRITE

Status

SCSI

Write

Status

If an initiator issues a WRITE command, the initiator must send the data for that command over the same

TCP connection that was used to deliver the SCSI command. The target must return the status over the

same TCP connection that was used to deliver the SCSI command.

iSCSI Overview, 74

Initiator Error Recovery Mechanisms


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74

The initiator mechanisms defined in connection with error recovery are:

NOP-OUT to probe sequence numbers of the target

Command retry

Recovery R2T support

Requesting retransmission of status/data/R2T using the SNACK facility

Acknowledging the receipt of the data

Reassigning the connection allegiance of a task to a different TCP connection

Terminating the entire iSCSI session to start afresh

For outstanding SCSI commands, it is assumed that iSCSI, in conjunction with SCSI at the initiator, is able to

keep enough information to be able to rebuild the command PDU, and that outgoing data is available in host

memory for retransmission. At the target, incoming data (read data) may be kept for recovery or it can be

reread from a device server.

iSCSI Overview, 75

Target Error Recovery Mechanisms


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75

The target mechanisms defined in connection with error recovery are:

NOP-IN to probe sequence numbers of the initiator

Requesting retransmission of data using the recovery R2T feature

SNACK support

Requesting that parts of read data be acknowledged

Allegiance reassignment support

Terminating the entire iSCSI session to force the initiator to start over

A target will keep the "status & sense for a command it has executed if it supports status retransmission. A

target that supports data retransmission is expected to be prepared to retransmit the outgoing data (i.e., Data-

In) on request until either the status for the completed command is acknowledged, or the data has been

separately acknowledged.

iSCSI Overview, 76

Module Summary


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76

! iSCSI is an IP based storage protocol allowing existingEthernet equipment to be used for Storage Networking

! the iSCSI protocol is broken into layers

! The iSCSI login process allows for authentication andhigher level processes to proceed

!

Data is placed within iSCSI PDUs for transmission! iSCSI maintains error correction within the session

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77

Closing Slide

Link to Knowledgelink to update your transcript and indicate that you have completed the course.

EMC Global Education IMPACT Course Completion


80/80

1. Logon to Knowledgelink (EMC Learning management system).

2. Click on 'My Development'.

3. Locate the entry for this learning event you wish to complete.

4. Click on the complete icon [ ].

Introduction to iSCSI - IMPACTCourse Completion Steps:

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Development Plan.

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Intro to Iscsi

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Transcript of Intro to Iscsi