IPS
Internet Draft
draft-ietf-ips-iscsi-name-disc-02.txt
Draft Title: iSCSI Naming and Discovery
Mark Bakke
Cisco
Joe Czap
IBM
Jim Hafner
IBM
Howard Hall
Pirus
Jack Harwood
EMC
John Hufferd
IBM
Yaron Klein
Sanrad
Marjorie Krueger
Hewlett-Packard
Lawrence Lamers
San Valley Systems
Todd Sperry
Adaptec
Joshua Tseng
Nishan
Kaladhar Voruganti
IBM
iSCSI Naming and Discovery
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 except that the right to
produce derivative works is not granted. Internet-Drafts are working
documents of the Internet Engineering.Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. Internet-Drafts are draft
Voruganti Internet Draft Expires Dec 2001 1
iSCSI Naming and Discovery Aug. 2001
documents valid for a maximum of six months and may be updated,
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cite them other than as "work in progress." The list of current
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Comments
Comments should be sent to the ips mailing list (ips@ece.cmu.edu) or
to kaladhar@us.ibm.com
Abstract
This document describes iSCSI [7] naming and discovery details. This
document complements the iSCSI Protocol draft. Flexibility is the key
guiding principle behind this document. That is, an
effort has been made to satisfy the needs of both small isolated
environments, as well as large environments requiring secure/scalable
solutions.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC-2119.
Table of Contents
1. Naming Requirements..............................................2
1.1. iSCSI Model....................................................2
1.2. SCSI Architecture Model........................................4
1.3. Consequences of the model......................................5
2. Naming Requirements..............................................6
2.1. iSCSI Names....................................................7
2.2. Initiator and Target Requirements for iSCSI Name support:.....14
3. iSCSI Discovery.................................................14
4. References......................................................20
5. Author's Addresses..............................................21
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1. Naming Requirements
1.1. iSCSI Model
This section describes that part of the iSCSI architectural model
that has the most bearing on the relationship between iSCSI and the
SCSI Architectural Model.
a) Network Entity
The Network Entity represents a device or gateway that is accessible
from the IP network. This device or gateway may support one or more
iSCSI Node. The iSCSI Node is accessed via a network portal (see
below).
b) iSCSI Node
There may be one or more iSCSI Storage Nodes within the Network
Entity. An iSCSI Node is identified by its iSCSI name. There is a
requirement for iSCSI names to be unique. iSCSI names are useful
because in some cases (e.g. when DHCP services [6] are used etc),
the combination of IP address and port number [6] cannot uniquely
identify an initiator or a target.
There is a default iSCSI Node object present at every target network
entity that may be accessed without specifying the iSCSI name for
the purpose of discovering a target nodes name(s). However, it is
necessary for the initiator to specify the full target iSCSI name to
instantiate a fully functional iSCSI session.
c) Network Portal
The Network Portal is a port through which access to any iSCSI Node
within the Network Entity can be obtained. A Network Entity must
have one or more Network Portals, each of which is usable by some
iSCSI Nodes contained in that Network Entity to gain access to the
IP network. A Network Portal in an initiator is identified by it IP
name or address. A Network Portal in a target is identified by its
IP name or address and its listening TCP port.
d) Portal Groups
iSCSI supports multiple connections within the same session; some
implementations will have the ability to do this across multiple
Network Portals. A Portal Group is a group of Network Portals which
collectively can support a multiple-connection session. A device
may contain one or more Portal Groups. Each Network Portal belongs
to exactly one portal group on each iSCSI node. Portal Groups are
identified within an iSCSI Node by a portal group tag, a simple
integer value. All Network Portals with the same portal group tag
are in the same Portal Group.
The following diagram shows an example of one such configuration on
a target and how a session may be established that shares Network
Portals within a Portal Group.
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----------------------------IP Network---------------------
| | |
+--------|---------------|--------------------|---------------------+
| +----|---------------|-----+ +----|---------+ |
| | +---------+ +---------+ | | +---------+ | |
| | | Network | | Network | | | | Network | | |
| | | Portal | | Portal | | | | Portal | | |
| | +--|------+ +---------+ | | +---------+ | |
| | | | | | | | |
| | | Portal | | | | Portal | |
| | | Group 1 | | | | Group 2 | |
| +--------------------------+ +--------------+ |
| | | | |
| +----------------------------+ +-----------------------------+ |
| | iSCSI Session (Target side)| | iSCSI Session (Target side) | |
| | | | | |
| | (iSCSI Name + TSID=0) | | (iSCSI Name + TSID=1) | |
| +----------------------------+ +-----------------------------+ |
| |
| iSCSI Target Node |
| (within Network Entity, not shown) |
+-------------------------------------------------------------------+
1.2. SCSI Architecture Model
This section describes the relationship between the SCSI
Architecture Model (SAM-2, see [cite?]) constructs of SCSI device,
SCSI port and I_T nexus and the iSCSI constructs described above.
This relationship implies implementation requirements in order to
conform to the SAM-2 model and other SCSI operational functions.
These implementation requirements are detailed in Section 3.3.
a) SCSI Device
This is the SAM-2 term for an entity that contains other SCSI
entities. For example, a SCSI Initiator Device contains one or more
SCSI Initiator Ports and zero or more application clients; a SCSI
Target Device contains one or more SCSI Target Ports and one or more
logical units. For iSCSI, the SCSI Device is the component within
an iSCSI Node that provides the SCSI functionality. As such there
can be at most one SCSI Device within a given iSCSI Node. The SCSI
Device Name is the same as the iSCSI Node name.
b) SCSI Port
This is the SAM-2 term for an entity in a SCSI device that provides
the SCSI functionality to interface with a service delivery
subsystem or transport. For iSCSI, the definition of SCSI Initiator
Port and SCSI Target Port are different.
SCSI Initiator Port: this maps to the endpoint of a session. An
iSCSI session is negotiated through the login process between an
iSCSI Intiator Node and an iSCSI Target Node. At successful
completion of this process, a SCSI Initiator Port is created within
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the iSCSI Initiator Node. The SCSI Initiator Port Name and SCSI
Initiator Port Identifier are both defined as the iSCSI Initiator
Name together with the ISID portion of the session identifier.
SCSI Target Port: this maps to a target Portal Group. The SCSI
Target Port Name and SCSI Target Port Identifier are both defined as
the iSCSI Target Name together with the portal group tag.
c) I_T Nexus
The I_T Nexus is a relationship between a SCSI Initiator Port and a
SCSI Target Port. For iSCSI, this relationship is a session. This
then is a relationship between the initiator end of a session (SCSI
Initiator Port) and the target portal group (SCSI Target Port)
through which the session is established.
1.3. Consequences of the model
This section describes the implementation and behavioral
requirements that result from the mapping of SCSI constructs to
iSCSI constructs defined above.
ISID RULE: Between a given iSCSI Initiator and iSCSI Target Portal
Group, there can be only one session with a given ISID. This does
not preclude use of the same ISID with a different Target Portal
Group on the same iSCSI Target Node (or on other iSCSI Target
Nodes), nor does it preclude other sessions with different ISIDs to
the same Target Portal Group.
The reason for this rule is to avoid instantiation of "parallel"
nexi between the same two SCSI initiator and SCSI target ports.
Certain nexus relationships contain explicit state (e.g., initiator-
specific mode pages or reservation state) that may need to be
preserved through changes or failures in the iSCSI layer (e.g.,
session collapses). In order for that state to be restored, the
initiator should reestablish its session (relogin) to the same
Target Portal Group using the previous ISID. This is because the
SCSI Initiator Port Identifier and the SCSI Target Port Identifier
(or relative target port) that the SCSI logical unit device server
uses to identify the nexus.
To facilitate compliance with the ISID RULE, the following should
hold:
iSCSI Initiator Requirements:
a) The iSCSI Name should be configurable parameter of each
initiator portal group.
b) The ISID name space of the iSCSI Initiator should be partitioned
among the intiator portal groups.
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iSCSI Target Requirements:
a) The iSCSI Name should be configurable parameter of each target
portal group.
b) The TSID name space of the iSCSI Initiator should be partitioned
among the target portal groups.
SCSI Mode Pages:
If the SCSI target does not maintain initiator-specific mode pages,
and an initiator makes changes to port-specific mode pages, the
changes may affect all other initiators logged in to that iSCSI
Target through the same Target Portal Group.
2. Naming Requirements
The concepts of names and addresses have been carefully separated in
iSCSI. A name is an identifier that specifies an end-point, such as
an initiator or target. The name must be location-independent; the
target can be moved to another address, or have multiple addresses,
but it is still the same target. An address is an identifier that
specifies a path to an end-point at which the target may currently
be found. Names are forever; addresses may change at any time.
This means that two types of identifiers are needed for iSCSI
initiators and targets:
- An iSCSI Node Name, or iSCSI Name, is a location-independent,
permanent identifier for an iSCSI initiator or target. It stays
constant for the life of the target. An iSCSI Name specifies an
iSCSI Node.
- An iSCSI Address specifies the location of an iSCSI initiator or
target. An iSCSI address consists of a host name or IP address,
a TCP port number (for the target), and the iSCSI Name of the
host or target. An iSCSI Address specifies an iSCSI Portal plus
an iSCSI Node.
- An iSCSI Identifier is either an iSCSI Name or an iSCSI Address.
Some specifications of iSCSI targets, such as a configuration
file or the iSCSI Boot mechanism [BOOT], require either a name
or an address to be stored in the same field. In this case, the
term "iSCSI Identifier" is specified to indicate that either the
name or the address can be used.
This set of structures has already been defined by the WWW and
internet folks. An iSCSI Identifier is functionally equivalent to a
Uniform Resource Identifier (URI), an iSCSI Name is functionally
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equivalent to a Uniform Resource Name (URN), and an iSCSI Address
fulfils the same function as a Uniform Resource Locator (URL).
A similar analogy exists for people. A person might be:
Robert Smith
SSN: 333-44-5555
Phone: +1 (763) 555.1212
Home Address: 555 Big Road, Minneapolis, MN 55444
Work Address: 222 Freeway Blvd, St. Paul, MN 55333
In this case, Robert's globally unique name is really his Social
Security Number (perhaps it should have a "us." in front of it); his
common name, "Robert Smith", is not guaranteed to be unique. Robert
has three locations at which he may be reached; two Physical
addresses, and a phone number. In this example, Robert's SSN is
like the iSCSI Name, his phone number and addresses are analogous to
the iSCSI Address, and "Robert Smith" would be a human-friendly
label for this person.
2.1. iSCSI Names
An iSCSI Node Name, or iSCSI name, is used to identify each iSCSI
initiator and target. The terms "initiator name" and "target name",
when used in this document, refer to iSCSI Node Names. This name is
designed to be globally unique, and is independent of the location
of the initiator or target. iSCSI names are formatted as UTF-8 text
strings.
iSCSI names may be assigned by a hardware manufacturer, software
manufacturer, or the end user. A naming authority scheme is
provided to ensure that each of these can confidently generate
unique names.
The iSCSI Name uniquely identifies iSCSI initiators and targets. The
Initiator Name corresponds to the logical operating system on which
the initiator is running, and the Target Name corresponds to the
target Storage Node entity.
iSCSI names are designed to fulfill the following requirements:
1. iSCSI names are globally unique. No two initiators or targets
should have the same name.
2. iSCSI names are permanent. An iSCSI initiator or target has the
same name for its lifetime.
3. iSCSI names do not imply a location or address. An iSCSI
initiator or target can move, or have multiple addresses. A
change of address does not cause a change of name.
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4. iSCSI names must not rely on a central name broker; the naming
authority must be distributed.
5. iSCSI names must support integration with existing unique naming
schemes.
6. iSCSI names must rely on existing naming authorities. iSCSI
must not create its own naming authority.
The encoding of an iSCSI name also has some requirements:
1. iSCSI names have one single encoding method when transmitted
over various protocols.
2. iSCSI names must be relatively simple to compare. The algorithm
for comparing two iSCSI names for equivalence must not rely on
any external server.
3. iSCSI names must be transcribable by humans. iSCSI names should
be kept as simple as possible, and should not use more than a
few special characters. They must also be case-insensitive, and
cannot include white space.
4. iSCSI names must be transport-friendly. They must be
transported using both binary and ASCII-based protocols, as well
as on paper.
An iSCSI Name really names a logical software entity, and is not
tied to a port or other hardware that can be changed. For instance,
an Initiator Name should name the iSCSI initiator driver, and not a
particular NIC or HBA card. When multiple NICs are used, they
should generally all present the same iSCSI Initiator Name to the
targets, since they are really to the same entity. In most
operating systems, the named entity is the operating system image.
Most hosts will have a single OS running; some of the really big
ones could have multiples.
A Target Name should similarly not be tied to hardware interfaces
which can be changed. A Target Name should identify the logical
target, and must be the same for the target regardless of the
physical portion being addressed. This gives iSCSI initiators an
easy way to determine that two targets it has discovered are really
two paths to the same target.
The iSCSI Name is designed to fulfill the functional requirements
for Uniform Resource Names (URN) [RFC1737]. Among these
requirements are that the name must have a global scope, independent
of address or location, and that it be persistent and globally
unique. It must be extensible, and scale with the use of naming
authorities. The encoding of the name should be transcribable by a
human, as well as be machine-readable. There are other requirements
as well; please read RFC1737 (only 5 pages) for definitions of these
requirements.
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The iSCSI Name may be displayed by user interfaces, but is generally
uninterpreted and used as an opaque, case-sensitive string for
comparison with other iSCSI Name values.
An iSCSI name is text-based. This was done for the following
reasons:
- A text-based identifier is transcribable, and is easier to
differentiate when looking at a user interface, or while
debugging problems with iSCSI login and discovery.
- iSCSI names are only used during login and discovery phases, so
the overhead does not get in the way of the data path.
- The iSCSI protocol communicates these via text strings, so it
"fits in" easily.
An iSCSI name consists of three parts: a type designator, followed
by a naming authority, with the remaining format designated by the
naming authority itself, subject to the following requirements.
An iSCSI name can be any Unicode character string with the following
properties:
- it is in Normalization Form C (see Unicode Standard Annex #15,
"Unicode Normalization Forms" at
http://www.unicode.org/unicode/reports/15)
- it contains only the ASCII dash character ('-'=U+002d) or the
ASCII dot character ('.'=U+002e) or is in one of the following
Unicode General Categories:
a) Lu (Letter, Uppercase)
b) Ll (Letter, Lowercase)
c) Lt (Letter, Titlecase)
d) Lm (Letter, Modifier)
e) Lo (Letter, Other)
f) Nd (Number, Decimal Digit)
g) Nl (Number, Letter)
h) No (Number, Other)
- when encoded in UTF-8, it is no more than 255 bytes
In particular, white space, punctuation (except as noted), marks and
symbols are not allowed.
When included in Text or Login messages, an iSCSI Name MUST be
formatted in UTF-8 form.
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For the purposes of comparison, computing hash values, or anything
else that operates on an iSCSI Name, iSCSI names (in their UTF-8
form) must be simply compared byte-for-byte.
The iSCSI Name does not define any new naming authorities. Instead,
it supports two existing authorities: an iSCSI-Qualified Name, using
domain names as an authority, similar to the Java class naming
heirarchy, and the EUI format used in Fibre Channel world- wide
names.
Since there are different types of naming authorities, there are
different types of iSCSI Names to make use of them. Each name is
prefixed with a short type designator string that indicates the type
of naming authority being used.
Here are the type designator strings that may currently be used:
iqn. - iSCSI Qualified Name
eui. - Remainder of the string is an EUI-64 address,
in ASCII hexadecimal.
As these two naming authorities will suffice in nearly every case
for both software and hardware-based entities, the creation of
additional type designators is discouraged. One of these two type
strings MUST be used when constructing an iSCSI name; any type
string not listed here is not allowed, as they cannot be guaranteed
to be unique.
The use of the naming authority means that iSCSI names can be
assigned by virtually any uniqueness scheme that can be devised by
OS vendors, driver or iSCSI NIC vendors, device vendors, gateway
vendors, and even the customer.
Type "iqn." (iSCSI Qualified Name)
This iSCSI name type can be used by any organization which owns a
Domain Name. This naming format is handy when an end user or
service provider wishes to assign the iSCSI Name for a target or
initiator. Customers which own domain names may not own an EUI,
OUI, SCSI Vendor ID, or any of the other assigned identifiers that
could be used as a naming authority.
To generate names of this type, the person or organization
generating the name must own a DNS domain name. This 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. For example, "ACME Storage
Arrays, Inc.", might own the domain "acme.com".
The organization generating names must also own an enterprise
number, obtained from IANA. Since a domain name can expire, be
aquired by another entity that wishes to generate iSCSI names, there
is a small possibility that the use of reversed domain names to
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indicate the naming authority could produce a name collision. The
enterprise number is used as a qualifier to the reversed domain
name. Enterprise numbers cannot be re-assigned.
The iSCSI qualified name string consists of:
- The string "iqn.", used to distinguish these names from other
types, such as "eui".
- A decimal enterprise number, assigned by IANA and owned by the
person or organization creating the iSCSI name.
- Another ".".
- A reversed domain name, owned by the person or organization
creating the iSCSI name. For example, our storage vendor
example would reverse its name to "com.acme". This is similar
to the process used to generate unique Java class names [22],
but without the restrictions on the domain name, since iSCSI
names allow hyphens, and does not have any reserved words.
- Another ".".
- Any string, within the character set and length boundaries, that
the owner of "acme.com" deems appropriate. This may contain
product types, serial numbers, host identifiers, software keys,
or anything else that makes sense to uniquely identify the
initiator or target.
Everything after the backwards domain name, followed by another dot
".", can be assigned as needed by the owner of the domain name. It
is the responsbility of the naming authority to ensure that the
iSCSI names it assigns are world wide unique.
The following is an example of a iSCSI qualified name from an
equipment vendor:
Ent Naming Defined by
Type # Auth Naming Authority
+-+ +--+ +------+ +--------------------+
| | | | | | | |
iqn.5886.com.acme.diskarrays-sn-a8675309
Where:
"iqn" specifies the use of the iSCSI qualified name as the
authority.
"5886" is the enterprise number owned by the naming authority.
"com.acme" defines the naming authority. The owner of the DNS
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name "acme.com" has the sole right of use of this name within
an iSCSI name, as well as the responsibility to keep the
remainder of the iSCSI name unique. In this case, acme.com
happens to manufacture disk arrays.
"diskarrays" was picked arbitrarily by acme.com to identify
the disk arrays they manufacture. Another product
that ACME makes might use a different name, and have it's
own namespace independent of the disk array group.
"sn" was picked by the disk array group of ACME to show that
what follows is a serial number. They could have just assumed
that all iSCSI Names are based on serial numbers, but they
thought that perhaps later products might be better identified
by something else. Adding "sn" was a future-proof measure.
"a8675309" is the serial number of the disk array, uniquely
identifying it from all other arrays.
The following is an example of a name that might be constructed by
an research organization:
Naming Defined by
Type Auth Naming Authority
+-+ +-------------------------+ +-----------+
| | | | | |
iqn.0.edu.pika-u.cs.users.oaks.proto.target4
In the above example, Professor Oaks of Pika University is building
research prototypes of iSCSI targets. Pika-U's computer science
department allows each user to use his or her user name as a naming
authority for this type of work. Professor Oaks chose to use
"proto.target4" for a particular target. Note that since this is a
research project, the Professor did not obtain an enterprise number,
and just used "0". This will ensure that his iSCSI names will not
conflict with commercially-assigned names, but accepts the risk that
it could conflict with another research organization if his domain
name is ever re-acquired.
The following is an example of an iSCSI name string from a storage
service provider:
Naming Defined by
Type Auth Naming Authority
+-+ +-------------+ +----------------------+
| | | | | |
iqn.5886.com.my-ssp.customers.4567.disks.107
In this case, a storage service provider (my-ssp.com) has decided to
re-name the targets from the manufacturer, to provide the
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flexibility to move the customer's data to a different storage
subsystem should the need arise.
My-ssp has configured the iSCSI Name on this particular target for
one of its customers, and has determined that it made the most sense
to track these targets by their Customer ID number and a disk
number. This target was created for use by customer #4567, and is
the 107th target configured for this customer.
Note that when reversing these domain names, the first
component(after the "iqn.") will always be a top-level domain name,
which includes "com", "edu", "gov", "org", "net", "mil", or one of
the two-letter country codes. The use of anything else as the first
component of these names is not allowed. In particular, companies
generating these names must not eliminate their "com." from the
string.
Again, these iSCSI names are NOT addresses. Even though they make
use of DNS domain names, they are used only to specify the naming
authority. An iSCSI name contains no implications of the iSCSI
target or initiator's location. The use of the domain name is only
a method of re-using an already ubiquitous name space.
Note that the SCSI Vendor ID or IEEE OUI could have been specified
as a naming authority. However, some large customers and service
providers may wish to use their own identification scheme, rather
than that provided by the manufacturer. These customers would not
likely have a registered Vendor ID, but the domain name we used is
ubiquitous, and was deemed more appropriate.
Type "eui." (IEEE EUI format)
The IEEE iSCSI name might be used when a manufacturer is already
basing unique identifiers on World-Wide Names as defined in the SCSI
SPC-2 specification.
It may also be used by a gateway representing a Fibre Channel or
SCSI device that is already adequately identified using a world-wide
name.
The format is "eui." followed by 16 hex digits.
Example iSCSI name :
Type EUI-64 WWN
+-+ +--------------+
| | | |
eui.02004567A425678D
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2.2. Initiator and Target Requirements for iSCSI Name support:
Each initiator and target implementation must support the use of
iSCSI names.
The initiator MUST send an InitiatorName and a TargetName as text
fields within the login request.
Initiators and targets shall support the receipt of iSCSI names of
up to the maximum length. If configuration of the initiator or
target name is allowed, the implementation shall support the maximum
length.
In their user interfaces, both shall support, at a minimum, the
display of the ASCII characters within the iSCSI Name's UTF-8
string.
If the other characters are unsupported, they may be displayed with
escape codes as specified in [RFC 2396].
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iSCSI Naming and Discovery Aug. 2001
3. iSCSI Discovery
The goal of iSCSI discovery is to allow an initiator to find the
targets to which it has access, and at least one address at which
each target may be accessed. This should generally be done using as
little configuration as possible. This section defines the
discovery mechanism only; no attempt is made to specify central
management of iSCSI devices within this document. Moreover, iSCSI
discovery mechanism only deals with target discovery and one still
needs to use the SCSI protocol for LUN discovery.
In order for an iSCSI initiator to establish an iSCSI session with
an iSCSI target, the initiator needs the IP address, TCP port
number and iSCSI target name information. The goal of iSCSI
discovery mechanism is to provide low overhead support for small
iSCSI setups, and scalable discovery solutions for large enterprise
setups. Thus, there are several methods that may be used to find
targets ranging from configuring a list of targets and addresses on
each initiator and doing no discovery at all, to configuring nothing
on each initiator, and allowing the initiator to discover targets
dynamically. The various discovery mechanisms differ in their
assumptions about what information is already available to the
initiators and what information needs to be still discovered.
iSCSI supports the following discovery mechanisms:
a. Static Configuration: This mechanism assumes that the IP address,
TCP port and the iSCSI target name information are already available
to the initiator.The initiators need to perform no discovery
in this approach. The initiator uses the IP address and the TCP port
information to establish a TCP connection, and it uses the
iSCSI target name information to establish an iSCSI session. This
discovery option is convenient for small iSCSI setups.
b. SendTargets: This mechanism assumes that the IP address and TCP
port information are already available to the initiator. The
initiator then uses this information to log into the canonical iSCSI
target present at the Network Entity. "iscsi" is the name of the
canonical target. The initiator then subsequently issues the
SendTargets text command to query information about the iSCSI
Targets available at the particular Network Entity (IP address).
SendTargets command details can be found in the iSCSI draft [7].
This discovery option is convenient for iSCSI gateways and routers.
c. Zero-Configuration: This mechanism assumes that the initiator
does not have any information about the target. In this option, the
initiator can either multicast discovery messages directly to the
targets or it can send discovery messages to storage name servers.
Currently, there are many general purpose discovery frameworks
available such as Salutation[2], Jini[2],UnPnP[2], SLP[17] and iSNS[8].
However, with respect to iSCSI, SLP can clearly perform the needed
discovery functions [21], while iSNS [8] can be used to provide related
management functions including notification, access management,
configuration, and discovery management. iSCSI equipment that
Voruganti Internet Draft Exp. Dec. 2001 15
iSCSI Naming and Discovery Aug. 2001
need discovery functions beyond SendTargets should at least implement
SLP, and then consider iSNS when extended discovery management
capabilities are required such as in larger storage networks.
It should be noted that since iSNS will support SLP, iSNS can
be used to help manage the discovery information returned by SLP.
Appendix A: iSCSI Name Notes
Some iSCSI Name Examples for Targets
- Assign to a target based on controller serial number
iqn.5886.com.acme.diskarray.sn.8675309
- Assign to a target based on serial number
iqn.5886.com.acme.diskarray.sn.8675309.oracle_database_1
Where oracle_database_1 might be a target label assigned by a user.
This would be useful for a controller that can present different
logical targets to different hosts.
Obviously, any naming authority may come up with its own scheme and
hierarchy for these names, and be just as valid.
A target iSCSI Name should NEVER be assigned based on interface
hardware, or other hardware that can be swapped and moved to other
devices.
Some iSCSI Name Examples for Initiators
- Assign to the OS image by fully qualified host name
iqn.5886.com.osvendor.dns.com.customer1.host_four
Note the use of two FQDNs - that of the naming
authority and also that of the host that is being
named. This can cause problems, due to limitations
imposed on the size of the iSCSI Name.
- Assign to the OS image by OS install serial number
iqn.5886.com.osvendor.newos5.12345-OEM-0067890-23456
Note that this breaks if an install CD is used more than once.
Depending on the O/S vendor's philosophy, this might be a feature.
- Assign to the OS image by a service provider
iqn.5886.com.mydisk.users.mbakke05657
Voruganti Internet Draft Exp. Dec. 2001 16
iSCSI Naming and Discovery Aug. 2001
Note that this could also be assigned to a particular iSCSI address
if more than one service provider is used.
Appendix B: iSCSI Proxies and Firewalls Taxonomy
iSCSI has been designed to allow SCSI initiators and targets to
communicate over an arbitrary network. This, making some assumptions
about authentication and security, means that in theory, the whole
internet could be used as one giant storage network.
However, there are many access and scaling problems that would come
up when this is attempted.
1. Most iSCSI targets may only meant to be accessed by one or a few
initiators. Discovering everything would be unnecessary.
2. The initiator and target may be owned by separate entities, each
with their own directory services, authentication, and other schemes.
An iSCSI-aware proxy may be required to map between these things.
3. Many environments use non-routable IP addresses, such as the 10.
network.
For these and other reasons, various types of firewalls and proxies
will be deployed for iSCSI, similar in nature to those already
handling protocols such as HTTP and FTP.
B.1. Port Redirector
A port redirector is a stateless device that is not aware of iSCSI.
It is used to do Network Address Translation (NAT), which can map IP
addresses between routable and non-routable domains, as well as map
TCP ports. While devices providing these capabilities can often
filter based on IP addresses and TCP ports, they generally do not
provide meaningful security, and are used instead to resolve internal
network routing issues.
Since it is entirely possible that these devices are used as routers
and/or aggregators between a firewall and an iSCSI initiator or
target, iSCSI connections must be operable through them.
Effects on iSCSI:
- iSCSI-level data integrity checks must not include information
from the TCP or IP headers, as these may be changed in between
the initiator and target.
Voruganti Internet Draft Exp. Dec. 2001 17
iSCSI Naming and Discovery Aug. 2001
- iSCSI messages that specify a particular initiator or target,
such as login requests and third party requests, should specify
the initiator or target in a location-independent manner. This
is accomplished using the iSCSI Name.
B.2. SOCKS server
A SOCKS server can be used to map TCP connections from one network
domain to another. It is aware of the state of each TCP connection.
The SOCKS server provides authenticated firewall traversal for
applications that are not firewall-aware. Conceptually, SOCKS is a
"shim-layer" that exists between the application (i.e., iSCSI) and
TCP.
To use SOCKS, the iSCSI initiator must be modified to use the
encapsulation routines in the SOCKS library. The initiator the opens
up a TCP connection to the SOCKS server, typically on the canonical
SOCKS port 1080. A subnegotiation then occurs, during which the
initiator is either authenticated or denied the connection request.
If authenticated, the SOCKS server then opens a TCP connection to the
iSCSI target using addressing information sent to it by the initiator
in the SOCKS shim. The SOCKS server then forwards iSCSI commands,
data, and responses between the iSCSI initiator and target.
Use of the SOCKS server requires special modifications to the iSCSI
initiator. No modifications are required to the iSCSI target.
As a SOCKS server can map most of the addresses and information
contained within the IP and TCP headers, including sequence numbers,
its effects on iSCSI are identical to those in the port redirector.
B.3. iSCSI Proxy
An iSCSI proxy is similar to proxies available in HTTP. The initiator
is aware of the actual addresses of the targets, but instead of
connecting to the addresses, connects instead to a proxy's address.
The proxy, in turn, connects to the actual targets. This is similar
to the HTTP/1.1 proxy, where the client passes the entire URL
(including IP and TCP address) to the proxy, rather than just the
path name.
An iSCSI proxy can provide some good iSCSI-level access
control and other functionality, while adding fairly light
configuration responsibilities.
Effects on iSCSI:
- When logging in to a target at a proxy address instead of the
actual address, the target should include the TargetAddress (IP
address and TCP port) of the target, in addition to its iSCSI Name.
Note, however, that this directly conflicts with the statement made
regarding NAT firewalls. Since the iSCSI Name can uniquely identify
Voruganti Internet Draft Exp. Dec. 2001 18
iSCSI Naming and Discovery Aug. 2001
an iSCSI device, the TargetAddress must then be used by the proxy as
a hint on where to find the iSCSI Name, and not as the final
authority.
- This is beginning to be covered in the iSCSI specification.
Having the address passed with the iSCSI Name would allow an iSCSI
proxy to exist without extra configuration or name services. Using
this type of proxy can eliminate the need to implement SOCKS.
B.4. SCSI gateway
This gateway presents logical targets (iSCSI Names) to the
initiators, and maps them to real iSCSI targets as it chooses. The
initiator sees this gateway as a real iSCSI target, and is unaware of
any proxy or gateway behavior. The gateway may manufacture its own
iSCSI Names,or use those provided by the real devices. This type of
gateway is used to represent parallel SCSI, Fibre Channel, SSA, or
other devices as iSCSI devices.
Nearly any capability that could be imagined is possible with this
type of gateway, but it may require more configuration than an iSCSI
proxy.
Effects on iSCSI:
- Since the initiator is unaware of any addresses beyond the gateway,
the gateway's own address is for all practial purposes the real
address of a target. Only the iSCSI Name needs to be passed. This
is already done in iSCSI, so there are no further requirements to
support SCSI gateways.
B.5. Stateful Inspection Firewall (stealth iSCSI firewall)
The Stealth model would exist as an iSCSI-aware firewall, that is
invisible to the initiator, but provides capabilities found in the
iSCSI proxy.
Effects on iSCSI:
- Since this is invisible, I don't think there are any additional
requirements on the iSCSI protocol for this one.
This one is more difficult in some ways to implement, simply because
it has to be part of a standard firewall product, rather than part of
an iSCSI-type product. For this reason, I would not expect to see
these implemented for a while.
Also note that this type of firewall is only effective in the
outbound direction (allowing an initiator behind the
firewall to connect to an outside target), unless the iSCSI target
is located in a DMZ. It does not provide adequate security
Voruganti Internet Draft Exp. Dec. 2001 19
iSCSI Naming and Discovery Aug. 2001
otherwise.
5. References
[1] Pascoe, R., "Building Networks on the Fly", in IEEE
Spectrum,March, 2001.
[2] John, R., "UPnP, Jini and Salutation- A look at some popular
coordination frameworks for future networked devices",
http://www.cswl.com/whiteppr/tech/upnp.html", June 17, 1999.
[3] http://www.srvloc.org
[4] Freed, N., "Behavior of and Requirements for Internet
Firewalls", RFC 2979, October 2000.
[5] ANSI/IEEE Std 802-1990, Name: IEEE Standards for Local and
Metropolitan Area Networks: Overview and Architecture
[6] Kessler, G. and Shepard, S., "A Primer On Internet and TCP/IP
Tools and Utilities", RFC 2151, June 1997.
[7] Satran, J., Sapuntzakis, C., Wakeley, M., Von Stamwitz, P.,
Haagens, R., Chadalapaka, M., Zeidner, E., Dalle Ore, L., Klein,
Y., "iSCSI", draft-ietf-ips-iscsi-07.txt, July, 2001.
[8] Gibbons, K., Tseng, J. and Monia, C., "iSNS Internet Storage
Name Service", draft-tseng-ips-isns-01.txt, July 2001.
[9] RFC 1737, "Functional Requirements for Uniform Resource Names".
[10] RFC 1035, "Domain Names - Implementation and Specification".
OUI - "IEEE OUI and Company_Id Assignments",
http://standards.ieee.org/regauth/oui/index.shtml
[11]EUI - "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority
http://standards.ieee.org/regauth/oui/tutorials/EUI64.html
[12] RFC 2396, "Uniform Resource Identifiers".
[13] RFC 2276, "Architectural Principles of URN Resolution".
[14] RFC 2483, "URI Resolution Services".
[15] RFC 2141, "URN Syntax".
[16] RFC 2611, "URN Namespace Definition Mechanisms".
[17] RFC 2608, SLP Version 2.
Voruganti Internet Draft Exp. Dec. 2001 20
iSCSI Naming and Discovery Aug. 2001
[18] RFC 2610, DHCP Options for the Service Location Protocol.
[19] P. Sarkar et al, "A Standard for Bootstrapping Clients using
the iSCSI Protocol", draft-ietf-ips-iscsi-boot-02.
[21] M. Bakke et al,"Finding iSCSI Targets and Name Servers using
SLP", draft-ietf-ips-iscsi-slp-01.txt, July, 2001.
[22] Sun Microsystems, "Java Language Specification", section 7.7
"Unique Package Names", 2000,
http://java.sun.com/docs/books/jls/second_edition/html/jTOC.doc.h
tml.
[23] Flanagan, et. al, "Java in a Nutshell", O'Reilly, 1997.
6. Author's Addresses
Address comments to:
Kaladhar Voruganti
650 Harry Road
IBM Almaden Research
San Jose, CA
USA
Email: kaladhar@us.ibm.com
Mark Bakke
Cisco Systems, Inc.
6450 Wedgwood Road
Maple Grove, MN 55311
Phone: +1 763 398-1054
Email: mbakke@cisco.com
Jim Hafner
IBM Research
Almaden Research Center
650 Harry Road
San Jose, CA 95120
Phone: +1 408-927-1892
Email: hafner@almaden.ibm.com
Joe Czap
IBM Corp.
600 Park Office Drive
RTP, NC 27709
Phone: +1 919 254-0828
Email: zapper@us.ibm.com
Josh Tseng
Nishan Systems
3850 North First Street
Voruganti Internet Draft Exp. Dec. 2001 21
iSCSI Naming and Discovery Aug. 2001
San Jose, CA 95134
Phone: 408 519-3749
Email: jtseng@nishansystems.com
Lawrence J. Lamers
SAN Valley Systems, Inc.
2105 South Bascom Avenue
Campbell, CA 95008
Phone: 408.234.0071
Email: ljlamers@ieee.org
Marjorie Krueger
Hewlett-Packard Corporation
8000 Foothills Blvd
Roseville, CA 95747-5668, USA
Phone: +1 916 785-2656
Email: marjorie_krueger@hp.com
Todd Sperry
Adaptec, Inc.
691 South Milpitas Boulevard
Milpitas, Ca. 95035
Phone: (408) 957-4980
Email: todd_sperry@adaptec.com
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