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IPS
Internet Draft
draft-ietf-ips-iscsi-name-disc-05.txt
Draft Title: iSCSI Naming and Discovery
Mark Bakke
Cisco
Jim Hafner
John Hufferd
Kaladhar Voruganti
IBM
Marjorie Krueger
Hewlett-Packard
Joshua Tseng
Nishan Systems
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
documents valid for a maximum of six months and may be updated,
replaced, or obsoleted by other documents at any time. It is
inappropriate to use Internet- Drafts as reference material or to
cite them other than as "work in progress." The list of current
Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-
abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
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
Internet Draft Naming and Discovery 2
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.
Acknowledgements
Joe Czap (IBM), Howard Hall (Pirus), Jack Harwood (EMC),
Yaron Klein (SANRAD), Larry Lamers (SAN Valley Systems),
and Todd Sperry (Adaptec) have participated and made
contributions during the weekly Naming and Discovery
teleconferences.
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.
Voruganti, K. Informational-Track Expires August 2002
Internet Draft Naming and Discovery 3
Table of Contents
1. iSCSI Naming Philosophy..........................................................3
2. iSCSI Names.................................................................................4
3. iSCSI ISID...................................................................................17
4. iSCSI Discovery.........................................................................20
5. Appendix A: iSCSI Naming Notes..........................................22
6. Appendix B: Proxy Description...............................................23
7. Appendix C: iSCSI Names and Security Identifiers..............26
8. References..................................................................................27
9. Author's Addresses.................................................................29
1. iSCSI Naming Philosophy
The notion of an iSCSI name is required at both the targets and at
the initiators. iSCSI name is required at the target because it
uniquely identifies a target as a storage resource for the initiators.
iSCSI initiator name is required at the initiator because it helps to
uniquely identify an initiator for the purpose of target resource
allocation (i.e., which initiator has access to which target
resource). iSCSI name is also used to provide a mechanism for world
wide unique identification of SCSI Initiator Ports (analogous to FC
WWPortnames). The SCSI port name is used by SCSI during SCSI
reservations, SCSI initiator specific task queue management and
SCSI mode page management. Furthermore, iSCSI initiator names can be
also potentially used by software layers such as security and
management software to uniquely identify initiators to targets.
It is necessary for the iSCSI names to be unique within the operation
domain of the end user. However, since user operation domains can
potentially merge with other user operation domains, the iSCSI naming
mechanism has been architected to ensure world wide uniqueness. In
order to ensure both world wide name uniqueness iSCSI provides for
the use of different types of naming authority mechanisms.
Furthermore, iSCSI names are associated with iSCSI nodes instead of
with network adapter cards to ensure the free movement of network
HBAs between hosts without carrying over the SCSI state information
(reservations, mode page settings etc).
Since there can be multiple separate iSCSI sessions (via different
iSCSI ports) between the same iSCSI initiator and target nodes,
iSCSI has introduced the notion of an initiator session id (ISID)
and a target session id (TSID) to help in uniquely identifying each
of the iSCSI sessions. The ISID and the TSID are not global identifiers
but together uniquely identify a session only within the context of a
Voruganti, K. Informational-Track Expires August 2002
Internet Draft Naming and Discovery 4
given named iSCSI initiator and iSCSI target.
In addition to the mandatory iSCSI concepts of iSCSI initiator name,
iSCSI target name, ISID and TSID, iSCSI also optionally allows for
the specification of initiator and target aliases. Initiator and
target aliases are optional constructs which help the users to
associate semantic meanings with a particular initiator or target.
2. iSCSI Names
The main addressable, discoverable entity in iSCSI is an iSCSI
Node. An iSCSI node can be either an initiator, a target, or
both.
The concepts of names and addresses have been carefully separated in
iSCSI:
- An iSCSI Name is a location-independent, permanent identifier
for an iSCSI node. An iSCSI node has one iSCSI name, which
stays constant for the life of the node. The terms "initiator
name" and "target name" also refer to an iSCSI name.
- An iSCSI Address specifies not only the iSCSI name of an iSCSI
node, but also a location of that node. The address consists of
a host name or IP address, a TCP port number (for the target),
and the iSCSI Name of the node. An iSCSI node can have any
number of addresses, which can change at any time, particularly
if they are assigned via DHCP.
A similar analogy exists for people. A person in the USA 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 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
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Internet Draft Naming and Discovery 5
human-friendly label for this person.
2.1. iSCSI Name Requirements
Each iSCSI node, whether an initiator or target, must have an
iSCSI name.
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.
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.
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 provide for the use of
international character sets, and must not allow the use of
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Internet Draft Naming and Discovery 6
different names that would be identical except for their case.
Whitespace characters must not be allowed.
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 node, 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.
2.2. iSCSI Name Encoding
An iSCSI name is a UTF-8 encoding of a string of Unicode
characters, with the following properties, described in [26]:
- it is in Normalization Form C [25]
- it contains only the following types of characters:
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Internet Draft Naming and Discovery 7
- ASCII dash character ('-'=U+002d)
- ASCII dot character ('.'=U+002e)
- Any character allowed by the output of the iSCSI
stringprep template [26]
- when encoded in UTF-8, it is no more than 255 bytes
The stringprep process is described in [24]; iSCSI's use of the
stringprep process is described in [26]. Stringprep is a
method designed by the Internationalized Domain Name (IDN) working
group to translate human-typed strings into a format that can be
compared as opaque strings, and does not include punctuation,
spacing, dicritical marks, or other characters that could get
in the way of transcribability. It also converts everything into its
equivalent of lower case.
Note that in most cases, the stringprep process does not need
to be implemented:
- If the names are just generated using lower-case (in any
character set) plus digits, no normalization is required.
- If the names are generated from some other all-ASCII
string, tolower() normalizes and isalnum() verifies.
- If the names are generated from more general,
internationalized text, either the equivalent of tolower()
and isalnum() appropriate
to the character set may be used, or the full stringprep
procedure can be used.
When included in Text or Login messages, an iSCSI Name MUST
be formatted in UTF-8 form.
Since iSCSI names encoded in UTF-8 are "normalized" (there is
one and only one representation for each possible name), they
may be safely compared byte-for-byte.
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Internet Draft Naming and Discovery 8
The iSCSI Name may be displayed by user interfaces, but its
contents are not parsed or interpreted by initiators and targets
themselves.
2.3. iSCSI Name Structure
An iSCSI name consists of Two parts: a type designator, followed by
a unique name string
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
hierarchy, 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.
2.3.1. 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,
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Internet Draft Naming and Discovery 9
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".
Since a domain name can expire, be acquired by another entity, and
used to generate iSCSI names by both owners, the domain name must
be additionally qualified by a date during which the naming authority
owned the domain name. A date code is provided as part of the IQN
format for this reason.
The iSCSI qualified name string consists of:
- The string "iqn.", used to distinguish these names from other
types, such as "eui".
- A date code, in yyyy-mm format. This date code uses the Gregorian
calendar. All four digits in the year must be present. Both
digits of the month must be present, with January == "01" and
December == "12". The dash must be present. The date
reflected in this code MUST be a date during which the naming
authority owned the domain name used in this format, and SHOULD be
the date on which the domain name was acquired by the naming
authority.
- 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".
- 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
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Internet Draft Naming and Discovery 10
".", can be assigned as needed by the owner of the domain name. It is
the responsibility of the Organizational (Company) naming authority to
ensure that the iSCSI names it assigns are world wide unique.
iSCSI has given the Organizational naming authority additional
flexibility by permitting it to hand out local naming authority to
subordinate organizations. In this way it will be possible for the
Organizational naming authority to assign for example, the string
"storage", to one subgroup naming authority and "storage.tape" to
another. In this case the subgroups may add a ":" following their
assigned subgroup string to ensure ongoing uniqueness. For example:
"storage:" and "storage.tape:". Also, additional sub-qualifiers can be
assigned and separated by a "." as explained above.
Using this approach, the subgroup with the sub-naming authority string
of "storage" might, overtime, also create some Tape products. In this
case, both subgroups might use the same qualifying names. It would be
expected in this case that a naming conflict might occur, however by
using the ":" appropriately the conflicts can be avoided. In this
example com.acme.storage:tape.sys1.xyz and
com.acme.storage.tape:sys1.xyz would not be in conflict even though the
same sub-names are used.
The following are examples of iSCSI qualified names from an
equipment vendor:
Organization Subgroup Naming Authority
Naming and/or string Defined by
Type Date Auth Org. or Local Naming Authority
+-+ +-----+ +------+ +--------------------------------+
| | | | | | | |
iqn.2001-04.com.acme.diskarrays-sn-a8675309
iqn.2001-04.com.acme.storage:tape.sys1.xyz
iqn.2001-04.com.acme.storage.tape:sys1.xyz
Where:
"iqn" specifies the use of the iSCSI qualified name as the
authority.
"2001-04" is the year and month on which the naming authority
acquired the domain name used in this iSCSI name.
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Internet Draft Naming and Discovery 11
"com.acme" defines the Organizational naming authority. The
owner of the DNS 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.
"storage:" is the string that represents another sub-naming
authority.
"storage.tape:" is still another sub-naming authority.
"sys1.xyz" is a naming sub-qualifier.
The following is an example of a name that might be constructed by
an research organization:
Organization String
Naming Defined by Org.
Type Date Authority Naming Authority
+-+ +-----+ +----------------------+ +-----------+
| | | | | | | |
iqn.2000-02.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.
The following is an example of an iSCSI name string from a storage
service provider:
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Organization String
Naming Defined by Org.
Type Date Authority Naming Authority
+-+ +-----+ +--------+ +----------------------+
| | | | | | | |
iqn.1995-11.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
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.
2.3.2. 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.
Voruganti, K. Informational-Track Expires August 2002
Internet Draft Naming and Discovery 13
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
2.4 iSCSI Alias
The iSCSI alias is a UTF-8 text string that may be used as an
additional descriptive name for an initiator and target. This
may not be used to identify a target or initiator during login,
and does not have to follow the uniqueness or other requirements
of the iSCSI name. The alias strings are communicated between the
initiator and target at login, and can be displayed by a user
interface on either end, helping the user tell at a glance whether
the initiators and/or targets at the other end appear to be
correct. The alias must NOT be used to identify, address, or
authenticate initiators and targets.
The alias is a variable length string, between 0 and 255 characters,
and is terminated with at least one NULL (0x00) character. No
other structure is imposed upon this string.
2.4.1 Purpose of an Alias
Initiators and targets are uniquely identified by an iSCSI Name.
These identifiers may be assigned by
a hardware or software manufacturer, a service provider, or even
the customer. Although these identifiers are nominally human-
readable, they are likely be be assigned from a point of view
different from that of the other side of the connection. For
instance, a target name for a disk array may be built from the
array's serial number, and some sort of internal target ID.
Although this would still be human-readable and transcribable,
it offers little assurance to someone at a user interface who
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Internet Draft Naming and Discovery 14
would like to see "at-a-glance" whether this target is really
the correct one.
The use of an alias helps solve that problem. An alias is
simply a descriptive name that can be assigned to an initiator
or target, that is independent of the name, and does not have
to be unique. Since it is not unique, the alias must be used
in a purely informational way. It may not be used to specify
a target at login, or used during authentication.
Both targets and initiators may have aliases.
2.4.2 Target Alias
To show the utility of an alias, here is an example using an
alias for an iSCSI target.
Imagine sitting at a desktop station that is using some iSCSI
devices over a network. The user requires another iSCSI disk,
and calls the storage services person (internal or external),
giving any authentication information that the storage device
will require for the host. The services person allocates a
new target for the host, and sends the Target Name for the new
target, and probably an address, back to the user. The user then
adds this Target Name to the configuration file on the host, and
discovers the new device.
Without an alias, a user managing an iSCSI host would click
on some sort of management "show targets" button to show the
targets to which the host is currently connected.
+--Connected-To-These-Targets----------------------
|
| Target Name
|
| iqn.1995-04.com.acme.sn.5551212.target.450
| iqn.1995-04.com.acme.sn.5551212.target.489
| iqn.1995-04.com.acme.sn.8675309
| iqn.2001-04.com.acme.storage:tape.sys1.xyz
| iqn.2001-04.com.acme.storage.tape:sys1.xyz
|
+--------------------------------------------------
In the above example, the user sees a collection of iSCSI Names, but
with no real description of what they are for. They will, of
course, map to a system-dependent device file or drive letter,
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Internet Draft Naming and Discovery 15
but it's not easy looking at numbers quickly to see if everything
is there.
If a more intelligent target configures an alias for each target,
perhaps at the time the target was allocated to the host, a more
descriptive name can be given. This alias may be sent back to the
initiator as part of the login response, or found in the iSCSI MIB. It
then might be used in a display such as this. The new display might
look like:
+--Connected-To-These-Targets----------------------
|
| Alias Target Name
|
| Oracle 1 iqn.1995-04.com.acme.sn.5551212.target.450
| Local Disk iqn.1995-04.com.acme.sn.5551212.target.489
| Exchange 2 iqn.1995-04.com.acme.sn.8675309
|
+--------------------------------------------------
This would give the user a better idea of what's really there.
In general, flexible, configured aliases will probably be
supported by larger storage subsystems and configurable gateways.
Simpler devices will likely not keep configuration data
around for things such as an alias. The TargetAlias string
could be either left unsupported (not given to the initiator
during login) or could be returned as whatever the "next best
thing" that the target has that might better describe it.
Since it does not have to be unique, it could even return
SCSI inquiry string data.
Note that if a simple initiator does not wish to keep or display
alias information, it can be simply ignored if seen in the login
response.
2.4.3 Initiator Alias
An initiator alias can be used in the same manner as a target
alias. An initiator may send the alias in a login request,
when it sends its iSCSI Initiator Name. The alias is not used for
authentication, but may be kept with the session information for
display through a management GUI or command-line interface (for a
more complex subsystem or gateway), or through the iSCSI MIB.
Note that a simple target can just ignore the Initiator Alias
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Internet Draft Naming and Discovery 16
if it has no management interface on which to display it.
Usually just the hostname would be sufficient for an initiator
alias, but a custom alias could be configured for the sake of the
service provider if needed. Even better would be a description of
what the machine was used for, such as "Exchange Server 1", or
"User Web Server".
Here's an example of a management interface showing a list of sessions
on an iSCSI target network entity.
For this display, the targets are using an internal target number,
which is a fictional field that has purely internal significance.
+--Connected-To-These-Initiators-------------------
|
| Target Initiator Name
|
| 450 iqn.1995-04.com.sw.cd.12345678-OEM-456
| 451 iqn.1995-04.com.os.hostid.A598B45C
| 309 iqn.1995-04.com.sw.cd.87654321-OEM-259
|
+--------------------------------------------------
And with the initiator alias displayed:
+--Connected-To-These-Initiators-------------------
|
| Target Alias Initiator Name
|
| 450 Web Server 4 iqn.1995-04.com.sw.cd.12345678-OEM-456
| 451 scsigate.yours.com iqn.1995-04.com.os.hostid.A598B45C
| 309 Exchange Server iqn.1995-04.com.sw.cd.87654321-OEM-259
|
+--------------------------------------------------
This gives the storage administrator a better idea of who is
connected to their targets. Of course, one could always do
a reverse DNS lookup of the incoming IP address to determine
a host name, but simpler devices really don't do well with that
particular feature due to blocking problems, and it won't
always work if there is a firewall or iSCSI gateway involved.
Again, these are purely informational and optional and require a
management application.
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Internet Draft Naming and Discovery 17
Aliases are extremely easy to implement. Targets just send
a TargetAlias whenever they send a TargetName. Initiators just
send an InitiatorAlias whenever they send an InitiatorName.
If an alias is received that does not fit, or seems invalid
in any way, it is ignored.
2.5. 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 initial login request on all connections within the
session.
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].
3. ISID
The ISID is an initiator-defined component of the session identifier
(SSID) and is structured as follows. See iSCSI [7] and Section 3.4
Conservative Reuse of ISIDs for further information regarding the
ISID.
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
+---------------+---------------+---------------+---------------+
0| T | A | B | C |
+---------------+---------------+---------------+---------------+
4| D |
+---------------+---------------+
The T field identifies the format and usage of A, B, C & D
as indicated below:
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T
00b OUI-format
A&B are 22 bits. OUI is the Naming Authority
(the I/G & U/L bits are omitted)
C&D are 24 bit Qualifier
01b EN - format (IANA Enterprise Number)
A - reserved
B&C EN (IANA Enterprise Number) is the Naming Authority
D - Qualifier
10b "Random"
A - reserved
B&C Random is the Naming Authority
D - Qualifier
11b A,B,C&D Reserved
For T field values 00b and 01b, a combination of A and B (for 00b)
or B and C (for 01b) identifies the vendor or organization whose
component (software or hardware) generates this ISID. This is the
Naming Authority field. See 3.2 for more information. A vendor or
organization with one or more OUIs, or one or more Enterprise Numbers,
must use at least one of these numbers and select the appropriate
value for the T field when its components generate
ISIDs. An OUI or EN value must be set in the corresponding fields
in network byte order (i.e., big-endian).
If the T field is 10b, B and C are set to a random 24 bit unsigned
integer value in network byte order (i.e., big-endian). See iSCSI[7]
and section 3.4) for how this affects the principle of "conservative
reuse".
The "Random" type (10b) is for the case where the component that
generates an ISID (SW or HW) is provided by an entity that has no OUI
or EN. This includes, for example,
- a user-written program that builds sessions (and has access to the
system level iSCSI Name)
- a university or other organization providing the component
- a testing tool
The T field of 11b is reserved.
3.2 ISID Naming Authority
If the Type field is 00b, the 22-bits of the Naming Authority field
must be the lower 22-bits of one of the IEEE OUI (Organization Unique
Identifier) a.k.a. "Company ID" assigned to the vendor whose component
is generating this ISID. The OUI is set in the Naming Authority field
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in network byte order (big-endian).
If the Type field is 01b, the Naming Authority field must be set to
one of the IANA Enterprise Numbers assigned to the vendor whose
component is generating this ISID. The Enterprise Number is set in
the Naming Authority field as a 24bit unsigned integer value in
network byte order (big-endian).
If the type field is 10b, the Naming Authority field is set randomly
as specified above. It is important to note that the "Random" type
does not guarantee uniqueness. The "Random" type has been introduced
because it allows ISIDs to be used in experimental or isolated iSCSI
setups. (See 3.4 on how this affects the principle of "conservative
reuse").
3.3 ISID Qualifier
The Qualifier field is a 16 or 24 bit unsigned integer value that
provides a range of possible values for the ISID within the selected
namespace. It may be set to any value, within the constraints
specified in the iSCSI protocol (see iSCSI [7] and 3.4 for
Consequences of the Model and Conservative Reuse of ISIDs).
3.4 Conservative reuse of ISIDs
The principle of "conservative reuse" of ISIDs (see iSCSI [7])
specifies that ISIDs should be reused as much as possible. This
principle is there to both minimize the disruption of legacy
applications and to better facilitate the SCSI features that rely
on persistent names for SCSI ports.
To facilitate conservative reuse, the Qualifier field of a set of
ISIDs should be generated using either a repeatable algorithm (e.g,
deterministic or pseudo-random but based on a fixed seed) or any
algorithm to initialize a value or set of values but stored in a
persistent location (e.g., registry or /etc file).
For the "Random" type, conservative reuse may not be an issue
(e.g., in a user application that doesn't care about reservations,
etc.). When it is an issue, the Naming Authority field should also
be generated by a mechanism similar to that for the Qualifier field
as specified above (e.g., defined in the SW at compilation time.)
3.5 Notes on ISIDs
(a) As noted, the structure of the ISID namespace provides each
vendor with its own piece of the ISID namespace. In effect, this
provides for a vendor-partitioning of that namespace within each
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initiator. An initiator will then fail to comply with the ISID
RULE only if a vendor fails to implement the ISID generation use
and reuse requirements correctly.
(b) This structure also allows for a consortium of companies to
develop common APIs or a common infrastructure for generation, use
and reuse of ISIDs. The consortium could, for example, select an
OUI from amongst the member companies to be used in the Naming
Authority field. Or, the consortium could request an IANA
Enterprise Number for the consortium itself and use this in the
naming authority field. Eventually, the OS implementers could
provide such APIs, in which case the OS vendor could use its own
OUI or EN in the naming authority. In short, the design allows for
a migration path from vendor-fragmented implementations to
coordinated common implementations for ISID generation.
(c) ISIDs have no global uniqueness requirements or properties.
That is handled by the iSCSI Name of the initiator. This means
that a vendor can use the same algorithm to generate ISIDs (under
its naming authority) in every initiator.
(d) If the ISID is derived from something assigned to a hardware
adapter or interface by a vendor as a preset default value, it must
have a way to be changed (configured) to a new default value. The
ISID value must be configurable so that a chosen ISID may be applied
to a Portal Group containing more than one interface. In addition,
any preset default value should be automatically adjusted to a common
ISID when placed into a Network Entity as part of a Portal Group.
Any configured ISID must also be persistent (e.g., across power
cycles, reboots, and hot swaps). Refer to iSCSI [7] iSCSI Name and
ISID/TSID.
4. 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
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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 establish a discovery session
to the Network Entity. 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],UPnP[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
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.
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Appendix A: iSCSI Name Notes
Some iSCSI Name Examples for Targets
- Assign to a target based on controller serial number
iqn.2001-04.com.acme.diskarray.sn.8675309
- Assign to a target based on serial number
iqn.2001-04.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.2001-04.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.2001-04.com.osvendor.newos5.12345-OEM-0067890-23456
Note that this breaks if an install CD is used more than once.
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Depending on the O/S vendor's philosophy, this might be a feature.
- Assign to the Raid Array by a service provider
iqn.2001-04.com.mydisk.users.mbakke05657
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
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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.
- 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 sub-negotiation 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. 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
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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.
Effects on iSCSI:
- Since the initiator is unaware of any addresses beyond the gateway,
the gateway's own address is for all practical 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.4. iSCSI Proxy
An iSCSI proxy is a SCSI gateway that happens to be terminating
the iSCSI protocol on both sides, rather than translate between
iSCSI and some other transport. Since an iSCSI initiator's
discovery or configuration of a set of targets makes use of
address-independent iSCSI names, iSCSI does not have the same
proxy addressing problems as HTTP, which includes address
information into its URLs. If a proxy is to provide services
to an initiator on behalf of a target, the proxy allows the
initiator to discover its address for the target, and the actual
target device is discovered only by the proxy. Neither the
initiator nor the iSCSI protocol needs to be aware of the
existence of the proxy.
Effects on iSCSI:
- Same as a SCSI gateway. The only other effect is that
iSCSI must separate data integrity checking on iSCSI headers
and iSCSI data, to allow the data integrity check on the
data to be propagated end-to-end through the proxy.
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, there are no additional
requirements on the iSCSI protocol for this one.
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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.
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
otherwise.
Appendix C
This document has described the creation and use of iSCSI Node Names.
There will be trusted environments where this is a sufficient form of
identification. In these environments the iSCSI Target may have an
Access Control List (ACL), which will contain a list of authorized
entities that are permitted to access a restricted resource (in this
case a Target Storage Controller). The iSCSI Target will then use
that ACL to permit (or not) certain iSCSI Initiators to access the
storage at the iSCSI Target Node. This form of ACL is used to prevent
trusted initiators from making a mistake and connecting to the wrong
storage controller.
It is also possible that the ACL and the iSCSI Initiator Node Name
can be used in conjunction with the SCSI layer for the appropriate
SCSI association of LUNs with the Initiator. The SCSI layer's use
of the ACL will not be discussed further in this document.
There will be situations where the iSCSI Nodes exist in untrusted
environments. That is, some iSCSI Initiator Nodes may be authorized
to access an iSCSI Target Node, however, because of the untrusted
environment, nodes on the network cannot be trusted to give the
correct iSCSI Initiator Node Names.
In untrusted environments an additional type of identification is
required to assure the target that it really knows the identity
of the requesting entity.
The authentication and authorization in the iSCSI layer is
independent of anything that IPSec might handle, underneath
or around the TCP layer. This means that the initiator node
needs to pass some type of security related identification
information (e.g. userid) to a security authentication process
such as SRP, CHAP, Kerberos etc. (These authentication processes
will not be discussed in this document).
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Upon the completion of the iSCSI security authentication, the
installation knows "who" sent the request for access. The
installation must then check to ensure that such a request,
from the identified entity, is permitted/authorized. This
form of Authorization is generally accomplished via an Access
Control List (ACL) as described above. Using this authorization
process, the iSCSI target will know that the entity is authorized to
access the iSCSI Target Node.
It may be possible for an installation to set a rule that the security
identification information (e.g. UserID) be equal to the iSCSI
Initiator Node Name. In that case, the ACL approach described above
should be all the authorization that is needed.
If, however, the iSCSI Initiator Node Name is not used as the security
identifier there is a need for more elaborate ACL functionality. This
means that the target requires a mechanism to map the security
identifier (e.g. UserID) information to the iSCSI Initiator Node Name.
That is, the target must be sure that the entity requesting access is
authorized to use the name, which was specified with the Login Keyword
"InitiatorName=".
For example, if security identifier 'Frank' is authorized to access
the target via iSCSI InitiatorName=xxxx, but 'Frank' tries to access the
target via iSCSI InitiatorName=yyyy, then this login should be rejected.
On the other hand, it is possible that 'Frank' is a roaming user (or a
Storage Administrator) that "owns" several different systems, and thus,
could be authorized to access the target via multiple different iSCSI
initiators. In this case, the ACL needs to have the names of all the
initiators through which 'Frank' can access the target.
There may be other more elaborate ACL approaches, which can also be
deployed to provide the installation/user with even more security with
flexibility.
The above discussion is trying to inform the reader that, not only is
there a need for access control dealing with iSCSI Initiator Node Names,
but in certain iSCSI environments there might also be a need for other
complementary security identifiers.
5. References
[1] Pascoe, R., "Building Networks on the Fly", in IEEE
Spectrum,March, 2002.
[2] John, R., "UPnP, Jini and Salutation- A look at some popular
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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-04.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.
[18] RFC 2610, DHCP Options for the Service Location Protocol.
[19] P. Sarkar et al, "A Standard for Bootstrapping Clients using
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the iSCSI Protocol", draft-ietf-ips-iscsi-boot-03.
[21] M. Bakke et al,"Finding iSCSI Targets and Name Servers using
SLP", draft-ietf-ips-iscsi-slp-01.txt, July, 2002.
[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.html.
[23] Flanagan, et. al, "Java in a Nutshell", O'Reilly, 1997.
[24] P. Hoffman, M. Blanchet, "Preparation of Internationalized
Strings", draft-hoffman-stringprep-00.txt, September, 2001.
[25] Unicode Standard Annex #15, "Unicode Normalization Forms",
http://www.unicode.org/unicode/reports/15
[26] M. Bakke, "String Profile for iSCSI Names",
draft-ietf-ips-iscsi-string-prep-00.txt, November 2001.
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
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Internet Draft Naming and Discovery 30
Phone: +1 408-927-1892
Email: hafner@almaden.ibm.com
Josh Tseng
Nishan Systems
3850 North First Street
San Jose, CA 95134
Phone: 408 519-3749
Email: jtseng@nishansystems.com
Marjorie Krueger
Hewlett-Packard Corporation
8000 Foothills Blvd
Roseville, CA 95747-5668, USA
Phone: +1 916 785-2656
Email: marjorie_krueger@hp.com
Phone: (408) 957-4980
Email: todd_sperry@adaptec.com
Voruganti, K. Informational-Track Expires August 2002
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