Internet Draft                                                Mark Bakke
<draft-ietf-ips-iscsi-slp-08.txt>                                  Cisco
Expires October 2004
                                                            John Hufferd
                                                      Kaladhar Voruganti

                                                        Marjorie Krueger

                                                             Todd Sperry

                                                              April 2004

            Finding iSCSI Targets and Name Servers Using SLP

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at

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Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.


   The iSCSI protocol provides a way for hosts to access SCSI devices
   over an IP network.  This document defines the use of the Service
   Location Protocol (SLP) by iSCSI hosts, devices, and management
   services, along with the SLP service type templates that describe the
   services they provide.


   This draft was produced by the iSCSI Naming and Discovery team,
   including Joe Czap, Jim Hafner, John Hufferd, and Kaladhar Voruganti
   (IBM), Howard Hall (Pirus), Jack Harwood (EMC), Yaron Klein (Sanrad),
   Marjorie Krueger (HP), Lawrence Lamers (San Valley), Todd Sperry
   (Adaptec), and Joshua Tseng (Nishan).  Thanks also to Julian Satran
   (IBM) for suggesting the use of SLP for iSCSI discovery, and to Matt
   Peterson (Caldera) and James Kempf (Sun) for reviewing the document
   from an SLP perspective.

Table of Contents

      1. Introduction.................................................2
      2. Notation Conventions.........................................3
      3. Terminology..................................................3
      4. Using SLP for iSCSI Service Discovery........................4
      5. iSCSI SLP Templates.........................................13
      6. Security Considerations.....................................19
      7. IANA Considerations.........................................20
      8. Summary.....................................................20
      9. Normative References........................................20
     10. Informative References......................................21
     11. Authors' Addresses..........................................22
     12. Full Copyright Notice.......................................22

1.  Introduction

   iSCSI [RFC3720] is a protocol used to transport SCSI [SAM2] commands,
   data, and status across an IP network.  This protocol is connection-
   oriented, and is currently defined over TCP.  iSCSI uses a client-
   server relationship.  The client end of the connection is an
   initiator, and sends SCSI commands; the server end of the connection
   is called a target, and receives and executes the commands.

   There are several methods an iSCSI initiator can use to find the
   targets to which it should connect.  Two of these methods can be
   accomplished without the use of SLP:

   - Each target and its address can be statically configured on the

   - Each address providing targets can be configured on the initiator;
     iSCSI provides a mechanism by which the initiator can query the
     address for a list of targets.

   The above methods are further defined in "iSCSI Naming and Discovery
   Requirements" [RFC3721].

   Each of the above methods requires a small amount of configuration to
   be done on each initiator.  The ability to discover targets and name
   services without having to configure initiators is a desirable
   feature.  The Service Location Protocol (SLP) [RFC2608] is an IETF
   standards track protocol that provides several features that will
   simplify locating iSCSI services.  This document describes how SLP
   can be used in iSCSI environments to discover targets, addresses
   providing targets, and storage management servers.

2.  Notation Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Terminology

   Here are some definitions that may aid readers that are unfamiliar
   with either SLP, SCSI, or iSCSI.  Some of these definitions have been
   reproduced from [RFC2608] and "Finding an RSIP Server with SLP"

   User Agent (UA)            A process working on the client's behalf
                              to establish contact with some service.
                              The UA retrieves service information from
                              the Service Agents or Directory Agents.

   Service Agent (SA)         A process working on behalf of one or more
                              services to advertise the services and
                              their capabilities.

   Directory Agent (DA)       A process which collects service
                              advertisements.  There can only be one DA
                              present per given host.

   Scope                      A named set of services, typically making
                              up a logical administrative group.

   Service Advertisement      A URL, attributes, and a lifetime
                              (indicating how long the advertisement is
                              valid), providing service access
                              information and capabilities description
                              for a particular service.

   Initiator                  A logical entity, typically within a host,
                              that sends SCSI commands to targets to be
                              executed.  An initiator is usually present
                              in the form of a device driver.

   Target                     A logical entity, typically within a
                              storage controller or gateway, that
                              receives SCSI commands from an initiator
                              and executes them.  A target includes one
                              or more Logical Units (LUs); each LU is a
                              SCSI device, such as a disk or tape drive.

   iSCSI Name                 A UTF-8 character string which serves as a
                              unique identifier for iSCSI initiators and
                              targets.  Its format and usage is further
                              defined in [RFC3721].

   iSCSI Client               A logical entity, typically a host, which
                              includes at least one iSCSI Initiator.

   iSCSI Server               A logical entity, typically a storage
                              controller or gateway, which includes at
                              least one iSCSI Target.

   Storage Management Server  An addressable entity that provides
                              management services that benefit an iSCSI
                              environment.  "Storage management server"
                              is used as a generic term, rather than a
                              specific protocol or service.

4.  Using SLP for iSCSI Service Discovery

   Two entities are involved in iSCSI discovery.  The end result is that
   an iSCSI initiator (e.g. a host) discovers iSCSI targets, usually
   provided by storage controllers or gateways.

   iSCSI targets are registered with SLP as a set of service URLs, one
   for each address on which the target may be accessed.  Initiators
   discover these targets using SLP service requests.  Targets that do
   not directly support SLP, or are under the control of a management
   service, may be registered by a proxy service agent as part of the
   software providing this service.

   iSCSI entities may also use SLP to discover higher-level management
   services where needed.

   This section first describes the use of SLP for discovery of targets
   by iSCSI initiators, and then describes the use of SLP to discover
   storage management servers.

   This document assumes that SLPv2 will be used when discovering iSCSI-
   related services; no attempt is made to include support for SLPv1.

4.1.  Discovering iSCSI Targets using SLP

   The following diagram shows the relationship between iSCSI clients,
   servers, initiators, and targets.  An iSCSI client includes at least
   one iSCSI initiator, and an SLP user agent (UA).  An iSCSI server
   includes at least one iSCSI target, and an SLP service agent (SA).
   Some entities, such as extended copy engines, include both initiators
   and targets.  These include both an SA, for its targets to be
   discovered, and a UA, for its initiator(s) to discover other targets.

              |          iSCSI Client           |
              |         +-----------+           |
              |         | iSCSI     |           |
              |         | initiator |           |
              |         | "myhost"  |           |
              |         +-----------+           |
              |                                 |
              | iSCSI Driver             |  UA  |
              |           TCP/UDP/IP            |
              |  Interface 1   |   Interface 2  |
                       |               |
     +------------+    |               |    +------------+
     |   SLP DA   |    |               |    |  SLP DA    |
     | (optional) |----+  IP Networks  +----| (optional) |
     +------------+    |               |    +------------+
                       |               |
              |   Interface 1   |   Interface 2   |
              |   |    |
              |            TCP/UDP/IP             |
              |       iSCSI Driver        |  SA   |
              |                                   |
              | +--------+ +--------+ +---------+ |
              | | iSCSI  | | iSCSI  | |  iSCSI  | |
              | | target | | target | |  target | |
              | | "one"  | | "two"  | | "three" | |
              | +--------+ +--------+ +---------+ |
              |            iSCSI Server           |
   In the above drawing, the iSCSI server has three iSCSI targets that
   the client could discover, named "one", "two" and "three".  The iSCSI
   client has an iSCSI initiator with the name "myhost".  The iSCSI
   client may use the initiator name in its SLP Service Requests as a
   filter to discover only targets that are configured to accept iSCSI
   connections from "myhost".

   Each iSCSI target and initiator has a unique name, called an iSCSI
   Name.  This identifier is the same regardless of the network path
   (through adapter cards, networks, interfaces on the storage device)
   over which the target is discovered and accessed.  For this example,
   the iSCSI names "one" and "two", and "three" are used for the
   targets; the initiator uses the name "myhost".  An actual iSCSI name
   would incorporate more structure, including a naming authority, and
   is not described here.

   Each of the iSCSI targets in the drawing can appear at two addresses,
   since two network interfaces are present.  Each target, would have
   two service URLs.

   An iSCSI target URL consists of its fully qualified host name or IP
   address, the TCP port on which it is listening, and its iSCSI name.
   An iSCSI server must register each of its individual targets at each
   of its network addresses.

   The iSCSI server constructs a service advertisement of the type
   "service:iscsi:target" for each of the service URLs it wishes to
   register.  The advertisement contains a lifetime, along with other
   attributes which are defined in the service template.

   If the server in the above drawing is listening at TCP port 3260 for
   both network addresses, the service URLs registered would be:







   The remainder of the discovery procedure is identical to that used by
   any client/server pair implementing SLP:

   1. If an SLP DA is found, the SA contacts the DA and registers
      the service advertisement.  Whether or not one or more SLPv2
      DAs are discovered, the SA maintains the advertisement itself
      and answers multicast UA queries directly.

   2. When the iSCSI initiator requires contact information for an
      iSCSI target, the UA either contacts the DA using unicast or
      the SA using multicast.  If a UA is configured with the address
      of the SA, it may avoid multicast and contact an SA using
      unicast.  The UA includes a query based on
      the attributes to indicate the characteristics of the
      target(s) it requires.

   3. Once the UA has the host name or address of the iSCSI server
      as well as the port number and iSCSI Target Name, it can begin the
      normal iSCSI login to the target.

   As information contained in the iSCSI target template may exceed
   common network datagram sizes, the SLP implementation for both UAs
   and SAs supporting this template MUST implement SLP over TCP.

4.1.1.  Finding Targets Based on Initiator Credentials

   To be allowed access to an iSCSI target, an initiator must be
   authenticated.  The initiator may be required by the target to
   produce one or more of the following credentials:

   - An iSCSI Initiator Name

   - An IP address

   - A CHAP, SRP, or Kerberos credential

   - Any combination of the above

   Most iSCSI targets allow access to only one or two initiators.  In
   the ideal discovery scenario, an initiator would send an SLP request,
   and receive responses ONLY for those targets to which the initiator
   is guaranteed a successful login.  To achieve this goal, the iSCSI
   target template contains the following attributes, each of which
   allows a list of values:

   1. auth-name - This attribute contains the list of initiator names
      allowed to access this target, or the value "any", indicating
      that no specific initiator name is required.

   2. auth-addr - This attribute contains the list of host names
      and/or IP addresses which will be allowed access to this target,
      or the value "any", indicating that no specific address or
      host name is required.  If a large number of addresses is to
      be allowed (perhaps a subnet), this attribute may contain the
      value "any".

   3. auth-cred - This attribute contains a list of "method/identifier"
      credentials that will be allowed access to the target, provided
      they can produce the correct password or other verifier during
      the login process.  If no specific credentials are required, the
      value "any" is used.

   The above identifiers follow the semantics described in the IP
   Storage Authentication MIB [AUTH-MIB].  Examples showing initiator
   searches based on auth-xxxx attributes are shown in the target-
   specific template section below.

   Also note that the auth-xxxx attributes are considered to be security
   policy information.  If these attributes are distributed, IPsec MUST
   be implemented as specified in the Security Implementation section

4.1.2.  Supporting Access by Multiple Identities to the Same Target

   If a target is to allow access to multiple host identities, more than
   one combination of auth-xxxx attributes will need to be present.
   Since service URLs must be unique, each of these must be registered
   under its own service URL.

   For systems that support the configuration of multiple identities to
   access a target, the service URL must contain an additional, opaque
   string defining the identity.  This appears after the iSCSI name in
   the URL string, and is separated by a "/".  Each registered (target-
   address, target-name, initiator-identity) tuple can then register its
   own set of auth-xxxx attributes.

   An initiator-identity is equivalent to the authentication identity
   defined in [AUTH-MIB].

4.1.3.  Using SLP in a Non-Multicast Environment

   In some networks, the use of multicast for discovery purposes is
   either unavailable or not allowed.  Such networks include public or
   service-provider networks that are placed in between an iSCSI client
   and server; these are probably most common between two iSCSI
   gateways, one at a storage service provider site, and one at a
   customer site.

   In these networks, an initiator may, instead or in addition to its DA
   configuration, allow the addresses of one or more SAs to be
   configured.  The initiator would then make unicast SLP service
   requests directly to these SAs, without the use of multicast to first
   discover them.

   This functionality is well within the scope of the current SLP
   protocol.  However, it does have two consequences for implementors:

   - A service-agent responding to requests for iSCSI targets MUST
     implement SLP over TCP; UDP only is not enough.  This is not
     an issue, since TCP is a requirement for iSCSI implementations
     that use SLP for other reasons.

   - An initiator configured to make direct, unicast requests to an
     SA will have to add this to the SLP API, if it is following the
     service location API defined in [RFC2614].  This capability
     is being added to the next revision of the API, in [2614BIS].

4.2.  Discovering Storage Management Services using SLP

   Storage management servers can be built to manage and control access
   to targets in a variety of ways.  They can also provide extended
   services beyond discovery, which could include storage allocation and
   management.  None of these services are defined here; the intent of
   this document is to allow these services to be discovered by both
   clients and servers, in addition to the target discovery already
   being performed.

   The following drawing shows an iSCSI client, an iSCSI server, and a
   storage management server.  To simplify the drawing, the second IP
   network is not shown, but is assumed to exist.  The storage
   management server would use its own protocol (smsp) to provide
   capabilities to iSCSI clients and servers; these clients and servers
   can both use SLP to discover the storage management server.

      |         iSCSI Client      |
      |                           |
      |       +-----------+       |
      |       | iSCSI     |       |
      |       | initiator |       |
      |       +-----------+       |
      |                           |
      +---------------+------+----+      +------------+
      | iSCSI Driver  | smsp | UA |      |  SLP DA    |
      +---------------+------+----+      |            |
      |        TCP/UDP/IP         |      | (optional) |
      +---------------+------+----+      +------------+
               |                               |
               |   IP Network                  |
               |                          |
               |                          |
      +---------------+-----------+     +---------------------+
      |        TCP/UDP/IP         |     | TCP/UDP/IP          |
      +---------------+------+----+     +---------------------+
      | iSCSI Driver  | smsp | UA |     |   SA    |   smsp    |
      +---------------+------+----+     +---------------------+
      |                           |     |                     |
      | +--------+ +--------+     |     | storage mgmt server |
      | | iSCSI  | | iSCSI  |     |     |                     |
      | | target | | target |     |     +---------------------+
      | |   1    | |   2    |     |
      | +--------+ +--------+     |
      |                           |
      |     iSCSI Server          |

   Note the difference between the storage management server model and
   the previously-defined target discovery model.  When target discovery
   was used, the iSCSI Server implemented an SA, to be discovered by the
   initiator's UA.  In the storage management server model, the iSCSI
   clients and servers both implement UAs, and the management server
   implements the SA.

   A storage management server's URL contains the domain name or IP
   address and TCP or UDP port number.  No other information is

   The storage management server constructs a service advertisement of
   the type "service:iscsi:sms" for each of the addresses at which it
   appears.  The advertisement contains the URL, a lifetime, along with
   other attributes which are defined in the service template.

   The remainder of the discovery procedure is identical to that used to
   discover iSCSI targets, except that both initiators and targets would
   normally be "clients" of the storage management service.

   Targets that support a storage management service implement a UA in
   addition to the SA.  A target may alternatively just implement the
   UA, and allow the storage management service to advertise its targets
   appropriately by providing an SA and registering the appropriate
   service:iscsi:target registrations on the target's behalf; the target
   device would not have to advertise its own targets.  This has no
   impact on the initiator.

   This allows the initiators' discovery of targets to be completely
   interoperable regardless of which storage management service is used,
   or whether one is used at all, or whether the target registrations
   are provided directly by the target or by the management service.

4.3.  NAT and NAPT Considerations

   Since SLP provides IP address and TCP port information within its
   payload, the addresses an SA or DA advertise may not be the same as
   those a UA must use if a Network Address(/Port) Translation
   (NAT/NAPT) device is present between the UA and the SA.  This may
   result in the UA discovering address information that is unusable.
   Also note that SLP advertisements that occur inside a private address
   realm may be unreachable outside that realm.  Below are some
   recommendations for dealing with SLPv2 and NAT/NAPT devices:

   - A fully-qualified domain name (i.e. not an IP address) SHOULD be
     used in service URLs, the mgmt-entity attribute, and the auth-addr
     attribute [RFC1900].

   - Configure the NAPT device to provide default mapping(s) for the
     well-known port(s) and use the default IANA-assigned iSCSI TCP port
     number in service URLs, when possible.

4.4.  Internationalization Considerations

   SLP allows internationalized strings to be registered and retrieved.
   Attributes in the template that are not marked with an 'L' (literal)
   will be registered in a localized manner.  An "en" (English)
   localization MUST be registered, and others MAY be registered.

   Attributes that include non-ASCII characters will be encoded using
   UTF-8, as discussed in [RFC3722] and [RFC3491].

5.  iSCSI SLP Templates

   Three templates are provided: an iSCSI target template, a management
   service template, and an abstract template to encapsulate the two.

5.1.  The iSCSI Abstract Service Type Template

   This template defines the abstract service "service:iscsi".  It is
   used as a top-level service to encapsulate all other iSCSI-related

   Name of submitter: Mark Bakke
   Language of service template: en
   Security Considerations: see section 6.

   Template Text:
   -------------------------template begins here-----------------------


     This is an abstract service type.  The purpose of the iscsi
     service type is to encompass all of the services used to support
     the iSCSI protocol.

     url-path=  ;  Depends on the concrete service type.

   --------------------------template ends here------------------------

5.2.  The iSCSI Target Concrete Service Type Template

   This template defines the service "service:iscsi:target".  An entity
   containing iSCSI targets that wishes them discovered via SLP would
   register each of them, with each of their addresses, as this service

   Initiators (and perhaps management services) wishing to discover
   targets in this way will generally use one of the following queries:

   1. Find a specific target, given its iSCSI Target Name:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   (
   2. Find all of the iSCSI Target Names that may allow access to a
      given initiator:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   (

   3. Find all of the iSCSI Target Names that may allow access to
      any initiator:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   (auth-name=any)

   4. Find all of the iSCSI Target Names that may allow access to
      this initiator, or that will allow access to any initiator:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   &(

   5. Find all of the iSCSI Target Names that may allow access to
      a given CHAP user name:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   (auth-cred=chap/my-user-name)

   6. Find all of the iSCSI Target Names that may allow access to
      a given initiator that supports two IP addresses, a CHAP
      credential and an SRP credential, and an initiator name:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   &(|(

   7. Find the iSCSI Target Names from which the given initiator is
      allowed to boot:

        Service: service:iscsi:target
        Scope:   initiator-scope-list
        Query:   (

   8. In addition, a management service may wish to discover all

        Service: service:iscsi:target
        Scope:   management-server-scope-list
        Query:   <empty-string>

   More details on booting from an iSCSI target are defined in [BOOT].

   Name of submitter: Mark Bakke
   Language of service template: en
   Security Considerations: see section 6.

   Template Text:
   -------------------------template begins here-----------------------


     This is a concrete service type.  The iscsi:target service type is
     used to register individual target addresses to be discovered by
     others.  UAs will generally search for these by including one of
     the following:

     - the iSCSI target name
     - iSCSI initiator identifiers (iSCSI name, credential, IP address)
     - the service URL

     url-path    = hostport "/" iscsi-name [ "/" identity ]
     hostport    = host [ ":" port ]
     host        = hostname / hostnumber  ; DNS name or IP address
     hostname    = *( domainlabel "." ) toplabel
     alphanum    = ALPHA / DIGIT
     domainlabel = alphanum / alphanum *[alphanum / "-"] alphanum
     toplabel    = ALPHA / ALPHA *[ alphanum / "-" ] alphanum
     hostnumber  = ipv4-number
     ipv4-number = 1*3DIGIT 3("." 1*3DIGIT)
     port        = 1*DIGIT
     iscsi-name  = iscsi-char ; iSCSI target name
     identity    = iscsi-char ; optional identity string
     iscsi-char  = ALPHA / DIGIT / escaped / ":" / "-" / "."
                   ; Intended to allow UTF-8 encoded strings
     escaped     = 1*(`' HEXDIG HEXDIG)
     ; The iscsi-name part of the URL is required and must be the iSCSI
     ; name of the target being registered.
     ; A device representing multiple targets must individually
     ; register each target/address combination with SLP.
     ; The identity part of the URL is optional, and is used to
     ; indicate an identity that is allowed to access this target.
     ; Example (split into two lines for clarity):
     ; service:iscsi:target://

   iscsi-name = string
   # The iSCSI Name of this target.
   # This must match the iscsi-name in the url-path.

   portal-group = integer
   # The iSCSI portal group tag for this address.  Addresses sharing
   # the same iscsi-name and portal-group tag can be used within the
   # same iSCSI session.  Portal groups are described in [RFC3720].

   transports = string M L
     # This is a list of transport protocols that the registered
     # entity supports.  iSCSI is currently supported over TCP,
     # but it is anticipated that it could be supported over other
     # transports, such as SCTP, in the future.

   mgmt-entity = string O
   # The fully qualified domain name, or IP address in dotted-decimal
   # notation, of the management interface of the entity containing
   # this target.

   alias = string O
   # The alias string contains a descriptive name of the target.

   auth-name = string M X
   # A list of iSCSI Initiator Names that can access this target.
   # Normal iSCSI names will be 80 characters or less; max length
   # is 255.
   # Normally, only one or a few values will be in the list.
   # Using the equivalence search on this will evaluate to "true"
   # if any one of the items in this list matches the query.
   # If this list contains the default name "any", any initiator
   # is allowed to access this target, provided it matches the
   # other auth-xxx attributes.
   # This attribute contains security policy information.  If this
   # attribute is distributed via an Attribute Reply message,
   # IPsec MUST be used. implemented.

   auth-addr = string M X
   # A list of initiator IP addresses (or host names) which will
   # be allowed access to this target.  If this list contains the
   # default name "any", any IP address is allowed access to this
   # target, provided it matches the other auth-xxx attributes.
   # This attribute contains security policy information.  If this
   # attribute is distributed via an Attribute Reply message,
   # IPsec MUST be used. implemented.

   auth-cred = string M X
   # A list of credentials which will be allowed access to the target
   # (provided they can provide the correct password or other
   # authenticator).  Entries in this list are of the form
   # "method/identifier", where the currently defined methods are
   # "chap" and "srp", both of which take usernames as their
   # identifiers.
   # This attribute contains security policy information.  If this
   # attribute is distributed via an Attribute Reply message,
   # IPsec MUST be used. implemented.

   boot-list = string M O
   # A list of iSCSI Initiator Names that can boot from this target.
   # This list works precisely like the auth-name attribute.  A name
   # appearing in this list must either appear in the access-list,
   # or the access-list must contain the initiator name "iscsi".
   # Otherwise, an initiator will be unable to find its boot target.
   # If boot-list contains the name "iscsi", any host can boot from it,
   # but I am not sure if this is useful to anyone.
   # If this attribute is not registered, this target is not "bootable".
   # Note that the LUN the host boots from is not specified here; a
   # host will generally attempt to boot from LUN 0.
   # It is quite possible that other attributes will need to be defined
   # here for booting as well.
   # This attribute contains security policy information.  If this
   # attribute is distributed via an Attribute Reply message,
   # IPsec MUST be used. implemented.

   --------------------------template ends here------------------------

5.3.  iSCSI Storage Management Service Templates

   This template defines the service "service:iscsi:sms".  An entity
   supporting one or more iSCSI management service protocols may
   register itself with SLP as this service type.

   iSCSI clients and servers wishing to discover storage management
   services using SLP will usually search for them by the protocol(s)
   they support:

        Service: service:iscsi:sms
        Scope:   initiator-scope-list
        Query:   (protocols=isns)

   Name of submitter: Mark Bakke
   Language of service template: en
   Security Considerations: see section 6.

   Template Text:
   -------------------------template begins here-----------------------


     This is a concrete service type.  The iscsi:sms service type
     provides the capability for entities supporting iSCSI to discover
     appropriate management services.

     url-path   = ; The URL of the management service [RFC2608].

   protocols = string M
   # The list of protocols supported by this name service.  This
   # list may be expanded in the future.  There is no default.
   # "isns"  - This management service supports the use of the iSNS
   #           protocol for access management, health monitoring, and
   #           discovery management services.  This protocol is defined
   #           in [ISNS].

   transports = string M L
   # This is a list of transport protocols that the registered
   # entity supports.
   tcp, udp
   server-priority = integer
   # The priority a client should give this server, when choosing
   # between multiple servers with the same protocol type.
   # When multiple servers are discovered for a given protocol type,
   # this parameter indicates their relative precedence. Server
   # precedence is protocol-specific; for some protocols, the primary
   # server may have the highest server-priority value, while for
   # others it may have the lowest. For example, with iSNS, the primary
   # server has the lowest value (value 0).

   --------------------------template ends here------------------------

6.  Security Considerations

   The SLPv2 security model as specified in [RFC2608] does not provide
   confidentiality, but does provide an authentication mechanism for UAs
   to assure that service advertisements only come from trusted SAs with
   the exception that it does not provide a mechanism to authenticate
   "zero-result responses".  See [RFC3723] for a discussion of the SLPv2
   [RFC2608] security model.

   Once a target or management server is discovered, authentication and
   authorization are handled by the iSCSI protocol, or by the management
   server's protocol.  It is the responsibility of the providers of
   these services to ensure that an inappropriately advertised or
   discovered service does not compromise their security.

   When no security is used for SLPv2, there is a risk of distribution
   of false discovery information. The primary countermeasure for this
   risk is authentication. When this risk is a significant concern,
   IPsec SAs and iSCSI in-band authentication SHOULD be used for iSCSI
   traffic subject to this risk to ensure that iSCSI traffic only flows
   between endpoints that have participated in IKE authentication and
   iSCSI in-band authentication.  For example, if an attacker
   distributes discovery information falsely claiming that it is an
   iSCSI target, it will lack the secret information necessary to
   successfully complete IKE authentication or iSCSI in-band
   authentication, and hence will be prevented from falsely sending or
   receiving iSCSI traffic.

   There remains a risk of a denial of service attack based on repeated
   use of false discovery information that will cause initiation of IKE
   negotiation. The countermeasures for this are administrative
   configuration of each iSCSI Target to limit the peers that it is
   willing to communicate with (i.e., by IP address range and/or DNS
   domain), and maintenance of a negative authentication cache to avoid
   repeatedly contacting an iSCSI Target that fails to authenticate.

   These three measures (i.e., IP address range limits, DNS domain
   limits, negative authentication cache) MUST be implemented.

   The auth-name, auth-addr, auth-cred, and boot-list attributes
   comprise security policy information.  When these are distributed,
   IPsec MUST be implemented.

6.1.  Security Implementation

   Security for SLPv2 in an IP storage environment is specified in

   IPsec SHOULD be implemented for SLPv2 as specified in [RFC3723]; this
   includes ESP with a non-null transform to provide both authentication
   and confidentiality.

   When SLPv2 can be used to distribute auth-name, auth-addr, auth-cred,
   boot-list information (see Section 5.2 above), IPsec MUST be
   implemented, as these items are considered to be sensitive security
   policy information.  If IPsec is not implemented, auth-name, auth-
   addr, auth-cred, and boot-list information MUST NOT be distributed
   via SLPv2, and MUST NOT be used if discovered via SLPv2.

   SLPv2 authentication is OPTIONAL to implement and use, and SLPv2
   authentication SHOULD be implemented when IPsec is not supported.

7.  IANA Considerations

   This document describes three SLP Templates.  When they have been
   reviewed and approved by the IESG, they should be registered in the
   IANA "SVRLOC Templates" registry.  This process is described in the
   IANA Considerations section of [RFC2609].

8.  Summary

   This document describes how SLP can be used by iSCSI initiators to
   find iSCSI targets and storage management servers.  Service type
   templates for iSCSI targets and storage management servers are

9.  Normative References

[RFC2608]   Guttman, E., Perkins, C., Veizades, J. and M. Day,  "Service
            Location Protocol, version 2", RFC 2608, June 1999.

[RFC2609]   Guttman, E., Perkins, C. and J. Kempf,  "Service Templates
            and service: Schemes", RFC 2609, June 1999.

[RFC2119]   Bradner, S.,  "Key Words for Use in RFCs to Indicate
            Requirement Levels", RFC 2119, March 1997.

[RFC3720]   Satran, J., Meth, K., Sapuntzakis, C., Chadalapaka, M. and
            E. Zeidner, "Internet Small Computer Systems Interface
            (iSCSI)", RFC 3720, March 2004.

[RFC3723]   Aboba, B., Tseng, J., Walker, J., Rangan, V. and F.
            Travostino, "Securing Block Storage Protocols over IP", RFC
            3723, March 2004.

10.  Informative References

[RFC2614]   Kempf, J. and E. Guttman,  "An API for Service Location",
            RFC 2614, June 1999.

[2614BIS]   Kempf, J. and E. Guttman,  "An API for Service Location",
            draft-kempf-svrloc-rfc2614bis-00.txt, February 2002.

[SAM2]      ANSI T10.  "SCSI Architectural Model 2", March 2000.

[RFC3721]   Bakke, M., Hafner, J., Hufferd, J., Voruganti, K., and M.
            Krueger, "Internet Small Computer Systems Interface (iSCSI)
            Naming and Discovery", RFC 3721, March 2004.

[AUTH-MIB]  Bakke, M. and J. Muchow, "Definitions of Managed Objects for
            User Identity Authentication", Work in Progress, draft-ietf-
            ips-auth-mib-04.txt, March 2003.

[ISNS]      Tseng, J., Gibbons, K., Travostino, F., Du Laney, C. and J.
            Souza, "Internet Storage Name Service", Work in Progress,
            draft-ietf-ips-isns-22.txt, February 2004.

[BOOT]      Sarkar, P., Missimer, D. and C. Sapuntzakis,  "A Standard
            for Bootstrapping Clients using the iSCSI Protocol", Work in
            Progress, draft-ietf-ips-iscsi-boot-12.txt, March 2004.

[RFC1900]   Carpenter, B. and Y. Rekhter, "Renumbering Needs Work", RFC
            1900, February 1996.

[RFC3105]   Kempf, J. and G. Montenegro, "Finding an RSIP Server with
            SLP", RFC 3105, October 2001.

[RFC3722]   Bakke, M.,  "String Profile for iSCSI Names", RFC 3722,
            March 2004.

[RFC3491]   Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile
            for Internationalized Domain Names",  RFC 3491, March 2003.

11.  Authors' Addresses

       Mark Bakke
       Cisco Systems, Inc.
       6450 Wedgwood Road
       Maple Grove, MN 55311
       Voice:  +1 763-398-1000

       Kaladhar Voruganti
       IBM Almaden Research Center
       650 Harry Road
       San Jose, CA 95120

       John L. Hufferd
       IBM Storage Systems Group
       5600 Cottle Road
       San Jose, CA 95193
       Voice: +1 408 256-0403

       Marjorie Krueger
       Hewlett-Packard Corporation
       8000 Foothills Blvd
       Roseville, CA 95747-5668, USA
       Voice: +1 916 785-2656

       Todd Sperry
       Adaptec, Inc.
       691 South Milpitas Boulevard
       Milpitas, Ca. 95035
       Voice: +1 408 957-4980

12.  Full Copyright Notice

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