The IPv4 Dynamic Host Configuration Protocol (DHCP) Option for the Internet Storage Name Service
RFC 4174

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Network Working Group                                           C. Monia
Request for Comments: 4174                                    Consultant
Category: Standards Track                                       J. Tseng
                                                     Riverbed Technology
                                                              K. Gibbons
                                                      McDATA Corporation
                                                          September 2005

      The IPv4 Dynamic Host Configuration Protocol (DHCP) Option
                for the Internet Storage Name Service

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes the Dynamic Host Configuration Protocol
   (DHCP) option to allow Internet Storage Name Service (iSNS) clients
   to discover the location of the iSNS server automatically through the
   use of DHCP for IPv4.  iSNS provides discovery and management
   capabilities for Internet SCSI (iSCSI) and Internet Fibre Channel
   Protocol (iFCP) storage devices in an enterprise-scale IP storage
   network.  iSNS provides intelligent storage management services
   comparable to those found in Fibre Channel networks, allowing a
   commodity IP network to function in a similar capacity to that of a
   storage area network.

Table of Contents

   1.  Introduction .................................................  2
       1.1.  Conventions Used in This Document ......................  2
   2.  iSNS Option for DHCP .........................................  3
       2.1.  iSNS Functions Field ...................................  5
       2.2.  Discovery Domain Access Field ..........................  6
       2.3.  Administrative Flags Field .............................  7
       2.4.  iSNS Server Security Bitmap ............................  8
   3.  Security Considerations ......................................  9
   4.  IANA Considerations .......................................... 11

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RFC 4174              DHCP Option Number for iSNS         September 2005

   5.  Normative References ......................................... 11
   6.  Informative References ....................................... 11

1.  Introduction

   The Dynamic Host Configuration Protocol for IPv4 provides a framework
   for passing configuration information to hosts.  Its usefulness
   extends to hosts and devices using the iSCSI and iFCP protocols to
   connect to block level storage assets over a TCP/IP network.

   The iSNS Protocol provides a framework for automated discovery,
   management, and configuration of iSCSI and iFCP devices on a TCP/IP
   network.  It provides functionality similar to that found on Fibre
   Channel networks, except that iSNS works within the context of an IP
   network.  iSNS thereby provides the requisite storage intelligence to
   IP networks that are standard on existing Fibre Channel networks.

   Existing DHCP options cannot be used to find iSNS servers for the
   following reasons:

   a) iSNS functionality is distinctly different from other protocols
      using DHCP options.  Specifically, iSNS provides a significant
      superset of capabilities compared to typical name resolution
      protocols such as DNS.  It is designed to support client devices
      that allow themselves to be configured and managed from a central
      iSNS server.

   b) iSNS requires a DHCP option format that provides more than the
      location of the iSNS server.  The DHCP option has to specify the
      subset of iSNS services that may be actively used by the iSNS
      client.

   The DHCP option number for iSNS is used by iSCSI and iFCP devices to
   discover the location and role of the iSNS server.  The DHCP option
   number assigned for iSNS by IANA is 83.

1.1.  Conventions Used in This Document

   iSNS refers to the Internet Storage Name Service framework, which
   consists of the storage network model and associated services.

   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 [RFC2119].

   All frame formats are in big-endian network byte order.  RESERVED
   fields SHOULD be set to zero.

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RFC 4174              DHCP Option Number for iSNS         September 2005

   This document uses the following terms:

      "iSNS Client" - iSNS clients are processes resident in iSCSI and