IPS Prasenjit Sarkar Internet Draft IBM Document: draft-sarkar-dhc-iscsi-boot-00.txt Category: Standards Track 27 August 2001 Qualifying the Root Path Option for iSCSI Boot Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [3]. 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 made obsolete 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. Abstract The Small Computer Systems Interface (SCSI) is a popular family of protocols for communicating with I/O devices, especially storage devices. iSCSI is a proposed transport protocol for SCSI that operates on top of TCP[4]. The iSCSI Boot Draft[5] is an informational draft that provides information on the mechanisms employed by an iSCSI boot client to locate and boot off an iSCSI boot server. This memo describes the mechanism by which an iSCSI boot client can obtain the identity of an iSCSI boot server using the DHCP service. 1. DHCP Option In order to use an iSCSI boot server, the following pieces of information are required. - The IP address of the iSCSI boot client (IPv4 or IPv6) - The IP transport endpoint for the iSCSI service delivery port for the iSCSI boot server. If the transport is TCP, for example, this Sarkar Expires: February 2002 [Page 1] Standards-Track iSCSI Boot DHCP Option 27 August 2001 has to resolve to an IP address and a TCP port number. - The eight-byte LUN structure identifying the device within the iSCSI boot server. At boot time, all or none of this information may be stored in the firmware of the iSCSI boot client. This section describes techniques for obtaining the required information pertaining to the iSCSI boot server. A DHCP server (v4 or v6) may instruct an iSCSI client how to reach its boot device. This is done using the variable length DHCP option named Root Path. The use of the option field is reserved for iSCSI boot use by prefacing the string with "iscsi:". The option field consists of an UTF-8[8] string. The string MUST contain only alphanumberic characters, "." , ":" and "-"; no other characters are permissible. The string has the following composition: iscsi:[":"[":"[":"[":"]]]] The fields "port", "protocol" and "LUN" are optional and should be left blank if there are no corresponding values. In addition, one or both of "servername" and "wwui" should be specified. As before, if either of the two fields is not specified, then the field should be left blank. Thv "servername" is the name of iSCSI server and contains either a valid domain name, a literal IPv4 address, or a literal IPv6 address. If the "servername" field contains a literal IPv4 address, the IPv4 address is in standard dotted decimal notation as defined in Section 2.1 of RFC 1123[6]. If the "servername" field contains an IPv6 address, the address is represented in the IPv6 address format x.x.x.x.x.x.x.x where the 'x's are the hexadecimal values of the eight 16-bit pieces of the address. Note that this format representation is specific to iSCSI boot. If the "servername" is a domain name, the name MUST be a fully qualified domian name (FQDN) and SHOULD abide by the rules specified in Sections 3.1 and 3.5 of RFC 1034[7] and the reply from the host configuration server SHOULD contain the Domain Name Server Option[1]. It must also be pointed out that the use of DNS for address translation in enterprise environments must contain adequate levels of fault tolerance and security. If the "servername" field contains 4 decimal components, the Sarkar Expires: February 2002 [Page 2] Standards-Track iSCSI Boot DHCP Option 27 August 2001 "servername" is assumed to be an IPv4 address. If there are more than 4 decimal components or if there is a hexadecimal component, the the "servername" is assumed to be an IPv6 address. If the least significant (rightmost) component is an approved domain extension, then the "servername" field is assumed to be a domain name. If the "servername" field is left blank, then no default value is assumed in its place. The "protocol" field is the decimal representation of the IANA- approved string for the trasport protocol to be used for iSCSI. If the protocol field is left bank, the default value is assumed to be "6" for TCP. The transport protocol MUST have been approved for use in iSCSI; currently, the only approved protocol is TCP. The "port" is the decimal representation of the port on which the iSCSI boot server is listening. If not specified, the port defaults to the well-known iSCSI port. The "LUN" field is a 16 byte hexadecimal representation of the 8-byte LU number in hex. Digits above 9 may be either lower or upper case, and all 16 nibbles must be present. If the LUN field is blank, then LUN 0 is assumed. Note that SCSI targets are allowed to present different LU numberings for different SCSI initiators, so that to our knowledge nothing precludes a SCSI target from exporting several different devices to several different SCSI initiators as their respective LU 0s. The "wwui" field is the World Wide Unique Identifier (WWUI) defined by the naming and discovery iSCSI draft[9] to uniquely identify an iSCSI target. The use of the wwui component is also defined by the iSCSI standard[4] and is to be used accordingly. Acknowledgments I wish to thank David Black and Glen Turner for assisting with the formulation of this draft. References [1] Alexander, S., and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, Lachman Technology, Inc., Bucknell University, October 1993. [2] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131, Bucknell University, March 1997. Sarkar Expires: February 2002 [Page 3] Standards-Track iSCSI Boot DHCP Option 27 August 2001 [3] Bradner, S., "The Internet Standards Process -- Revision 3", RFC 2026, October 1996. [4] Satran, J. et al., "iSCSI", Internet-Draft, July 2001. [5] Sarkar, P. et al., "Bootstrapping clients using the iSCSI protocol", Internet-Draft, February 2001. [6] Braden, R., "Requirements for Internet Hosts - Application and Support", RFC 1123, October 1989. [7] Mockaopertis, P., "Domain Names - Concepts and Facilities", RFC 1034, November 1987. [8] Yergeau, F., "UTF-8: A Transformation Format for ISO-10646", RFC 2279, January 1998. [9] Bakke, M. et al., "iSCSI Naming and Discovery", Internet-Draft, July 2001. Author's Address Prasenjit Sarkar IBM Almaden Research Center 650 Harry Road San Jose, CA 95120, USA Phone: +1 408 927 1417 Email: psarkar@almaden.ibm.com Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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Sarkar Expires: February 2002 [Page 4] Standards-Track iSCSI Boot DHCP Option 27 August 2001 This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." Sarkar Expires: February 2002 [Page 5]