dhc Group R. Droms Internet-Draft B. Volz Intended status: Informational O. Troan Expires:
February 11,May 31, 2007 Cisco Systems, Inc. August 10,November 27, 2006 DHCPv6 Relay Agent Assignment Notification (RAAN) Option draft-ietf-dhc-dhcpv6-agentopt-delegate-01.txtdraft-ietf-dhc-dhcpv6-agentopt-delegate-02.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on February 11,May 31, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract The DHCP Relay Agent Assignment Notification (RAAN) option is sent from a DHCP server to a DHCP relay agent to inform the relay agent of IPv6 addresses that have been assigned or IPv6 prefixes that have been delegated to DHCP clients. 1. Introduction The DHCP Relay Agent Assignment Notification (RAAN) option encapsulates address and prefix options to indicate that an address or prefix has been assigned. The option may also carry other information required by the network element for configuration related to the assigned address or prefix. For example, a network administrator uses the RAAN option to inform a relay agent of a prefix that has been delegated through DHCP PD to a DHCP client. The relay agent notifies the network element on which it is implemented of the delegation information so the network element can add routing information about the delegated prefix into the appropriaterouting protocols.infrastructure. 2. Terminology 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 . The term "DHCP" in this document refers to DHCP for IPv6, as defined in RFC 3315 . The terms "DHCP prefix delegation" and "DHCP PD" refer DHCP for IPv6 prefix delegation, as defined in RFC 3633  Additional terms used in the description of DHCP and DHCP prefix delegation are defined in RFC 3315 and RFC 3633. In this document "assigning" an IPv6 prefix is equivalent to "delegating" a prefix. 3. Option semanticsSemantics and Usage The RAANnRAAN option carries information about assigned IPv6 addresses and prefixes. It encapsulates anIA Address optionoptions (RFC 3315) or anand/or IA Prefix optionoptions (RFC 3633), and possibly other options that carry other information related to the assigned IPv6 address or prefix. The DHCP server MAY include this option in a Reply message sent to a client that includes assigned addresses and/or prefixes. If the DHCP server does include this option in a Reply message, it MUST include it in the option area of the Relay-reply message sent to the relay agent intended as the recipient of the option. The DHCP serveris responsible for synchronizing any state created by a node through the use of the RAAN option. For example, if a DHCP server receives a Release message for a delegated prefix, it causes the node to delete any state associated with that prefix by sending ana RAAN option containing an IA Prefix option with the released prefix and a valid lifetime of zero. A relay agent that receivesWhen a DHCP server sends this option SHOULD pass the informationto the node in which thea relay agent is instantiated. The node MAY make use of the information received fromagent, it MUST include all addresses and prefixes assigned to the relay agent. If a node creates state basedclient on the information included in this option, it MUST remove that state whenlink to which the lifetime as specified inoption refers at the time the option expires.is sent. Examples of use: o Populate an ACL with an assigned IPv6 address if the network device in which the relay agent is instantiated implements asecurity policy requires limiting IPv6 forwarding to devices that have obtained an address through DHCP o Inject routing information into a routing infrastructure about a delegated prefix on behalf of a requesting router 4. Relay Agent Behavior A relay agent that wants information from the server in a RAAN option includes an ORO requesting the RAAN option in its Relay-Forw message. A relay agent may do this for any relayed message, regardless of the message type or the message contents. When a relay agent receives a Relay-Reply message containing a RAAN option, the relay agent may forward that option data to the node in which the relay agent is instantiated. If no RAAN option is included in the Relay-Reply, the relay agent MUST NOT assume anything with regard to RAAN data and MUST NOT forward any indication to the node in which the relay agent is instantiated. If a node creates state based on the information included in this option, it MUST remove that state when the lifetime as specified in the option expires. 5. Server Behavior When a server is responding to a request and the ORO contains an RAAN option, the server SHOULD include a RAAN option with all of the addresses and prefixes that have been (or are being assigned) to the client. If no addresses or prefixes are assigned, the server SHOULD send a RAAN option with no addresses or prefixes. If the DHCP server does include this option in a Relay-Reply message, it MUST include it in the option area of the Relay-Reply message sent to the relay agent intended as the recipient of the option. If the message received from the client contains no Client Identifier option or the server is otherwise unable to identify the client or the client's link (perhaps because of missing or invalid data in the request), the server MUST NOT include a RAAN option in the response. 6. Option format The RAAN option has the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | encapsulated-options | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_AGENT_NOTIFY (TBD) length length of encapsulated options, in octets encapsulated-options DHCP options to be delivered by the Relay Agentrelay agent Assignment Notification option 5.7. Encapsulating DHCP options in the RAAN Option The contents of options encapsulated in the RAAN option are interpreted according to the use of those options in the node on which the relay agent is implemented. For the purposes of address and prefix assignment, the uses of the DHCP IA Address and IA Prefix options are defined in this document. Note that the contents of these options are not necessarily the same as in the corresponding options sent to the DHCP client. For example, the node that receives the information from these options may be instructed to usethis document. Note that the information for a shorter periodcontents of time thanthese options are not necessarily the client by setting a shorter valid-lifetimesame as in the this option. 5.1.corresponding options sent to the DHCP client. 7.1. IA Address option The fields in an IA Address option (OPTION_IAADDR, option code 5) are used as follows: IPv6 address The IPv6 address assigned in this DHCP message preferred-lifetime Not used atby the timerelay agent; the server SHOULD set this document was publishedfield to the preferred-lifetime of the corresponding IA Address options in the message to be forwarded to the client valid-lifetime The expirationlifetime of the information carried in this IA Address option, expressed in units of seconds; the expiration-lifetime is a relative time, giving the duration relative to the current time of the information in this IA Address option;if the valid-lifetime is 0, the information is no longer valid.valid IAaddr-options Not used 5.2.by the relay agent; the server SHOULD set this field to the IAaddr-options of the corresponding IA Address option in the message to be forwarded to the client 7.2. IA Prefix option The fields in an IA Prefix option (OPTION_IAPREFIX, option code 28) are used as follows: preferred-lifetime Not used by the relay agent; the server SHOULD set this field to the preferred-lifetime of the corresponding IA Prefix options in the message to be forwarded to the client valid-lifetime The expirationlifetime of the information carried in this IA Prefix option, expressed in units of seconds; the expiration-lifetime is a relative time, giving the duration relative to the current time of the information in this IA Prefix option;if the valid-lifetime is 0, the information is no longer valid.valid prefix-length length for this prefix in bits IPv6-prefix The IPv6 prefix assigned in this DHCP message IAprefix-options Not used atby the timerelay agent; the server SHOULD set this document was published 6.field to the IAprefix-options of the corresponding IA Prefix option in the message to be forwarded to the client 8. Requesting assignment information from the DHCP server If a relay agent requires the DHCP server to provide information about assigned addresses and prefixes, it MUST include an Option Request option, requesting the Assignment Notification option, as described in section 22.7 of RFC 3315. 7.9. Reordering received DHCP messages The relay agent MUST use the Server Reply Sequence Number (SRSN) option  to detect and discard RAAN options contained in DHCP messages that are received out of order. 8.10. IANA considerations IANA is requested to assign an option code from the "DHCPv6 and DHCPv6 options" registry http://www.iana.org/assignments/dhcpv6-parameters to OPTION_AGENT_NOTIFY. 9.11. Security considerations Security issues related to DHCP are described in RFC 3315 and RFC 3633. The RAAN option may be used to mount a denial of service attack by causing a node to incorrectly populate an ACL or incorrectly configure routing protocolinformation for a delegated prefix. This option may also be used to insert invalid prefixes into the routing infrastrutureinfrastructure or add invalid IP addresses to ACLs in nodes. Communication between a server and a relay agent, and communication between relay agents, can be secured through the use of IPSec, as described in section 21.1 of RFC 3315. 10.12. Changes in this revisionlog If this section is included in the document when it is submitted for publication, the RFC Editor is requested to remove it. Changes in rev -01: o Added section describing use of "Server Reply Sequence Number" option to allow resequencing of out-of-order messages 11.Changes in rev -02: o Made editorial change in section 1: s/the appropriate routing protocols/the routing infrastructure/ o Updated first paragraph in Section 3 to allow multiple IA Address options and/or IA Prefix options o Renamed section "Options Semantics and Usage" o Added paragraph to section "Option Semantics and Usage" requiring that the DHCP server must include all addresses/prefixes for the client (on that link) in the RAAN option o Added list of use cases to section "Option Semantics and Usage" o Added section "Relay Agent Behavior" o Added section "Server Behavior"; moved second paragraph of section "Option Semantics and Usage" to "Server Behavior" o Updated reference to draft-ietf-dhc-dhcpv6-srsn-option-00 o Clarified descriptions of various option fields in section "Encapsulating DHCP options in the RAAN Option" 13. Normative References  Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003.  Volz, B. and R. Droms, "DHCPv6 Server Reply Sequence Number Option", draft-volz-dhc-dhcpv6-srsn-option-00draft-ietf-dhc-dhcpv6-srsn-option-00 (work in progress), AugustNovember 2006. Authors' Addresses Ralph Droms Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 USA Phone: +1 978.936.1674 Email: firstname.lastname@example.org Bernie Volz Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 USA Phone: +1 978.936.0382 Email: email@example.com Ole Troan Cisco Systems, Inc. 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