Mobile IPv6 Internet Draft B. Haley Document: draft-haley-mip6-mh-signaling-01.txt Hewlett-Packard Company Sri Gundavelli Cisco Systems Expires: April, 2006 October 2005 Mobility Header Signaling Message draft-haley-mip6-mh-signaling-01.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 Abstract This document describes an extension to the Mobile IPv6 base protocol [2] by defining a new Mobility Header message type that can be used for sending notification messages between a mobile node, its correspondent nodes, and its home agent. The purpose of this extension is to provide an extensible framework by which Mobile IPv6 entities can exchange notification messages indicating that certain events have occurred. Conventions used in this document Haley & Gundavelli Expires - April 2006 [Page 1] Mobility Header Signaling Message October 2005 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 [1]. Table of Contents 1. Introduction...................................................2 2. Scenarios......................................................3 2.1 Binding Revocation.........................................3 2.2 Home Agent switchover......................................3 2.3 Failure of Back Haul Connectivity..........................3 2.4 Explicit Network Mobility (NEMO) Prefix Recovery...........3 2.5 Billing Event..............................................3 3. Operation Overview.............................................4 3.1 Typical Flow of a Signaling Message........................4 3.2 Participating Entities.....................................4 4. Mobility Header Signaling Messages.............................4 4.1 Mobility Header Signaling Request Message..................5 4.2 Mobility Header Signaling Acknowledgement Message..........6 5. Signaling Requests.............................................7 5.1 Sending Signaling Requests.................................7 5.2 Receiving Signaling Messages...............................8 5.2.1 Mobile Node Operation....................................8 5.2.2 Home Agent Operation.....................................8 5.2.3 Correspondent Node Operation.............................9 5.3 Retransmissions............................................9 6. Signaling Acknowledgements.....................................9 6.1 Sending Signaling Acknowledgements.........................9 7. Protocol Constants............................................10 8. IANA Considerations...........................................10 9. Security Considerations.......................................10 9.1 Mobile Node to Home Agent Messages........................10 9.2 Mobile Node to Correspondent Node Messages................10 10. References...................................................11 10.1 Normative References.....................................11 10.2 Informative references...................................11 Acknowledgments..................................................11 Author's Addresses...............................................11 1. Introduction The Mobile IPv6 base specification [2] does not provide any mechanism for a home agent, mobile node or correspondent node to exchange signaling or status messages among themselves during a mobility session. The ability to send asynchronous notification events is useful in many types of services for which cooperation between these entities is required. For example, a home agent may wish to Haley & Gundavelli Expires - April 2006 [Page 2] Mobility Header Signaling Message October 2005 terminate the binding of a mobile node, or it may wish to handoff that binding to some other home agent on the home network. This specification defines a generic notification header that can be used by a home agent, mobile node and correspondent node for sending and receiving notification events during the lifetime of a mobility session. This specification, however, does not define any specific notification message types that can be carried within this generic notification header. The specific event and the corresponding action that the receiving entity needs to take on receiving that event should be defined in the document for that specific message type. 2. Scenarios Here are some example scenarios where a home agent signaling message would be useful. 2.1 Binding Revocation There are a number of reasons a home agent might wish to revoke the binding of a mobile node, for example it might be overloaded or going off-line for maintenance. The mobile node must be notified before such an administrative action can take place. Upon receiving this event, the mobile node can release the system resources and may attempt to contact a different home agent, or may take a different action. 2.2 Home Agent switchover A home agent may wish to handoff a given mobility binding to a different home agent on the home network, for example as described in [ID-HA-Switch]. 2.3 Failure of Back Haul Connectivity Upon detecting a failure of its back haul connectivity, a home agent may wish to notify all of its mobile nodes about this situation so they can find other home agents with better service. 2.4 Explicit Network Mobility (NEMO) Prefix Recovery A home agent may decide to withdraw a routing prefix attached to a mobile router. The home agent can notify a mobile router about this action so it can remove the routing state for that prefix. 2.5 Billing Event Haley & Gundavelli Expires - April 2006 [Page 3] Mobility Header Signaling Message October 2005 A home agent can notify a mobile node about its service usage, or about its pending account balance as an informational event. 3. Operation Overview The concept is that Mobile IPv6 entities can send notifications when a certain event or a state change occurs. The actual reason for sending a notification is outside the scope of this document. 3.1 Typical Flow of a Signaling Message +----+ Signaling Request +----+ | |------------------------------>| | | |<------------------------------| | +----+ Signaling Acknowledgement +----+ MIPv6 Entity MIPv6 Entity 3.2 Participating Entities Signaling messages may be exchanged between a mobile node and its home agent, or a mobile node and a Mobile IPv6 capable correspondent node that has a current binding cache entry for that mobile node. Signaling messages MUST NOT be exchanged between a mobile node and a correspondent node that is not Mobile IPv6 capable or has no binding cache entry for that mobile node. Signaling messages MUST NOT be exchanged between the home agent of a mobile node and a correspondent node of the mobile node, as there will not be any trust relationship between these two entities. The two participating entities exchanging signaling messages MUST have a security relationship and should have the ability to detect message replay and man-in-the-middle attacks. 4. Mobility Header Signaling Messages The messages described below follow the Mobility Header format specified in Section 6.1 of [2]: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Proto | Header Len | MH Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Checksum | | Haley & Gundavelli Expires - April 2006 [Page 4] Mobility Header Signaling Message October 2005 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | . . . Message Data . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 4.1 Mobility Header Signaling Request Message The Signaling Request is used by one Mobile IPv6 entity to signal another entity that there is an event that requires attention. This packet is sent as described in Section 5.1. The Signaling Request uses the MH Type value (TBD). When this value is indicated in the MH Type field, the format of the Message Data field in the Mobility Header is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A| Reserved | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Acknowledge (A) The Acknowledge (A) bit is set by the sender to request a Signaling Acknowledgement (Section 4.2) be returned upon receipt of a Signaling Request. Reserved These fields are unused. They MUST be initialized to zero by the sender, and MUST be ignored by the receiver. Sequence # An 8-bit unsigned integer used by the receiving node to sequence Signaling Requests and by the sending node to match a returned Signaling Acknowledgement with this Signaling Request. Haley & Gundavelli Expires - April 2006 [Page 5] Mobility Header Signaling Message October 2005 Mobility options Variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero of more TLV-encoded mobility options. The encoding and format of defined options MUST follow the format specified in Section 6.2 of [2]. The receiver MUST ignore and skip any options with it does not understand. This specification does not define any options valid for the Signaling Request message. If no options are present in this message, no padding is necessary and the Header Len field in the Mobility Header will be set to 0. 4.2 Mobility Header Signaling Acknowledgement Message The Signaling Acknowledgement is used to acknowledge receipt of a Signaling Request (Section 4.1). This packet is sent as described in Section 6.1. The Signaling Acknowledgement uses the MH Type value (TBD). When this value is indicated in the MH Type field, the format of the Message Data field in the Mobility Header is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Status | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . . . Mobility options . . . | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Status 8-bit unsigned integer indicating the disposition of the Signaling Request. Values of the Status field less than 128 indicate that the Signaling Request was accepted by the receiving node. Values greater than or equal to 128 indicate that the Signaling Request was rejected by the receiving node. The following Status values are currently defined: 0 Signaling Request accepted Haley & Gundavelli Expires - April 2006 [Page 6] Mobility Header Signaling Message October 2005 128 Reason unspecified 129 Administratively prohibited 130 Insufficient resources 131 Unsupported mobility option 132 Not home agent for this mobile node Sequence # The sequence number in the Signaling Acknowledgement is copied from the sequence number field in the Signaling Request. It is used by the receiving node in matching this Signaling Acknowledgement with an outstanding Signaling Request. Mobility options Variable-length field of such length that the complete Mobility Header is an integer multiple of 8 octets long. This field contains zero of more TLV-encoded mobility options. The encoding and format of defined options MUST follow the format specified in Section 6.2 of [3]. The receiver MUST ignore and skip any options with it does not understand. This specification does not define any options valid for the Signaling Request message. If no options are present in this message, no padding is necessary and the Header Len field in the Mobility Header will be set to 0. 5. Signaling Requests 5.1 Sending Signaling Requests When sending a Signaling Request message, the sending node constructs the packet as it would any other Mobility Header, except: o The MH Type field MUST be set to (TBD). o The Acknowledge (A) bit MAY be set to indicate the receiver must send a Signaling Acknowledgement. The Signaling Request message MUST meet the security requirements outlined in Section 9.1 or 9.2, depending on the association it has with the target entity. Haley & Gundavelli Expires - April 2006 [Page 7] Mobility Header Signaling Message October 2005 5.2 Receiving Signaling Messages Upon receiving a Signaling Request message, the Mobility Header MUST be verified as specified in [2], specifically: o The Checksum, MH type, Payload Proto and Header Len fields MUST meet the requirements of Section 9.2 of [2]. o The Signaling Request message MUST meet the security requirements outlined in Section 9.1 or 9.2, depending on the association it has with the sending entity. If the packet is dropped due to the above tests, the receiving node MUST follow the processing rules as Section 9.2 of [2] defines and MUST NOT send a Signaling Acknowledgement. For example, it MUST send a Binding Error message with the Status field set to 2 (unrecognized MH Type value) if it does not support the message type. If the Signaling Request is valid according to the tests above, then it is processed further as follows: o If the receiving node does not allow Signaling Request messages, it MUST reject the request and SHOULD return a Signaling Acknowledgement to the sender in which the Status field is set to 129 (administratively prohibited). o If the receiving node does not support the type of Mobility Option in the Signaling Request message, it MUST reject the request and SHOULD return a Signaling Acknowledgement to the sender in which the Status field is set to 131 (unsupported mobility option). Subsequent checks depend on the current mode of operation of the node. 5.2.1 Mobile Node Operation If the mobile node rejects the Signaling Request message for any other reason than specified in Section 5.2, it SHOULD return a Signaling Acknowledgement to the sender in which the Status field is set to 128 (reason unspecified). 5.2.2 Home Agent Operation If the receiving node is a home agent, it MUST perform these additional checks: Haley & Gundavelli Expires - April 2006 [Page 8] Mobility Header Signaling Message October 2005 o If the home agent has no entry marked as a home registration in its Binding Cache for the sending node, then this node MUST reject the request and SHOULD return a Signaling Acknowledgement in which the Status field is set to 132 (not home agent for this mobile node). o If the home agent cannot process the Signaling Request message because it is over-utilized, it MUST reject the request and SHOULD return a Signaling Acknowledgement in which the Status field is set to 130 (insufficient resources). If the home agent rejects the Signaling Request message for any other reason, it SHOULD return a Signaling Acknowledgement to in which the Status field is set to 128 (reason unspecified). 5.2.3 Correspondent Node Operation If the correspondent node rejects the Signaling Request message for any other reason than specified in Section 5.2, it SHOULD return a Signaling Acknowledgement to the sender in which the Status field is set to 128 (reason unspecified). 5.3 Retransmissions If the sender has set the Acknowledge (A) bit in the Signaling Request, but does not receive a Signaling Acknowledgement, then it MAY retransmit the message, until a response is received. The initial value for the retransmission timer is INITIAL_MH_SIGNAL_TIMEOUT. The retransmissions by the sender MUST use an exponential back-off mechanism, in which the timeout period is doubled upon each retransmission, until either the sender gets a response from the target node, or the timeout period reaches the value MAX_MH_SIGNAL_TIMEOUT. 6. Signaling Acknowledgements 6.1 Sending Signaling Acknowledgements A Signaling Acknowledgement should be sent to indicate receipt of a Signaling Request as follows: o If the Signaling Request was discarded because it does not meet the requirements as specified in [2] described in Section 5.2, a Signaling Acknowledgement MUST NOT be sent. Otherwise, the treatment depends on the below rule. Haley & Gundavelli Expires - April 2006 [Page 9] Mobility Header Signaling Message October 2005 o If the Acknowledgement (A) bit is set in the Signaling Request, a Signaling Acknowledgement MUST be sent. Otherwise, the treatment depends on the below rule. o If the Signaling Request was discarded for any other reason, a Signaling Acknowledgement SHOULD be sent. If the Source Address field of the IPv6 header that carried the Signaling Request does not contain a unicast address, the Signaling Acknowledgement MUST NOT be sent, and the Signaling Request packet MUST be silently discarded. Otherwise, the acknowledgement MUST be sent to the Source Address. 7. Protocol Constants INITIAL_MH_SIGNAL_TIMEOUT 5 seconds MAX_MH_SIGNAL_TIMEOUT 20 seconds 8. IANA Considerations A new Mobility Header type is required for the following new message described in Section 4: (TBD) Signaling Request (TBD) Signaling Acknowledgement 9. Security Considerations 9.1 Mobile Node to Home Agent Messages As with other messages in [2], the Signaling Request and Acknowledgement messages MUST use the home agent to mobile node ESP encryption SA for confidentiality protection, and MUST use the home agent to mobile node ESP authentication SA for integrity protection. The Signaling Request message MAY use the IPsec ESP SA in place for Binding Updates and Acknowledgements as specified in Section 5.1 of [2], in order to reduce the number of configured security associations. This also gives the message authenticity protection. 9.2 Mobile Node to Correspondent Node Messages The entities exchanging Signaling Requests and Acknowledgements MUST have a trust relation and the messages MUST be protected by an IPSec SA. These messages are thus not vulnerable to replay or man-in-the- middle attacks. Haley & Gundavelli Expires - April 2006 [Page 10] Mobility Header Signaling Message October 2005 10. References 10.1 Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [2] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in IPv6", RFC 3775, June, 2004. [3] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to Protect Mobile IPv6 Signaling Between Mobile Nodes and Home Agents", RFC 3776, June, 2004. 10.2 Informative references [ID-HA-Switch] Haley, B., Devarapalli, V., Kempf, J., and Deng, H., "Mobility Header Home Agent Switch Message", draft-haley-mip6-ha- switch-00.txt (work in progress), April, 2005. Acknowledgments Thanks to Hui Deng, James Kempf and Vijay Devarapalli for their initial review of the draft. Author's Addresses Brian Haley Hewlett-Packard Company 110 Spitbrook Road Nashua, NH 03062, USA Email: brian.haley@hp.com Sri Gundavelli Cisco Systems 170 West Tasman Drive San Jose, CA 95134, USA Email: sgundave@cisco.com Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Haley & Gundavelli Expires - April 2006 [Page 11] Mobility Header Signaling Message October 2005 Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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. Copyright Statement Copyright (C) The Internet Society (2005). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Haley & Gundavelli Expires - April 2006 [Page 12]