NETEXT WG S. Gundavelli Internet-Draft K. Leung Intended status: Standards Track Cisco Expires: December 4, 2009 R. Koodli Starent Networks June 02, 2009 Retransmitted Message Identification Option for Proxy Mobile IPv6 draft-gundavelli-netext-pmipv6-retransmit-option-00.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 December 4, 2009. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract The Proxy Mobile IPv6 base protocol does not provide any mechanism Gundavelli, et al. Expires December 4, 2009 [Page 1] Internet-Draft Retransmitted Message Identification June 2009 for the receiver of a mobility signaling message to determine if the received message is the original message or a retransmitted message of an earlier sent message. The absence of such a semantic in some cases results in inefficient processing of the signaling messages and will lead to additional processing load and network traffic. This document defines a new mobility option, Retransmitted Message Identification option for use in Proxy Binding Update and Proxy Binding Acknowledgement messages. This option enables the mobility entities to use proper message identifiers and retransmit markings on the signaling messages. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Signaling and other Considerations . . . . . . . . . . . . . . 3 4. Retransmitted Message Identification (RMI) Option . . . . . . . 5 5. Protocol Configuration Variables . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Gundavelli, et al. Expires December 4, 2009 [Page 2] Internet-Draft Retransmitted Message Identification June 2009 1. Introduction The Proxy Mobile IPv6 protocol [RFC-5213] does not provide the ability for the sender of a signaling message to mark retransmitted messages with a proper tag, so the receiver can differentiate between the original message to a retransmitted message. This semantic is important for the receiver to determine when to ignore processing a retransmitted packet, or for various other reasons. This document defines a new mobility option, Retransmitted Message Identification (RMI) option, that can be used by a local mobility anchor and a mobile access gateway for exchanging message and retransmit identifiers. Following explains how the option helps in detecting retransmitted messages. MAG LMA | PBU RMI(MesgId: 1, RetransId: 0) | |---------------------------------------------->| * New message | PBA RMI(MesgId: 1, RetransId: 0) | |<----------------------------------------------| | | | | | PBU RMI(MesgId: 2, RetransId: 0) | |---------------------------------------------->| * Lost message | No Response from MAG | | | | PBU RMI(MesgId: 2, RetransId: 1) | |---------------------------------------------->| * Retransmitted | | message | PBA RMI(MesgId: 2, RetransId: 1) | |<----------------------------------------------| Figure 1: RMI Option Usage 2. Conventions 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 [RFC-2119]. 3. Signaling and other Considerations The following are the signaling considerations with respect to Gundavelli, et al. Expires December 4, 2009 [Page 3] Internet-Draft Retransmitted Message Identification June 2009 supporting the retransmitted message identification capability. o The mobile access gateway can choose to enable the retransmitted message identification feature by including the Retransmitted Message Identification (RMI) option (Section 4.0) in the Proxy Binding Update that it sends to the local mobility anchor. The configuration variable, EnableRetransmittedMessageIdentification, can be used for controlling this aspect. o For constructing the RMI option, each newly generated message MUST have a unique message identifier (mid). This identifier is specified in the mid field of the RMI option. The retransmit identifier (rid) for the initial message will be set to value of zero, this is specified in the rid field of the RMI option. The mobile access gateway can maintain this message identifier as a monotonically increasing counter maintained on a per packet basis for each mobile node's session. o The mobile access gateway may retransmit a Proxy Binding Update message if it did not get a response to the previously transmitted request. When retransmitting a message, the message identifier in the RMI option MUST remain fixed and the retransmit identifier MUST be increased by one. All other content in the message including the options MUST be identical, except the sequence number and the value in the Time Stamp option which can be different. o The conceptual Binding Update List entry data structure maintained by the mobile access gateway, described in Section 6.1 of [RFC- 5213], MUST be extended to store the last sent message identifier and the retransmit identifier. o The local mobility anchor MUST include the RMI option in the Proxy Binding Acknowledgement message, if the same option was present in the received Proxy Binding Update. Otherwise, it MUST NOT include the option. When this option is included in the message, the message identifier and the retransmit identifier MUST be set to the option values present in the request. o If the local mobility anchor does not support the RMI option, it SHOULD ignore the option and continue processing the rest of the Proxy Binding Update message. The absence of the RMI option in the Proxy Binding Acknowledgement indicates that the sender does not support the Retransmitted Message Identification capability and in such case the mobile access gateway MUST NOT include the RMI option in the subsequent Proxy Binding Update messages that it sends to that local mobility anchor. Gundavelli, et al. Expires December 4, 2009 [Page 4] Internet-Draft Retransmitted Message Identification June 2009 o If the local mobility anchor receives a Proxy Binding Update message while in the middle of processing a request (such as waiting for response from AAA) with the same message identifier, but with a different retransmit identifier, the message MUST be silently ignored. o The conceptual Binding Cache entry data structure maintained by the local mobility anchor, described in Section 5.1 of [RFC-5213], MUST be extended to store the last received message identifier and the retransmit identifier. 4. Retransmitted Message Identification (RMI) Option A new option, Retransmitted Message Identification (RMI) option is defined for using it in Proxy Binding Update and Proxy Binding Acknowledgement messages exchanged between a local mobility anchor and a mobile access gateway. This option is used for carrying message and retransmission identifiers. The alignment requirement for this option is 4n. Gundavelli, et al. Expires December 4, 2009 [Page 5] Internet-Draft Retransmitted Message Identification June 2009 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Reserved | Retransmit-Id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message Identifier (mid) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type Length 8-bit unsigned integer indicating the length in octets of the option, excluding the type and length fields. The value for this field MUST be set to 6. Retransmission Identifier (rid) A 8-bit field for carrying the retransmission identifier. This value will be set to zero for the first transmission of any newly generated signaling message and the value will be monotonically increased in each of the subsequent retransmissions of the same message uniquely identified by the message identifier. Message Identifier (mid) A 32-bit field for identifying the message. Each newly generated Proxy Binding Update message will have a unique identifier, however the Proxy Binding Acknowledgement will always carry the identifier that was present in the request. Any retransmitted messages will carry the same identifier that was present in the initial message. Figure 2: Retransmitted Message Identification (RMI) Option 5. Protocol Configuration Variables The mobile access gateway MUST allow the following variables to be configured by the system management. The configured values for these protocol variables MUST survive server reboots and service restarts. EnableRetransmittedMessageIdentification Gundavelli, et al. Expires December 4, 2009 [Page 6] Internet-Draft Retransmitted Message Identification June 2009 This flag indicates whether or not the mobile access gateway should include the retransmitted message identification option in the mobility signaling messages that it sends to the local mobility anchor. The default value for this flag is set to FALSE, indicating that the mobile access gateway MUST NOT include this option in any of the Proxy Binding Update messages. When the value for this flag is set to TRUE, the mobile access gateway MUST include this option in all the Proxy Binding Update messages. 6. IANA Considerations This specification defines a new Mobility Header option, the Retransmitted Message Identification option. This option can be carried in mobility header messages. This option is described in Section 4.0. The Type value for this option needs to be assigned from the same numbering space as allocated for the other mobility options, as defined in [RFC-3775]. 7. Security Considerations The Retransmitted Message Identification option defined in this specification is for use in mobility signaling messages, Proxy Binding Update and Proxy Binding Acknowledgement messages. This option is carried like any other mobility header option as specified in [RFC-3775] and does not require any special security considerations. The required security mechanisms specified in the base Proxy Mobile IPv6 protocol [RFC-5213] for protecting these signaling messages are sufficient when carrying these mobility options. 8. Acknowledgements The authors would like to thank Venkatesh Gota, Ashwin Kabadi and Vojislav Vucetic on the discussions related to the similar semantics present in GTP and making the motivation for this work stronger. 9. References Gundavelli, et al. Expires December 4, 2009 [Page 7] Internet-Draft Retransmitted Message Identification June 2009 9.1. Normative References [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC-3775] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in IPv6", RFC 3775, June 2003. [RFC-5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. 9.2. Informative References [ID-PMIP6-IPv4] R. Wakikawa and S. Gundavelli, "IPv4 Support for Proxy Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-12, April 2009. Authors' Addresses Sri Gundavelli Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: sgundave@cisco.com Kent Leung Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: kleung@cisco.com Rajeev Koodli Starent Networks 30 International Place Tewksbury, MA Email: rkoodli@starentnetworks.com Gundavelli, et al. Expires December 4, 2009 [Page 8]