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Internet Engineering Task Force (IETF)                       G. TsirtsisRequest for Comments: 6626                                       V. ParkUpdates:5177                                               V. NarayananCategory: Standards Track                                       QualcommISSN: 2070-1721                                                 K. Leung                                                                   Cisco                                                                May 2012Dynamic Prefix Allocation forNetwork Mobility for Mobile IPv4 (NEMOv4)Abstract   The base Network Mobility for Mobile IPv4 (NEMOv4) specification   defines extensions to Mobile IPv4 for mobile networks.  This   specification defines a dynamic prefix allocation mechanism for   NEMOv4.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6626.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Tsirtsis, et al.             Standards Track                    [Page 1]

RFC 6626          Dynamic Prefix Allocation for NEMOv4          May 2012Table of Contents1. Introduction ....................................................22. Requirements Notation ...........................................23. Dynamic Mobile Prefix Allocation ................................23.1. Mobile Client Considerations ...............................23.2. Home Agent Considerations ..................................34. Security Considerations .........................................45. IANA Considerations .............................................46. Acknowledgements ................................................47. Normative References ............................................41.  Introduction   The base NEMOv4 specification [RFC5177] defines extensions to Mobile   IPv4 [RFC5944] for mobile networks.  This specification adds support   for dynamic allocation of mobile prefixes by the home agent.2.  Requirements Notation   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].3.  Dynamic Mobile Prefix Allocation   The following extension is defined according to this specification.3.1.  Mobile Client Considerations   According to this specification, the Prefix field of the Mobile   Network Request extension MUST be set to zero to indicate that the   Mobile Router requests mobile network prefix(es) be assigned to it by   the home agent.  In this case, the Mobile Router MAY set the prefix   length field of such extensions to zero or to a length of its choice   as a hint to the home agent.  According to this specification, Mobile   Network Request extensions with the Prefix field set to zero MAY be   included in a registration request message either during initial   registration or during a subsequent registration.   When a Mobile Router receives a registration reply, it MUST process   it as defined in Mobile IPv4 [RFC5944] and [RFC5177].  If one or more   network acknowledgement extensions are included with the Code field   set to "Success", the Mobile Router SHOULD treat the prefixes in the   corresponding Prefix fields as allocated prefixes and create the   appropriate bindings as defined in [RFC5177].Tsirtsis, et al.             Standards Track                    [Page 2]

RFC 6626          Dynamic Prefix Allocation for NEMOv4          May 2012   In response to a registration request with a Mobile Network Request   extension with the Prefix field set to zero, if a Mobile Router   receives a registration reply with a network acknowledgement   extension including Code field set to 1 "invalid prefix", it may use   it as a hint that the home agent does not support dynamic prefix   allocation.3.2.  Home Agent Considerations   A home agent receiving a Mobile Network Request extension with the   Prefix field set to zero MAY return a Mobile Network Acknowledgement   extension [RFC5177] with the Prefix field set to the prefix allocated   to the Mobile Router.  The length of that prefix is at the discretion   of the home agent.  The home agent MAY take into account the prefix   length hint if one is included in the Mobile Network Request   extension.  Once the home agent allocates a prefix, it MUST maintain   the prefix registration table as defined in [RFC5177].   Alternatively, the home agent MAY return a Mobile Network   Acknowledgement extension with the Code field set to one of the   negative codes defined in [RFC5177].   Dynamic mobile prefix allocation, as defined in this specification,   MAY be combined with dynamic home address allocation, as defined in   [RFC5177].  In other words, the home address field of the   registration request message MAY be set to zero while the message   also includes one or more Mobile Network Request extensions with the   Prefix field also set to zero.   Once the home agent allocates a prefix, it MUST maintain the prefix   registration table as defined in [RFC5177].  The lifetime of the   allocated prefix will be equal to the lifetime of the binding cache   entry.  The Mobile Router may request for multiple mobile network   prefixes to be assigned by the home agent.  For a Mobile Network   Prefix for which the assignment was unsuccessful, the Code field in   the corresponding Mobile Network Acknowledgement extension should be   set to 4 (MOBNET_UNASSIGNED).   For dynamic prefix allocation, the Mobile Router's home address MAY   be used to identify the client if it is not set to zero.  Otherwise,   as defined in the Network Access Identifier (NAI) extension [RFC2794]   of Mobile IPv4 [RFC2794], the NAI extension needs to be included in   the registration request, in which case the same extension SHOULD be   used to identify the Mobile Router for prefix allocation purposes.Tsirtsis, et al.             Standards Track                    [Page 3]

RFC 6626          Dynamic Prefix Allocation for NEMOv4          May 20124.  Security Considerations   This specification operates in the security constraints and   requirements of Mobile IPv4 [RFC5944], NAI [RFC2794], and [RFC5177].   Home agent implementations SHOULD take steps to prevent address   exhaustion attacks.  One way to limit the effectiveness of such an   attack is to limit the number and size of prefixes any one Mobile   Router can be allocated.5.  IANA Considerations   A new value has been assigned in the Mobile Network Acknowledgement   Extension registry: 4 - Home Agent cannot assign a mobile network   prefix (MOBNET_UNASSIGNED).6.  Acknowledgements   The authors would like to thank Pete McCann, Alexandru Petrescu,   Ralph Droms, and Jari Arkko for their reviews and comments.7.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2794]  Calhoun, P. and C. Perkins, "Mobile IP Network Access              Identifier Extension for IPv4",RFC 2794, March 2000.   [RFC5177]  Leung, K., Dommety, G., Narayanan, V., and A. Petrescu,              "Network Mobility (NEMO) Extensions for Mobile IPv4",RFC 5177, April 2008.   [RFC5944]  Perkins, C., "IP Mobility Support for IPv4, Revised",RFC 5944, November 2010.Tsirtsis, et al.             Standards Track                    [Page 4]

RFC 6626          Dynamic Prefix Allocation for NEMOv4          May 2012Authors' Addresses   George Tsirtsis   Qualcomm   EMail: tsirtsis@googlemail.com   Vincent Park   Qualcomm   Phone: +908-443-8141   EMail: vpark@qualcomm.com   Vidya Narayana   Qualcomm   Phone: +858-845-2483   EMail: vidyan@qualcomm.com   Kent Leung   Cisco   Phone: +408-526-5030   EMail: kleung@cisco.comTsirtsis, et al.             Standards Track                    [Page 5]