Network Working Group V. Sastry Request for Comments: 4917 Samsung Electronics Category: Standards Track K. Leung A. Patel Cisco Systems June 2007 Mobile IPv4 Message String Extension Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The IETF Trust (2007).
AbstractThis document specifies a new extension for use in Mobile IPv4. This extension can be added by the Home Agent and the Foreign Agent to Registration Reply messages. This extension carries a text string that is intended for the user of the Mobile Node. 1. Introduction ....................................................2 2. Terminology .....................................................2 3. Mobile IPv4 Message String Extension Format .....................2 4. Operation and Use of the Message String Extension ...............3 5. Security Considerations .........................................4 6. IANA Considerations .............................................4 7. Acknowledgements ................................................5 8. Normative References ............................................5
RFC2119]. RFC3344]. The Message String Extension is a skippable extension. 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 | Sub-Type | Text .... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 145: An 8-bit identifier of the type mobility option.
Length: An 8-bit unsigned integer. Length of the extension, in bytes, excluding the extension Type and the extension Length fields. This field MUST be set to 1 plus the total length of the Text field. Sub-Type: 1: Extension comes from the Home Agent 2: Extension comes from the Foreign Agent Text: The Text field is one or more octets, and its contents are implementation dependent. It is intended to be human readable, and MUST NOT affect the operation of the protocol. The message MUST be in UTF-8 encoded ISO-10646 [RFC3629] characters. The number of octets in the encoded representation of the message is always exactly the value of the Length field minus one. (The number of unicode characters represented by this octet sequence may be smaller than the number of octets.)
String Extension with the text "Welcome to www.serviceprovider.example.com". The Mobile Node could display this on the user interface, thus confirming a successful creation of binding on Home Agent. In the case that the message is not originated by the Home Agent itself, but for instance, is received from a RADIUS server [RFC2865], it could be received in some other encoding than UTF-8. If so, the Home Agent MUST convert the message to UTF-8 encoded ISO-10646 [RFC3629] characters. RFC3344] and emphasized below. If the extension is added by the Home Agent (extension with subtype 1) to a Registration Reply or Registration Revocation message, it MUST appear before Mobile-Home Authentication Extension [RFC3344]. If the extension is added by the Foreign Agent (extension with subtype 2) to a Registration Reply message, it MUST appear after Mobile-Home Authentication Extension [RFC3344] whenever present. Also the extension MUST appear before the Mobile-Foreign Authentication Extension whenever present. However, since security association between the Mobile Node and Foreign Agent is optional, it is possible that the extension is not authenticated in this case. There is no confidentiality provided by the extension; the message is transferred unencrypted, and if sensitive information is sent for display purposes, it may need to be protected by other means. Section 3 from the space of numbers for skippable mobility extensions (i.e., 128-255) defined for Mobile IPv4 [RFC3344] at http://www.iana.org/assignments/mobileip-numbers. This specification also creates a new subtype space for the type number of this extension. The subtype values 1 and 2 are defined in this specification. The subtype value 1 is reserved for use by the
Home Agent and subtype value 2 is reserved for use by the Foreign Agent. Similar to the procedures specified for Mobile IPv4 [RFC3344] number spaces, future allocations from this number space require expert review [RFC2434]. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000. [RFC3344] Perkins, C., Ed., "IP Mobility Support for IPv4", RFC 3344, August 2002. [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63, RFC 3629, November 2003.
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