MIPv6 node identifier: Mobile Node Identifier Option for Mobile IPv6 (MIPv6)
A Mobile IPv6 option that lets a mobile node identify itself with a name such as a user@realm NAI instead of only its home address.
Patel, A., Leung, K., Khalil, M., Akhtar, H., and K. Chowdhury, "Mobile Node Identifier Option for Mobile IPv6 (MIPv6)", RFC 4283, DOI 10.17487/RFC4283, December 2005, <https://www.rfc-editor.org/info/rfc4283>.
@misc{rfc4283,
series = {Request for Comments},
number = 4283,
howpublished = {RFC 4283},
publisher = {RFC Editor},
doi = {10.17487/RFC4283},
url = {https://www.rfc-editor.org/info/rfc4283},
author = {A. Patel and K. Leung and M. Khalil and H. Akhtar and K. Chowdhury},
title = {{Mobile Node Identifier Option for Mobile IPv6 (MIPv6)}},
pagetotal = 8,
year = 2005,
month = dec,
} RFC text
Contents
Network Working Group A. Patel
Request for Comments: 4283 K. Leung
Category: Standards Track Cisco Systems
M. Khalil
H. Akhtar
Nortel Networks
K. Chowdhury
Starent Networks
November 2005
Mobile Node Identifier Option for Mobile IPv6 (MIPv6)
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 Internet Society (2005).
Abstract
Mobile IPv6 (MIPv6) defines a new Mobility header that is used by
mobile nodes, correspondent nodes, and home agents in all messaging
related to the creation and management of bindings. Mobile IPv6
nodes need the capability to identify themselves using an identity
other than the default home IP address. Some examples of identifiers
include Network Access Identifier (NAI), Fully Qualified Domain Name
(FQDN), International Mobile Station Identifier (IMSI), and Mobile
Subscriber Number (MSISDN). This document defines a new mobility
option that can be used by Mobile IPv6 entities to identify
themselves in messages containing a mobility header.
Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................3
3. Mobile Node Identifier Option ...................................3
3.1. MN-NAI Mobility Option .....................................4
3.2. Processing Considerations ..................................4
4. Security Considerations .........................................4
4.1. General Considerations .....................................4
4.2. MN-NAI Considerations ......................................4
5. IANA Considerations .............................................5
6. Acknowledgements ................................................5
7. Normative References ............................................5
8. Informative Reference ...........................................6
1. Introduction
The base specification of Mobile IPv6 [RFC3775] identifies mobility
entities using an IPv6 address. It is essential to have a mechanism
wherein mobility entities can be identified using other identifiers
(for example, a Network Access Identifier (NAI) [RFC4282],
International Mobile Station Identifier (IMSI), or an application/
deployment specific opaque identifier).
The capability to identify a mobility entity via identifiers other
than the IPv6 address can be leveraged for performing various
functions, for example,
o authentication and authorization using an existing AAA
(Authentication, Authorization, and Accounting) infrastructure or
via an HLR/AuC (Home Location Register/Authentication Center)
o dynamic allocation of a mobility anchor point
o dynamic allocation of a home address
This document defines an option with a subtype number that denotes a
specific type of identifier. One instance of subtype, the NAI, is
defined in Section 3.1. It is anticipated that other identifiers
will be defined for use in the mobility header in the future.
This option SHOULD be used when Internet Key Exchange (IKE)/IPsec is
not used for protecting binding updates or binding acknowledgements
as specified in [RFC3775]. It is typically used with the
authentication option [RFC4285]. But this option may be used
independently. For example, the identifier can provide accounting
and billing services.
2. Terminology
The keywords "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. Mobile Node Identifier Option
The Mobile Node Identifier option is a new optional data field that
is carried in the Mobile IPv6-defined messages that includes the
Mobility header. Various forms of identifiers can be used to
identify a Mobile Node (MN). Two examples are a Network Access
Identifier (NAI) [RFC4282] and an opaque identifier applicable to a
particular application. The Subtype field in the option defines the
specific type of identifier.
This option can be used in mobility messages containing a mobility
header. The subtype field in the option is used to interpret the
specific type of identifier.
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 Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subtype | Identifier ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Type:
MN-ID-OPTION-TYPE has been assigned value 8 by the IANA. It is
an 8-bit identifier of the type mobility option.
Option Length:
8-bit unsigned integer, representing the length in octets of
the Subtype and Identifier fields.
Subtype:
Subtype field defines the specific type of identifier included
in the Identifier field.
Identifier:
A variable length identifier of type, as specified by the
Subtype field of this option.
This option does not have any alignment requirements.
3.1. MN-NAI Mobility Option
The MN-NAI mobility option uses the general format of the Mobile Node
Identifier option as defined in Section 3. This option uses the
subtype value of 1. The MN-NAI mobility option is used to identify
the mobile node.
The MN-NAI mobility option uses an identifier of the form user@realm
[RFC4282]. This option MUST be implemented by the entities
implementing this specification.
3.2. Processing Considerations
The location of the MN Identifier option is as follows: When present,
this option MUST appear before any authentication-related option in a
message containing a Mobility header.
4. Security Considerations
4.1. General Considerations
Mobile IPv6 already contains one mechanism for identifying mobile
nodes, the Home Address option [RFC3775]. As a result, the
vulnerabilities of the new option defined in this document are
similar to those that already exist for Mobile IPv6. In particular,
the use of a permanent, stable identifier may compromise the privacy
of the user, making it possible to track a particular device or user
as it moves through different locations.
4.2. MN-NAI Considerations
Since the Mobile Node Identifier option described in Section 3
reveals the home affiliation of a user, it may assist an attacker in
determining the identity of the user, help the attacker in targeting
specific victims, or assist in further probing of the username space.
These vulnerabilities can be addressed through various mechanisms,
such as those discussed below:
o Encrypting traffic at the link layer, such that other users on the
same link do not see the identifiers. This mechanism does not
help against attackers on the rest of the path between the mobile
node and its home agent.
o Encrypting the whole packet, such as when using IPsec to protect
the communications with the home agent [RFC3776].
o Using an authentication mechanism that enables the use of privacy
NAIs [RFC4282] or temporary, changing "pseudonyms" as identifiers.
In any case, it should be noted that as the identifier option is only
needed on the first registration at the home agent and subsequent
registrations can use the home address, the window of privacy
vulnerability in this document is reduced as compared to [RFC3775].
In addition, this document is a part of a solution to allow dynamic
home addresses to be used. This is an improvement to privacy as
well, and it affects both communications with the home agent and the
correspondent nodes, both of which have to be told the home address.
5. IANA Considerations
The values for new mobility options must be assigned from the Mobile
IPv6 [RFC3775] numbering space.
The IANA has assigned the value 8 for the MN-ID-OPTION-TYPE.
In addition, IANA has created a new namespace for the subtype field
of the Mobile Node Identifier option. The currently allocated values
are as follows:
NAI (defined in [RFC4282]).
New values for this namespace can be allocated using Standards Action
[RFC2434].
6. Acknowledgements
The authors would like to thank Basavaraj Patil for his review and
suggestions on this document. Thanks to Jari Arkko for review and
suggestions regarding security considerations and various other
aspects of the document.
7. Normative References
[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.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility
Support in IPv6", RFC 3775, June 2004.
[RFC3776] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec
to Protect Mobile IPv6 Signaling Between Mobile Nodes
and Home Agents", RFC 3776, June 2004.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
Network Access Identifier", RFC 4282, November 2005.
8. Informative Reference
[RFC4285] Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
Chowdhury, "Authentication Protocol for Mobile IPv6",
RFC 4285, November 2005.
Authors' Addresses
Alpesh Patel
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Phone: +1 408-853-9580
EMail: alpesh@cisco.com
Kent Leung
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
US
Phone: +1 408-526-5030
EMail: kleung@cisco.com
Mohamed Khalil
Nortel Networks
2221 Lakeside Blvd.
Richardson, TX 75082
US
Phone: +1 972-685-0574
EMail: mkhalil@nortel.com
Haseeb Akhtar
Nortel Networks
2221 Lakeside Blvd.
Richardson, TX 75082
US
Phone: +1 972-684-4732
EMail: haseebak@nortel.com
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA 01876
US
Phone: +1 214 550 1416
EMail: kchowdhury@starentnetworks.com
Full Copyright Statement
Copyright (C) The Internet Society (2005).
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AI ELI5
On this page
§1Why Another Identifier Is Needed
The base Mobile IPv6 specification (RFC 3775) identifies mobility entities using an IPv6 address. RFC 4283 argues that it is essential to also identify them by other identifiers, for example a Network Access Identifier (NAI), an International Mobile Station Identifier (IMSI), or an application or deployment specific opaque identifier.
The RFC lists three things this makes possible: authentication and authorization using an existing AAA infrastructure or an HLR/AuC, dynamic allocation of a mobility anchor point, and dynamic allocation of a home address.
The option SHOULD be used when IKE/IPsec is not used to protect binding updates or binding acknowledgements. It is typically used together with the authentication option (RFC 4285), but it may be used on its own, for example to support accounting and billing.
Sometimes your address is not enough to say who you are. Like at school, the teacher wants your name, not just your seat number.
§3The Mobile Node Identifier Option
The Mobile Node Identifier option is a new optional data field carried in Mobile IPv6 messages that include the Mobility header. It has four parts: Option Type, Option Length, Subtype and Identifier.
The option type, called MN-ID-OPTION-TYPE, has been assigned the value 8 by IANA and is an 8-bit field. The option length is an 8-bit unsigned integer counting the octets of the Subtype and Identifier fields. The Subtype says what kind of identifier is in the variable length Identifier field. The option does not have any alignment requirements.
The option is a small label with four boxes: what kind of label it is, how long it is, what kind of name it carries, and the name itself.
§3.1The MN-NAI Subtype
The MN-NAI mobility option uses the general format above with subtype value 1. It identifies the mobile node with an identifier of the form user@realm, as defined for the Network Access Identifier in RFC 4282.
Entities that implement this specification MUST implement the MN-NAI option. The RFC expects that other identifier types will be defined for the option in the future.
Subtype 1 means the name is written like an email address, such as a username, an at sign and the place it belongs to.
- 8MN-ID-OPTION-TYPE — Option type value assigned by IANA to the Mobile Node Identifier option.
- 1NAI subtype — Identifier of the form user@realm.
§3.2Where the Option Goes in a Message
There is one processing rule. When the Mobile Node Identifier option is present in a message containing a Mobility header, it MUST appear before any authentication-related option.
The reasoning is not spelled out in the RFC, but the rule fits its main use: the identifier says who is asking, and the authentication option that follows is then checked for that identity.
Say your name first, then show your proof. The name tag must come before the ID card.
§4Privacy and Security Considerations
Mobile IPv6 already has one way to identify nodes, the Home Address option, so the new option's vulnerabilities are similar to existing ones. The main concern is privacy: a permanent, stable identifier may make it possible to track a particular device or user as it moves between locations.
The MN-NAI reveals the home affiliation of a user. This may help an attacker identify the user, target specific victims, or probe the username space.
The RFC suggests three ways to reduce this: encrypting traffic at the link layer (which does not help against attackers elsewhere on the path to the home agent), encrypting the whole packet with IPsec as in RFC 3776, or using an authentication mechanism that allows privacy NAIs or temporary pseudonyms.
The RFC also notes that the identifier is only needed on the first registration at the home agent, and later registrations can use the home address. That shrinks the window of privacy exposure compared with RFC 3775.
A name tag that never changes lets a stranger follow you around. You can hide it, cover it up, or wear a nickname that changes.
§5IANA Assignments
New mobility options must be assigned from the Mobile IPv6 numbering space. IANA has assigned the value 8 to MN-ID-OPTION-TYPE.
IANA also created a new namespace for the Subtype field. The only allocated value is the NAI, defined in RFC 4282. New values can be allocated using Standards Action (RFC 2434).
A keeper of the list gave this label the number 8 and started a list of name kinds, where only the username kind is on it so far.