Network Working Group J. Korhonen
Internet-Draft U. Nilsson
Intended status: Informational TeliaSonera
Expires: May 29, 2009 November 25, 2008
Service Selection for Mobile IPv4
draft-korhonen-mip4-service-06.txt
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Abstract
In some Mobile IPv4 deployments identifying the mobile node or the
mobility service subscriber is not enough to distinguish between
multiple services possibly provisioned to the said mobile node and
its mobility service subscription. A capability to specify different
services in addition to the mobile node identity can be leveraged to
provide flexibility for mobility service providers to provide
multiple services within a single mobility service subscription.
This document describes a Service Selection Extension for Mobile IPv4
that is intended to assist home agents to make specific service
selections for the mobility service subscription during the
registration procedure.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Service Selection Extension . . . . . . . . . . . . . . . . . 4
4. Processing Considerations . . . . . . . . . . . . . . . . . . 5
4.1. Mobile Node Considerations . . . . . . . . . . . . . . . . 5
4.2. Home Agent Considerations . . . . . . . . . . . . . . . . 6
4.3. Foreign Agent Considerations . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
Mobile IPv4 [RFC3344] can identify mobile nodes in various ways,
including home addresses [RFC3344] and Network Access Identifiers
(NAI) [RFC4282][RFC2794]. In some Mobile IPv4 deployments
identifying the mobile node or the mobility service subscriber via a
Proxy Mobile IPv4 client [I-D.leung-mip4-proxy-mode] (hereafter the
mobile node and the Proxy Mobile IPv4 client are used
interchangeably) is not enough to distinguish between multiple
services possibly provisioned to the said mobile node and its
mobility service subscription.
The capability to specify different services in addition to the
mobile node identity can be leveraged to provide flexibility for
mobility service providers to provide multiple services within the
same mobility service subscription. For example:
o Provide an enterprise data access for which the mobility service
provider hosts connectivity and mobility services on behalf of the
enterprise.
o Provide access to service domains that are otherwise not
accessible from public networks because of some mobility service
provider's business reasons.
o Provide simultaneous access to different service domains that are
separated based on policies of the mobility service provider.
o Enable easier policy assignment for mobility service providers
based on the subscribed services.
This document describes a Service Selection Extension for Mobile IPv4
that is intended to assist home agents to make specific service
selections for the mobility service subscription during the
registration procedure. The service selection may affect home agent
routing decisions, Home Address assignment policies, firewall
settings, and security policies. The Service Selection extension
SHOULD be used in every Registration Request that makes a new
registration to the home agent. The Service Selection extension from
the Registration Request MAY be echoed back in the Registration
Reply.
In absence of a specifically indicated service the home agent MUST
act as if the default service, plain Internet access had been
requested. There is no absolute requirement that this default
service be allowed to all subscribers, but it is highly RECOMMENDED
in order to avoid having normal subscribers employ operator-specific
configuration values in order to get basic service.
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Some of the potential use-cases were listed earlier in this section.
The general aim is better manageability of services and service
provisioning from both operators and service providers point of view.
However, it should be understood that there are potential deployment
possibilities where selecting a certain service may restrict
simultaneous access to other services from an user point of view.
For example, services may be located in different administrative
domains or external customer networks that practice excessive
filtering of inbound and outbound traffic.
2. Requirements
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. Service Selection Extension
At most one Service Selection extension MAY be included in any Mobile
IPv4 Registration Request message. It SHOULD be included at least in
the Registration Request message that is sent for the initial binding
registration when the mobile node and the home agent do not have an
existing binding. The Service Selection extension MUST be placed in
the Registration Request message as follows:
o When present the extension MUST appear after the MN-NAI extension,
if the MN-NAI is also present in the message
o If the extension was added by the mobile node to a Registration
Request it MUST appear prior any authentication-enabling
extensions [RFC3344][RFC4721]
o In the event the foreign agent adds the Service Selection
extension to a Registration Request, the extension MUST appear
prior to any Foreign-Home authentication-enabling extensions
[RFC3344]
The Home Agent MAY echo the received Service Selection extension
option back in a Mobile IPv4 Registration Reply message. The echoed
Service Selection extension MUST be an unchanged copy of the Service
Selection extension received in the corresponding Registration
Request message. The Service Selection extension MUST be placed in
the Registration Reply message as follows:
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o If the extension was originally added by the mobile node to a
Registration Request it MUST appear in the Registration Reply
prior any authentication-enabling extensions [RFC3344][RFC4721]
o If the foreign agent added the Service Selection extension to a
Registration Request, the extension MUST appear in the
Registration Reply prior to any Foreign-Home authentication-
enabling extensions [RFC3344]
The Service Selection extension has the following format:
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 = TBD | Length | Identifier... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Selection Extension
o Type: 8-bit identifier set to TBD (to be defined by IANA) of the
type of this skippable extension.
o Length: 8-bit unsigned integer, representing the length of the
Service Selection Extension in octets, excluding the Type and
Length fields. A value of zero (0) is not allowed.
o Identifier: A variable-length encoded service identifier string
used to identify the requested service. The identifier string
length is between 1 and 255 octets. This specification allows
international identifier strings that are based on the use of
Unicode characters, encoded as UTF-8 [RFC3629], and formatted
using Normalization Form KC (NFKC) as specified in [NFKC].
'ims', 'voip' and 'voip.companyxyz.example.com' are valid examples
of Service Selection extension Identifiers. At minimum the
Identifier MUST be unique among the home agents the mobile node is
authorized to register to.
4. Processing Considerations
4.1. Mobile Node Considerations
A mobile node or its proxy representative MAY include the Service
Selection extension into any Registration Request message. The
Service Selection extension can be used with any mobile node
identification method. The extension is used to identify the service
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to be associated with the mobility session and SHOULD only be
included into the initial Registration Request message sent to a home
agent. If the mobile node wishes to change the selected service, it
is RECOMMENDED that the mobile node de-register the existing binding
with the home agent before proceeding with a binding registration for
a different service. The provisioning of the service identifiers to
the mobile node or its proxy representative is out of scope of this
specification.
If the mobile node receives a Registration Reply message with a Code
set to SERVICE_AUTHORIZATION_FAILED and the mobile node has an
existing binding with the Home Address used in the failed
Registration Request message, the mobile node MUST delete the
existing binding. If there is no existing binding the mobile node
proceeds as with any failed initial registration.
4.2. Home Agent Considerations
Upon receiving the Service Selection extension the home agent
authenticates and authorizes the mobile node. If the home agent
supports the Service Selection it MUST also verify that the mobile
node is authorized to the service identified by the Service Selection
extension. The services the mobile node is authorized to SHOULD be
part of the general mobile node subscription data. If the mobile
node is not authorized to the service the home agent MUST deny the
registration and send a Registration Reply with a Code
SERVICE_AUTHORIZATION_FAILED (error code TBD).
The Service Selection extension is used to assist the mobile node
authorization phase and identifies a specific service that is to be
authorized. The Service Selection extension MAY also affect the Home
Address allocation when for example used with the MN-NAI extension.
For example, for the same NAI there MAY be different Home Addresses
depending on the identified service. Furthermore, the Service
Selection extension MAY also affect the routing of the outbound IP
packets in the home agent depending on the selected service. The
home agent MAY also apply different policy or quality of service
treatment to traffic flows based on the selected service.
If the newly arrived Registration Request message with a Service
Selection extension indicates a change in the selected service, then
the home agent MUST re-authorize the mobile node. Depending on the
home agent policies, the services policies, Home Address allocation
policies and the subscription policies the home agent may or may not
be able to authorize the mobile node to the new service. For example
the existing service and the new service could require different Home
Addresses. If the authorization fails then the home agent MUST deny
the registration, delete any binding with the existing Home Address
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and send a Registration Reply with a Code set to
SERVICE_AUTHORIZATION_FAILED (error code TBD).
Depending on the local home agent policy, the home agent MAY echo
back the Service Selection extension in the corresponding
Registration Reply message towards the mobile node or the foreign
agent. The home agent MUST NOT change the content of the echoed
Service Selection extension.
4.3. Foreign Agent Considerations
A foreign agent MUST skip the Service Selection extension if the
Registration Request already contains the Service Selection
extension. If the Registration Request does not contain the Service
Selection extension the foreign agent MAY add the Service Selection
extension to the Registration Request message. How the foreign agent
learns the service the mobile nodes needs to authorize to is outside
of scope of this document.
In the case a foreign agent added the Service Selection extension to
the Registration Request on behalf of the mobile node, it MUST verify
whether the corresponding Registration Reply message from a home
agent also contains an echoed Service Selection extension. If the
received Registration Reply message contains the echoed Service
Selection extension, the foreign agent MUST NOT include the extension
to the Registration Reply message that gets forwarded to the mobile
node.
5. Security Considerations
The protection for the Service Selection extension depends on the
service that is being identified and eventually selected. If the
service selection information should not be revealed on the wire it
should be protected in a manner similar to Registration Requests and
Registration Replies. The Service Selection extension is protected
by the same authentication enabling extension as the rest of the
Registration Request message.
The home agent MUST verify that the mobile node is authorized to the
service included in the Service Selection extension. The Service
Selection extension authorization is part of the normal mobile node
registration and authentication procedure. Both registration
authentication and service authorization MUST succeed before the
mobile node is allowed to register to the home agent.
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6. IANA Considerations
A new Mobile IPv4 skippable Extension type is required for the
following new Extension described in Section 3. The Extension type
must be from the 'skippable Extension' range (128-255):
Service Selection Extension is set to TBD
A new Mobile IPv4 registration denied by home agent error code is
required. The error code must be allocated from the 'Error Codes
from the Home Agent' range (128-192):
SERVICE_AUTHORIZATION_FAILED is set to TBD
7. Acknowledgements
The authors would like to thank Henrik Levkowetz, Kent Leung and Jari
Arkko for their comments.
8. References
8.1. Normative References
[NFKC] Davis, M. and M. Durst, "Unicode Standard Annex #15;
Unicode Normalization Forms", Unicode 5.0.0, October 2006.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3344] Perkins, C., "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.
8.2. Informative References
[I-D.leung-mip4-proxy-mode]
Leung, K., "WiMAX Forum/3GPP2 Proxy Mobile IPv4",
draft-leung-mip4-proxy-mode-09 (work in progress),
August 2008.
[RFC2794] Calhoun, P. and C. Perkins, "Mobile IP Network Access
Identifier Extension for IPv4", RFC 2794, March 2000.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
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Network Access Identifier", RFC 4282, December 2005.
[RFC4721] Perkins, C., Calhoun, P., and J. Bharatia, "Mobile IPv4
Challenge/Response Extensions (Revised)", RFC 4721,
January 2007.
Authors' Addresses
Jouni Korhonen
TeliaSonera Corporation.
P.O.Box 970
FIN-00051 Sonera
FINLAND
Email: jouni.nospam@gmail.com
Ulf Nilsson
TeliaSonera Corporation.
Marbackagatan 11
S-123 86 Farsta
SWEDEN
Email: ulf.s.nilsson@teliasonera.com
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