Re: [Mip6] WG LC: Yoshihiro Ohba's review

Hi all,

   please find below a review of Yoshihiro Obha for the document
   draft-ietf-mip6-aaa-ha-goals-03.txt.

   Thanks a lot yoshi for this review.

Mobile IPv6 WG                                               G. Giaretta
Internet-Draft                                               I. Guardini
Intended status: Standards Track                              E. Demaria
Expires: March 16, 2007                                   Telecom Italia
                                                            J. Bournelle
                                                                 GET/INT
                                                                R. Lopez
                                                         Univ. of Murcia
                                                      September 12, 2006

                       AAA Goals for Mobile IPv6
                    draft-ietf-mip6-aaa-ha-goals-03

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   In commercial deployments Mobile IPv6 can be a service offered by a
   Mobility Services Provider (MSP).  In this case all protocol

YO: Why just for commercial deployments?  I think it is also useful
for other AAA deployments such as enterprise usage.

   operations may need to be explicitly authorized and traced, requiring

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   the interaction between Mobile IPv6 and the AAA infrastructure.
   Integrating the AAA infrastructure offers also a solution component
   for Mobile IPv6 bootstrapping in integrated and split scenarios.

YO: I believe readers do not understand the above sentence without
explaining what integrated and split scenarios are.  Can we simply
remove the above sentence from Abstract?

   This document describes various scenarios where a AAA interface for
   Mobile IPv6 is actually required.  Additionally, it lists design
   goals and requirements for such an interface.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Bootstrapping Scenarios  . . . . . . . . . . . . . . . . . . .  4
     4.1.  Split Scenario . . . . . . . . . . . . . . . . . . . . . .  4
     4.2.  Integrated Scenario  . . . . . . . . . . . . . . . . . . .  5
   5.  Goals for the Split Scenario . . . . . . . . . . . . . . . . .  6
     5.1.  General goals  . . . . . . . . . . . . . . . . . . . . . .  6
     5.2.  Service Authorization  . . . . . . . . . . . . . . . . . .  7
     5.3.  Accounting . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.4.  Mobile Node Authentication . . . . . . . . . . . . . . . .  8
     5.5.  Provisioning of Configuration Parameters . . . . . . . . .  8
   6.  Goals for the Integrated Scenario  . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     10.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     10.2. Informative References . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
   Intellectual Property and Copyright Statements . . . . . . . . . . 12

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1.  Introduction

   Mobile IPv6 [1] was originally designed as a protocol without any
   integration with the AAA infrastructure.  Nonetheless, in some
   environments it might be desirable to authenticate the user based on
   existing credentials stored at the AAA server to authorize protocol
   operations, to enable accounting and credit control.  Due to this
   requirement, Mobile IPv6 might require the interaction with the AAA
   infrastructure.  Integrating the AAA infrastructure offers also a
   solution component for Mobile IPv6 bootstrapping [2] in split [3] and
   integrated [4] scenarios.

YO: The first sentence may give an impression that we are going to
modifiy Mobile IPv6 protocol to interface with AAA, which is not true.
I think what we should probably convey here is something like:

"
   Mobile IPv6 [1] provides the basic IP mobility functionality for
   IPv6.  When Mobile IPv6 is used in tightly managed environments
   with the use of the AAA (Authentication, Authorization and
   Accounting) infrastructure, an interface between Mobile IPv6 and
   AAA protocols needs to be defined.  Also, two scenarios for
   bootstrapping Mobile IPv6 service [2], i.e., split [3] and
   integrated [4] scenarios, must be supported by such an interface.
"

   This document describes various scenarios where a AAA interface is
   required.  Additionally, it lists design goals and requirements for
   such an interface.

   This document only describes requirements, goals and scenarios.  It
   does not provide solutions.

   Notice that this document builds on the security model of the AAA
   infrastructure.  As such, the end host/user shares credentials with
   the home AAA server and the communication between the AAA server and
   the AAA client may be protected.  If the AAA server and the AAA
   client are not part of the same administrative domain, then some sort
   of contractual relationship between the involved administrative
   domains is typically in place in form of roaming agreements.

YO: This document seems to assume the use of IPsec between MN and HA
for securing Mobile IPv6 signaling.  But the AAA interface could also
be used for RFC 4285.  So I think it might be good to mention in this
section that the document may not preclude the use of alternative
methods for securing Mobile IPv6 signaling between MN and HA while
this document focuses on the use of IPsec between MN and HA.

2.  Terminology

   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 [5].

   Some of the terms are also extracted from [2].

3.  Motivation

YO: I think that most of the contents of this section is already
described in RFC 4680.  Can we simply remove this section and just
refer to RFC 4680 in the Introduction?

   Mobile IPv6 specification [1] requires that Mobile Nodes (MNs) are
   provisioned with a set of configuration parameters, namely the Home
   Address and the Home Agent Address, in order to accomplish a home
   registration.  Moreover, MNs and Home Agents (HAs) must share the
   cryptographic material needed in order to setup IPsec security
   associations to protect Mobile IPv6 signaling (e.g. shared keys or
   certificates).

   One approach is to statically provision the necessary configuration

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   parameters at MNs and HAs.  This solution is sub-optimal from a
   deployment perspective, especially in large networks with a lot of
   users (e.g., a mobile operator network).  For this reason the Mobile
   IPv6 bootstrapping problem was investigated and is described in [2].
   Based on the analysed scenarios, two solutions were developed.  The
   solution for the split scenario is described in [3] and the one for
   the integrated scenario can be found at [4].  A key point behind
   these scenarios is that, whenever static provisioning is not
   feasible, the AAA infrastructure of the MSP can be used as the
   central element to enable dynamic Mobile IPv6 bootstrapping.  In this
   case the AAA infrastructure can be exploited to offload the end
   host's authentication to the AAA server as well as to deliver the
   necessary configuration parameters to the HA.

   Moreover, in case Mobile IPv6 is a service offered by a Mobility
   Service Provider (MSP), all protocol operations (e.g., home
   registrations) may need to be explicitly authorized and monitored
   (e.g., for accounting purposes).  This can be accomplished relying on
   the AAA infrastructure of the MSP that stores user profiles and
   credentials.

   In the split scenario, the deployment of this service model requires
   the availability of an interface between the Home Agent and the AAA
   infrastructure.  The core capabilities that should be supported by
   this interface include Mobile IPv6 service authorization and
   maintenance (e.g. asynchronous service termination) as well as the
   exchange of accounting data.  This basic set of features is needed in
   any Mobile IPv6 bootstrapping scenario.  In the integrated scenario,
   the AAA server also delivers some Mobile IPv6 parameters to the NAS.

4.  Bootstrapping Scenarios

   This section describes some bootstrapping scenarios in which a
   communication between the AAA infrastructure of the Mobility Service
   Provider and the Home Agent is needed.

YO: Section 4.2 also discusses communication between NAS and the AAA
infrastructure of ASP.

4.1.  Split Scenario

   In the split scenario [3], there is the assumption that the mobility
   service and network access service are not provided by the same
   administrative entity.  This implies that the mobility service can be
   authorized by a different entity deploying its own AAA
   infrastructure.  The entity offering the mobility service is called
   Mobility Service Provider (MSP) while the entity authorizing the
   service is the Mobility Service Authorizer (MSA).

YO: Can we define MSP, MSA, ASP and ASP in Section 2?  I know those
terms are defined in [2], but we can reiterate the definition in this
document.  Once the terms are defined, we can remove the last
sentence.

   In this scenario, the Mobile Node discovers the Home Agent Address

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   using the Domain Name Service (DNS).  It queries the address based on
   the Home Agent name or by service name.  In the former case, the
   Mobile Node is configured with the Fully Qualified Domain Name (FDQN)
   of the Home Agent.  In the latter case, [3] defines a new service
   resource record (SRV RR).

   Then the Mobile Node performs an IKEv2 [6] exchange with the HA to
   setup IPsec SAs (to protect Mobile IPv6 signaling) and to configure
   its Home Address (HoA).  The IKEv2 Mobile Node to Home Agent
   authentication can be done using either public key signatures or the
   Extensible Authentication Protocol (EAP).

YO: I think this authentication must be mutually done, not one
one-way.  Also public key may be used within EAP methods as described
in the next paragraph.  So I think the above sentence can be revised
as follows:

"
Mutual authentication for IKEv2 between Mobile Node and Home Agent can
be done with or without use of Extensible Authentication Protocol
(EAP).
"

   If EAP is used for authentication, the operator can choose any
   available EAP methods.  Note that even if EAP is used, the MN
   authenticates the HA using public key based authentication.  Based on

YO: I don't see a significance of mentioning public key based
authentication in this section.  This note can be removed.

   IKEv2, the HA may rely on a remote EAP server.  In this case, a AAA
   protocol such as RADIUS EAP [7]/Diameter EAP [8] must be used between
   the HA and the home EAP server.  This allows a pool of HAs to rely on
   the same EAP server to authenticate Mobile Nodes.   In this case, a AAA 
   protocol such as RADIUS EAP [7]/Diameter EAP [8] must be used between
   the HA and the home EAP server.  This allows a pool of HAs to rely on
   the same EAP server to authenticate Mobile Nodes.  It also allows the
   roaming mobility case in which the Mobile Node obtains the mobility
   service in a different administrative domain (MSP != MSA).

Probably the above paragraph can be simplified something like:

"
   If EAP is used for authentication, the operator can choose any
   available EAP methods.  Use of EAP with the AAA infrastructure
   allows the HA for not necessarily maintaining authentication
   credentials for each Mobile Node by itself.  It also allows roaming
   in terms of Mobile IPv6 service where MSP and MSA belong to
   different administrative domains.
"

   The Mobile Node may also want to update its FQDN in the DNS with the
   newly allocated Home Address. [3] recommends that the HA performs the
   DNS entry update on behalf of the Mobile Node.  For that purpose, the
   Mobile Node indicates its FDQN in the IKEv2 exchange (IDii field in
   IKE_AUTH) and adds a DNS Update Option in the Binding Update message
   sent to the HA.

   When the Mobile Node uses a Home Agent belonging to a different
   administrative domain (MSP != MSA), the local HA may not share a
   security association with the home DNS server.  In this case, [3]
   suggests that the home AAA server is responsible for the update.
   Thus, the HA should send to the home AAA server the (FDQN, HoA) pair.

   Note that the AAA exchange between the HA and the AAA server is
   normally terminated before the HA receives the Binding Update
   message.  The reason is that the authentication has succeeded if the
   Mobile Node is able to send the BU.

YO: What is the siginificance of having this note in this section?
Can we simply remove this note?

4.2.  Integrated Scenario

   In the integrated scenario [4], the assumption is that the user is
   authenticated and authorized by the same authorizer than network
   access service.  The Mobility Service Authorizer (MSA) and the Access
   Service Authorizer (ASA) are the same entity.

YO: The above text may be changed to:

"
   In the integrated scenario [4], the user is authenticated and
   authorized for both network access service and mobility service by
   the same administrative domain.  In this case, the Mobility Service
   Authorizer (MSA) and the Access Service Authorizer (ASA) are the
   same entity.
"

   Two scenarios are possible.  In the first case, the Home Agent is
   allocated by the user's home domain.  In the second case it is

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   allocated by an entity in the visited domain.  In both cases, it is

s/by an entity in the visited domain/by the visited domain/.

   assumed that the AAA server in the home domain (AAAH) authorizes both
   network access service and mobility service.

YO: The context of the last sentence is already covered in the first
paragraph and can be removed.

   In this scenario, Mobile Node discovers the Home Agent Address using
   DHCPv6.  During network access service authentication and
   authorization, AAAH also verifies if authenticating user is
   authorized to use mobility service.  In affirmative case, the AAAH
   sends the information about the assigned home agent to the Network
   Access Server (NAS) where the Mobile Node is currently attached.
   Then, the NAS stores the received information.  To request home agent
   data, the Mobile Node sends a DHCPv6 Information Request to the
   All_DHCP_Relay_Agents_and_Servers multicast address.  With this
   request, the Mobile Node can specify if it wants a home agent
   provided by the visited domain (ASP/MSP) or by the home domain (ASA/
   MSA).  In both cases, the NAS acts a DHCPv6 relay.  When the NAS
   receives the DHCPv6 Information Request then it sends home agent
   information received from AAAH in a new DHC Relay Agent Option as
   defined in [9].

   In case the Mobile Node cannot acquire home agent information via
   DHCPv6, it can try the default mechanism based on DNS described in
   [3].  After the Mobile Node has acquired the home agent information,
   the mechanism used to bootstrap the HoA, IPsec Security Association,
   and Authentication and Authorization with the MSA is the same
   described in the bootstrapping solution for split scenario [3].

5.  Goals for the Split Scenario

   Section 4 raises the need to define extensions for the AAA protocol
   used between the AAAH server and the HA.  The following sections list
   a set of goals.

5.1.  General goals

YO: If the intent is to describe general AAA goals in this document,
the current set of goals described in this section is insufficient.
You may take a look at Section 2.1 of RFC 2989 for more detailed list.

   G1.1  The AAAH server and the HA MUST be able to authenticate each
      other (mutual authentication) in order to prevent the installation
      of unauthorized state on the HA.  In some deployment scenarios, it
      may not be feasible for HA and AAAH to mutually authenticate each
      other.  For example, let us consider the case where MSP is not the
      MSA.  In such a case, several AAA intermediate proxies could
      forward MIP6 bootstrapping information back and forth between HA
      and AAA.  Thus, to prevent the installation of unauthorized state
      on the HA, the path between HA and AAAH should be trustworthy>/

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   G1.2  The AAA-HA interface MUST provide integrity protection in order
      to prevent any alteration of exchanged data (e.g., Mobile IPv6
      configuration parameters).

   G1.3  The AAA-HA interface MUST provide replay protection.

   G1.4  The AAA-HA interface SHOULD provide confidentiality since it
      may be used to transfer keying material (e.g., shared key
      generated during EAP method authentication).

   G1.5  The AAA-HA interface SHOULD support inactive peer detection.
      This functionality can be used by the AAAH server to maintain a
      list of active HAs.

YO: This can be done outside of AAA protocols.  AAAH server can just
ping to HAs.  I don't think this requiremet is a AAA requirement.

5.2.  Service Authorization

   G2.1  The AAA-HA interface SHOULD allow the use of Network Access
      Identifier (NAI) to identify the user.

YO: Why this is not "MUST allow"?

   G2.2  The HA SHOULD be able to query the AAAH server to verify Mobile
      IPv6 service authorization for the mobile node.

YO: I don't understand what "verify Mobile IPv6 service authorization
for the mobile node " means.  Please elaborate more on this goal.

   G2.3  The AAAH server MAY assign explicit operational limitations and
      authorization restrictions on the HA (e.g., packet filters, QoS
      parameters).

   G2.4  The AAAH server MUST be able to send an authorization lifetime
      to the HA to limit Mobile IPv6 session duration for the MN.

   G2.5  The HA MUST be able to request to the AAAH server an extension
      of the authorization lifetime granted to the MN.

   G2.6  The AAAH server MUST be able to force the HA to terminate an
      active Mobile IPv6 session for authorization policy reasons (e.g.,
      credit exhaustion).

5.3.  Accounting

   G3.1  The AAA-HA interface MUST support the transfer of accounting
      records needed for service control and charging.  These include
      (but may not be limited to): time of binding cache entry creation
      and deletion, octets sent and received by the mobile node in bi-
      directional tunneling, etc.

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5.4.  Mobile Node Authentication

   G4.1  The AAA-HA interface MUST support pass-through EAP
      authentication with the HA working as EAP authenticator operating
      in pass-through mode and the AAAH server working as back-end
      authentication server.

YO: We can simplify the text something like:

"
   G4.1  The AAA-HA interface MUST allow the HA to act as a pass-through EAP
      authenticator.
"

5.5.  Provisioning of Configuration Parameters

   G5.1  The HA SHOULD be able to communicate to the AAAH server the
      Home Address allocated to the MN (e.g., for allowing the AAAH
      server to perform a DNS update on behalf of the MN).

YO: FQDN is missing here.

YO: Also, I am wondering if there is an option in which AAAH assigns a
home address or a home address prefix and communicate the assignment
to the HA.

   G5.2  The AAAH SHOULD be able to indicate to the HA if the MN is
      authorized to autoconfigure its Home Address.

YO: Why this is not "MUST be able to"? 

6.  Goals for the Integrated Scenario

   In the integrated scenario, the AAA server provides the HA
   information to the NAS as part of the whole AAA operations for
   network access.  Next goals are considered in addition to those
   described in section Section 5.

   G6.1  The AAAH server MUST be able to communicate the Home Agent
      Information (IP Address or FQDN) to the NAS.

   G6.2  The NAS SHOULD be able to notify that it supports the
      functionalities described in [4].

YO: The NAS notifies to whom?  I guess the NAS notifies AAAH server of
the functionalities.  If so, please explicitly mention it.  Also why
this is not "MUST be able to"?

   G6.3  The ASP/MSP SHOULD be able to indicate to the MSA if it can
      allocate a Home Agent to the MN.

YO: Why MSP is mentioned here?  Also why this is not "MUST be able to"?

   G6.4  The AAA server of the MSA MUST be able to indicate to the NAS
      whether the MN is authorized to use a local Home Agent (i.e. a
      Home Agent in the ASP/MSP)

YO: "MSA" should read "ASA/MSA".  Also "ASP/MSP" should read "MSP".

YO: Also, I would like to see the following discussions in this section:

- Whether the AAA-HA interface as well as AAA-NAS interface allow
authentication and authorization messages to be processed by different
AAA servers.

- In the integrated case, whether the AAA server for the AAA-HA
interface and the AAA server for the AAA-NAS interface can be
different.

7.  IANA Considerations

   This document does not require actions by IANA.

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8.  Security Considerations

   As stated in Section 5.1 the AAA-HA interface must provide mutual
   authentication, integrity and replay protection.  Furthermore, if
   security parameters (e.g., IKE pre-shared key) are transferred
   through this interface, confidentiality is strongly recommended to be
   supported.  However note that AAA protocols does not support this
   unless it exists a direct connection between corresponding entities.

YO: Is there any scenario in which security parameters are not
transferred through this interface?

9.  Acknowledgements

   The authors would like to thank James Kempf, Alper Yegin, Vijay
   Devarapalli, Basavaraj Patil, Gopal Dommety and Madjid Nakhjiri for
   their comments and feedback.  Moreover the authors would like to
   thank Hannes Tschofenig for his deep technical and editorial review
   of the draft.

10.  References

10.1.  Normative References

   [1]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
        IPv6", RFC 3775, June 2004.

   [2]  Giaretta, G. and A. Patel, "Problem Statement for bootstrapping
        Mobile IPv6", draft-ietf-mip6-bootstrap-ps-05 (work in
        progress), May 2006.

YO: Replace the reference with RFC 4640.

   [3]  Giaretta, G., "Mobile IPv6 bootstrapping in split scenario",
        draft-ietf-mip6-bootstrapping-split-02 (work in progress),
        March 2006.

YO: The draft seems to be expired.

   [4]  Chowdhury, K. and A. Yegin, "MIP6-bootstrapping via DHCPv6 for
        the Integrated Scenario",
        draft-ietf-mip6-bootstrapping-integrated-dhc-01 (work in
        progress), June 2006.

   [5]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

10.2.  Informative References

   [6]   Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
         RFC 4306, December 2005.

   [7]   Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial

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         In User Service) Support For Extensible Authentication Protocol
         (EAP)", RFC 3579, September 2003.

   [8]   Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
         Authentication Protocol (EAP) Application", RFC 4072,
         August 2005.

   [9]   Yegin, A., "DHCP Option for Home Agent Discovery in MIPv6",
         draft-jang-dhc-haopt-02 (work in progress), March 2006.

   [10]  Chowdhury, K. and A. Lior, "RADIUS Attributes for Mobile IPv6
         bootstrapping", draft-chowdhury-mip6-bootstrap-radius-01 (work
         in progress), November 2004.

YO: This draft seems to be expired.

   [11]  Giaretta, G., "MIPv6 Authorization and Configuration based on
         EAP", draft-giaretta-mip6-authorization-eap-03 (work in
         progress), March 2006.

YO: This draft seems to be expired.

(snip)

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