[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00 01 02 03 04 05 06 07 RFC 5221

IPv6 Operations Working Group                               A. Matsumoto
Internet-Draft                                               T. Fujisaki
Intended status: Standards Track                                     NTT
Expires: May 5, 2007                                           R. Hiromi
                                                             K. Kanayama
                                                           Intec Netcore
                                                                Nov 2006


     Requirements for distributing RFC3484 address selection policy
                draft-ietf-v6ops-addr-select-req-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 5, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   RFC3484 defines source and destination address selection algorithms
   that are commonly deployed in current popular OSs.  Meanwhile, there
   is a possibility to provide multiple addresses in one physical
   network.  In such a multi-prefix environment, end-hosts could
   encounter some troubles in the communication because of default use



Matsumoto, et al.          Expires May 5, 2007                  [Page 1]

Internet-Draft            Address Selection Req                 Nov 2006


   of the RFC3484 mechanism.

   Therefore, extending various rules beyond the default use of the
   RFC3484 mechanism should be considered.  We propose a concept of
   distribution of address selection policy to an end-host as a solution
   to these possible problems.

   In this document, we describe detailed requirements of address
   selection policy distribution.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Scope of this document . . . . . . . . . . . . . . . . . .  3
   2.  Policy distribution model and terminology  . . . . . . . . . .  4
   3.  Requirements of Policy distribution  . . . . . . . . . . . . .  5
     3.1.  Contents of Policy Table . . . . . . . . . . . . . . . . .  5
     3.2.  Timing . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.3.  Redistribution of changed Policy Table . . . . . . . . . .  5
     3.4.  Sections . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.5.  Generating Policy Table per CPE/Node . . . . . . . . . . .  6
     3.6.  Security . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Solutions for RFC3484 policy distribution  . . . . . . . . . .  6
     4.1.  Policy distribution with router advertisement (RA)
           message option . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Policy distribution in DHCPv6  . . . . . . . . . . . . . .  7
     4.3.  Using other protocols  . . . . . . . . . . . . . . . . . .  7
     4.4.  Defining a new protocol  . . . . . . . . . . . . . . . . .  8
     4.5.  Converting routing information to policy table . . . . . .  8
   5.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  Routing System Assistance for Address Selection by
           Fred Baker . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  3484-update  . . . . . . . . . . . . . . . . . . . . . . .  9
     5.3.  shim6  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.4.  policy distribution mechanism  . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
   Intellectual Property and Copyright Statements . . . . . . . . . . 14








Matsumoto, et al.          Expires May 5, 2007                  [Page 2]

Internet-Draft            Address Selection Req                 Nov 2006


1.  Introduction

   One physical network can have multiple logical networks.  In that
   case, an end-host has multiple IP addresses.  In the IPv4-IPv6 dual
   stack environment or in a site connected to both ULA [RFC4193] and
   global scope networks, an end-host has multiple IP addresses.  These
   are examples of the networks that we focus on in this document.  In
   such an environment, an end-host will encounter some communication
   trouble documented in PS.  [I-D.ietf-v6ops-addr-select-ps]

   RFC 3484 [RFC3484] defines both source and destination address
   selection algorithms.  RFC 3484 defines a default address table, and
   enables adding other entries to this table.  Flexible address
   selection can be carried out.

   In addition, the distribution of an address policy table is an
   important matter.  RFC 3484 describes all the algorithms for setting
   the address policy table, but it makes no mention of
   autoconfiguration.

   To make a smooth connection with the appropriate source and
   destination address selection inside a multi-prefix environment,
   nodes must be informed about routing policies of their upstream
   networks and possible source address selection policies.  Then, those
   nodes must put those policies into individual policy tables.

   On the other hand, the RFC3484 mechanism is commonly deployed.
   However, manual configuration of the policy table is not a feasible
   idea and some automatic mechanism is needed.

   Therefore, we propose a concept of distribution of address selection
   policy from a network to an end-host to cooperate with the RFC3484
   mechanism as a solution to these possible problems.

   In this document, requirements for distribution of the address
   selection policy are described for promotional use of the RFC3484
   mechanism.  Our goal is to carry our autoconfiguration with
   distribution mechanism for utilization of RFC3484 more effectively.

1.1.  Scope of this document

   Revising address selection rules defined in RFC 3484 is out of our
   scope.

   The routing information from an upstream network is necessary, but in
   this document, we are focused on how to select source and destination
   addresses at the RFC3484 address policy table of the end-host.




Matsumoto, et al.          Expires May 5, 2007                  [Page 3]

Internet-Draft            Address Selection Req                 Nov 2006


   In addition, there must be some practical ways or considerations
   other than the RFC3484 policy table to solve the address selection
   problem, such as utilization of some routing protocols or operational
   technique with a specific route but these discussions are out of our
   scope.  However, we select some examples of other mechanisms in
   Section 5 only for comparison.


2.  Policy distribution model and terminology

   The distribution model:

  Fig. 1:   (basic model)
  Policies transferred from the Policy Broker to the Node over an access
  network.
   +----+                               +-------------+
   |Node|<----------/policies/----------|Policy Broker|
   +----+                               +-------------+

  Fig. 2:   (extended model)
   +----+                 +--------------+    +-------------+
   |Node|<---/policies/---|PolicyEnforcer|<---|Policy Broker|
   +----+                 +--------------+    +-------------+

   Essentials (or Principles):

   The distribution of Policy, which means that the address selection
   policy of RFC3484 is sent to nodes, has the following functions.

   *  Policy Broker, which means a Policy originator in xSP, for
      example, a dhcp server, originates its policy and sends it to a
      Node using some prefix-assignment Protocols.

   *  A Node receives a Policy as a client.  Then the client puts those
      policies into its own Policy Table, which means the address
      selection table defined in RFC3484.

   *  Policy Broker should make the Policy so that it can be easily
      embedded into Nodes.  The Policy message format should be defined
      based on the algorithm specified in RFC3484.

   *  There might be a situation in which a Policy Broker and Node are
      disconnected, and no direct message is exchanged.  In this case,
      there is a middle box defined as a Policy Enforcer, for example,
      CPE illustrated in Fig. 2, and it relays the policy to the Node.
      Requirements should be considered to include the policy-relay
      case.




Matsumoto, et al.          Expires May 5, 2007                  [Page 4]

Internet-Draft            Address Selection Req                 Nov 2006


   Terminology:


    Node:                    end-host, end-terminal
    CPE:                     Customer premises equipment
    PE:                      Provider Edge device
    NAS:                     Network Access Server


  Policy:                  address selection policy for RFC3484 rule set
  Policy Enforcer:         optionally attached equipment to relay policy
  Policy Broker/Server:    Policy Originator in xSP(mandate)
  Prefix Delegation Protocol: Protocols to carry prefix information data
  address selection table: address selection table defined in RFC3484
  Policy Table:            address selection table defined in RFC3484


3.  Requirements of Policy distribution

   The purpose of the Policy distribution mechanism is to distribute a
   Policy Table to Nodes and configure the Policy Table on the Nodes
   automatically.  The use of a distributed Policy Table on Nodes for
   other purposes (e.g, configuring routing Table on the Nodes) is out
   of the scope of this document.

3.1.  Contents of Policy Table

   A Policy Table is a set of Policies described in RFC 3484.  Each
   Policy consists of four elements: prefix value, precedence value,
   label value, and zone index value.  The Policy distribution mechanism
   should be able to distribute a Policy Table that has one or more
   Policies to Nodes.

3.2.  Timing

   The Policy Table should be distributed to Nodes by a Policy broker at
   any time when Nodes send a request for the Policy.

3.3.  Redistribution of changed Policy Table

   When a Policy broker has any change in a Policy Table that is
   distributed to Nodes, the Policy broker should redistribute the
   latest Policy Table to Nodes.

3.4.  Sections

   The Policy distribution mechanism should support being performed in
   two kinds of sections: from PE to CPE and from CPE to Node.  Policy



Matsumoto, et al.          Expires May 5, 2007                  [Page 5]

Internet-Draft            Address Selection Req                 Nov 2006


   distribution mechanisms provided in each section may or many not be
   the same.

3.5.  Generating Policy Table per CPE/Node

   The Policy distribution mechanism should allow for generating an
   appropriate Policy Table per Node.  For example, in some cases, each
   Node may have a different set of assigned prefixes.  In such a case,
   the appropriate Policy Table for each Node may also be different, and
   a Policy broker may be needed to generate the Policy Table according
   to the identity of the Node.

3.6.  Security

   The Policy distribution mechanism should provide for reliable, secure
   distribution of the Policy distribution from a Policy broker to
   Nodes.


4.  Solutions for RFC3484 policy distribution

   As described in section 4.1, the address selection policy table
   consists of four elements: prefix value, precedence, label, and zone-
   index.  The policy distribution mechanism will deliver lists of these
   elements.

4.1.  Policy distribution with router advertisement (RA) message option

   The RA message can be used to deliver a policy table by adding a new
   ND option.  Existing ND transport mechanisms (i.e., advertisements
   and solicitations) are used.  Advantages and disadvantages are almost
   the same as those described in [DNS configuration RFC, RA section].

   In addition, an advantage and disadvantages of distributing a policy
   table are as follows.

   Advantages:
   -  The RA message is used to deliver IPv6 address prefixes.
      Therefore, delivering policies for selecting addresses with the
      address attached to the host would be natural.

   Disadvantages:
   -  The RA message is limited in size, and the RA may not be
      sufficient to deliver full policies.  The same compression
      techniques, which were adopted in RFC4191 [RFC4191] can be used to
      increase the number of policies delivered by RA messages.





Matsumoto, et al.          Expires May 5, 2007                  [Page 6]

Internet-Draft            Address Selection Req                 Nov 2006



   -  Currently, RA messages are not used between a PE and CPE.  Other
      protocols may be necessary to deliver a policy table.

   -  Configuring a policy table in each router that advertises RA
      messages with an address prefix is necessary, so if a site has a
      lot of routers, there will be a higher management cost.

   -  Delivering a specific policy table to one node is impossible
      because RA messages are multicast.

4.2.  Policy distribution in DHCPv6

   By defining a new DHCPv6 option like
   [I-D.fujisaki-dhc-addr-select-opt], a policy table can be delivered.
   The advantages and disadvantages are almost the same as those
   described in [DNS configuration RFC, DHCPv6 section].

   In addition, there are the following advantages and disadvantages.

   Advantages:
   -  Currently, DHCPv6 prefix delegation is mainly used between a PE
      and CPE.  Delivering a policy table with prefixes is possible.

   -  A DHCPv6 server can deliver a host-specific policy table.

   -  By using a DHCPv6 relay mechanism, managing a policy table from a
      central server is possible.

   Disadvantages:
   -  The DHCPv6 message size is limited to the maximum UDP transmission
      size, so delivering complex policies by DHCPv6 may be impossible.

4.3.  Using other protocols

   Using other protocols (i.e., http and ftp) to deliver the policy
   table is possible.

   Advantages:
   -  No new transport mechanisms are necessary.

   Disadvantages:
   -  Other service discovery mechanisms will be necessary.








Matsumoto, et al.          Expires May 5, 2007                  [Page 7]

Internet-Draft            Address Selection Req                 Nov 2006


   -  The procedure to distribute information should be defined (e.g.,
      when to distribute and where the information is stored).

   -  Existing protocols may not have a mechanism to inform clients
      about policy changes.

4.4.  Defining a new protocol

   Defining a new protocol to deliver a policy table will have the
   following advantages and disadvantages.

   Advantages:
   -  Defining a protocol suitable for policy distribution may be
      possible.

   Disadvantages:
   -  In addition to the disadvantages of 4.3, a new transport mechanism
      needs to be defined.

4.5.  Converting routing information to policy table

   In an environment in which routing information and network links are
   separated (e.g., between PE and CPE), converting routing information
   to a policy table is possible.  However, when intermediate routers
   and nodes receive next-hop information, that is aggregated as a
   default route or neighbor router, and cannot generate policy table [a
   policy table cannot be generated].

   Advantages:
   -  No new distribution mechanism is necessary.

   Disadvantages:
   -  This mechanism can be used only in a limited environment.


5.  Discussion

   Other than this policy distribution mechanism, a few mechanisms are
   proposed.  This section quickly reviews each proposal including a
   policy distribution mechanism.

5.1.  Routing System Assistance for Address Selection by Fred Baker

   Fred Baker proposed to us about this mechanism.  A host asks the DMZ
   routers or the local router which is the best pair of source and
   destination addresses when the host has a set of addresses A and
   destination host has a set of addresses B. And then, the host uses
   the policy provided by the server/routing system as a guide in



Matsumoto, et al.          Expires May 5, 2007                  [Page 8]

Internet-Draft            Address Selection Req                 Nov 2006


   applying the response.  He also proposed a mechanism that utilizes
   ICMP error message to change the source address of the existing
   session.  This point resembles 5.2 3484-update mechanism, so the
   following evaluation is based only on the first part of his proposal.

   Advantages:
   -  A host can choose the best address pair that reflects the dynamic
      changing routing status.

   -  The destination address selection can be handled in this
      mechanisim as well as source address selection.

   Disadvantages:
   -  A host can choose the best address pair that reflects the dynamic

   -  A host has to consult the routing system every time it starts a
      connection if the host doesn't have address selection information
      for the destination host or the information lifetime is expired.
      This could be a possible scalability problem.

   -  A host has to wait until the response is received from the routing
      system.

   -  The existing host/router OS implementation has to be changed a
      lot.  In the existing TCP/IP protocol stack implementation,
      destination address selection is mainly the role of the
      application and not that of the kernel unlike source address
      selection.  Therefore, implementing this model without causing any
      affects on applications is not so easy.

5.2.  3484-update

   M. Bagnulo proposed a new method of address selection in his draft.
   [I-D.bagnulo-rfc3484-update] When the host notices that a network
   failure occurs or packets are dropped somewhere in the network by for
   example, an ingress filter, the host changes the source address of
   the connection to another source address.  The host stores a cache of
   address selection information so that the host can select an
   appropriate source address for new connections.

   Advantages:
   -  A host can choose the best address that reflects the dynamic
      changing routing status.

   Disadvantages:






Matsumoto, et al.          Expires May 5, 2007                  [Page 9]

Internet-Draft            Address Selection Req                 Nov 2006


   -  A host has to learn address selection information per destination
      host.  The number of cache entries can be too big.

   -  The existing host/router OS implementation has to be changed a
      lot.  In particular, changing the source address of the existing
      connection is not so easy and has a big impact on the existing
      TCP/IP protocol stack implementation.

   -  There is not so much experience with this kind of address
      selection cache mechanism.

   -  The host tries every address one-by-one, so the user has to wait
      for a long time before the appropriate address pair is found.

5.3.  shim6

   shim6 is designed for site-multihoming.  This mechanism introduces a
   new method of address selection for session initiation and session
   survivability, which is documented in
   [I-D.ietf-shim6-locator-pair-selection] and
   [I-D.ietf-shim6-failure-detection].

   The shim6 host detects connection failures and changes the source
   address during the session.

   Advantages:
   -  The shim6 host performs address selection that reflects network
      failures in the source and destination end-to-end link.  Moreover,
      network failure avoidance can be achieved by end hosts themselves.

   Disadvantages:
   -  A host has to learn address selection information per destination
      host.  The number of cache entry can be too big.

   -  The existing host/router OS implementation has to be changed
      significantly.

   -  The host tries every address one-by-one, so the user has to wait
      for a long time before the appropriate address pair is found.

5.4.  policy distribution mechanism

   This mechanism takes advantages of RFC 3484 Policy Table that is
   widely deployed already.  By distributing policies for Policy Table,
   you can auto-configure a host's address selection policy.

   Advantages:




Matsumoto, et al.          Expires May 5, 2007                 [Page 10]

Internet-Draft            Address Selection Req                 Nov 2006


      - A host can receive and understand address selection information
      before the host starts a connection.  Therefore, the amount of
      traffic and connection overhead time can be minimized.
      - A host does not need any other address-selection-related
      information once that host receives the address selection policy
      set.  This can also reduce the amount of traffic.
      - The existing OS implementation does not need to be changed
      significantly on the OS that implements the RFC 3484 policy table.
      Only the delivery mechanism to the table has to be prepared.
      - Destination address selection can also be controlled by this
      mechanism.

   Disadvantages:
      - No other address selection rule that is beyond the RFC 3484
      policy table framework can be implemented.
      - The OS implementation has to be changed, and the policy
      distribution server, such as a gateway router, has to be prepared.
      - When DHCP or RA is used for transport mechanism of policy table,
      frequently changing policy cannot be delivered to hosts quickly
      because of the nature of these protocols.


6.  Security Considerations

   Address false-selection can lead to serious security problem, such as
   session hijack.  However, it should be noted that address selection
   is eventually up to end-hosts.  We have no means to enforce one
   specific address selection policy to every end-host.  So, a network
   administrator has to take countermeasures for unexpected address
   selection.


7.  IANA Considerations

   This document has no actions for IANA.


8.  References

8.1.  Normative References

   [I-D.ietf-v6ops-addr-select-ps]
              Matsumoto, A., "Problem Statement of Default Address
              Selection in Multi-prefix Environment:  Operational Issues
              of RFC3484 Default Rules",
              draft-ietf-v6ops-addr-select-ps-00 (work in progress),
              November 2006.




Matsumoto, et al.          Expires May 5, 2007                 [Page 11]

Internet-Draft            Address Selection Req                 Nov 2006


   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.

8.2.  Informative References

   [I-D.arifumi-ipv6-policy-dist]
              Matsumoto, A., "Practical Usages of Address Selection
              Policy Distribution", draft-arifumi-ipv6-policy-dist-01
              (work in progress), June 2006.

   [I-D.bagnulo-rfc3484-update]
              Bagnulo, M., "Updating RFC 3484 for multihoming support",
              draft-bagnulo-rfc3484-update-00 (work in progress),
              June 2006.

   [I-D.fujisaki-dhc-addr-select-opt]
              Fujisaki, T., "Distributing Default Address Selection
              Policy using DHCPv6",
              draft-fujisaki-dhc-addr-select-opt-02 (work in progress),
              June 2006.

   [I-D.ietf-shim6-failure-detection]
              Arkko, J. and I. Beijnum, "Failure Detection and Locator
              Pair Exploration Protocol for IPv6  Multihoming",
              draft-ietf-shim6-failure-detection-06 (work in progress),
              September 2006.

   [I-D.ietf-shim6-locator-pair-selection]
              Bagnulo, M., "Default Locator-pair selection algorithm for
              the SHIM6 protocol",
              draft-ietf-shim6-locator-pair-selection-01 (work in
              progress), October 2006.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, November 2005.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.













Matsumoto, et al.          Expires May 5, 2007                 [Page 12]

Internet-Draft            Address Selection Req                 Nov 2006


Authors' Addresses

   Arifumi Matsumoto
   NTT PF Lab
   Midori-Cho 3-9-11
   Musashino-shi, Tokyo  180-8585
   Japan

   Phone: +81 422 59 3334
   Email: arifumi@nttv6.net


   Tomohiro Fujisaki
   NTT PF Lab
   Midori-Cho 3-9-11
   Musashino-shi, Tokyo  180-8585
   Japan

   Phone: +81 422 59 7351
   Email: fujisaki@syce.net


   Ruri Hiromi
   Intec Netcore, Inc.
   Shinsuna 1-3-3
   Koto-ku, Tokyo  136-0075
   Japan

   Phone: +81 3 5665 5069
   Email: hiromi@inetcore.com


   Ken-ichi Kanayama
   Intec Netcore, Inc.
   Shinsuna 1-3-3
   Koto-ku, Tokyo  136-0075
   Japan

   Phone: +81 3 5665 5069
   Email: kanayama@inetcore.com











Matsumoto, et al.          Expires May 5, 2007                 [Page 13]

Internet-Draft            Address Selection Req                 Nov 2006


Full Copyright Statement

   Copyright (C) The Internet Society (2006).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat and any
   assurances of licenses to be made available, or the result of an
   attempt made to obtain a general license or permission for the use of
   such proprietary rights by implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





Matsumoto, et al.          Expires May 5, 2007                 [Page 14]


Html markup produced by rfcmarkup 1.107, available from http://tools.ietf.org/tools/rfcmarkup/