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Versions: (draft-blanchet-mif-problem-statement) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 6418

Network Working Group                                        M. Blanchet
Internet-Draft                                                  Viagenie
Intended status: Informational                                  P. Seite
Expires: February 15, 2011                       France Telecom - Orange
                                                         August 14, 2010


                 Multiple Interfaces Problem Statement
                draft-ietf-mif-problem-statement-07.txt

Abstract

   A multihomed host receives node configuration information from each
   of its provisioning domain.  Some configuration objects are global to
   the node, some are local to the interface.  Various issues arise when
   multiple conflicting node-scoped configuration objects are received
   on multiple interfaces.  Similar situations also happen with single
   interface host connected to multiple networks.  This document
   describes these issues.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on February 15, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Scope and Existing Work  . . . . . . . . . . . . . . . . . . .  4
     3.1.  Below IP Interaction . . . . . . . . . . . . . . . . . . .  4
     3.2.  Hosts Requirements . . . . . . . . . . . . . . . . . . . .  5
     3.3.  Mobility and other IP protocols  . . . . . . . . . . . . .  5
     3.4.  Address Selection  . . . . . . . . . . . . . . . . . . . .  5
     3.5.  Finding and Sharing IP Addresses with Peers  . . . . . . .  6
     3.6.  Socket API and connection manager  . . . . . . . . . . . .  6
   4.  Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  DNS resolution issues  . . . . . . . . . . . . . . . . . .  7
     4.2.  Routing  . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.3.  Address Selection Policy . . . . . . . . . . . . . . . . .  9
     4.4.  Single Interface on Multiple Provisioning Domains  . . . . 10
   5.  Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   9.  Authors  . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   11. Informative References . . . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16






















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1.  Introduction

   A multihomed host have multiple provisioning domains (via physical
   and/or virtual interfaces).  For example, a node may be
   simultaneously connected to a wired Ethernet LAN, a 802.11 LAN, a 3G
   cell network, one or multiple VPN connections or one or multiple
   automatic or manual tunnels.  Current laptops and smartphones
   typically have multiple access network interfaces and, thus, may be
   simultaneously connected to different provisioning domains.

   A multihomed host receives node configuration information from each
   of its access networks, through various mechanisms such as DHCPv4
   [RFC2131], DHCPv6 [RFC3315], PPP [RFC1661] and IPv6 Router
   Advertisements [RFC4861].  Some received configuration objects are
   specific to an interface such as the IP address and the link prefix.
   Others are typically considered by implementations as being global to
   the node, such as the routing information (e.g. default gateway), DNS
   servers IP addresses and address selection policies.

   When the received node-scoped configuration objects have different
   values from each provisioning domains, such as different DNS servers
   IP addresses, different default gateways or different address
   selection policies, the node has to decide which it will use or how
   it will merge them.

   Several issues regarding how the node-scoped configuration objects
   are used in a multihomed node environment have been raised.  The
   following sections define the MIF host and the scope of this
   document, describe related work, list the symptoms and then the
   underlying problems.

   A companion document [I-D.ietf-mif-current-practices] discusses
   current practices.


2.  Terminology

   Administrative domain

      A group of hosts, routers, and networks operated and managed by a
      single organization [RFC1136].

   Provisioning domain

      A set of consistent configuration information (e.g.  Default
      router, Network prefixes, DNS,...).  One administrative domain can
      contain multiple provisioning domains.




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   A MIF (Multiple InterFaces) host has the following characteristics:

   o  A [RFC1122] IPv4 and/or [RFC4294] IPv6 compliant host
   o  A MIF host is configured with more than one IP addresses
      (excluding loopback, link-local)
   o  A MIF host can attach to more than one provisioning domains, as
      presented to the IP stack.
   o  The interfaces may be logical, virtual or physical.
   o  Configuration objects come from one or more administrative
      domains.
   o  The IP addresses may be from the same or from different address
      families, such as IPv4 and IPv6.
   o  Communications using these IP addresses may happen simultaneously
      and independently.
   o  Some communications using these IP addresses are possible on all
      the provisioning domains, while some are only possible on a
      smaller set of the provisioning domains.
   o  While the MIF host may forward packets between its interfaces,
      forwarding packets is not taken into account in this definition.

   Reference to IP version

      When a protocol keyword such as IP, PPP, DHCP is used without any
      reference to a specific IP version, then it implies both IPv4 and
      IPv6.  A specific IP version keyword such as DHCPv4 or DHCPv6 is
      specific to that IP version.


3.  Scope and Existing Work

   This section describes existing related work and defines the scope of
   the problem.

3.1.  Below IP Interaction

   Network discovery and selection on lower layers as defined by
   [RFC5113] is out of scope of this document.  Moreover, lower layer
   interaction such as IEEE 802.21 is also out of scope.

   Some mechanisms (e.g., based on a logical IP interface)
   allow sharing a single IP address across multiple interfaces
   (e.g., WiMAX and CDMA, LTE and HSPA, etc.) to disparate networks.
   From the IP stack view on the node, there is only a single interface
   and single IP address.  Therefore, this situation is out of scope of
   this current problem statement.  Furthermore, link aggregation done
   under IP where a single interface is shown to the IP stack is also
   out of scope.




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3.2.  Hosts Requirements

   The requirements for Internet Hosts [RFC1122] describe the multihomed
   host as if it has multiple IP addresses, which may be associated with
   one or more physical interfaces connected to the same or different
   networks.

   The host maintains a route cache table where each entry contains the
   local IP address, the destination IP address, Type-of-Service and
   Next-hop gateway IP address.  The route cache entry would have data
   about the properties of the path, such as the average round-trip
   delay measured by a transport protocol.

   As per [RFC1122], two models are defined:
   o  The "Strong" host model defines a multihomed host as a set of
      logical hosts within the same physical host.  In this model a
      packet must be sent on an interface that corresponds to the source
      address of that packet.
   o  The "Weak" host model describes a host that has some embedded
      gateway functionality.  In the weak host model, the host can send
      and receive packets on any interface.

   The multihomed host computes routes for outgoing datagrams
   differently depending on the model.  Under the strong model, the
   route is computed based on the source IP address, the destination IP
   address and the Type-of-Service.  Under the weak model, the source IP
   address is not used, but only the destination IP address and the
   Type-of-Service.

3.3.  Mobility and other IP protocols

   This document is only concerned with the situation where the hosts
   implement [RFC1122] for IPv4 and [RFC4294] for IPv6 and not special-
   purpose support for transport layers, mobility, multi-homing, or
   identifier-locator split mechanisms.  Dealing with multiple
   interfaces with such mechanisms is somewhat separate problem and
   under active study elsewhere in the IETF [RFC4960], [RFC5206],
   [RFC5533], [RFC5648], [I-D.ietf-mptcp-architecture].

3.4.  Address Selection

   The Default Address Selection specification [RFC3484] defines
   algorithms for source and destination IP address selections.  It is
   mandatory to be implemented in IPv6 nodes, which also means dual-
   stack nodes.  A node-scoped policy table managed by the IP stack is
   defined.  Provisions are made to change or update the policy table,
   however, no mechanism is defined.




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   Issues on using the Default Address Selection were found in [RFC5220]
   and [RFC5221] in the context of multiple prefixes on the same link.
   New work [I-D.ietf-6man-addr-select-sol] discusses the multiple
   attached networks scenarios and how to update the policy table.

3.5.  Finding and Sharing IP Addresses with Peers

   Interactive Connectivity Establishment (ICE [RFC5245]) is a technique
   for NAT traversal for UDP-based (and TCP) media streams established
   by the offer/answer model.  The multiplicity of IP addresses and
   ports in SDP offers are tested for connectivity by peer-to-peer
   connectivity checks.  The result is candidate IP addresses and ports
   for establishing a connection with the other peer.  However, ICE does
   not solve issues when incompatible configuration objects are received
   on different interfaces.

   Some application protocols do referrals of IP addresses and port
   numbers for further exchanges.  For instance, applications can
   provide reachability information to itself or to a third party.  The
   general problem of referrals is related to the multiple interface
   problem, since, in this context, referrals must provide consistent
   information depending on which provisioning domain is used.  The
   general referral problem has been studied in
   [I-D.carpenter-behave-referral-object] and
   [I-D.ietf-shim6-app-refer], but no solutions exist today.

3.6.  Socket API and connection manager

   Application Programming Interface (API) may expose objects that user
   applications may use for dealing with multiple interfaces.  For
   example, [RFC3542] shows how an application using the Advanced
   sockets API can specify the interface or the source IP address,
   through simple bind() operation or IPV6_PKTINFO socket option.

   There are other examples of API dealing with similar issues to MIF.
   For instance, [RFC5014] defines API to influence the default address
   selection mechanism by specifying attributes of the source addresses
   it prefers.  [I-D.ietf-shim6-multihome-shim-api] gives another
   example in a multihoming context, by defining a socket API enabling
   interactions between applications and the multihoming shim layer for
   advanced locator management, and access to information about failure
   detection and path exploration.

   In the MIF context, some implementations, specially in the mobile
   world, rely on higher-level connection managers to deal with issues
   brought by multiple provisioning domains.  Typically, the connection
   manager can select the provisioning domain when application is domain
   scoped.  Connection managers usually leverage on API to gather



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   information and/or for control purpose.  However, there is no
   standardized high level API, and implementations differ also in the
   functionality that they provide.  In addition, these mechanisms do
   not necessarily behave the same way across different platform and OS
   in the presence of the MIF problems [I-D.ietf-mif-current-practices].
   This lack of harmonization is an issue since it may lead to multiple
   instantiation of a cross platform/OS connection manager or
   application.


4.  Symptoms

   This section describes the various symptoms found using a MIF host
   that has already received configuration objects from its various
   provisioning domains.  They occur, for example, when:

   1.  one interface is on the Internet and one is on a corporate
       private network.  The latter may be through VPN.
   2.  one interface is on one access network (i.e. wifi) and the other
       one is on another access network (3G) with specific services.

4.1.  DNS resolution issues

   A MIF host (H1) has an active interface(I1) connected to a network
   (N1) which has its DNS server (S1) and another active interface (I2)
   connected to a network (N2) which has its DNS server (S2).  S1 serves
   with some private namespace "private.example.com".  The user or the
   application uses a name "a.private.example.com" which is within the
   private namespace of S1 and only resolvable by S1.  Any of the
   following situations may occur:

   1.  H1 stack, based on its routing table, uses I2 to reach S1 to
       resolve "a.private.example.com".  H1 never reaches S1.  The name
       is not resolved.
   2.  H1 keeps only one set of DNS server addresses from the received
       configuration objects and kept S2 address.  H1 sends the forward
       DNS query for a.private.example.com to S2.  S2 responds with an
       error for an non-existent domain (NXDOMAIN).  The name is not
       resolved.  This issue also arises when performing reverse DNS
       lookup.  In the same situation, the reverse DNS query fails.
   3.  H1 keeps only one set of DNS server addresses from the received
       configuration objects and kept S2 address.  H1 sends the DNS
       query for a.private.example.com to S2.  S2 asks its upstream DNS
       and gets an IP address for a.private.example.com.  However, the
       IP address is not the same one S1 would have given.  Therefore,
       the application tries to connect to the wrong destination host,
       or to the wrong interface of the latter, which may imply security
       issues or result in lack of service.



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   4.  S1 or S2 has been used to resolve "a.private.example.com" to an
       [RFC1918] address.  Both N1 and N2 are [RFC1918] addressed
       networks.  IPv4 source address selection may face challenges, as
       due address overlapping the source/destination IP addresses do
       not necessarily provide enough information for making proper
       address selection decisions.
   5.  H1 has resolved an FQDN to locally valid IP address when
       connected to N1.  After movement from N1 to N2, the host tries to
       connect to the same IP address as earlier, but as the address was
       only locally valid, connection setup fails.  Similarly, H1 may
       have received NXDOMAIN for an FQDN when connected to N1.  After
       movement from N1 to N2, the host should not assume the FQDN
       continues to be nonexistent.
   6.  H1 requests AAAA record from a DNS server on a network that uses
       protocol translators and DNS64 [I-D.ietf-behave-dns64].  If the
       H1 receives synthesized AAAA record, it is guaranteed to be valid
       only on the network it was learned from.  If the H1 uses
       synthesized AAAA on an network interface it is not valid on, the
       packets will be dropped by the network.

   A MIF host may also be provisioned with a Interface-specific suffix
   search list ([I-D.ietf-mif-current-practices]).  In this situation,
   if H1 sends DNS query on I1 using the search list tied to I2, the
   namespace could be not valid on I1 and the name could be not
   resolved.

4.2.  Routing

   A MIF host (H1) has an active interface(I1) connected to a network
   (N1) and another active interface (I2) connected to a network (N2).
   The user or the application is trying to reach an IP address (IP1).
   Any of the following situations may occur:

   1.  For IP1 , H1 has one default route (R1) via network (N1).  So,
       trying to reach IP1, H1 stack uses R1 and sends through I1.  If
       IP1 is only reachable by N2, IP1 is never reached or is not the
       right target.
   2.  For the IP1 address family, H1 has one default route (R1, R2) per
       network (N1, N2).  IP1 is reachable by both networks, but N2 path
       has better characteristics, such as better round-trip time, least
       cost, better bandwidth, etc....  These preferences could be
       defined by user, by the provider, by discovery or else.  H1 stack
       uses R1 and tries to send through I1.  IP1 is reached but the
       service would be better by I2.
   3.  For the IP1 address family, H1 has a default route (R1), a
       specific X.0.0.0/8 route R1B (eg.  RFC1918 prefix) to N1 and a
       default route (R2) to N2.  IP1 is reachable by N2 only, but the
       prefix (X.0.0.0/8) is used in both networks.  Because of the most



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       specific route R1B, H1 stack sends through I2 and never reach the
       target.

   A MIF host may have multiple routes to a destination.  However, by
   default, it does not have any hint concerning which interface would
   be the best to use for that destination.  For example, a service
   provider might want to influence the routing table of the host
   connecting to its network.

   A host usually has a node-scoped routing table.  Therefore, when a
   MIF host is connected to multiple provisioning domains where each
   service provider wants to influence the routing table of the host,
   then conflicts might arise from the multiple routing information
   being pushed to the host.

   A user on such multihomed host might want a local policy to influence
   which interface will be used based on various conditions.

   On a MIF host, some source addresses are not valid if used on some
   interfaces.  For example, an RFC1918 source address might be
   appropriate on the VPN interface but not on the public interface of
   the MIF host.  If the source address is not chosen appropriately,
   then sent packets might be filtered in the path if source address
   filtering is in place ([RFC2827],[RFC3704]) and reply packets might
   never come back to the source.

4.3.  Address Selection Policy

   Even if not yet specified, the distribution of address selection
   policy is sometimes evoked.  If deployed, such a mechanism could
   bring specific issue in a multiple provisioning domain context.  Lets
   consider a MIF host(H1) with an active interface(I1) connected to a
   network (N1) and another active interface (I2) connected to a network
   (N2).  When the user or the application is trying to reach an IP
   address (IP1), the following situations may occur:
      H1 receives from both networks (N1 and N2) an update of its
      default address selection policy.  However, the policies are
      specific to each network.  The policies are merged by H1 stack.
      Based on the merged policy, the chosen source address is from N1
      but packets are sent to N2.  The source address is not reachable
      from N2, therefore the return packet is lost.

   Merging address selection policies may have important impacts on
   routing.







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4.4.  Single Interface on Multiple Provisioning Domains

   When a MIF host using a single interface is connected to multiple
   networks with different default routers, similar issues as described
   above happen.  Even with a single interface, a node may wish to
   connect to more than one configuration domain: that node may use more
   than one IP source address and may have more than one default router.
   The node may want to access services that can only be reached using
   one of the provisioning domain, so it needs to use the right outgoing
   source address and default gateway to reach that service.  In this
   situation, that node may also need to use different DNS servers to
   get domain names in those different provisioning domains.


5.  Problems

   This section lists the underlying problems leading to the issues
   discussed in the previous section.  The problems can be divided into
   five categories: 1) Configuration 2) DNS resolution 3) Routing 4)
   Address selection and 5) connection management and API.  They are
   shown as below:

   1.  Configuration.  In a MIF context, configuration information
       specific to a provisioning domain may be ignored because:
       1.  Configuration objects (e.g.  DNS servers, NTP servers, ...)
           are node-scoped.  So the IP stack is not able to maintain the
           mapping between information and corresponding provisioning
           domain.
       2.  Same configuration objects (e.g.  DNS server addresses, NTP
           server addresses, ..) received from multiple provisioning
           domains may be overwritten.
       3.  Host implementations usually do not keep separate network
           configuration (such as DNS server addresses) per provisioning
           domain.
   2.  DNS resolution
       1.  Some FQDN can be resolvable only via a specific interface
           (e.g. intranet services).  However, DNS query could be send
           to the wrong interface because DNS server addresses may be
           node-scoped.
       2.  A DNS answer can be valid only on a specific interface but
           applications may be not aware of that mapping because DNS
           answers may be not kept with the interface from which the
           answer comes from.
   3.  Routing
       1.  In the MIF context, routing information could be specific to
           each interface.  This could lead to routing issue because, in
           current host implementations, routing tables are node-scoped.




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       2.  Interfaces of a MIF host can provide different
           characteristics (e.g. round-trip time, least cost, better
           bandwidth, etc....).  So, user, applications or network
           provider may wish to influence routing to take benefit of
           this heterogeneity.  However, with current host
           implementations, neither the Type-of-Service nor path
           characteristics can be taken into account in the routing
           table.
   4.  Address selection
       1.  Default Address Selection policies may be specific to their
           corresponding provisioning domain.  However, a MIF host may
           not be able to manage per-provisioning domain address
           selection policies because default Address Selection policy
           is node-scoped.
       2.  On a MIF host, some source addresses are not valid if used on
           some interfaces or even on some default routers on the same
           interface.  In this situation, the source address should be
           taken into account in the routing table; but current host
           implementations do not support such a feature.
       3.  Source address or address selection policies could be
           specified by applications.  However, there is no advanced
           APIs to allow applications realizing such operations.
   5.  Connection management and API
       1.  Some implementations, specially in the mobile world, have
           higher-level API and/or connection manager to address MIF
           issues.  These mechanisms are not standardized and do not
           necessarily behave the same way across different OS, and/or
           platforms, in the presence of the MIF problems.  This lack of
           consistency is an issue for user and operator who could
           experience different connection manager behaviors depending
           on the terminal.
       2.  Provisioning domain selection is a feature of connection
           management.  Domain selection can be tricky due to lot of
           different situations and selection criteria: some
           applications are domain-scoped, or may have a preferred
           provisioning domain (e.g. according to available QoS).  Each
           actor (end-user, operator, service provider, etc.) may also
           have their preferred provisioning domains (e.g. single out
           lower cost domain), possibly per application.
       3.  The different actors may provide different, and sometimes
           contradictory, domain selection policies to the connection
           management function.  The connection manager can typically
           address the issue, but not all connection managers are able
           to.
       4.  A MIF host can support different connection managers, which
           may have contradictory ways to solve the MIF issues.  For
           instance, because of different selection algorithms, two
           different connection managers could select different domains



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           in a same context.  Or, when dealing with different domain
           selection policies, a connection manager may give precedence
           to user policy while another could favor mobile operator
           policy.


6.  Summary

   A MIF host receives node configuration information from each of its
   provisioning domains.  Some configuration objects are global to the
   node, some are local to the interface.  Various issues arise when
   multiple conflicting node-scoped configuration objects are received
   via multiple provisioning domains.  Similar situations also happen
   with single interface host connected to multiple networks.
   Therefore, there is a need to define the appropriate behavior of an
   IP stack and possibly define protocols to manage these cases.


7.  Security Considerations

   The problems discussed in this document have security implications,
   such as when the packets sent on the wrong interface might be leaking
   some confidential information.  Moreover, the undetermined behavior
   of IP stacks in the multihomed context bring additional threats where
   an interface on a multihomed host might be used to conduct attacks
   targeted to the networks connected by the other interfaces.

   Additional security concerns raise up when information is provided to
   the host so that it could make a more intelligent decision (e.g.
   provide selection policies to the connection manager).  This
   additional information should be protected in some manner.


8.  IANA Considerations

   This document has no actions for IANA.


9.  Authors

   This document is a joint effort with authors of the MIF requirements
   draft [I-D.yang-mif-req].  The authors of this document, in
   alphabetical order, include: Marc Blanchet, Jacqni Qin, Pierrick
   Seite, Carl Williams and Peny Yang.







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10.  Acknowledgements

   The initial Internet-Drafts prior to the MIF working group and the
   discussions during the MIF BOF meeting and on the mailing list around
   the MIF charter scope on the mailing list brought very good input to
   the problem statement.  This draft steals a lot of text from these
   discussions and initial drafts (e.g.  [I-D.yang-mif-req],
   [I-D.hui-ip-multiple-connections-ps],
   [I-D.savolainen-mif-dns-server-selection]).  Therefore, the editor
   would like to acknowledge the following people (in no specific
   order), from which some text has been taken from: Jari Arkko, Keith
   Moore, Sam Hartman, George Tsirtsis, Scott Brim, Ted Lemon, Bernie
   Volz, Giyeong Son, Gabriel Montenegro, Julien Laganier, Teemu
   Savolainen, Christian Vogt, Lars Eggert, Margaret Wasserman, Hui
   Deng, Ralph Droms, Ted Hardie, Christian Huitema, Remi Denis-
   Courmont, Alexandru Petrescu, Zhen Cao. Sorry if some contributors
   have not been named.


11.  Informative References

   [I-D.carpenter-behave-referral-object]
              Carpenter, B., Boucadair, M., Halpern, J., Jiang, S., and
              K. Moore, "A Generic Referral Object for Internet
              Entities", draft-carpenter-behave-referral-object-01 (work
              in progress), October 2009.

   [I-D.hui-ip-multiple-connections-ps]
              Hui, M. and H. Deng, "Problem Statement and Requirement of
              Simple IP Multi-homing of the Host",
              draft-hui-ip-multiple-connections-ps-02 (work in
              progress), March 2009.

   [I-D.ietf-6man-addr-select-sol]
              Matsumoto, A., Fujisaki, T., and R. Hiromi, "Solution
              approaches for address-selection problems",
              draft-ietf-6man-addr-select-sol-03 (work in progress),
              March 2010.

   [I-D.ietf-behave-dns64]
              Bagnulo, M., Sullivan, A., Matthews, P., and I. Beijnum,
              "DNS64: DNS extensions for Network Address Translation
              from IPv6 Clients to IPv4 Servers",
              draft-ietf-behave-dns64-10 (work in progress), July 2010.

   [I-D.ietf-mif-current-practices]
              Wasserman, M. and P. Seite, "Current Practices for
              Multiple Interface Hosts",



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              draft-ietf-mif-current-practices-03 (work in progress),
              August 2010.

   [I-D.ietf-mptcp-architecture]
              Ford, A., Raiciu, C., Barre, S., and J. Iyengar,
              "Architectural Guidelines for Multipath TCP Development",
              draft-ietf-mptcp-architecture-01 (work in progress),
              June 2010.

   [I-D.ietf-shim6-app-refer]
              Nordmark, E., "Shim6 Application Referral Issues",
              draft-ietf-shim6-app-refer-00 (work in progress),
              July 2005.

   [I-D.ietf-shim6-multihome-shim-api]
              Komu, M., Bagnulo, M., Slavov, K., and S. Sugimoto,
              "Socket Application Program Interface (API) for
              Multihoming Shim", draft-ietf-shim6-multihome-shim-api-13
              (work in progress), February 2010.

   [I-D.savolainen-mif-dns-server-selection]
              Savolainen, T., "Improved DNS Server Selection for Multi-
              Homed Hosts", draft-savolainen-mif-dns-server-selection-03
              (work in progress), June 2010.

   [I-D.yang-mif-req]
              Yang, P., Seite, P., Williams, C., and J. Qin,
              "Requirements on multiple Interface (MIF) of simple IP",
              draft-yang-mif-req-00 (work in progress), March 2009.

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC1136]  Hares, S. and D. Katz, "Administrative Domains and Routing
              Domains: A model for routing in the Internet", RFC 1136,
              December 1989.

   [RFC1661]  Simpson, W., "The Point-to-Point Protocol (PPP)", STD 51,
              RFC 1661, July 1994.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, March 1997.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:



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              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

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

   [RFC3542]  Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
              "Advanced Sockets Application Program Interface (API) for
              IPv6", RFC 3542, May 2003.

   [RFC3704]  Baker, F. and P. Savola, "Ingress Filtering for Multihomed
              Networks", BCP 84, RFC 3704, March 2004.

   [RFC4294]  Loughney, J., "IPv6 Node Requirements", RFC 4294,
              April 2006.

   [RFC4477]  Chown, T., Venaas, S., and C. Strauf, "Dynamic Host
              Configuration Protocol (DHCP): IPv4 and IPv6 Dual-Stack
              Issues", RFC 4477, May 2006.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",
              RFC 4960, September 2007.

   [RFC5014]  Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
              Socket API for Source Address Selection", RFC 5014,
              September 2007.

   [RFC5113]  Arkko, J., Aboba, B., Korhonen, J., and F. Bari, "Network
              Discovery and Selection Problem", RFC 5113, January 2008.

   [RFC5206]  Nikander, P., Henderson, T., Vogt, C., and J. Arkko, "End-
              Host Mobility and Multihoming with the Host Identity
              Protocol", RFC 5206, April 2008.

   [RFC5220]  Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,
              "Problem Statement for Default Address Selection in Multi-
              Prefix Environments: Operational Issues of RFC 3484
              Default Rules", RFC 5220, July 2008.

   [RFC5221]  Matsumoto, A., Fujisaki, T., Hiromi, R., and K. Kanayama,



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              "Requirements for Address Selection Mechanisms", RFC 5221,
              July 2008.

   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245,
              April 2010.

   [RFC5533]  Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
              Shim Protocol for IPv6", RFC 5533, June 2009.

   [RFC5648]  Wakikawa, R., Devarapalli, V., Tsirtsis, G., Ernst, T.,
              and K. Nagami, "Multiple Care-of Addresses Registration",
              RFC 5648, October 2009.


Authors' Addresses

   Marc Blanchet
   Viagenie
   2600 boul. Laurier, suite 625
   Quebec, QC  G1V 4W1
   Canada

   Email: Marc.Blanchet@viagenie.ca
   URI:   http://www.viagenie.ca


   Pierrick Seite
   France Telecom - Orange
   4, rue du Clos Courtel, BP 91226
   Cesson-Sevigne  35512
   France

   Email: pierrick.seite@orange-ftgroup.com
















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