MIF Working Group                                              D. Anipko
Internet-Draft                                     Microsoft Corporation
Intended status: Informational                             July 26, 2013
Expires: January 25, 2014

               Multiple Provisioning Domain Architecture


   This document is a product of the work of MIF architecture design
   team.  It outlines a solution framework for some of the issues,
   experienced by nodes that can be attached to multiple networks.  The
   framework defines the notion of a Provisioning Domain (PVD) - a
   consistent set of network configuration information, and PVD-aware
   nodes - nodes which learn PVDs from the attached network(s) and/or
   other sources and manage and use multiple PVDs for connectivity
   separately and consistently.

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
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   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 January 25, 2014.

Copyright Notice

   Copyright (c) 2013 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
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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text

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   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 . . . . . . . . . . . . . . . . . . . . . . . . .  2
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  3
   2.  Definitions and types of PVDs  . . . . . . . . . . . . . . . .  3
     2.1.  Explicit and implicit PVDs . . . . . . . . . . . . . . . .  4
     2.2.  Incremental deployment of explicit PVDs  . . . . . . . . .  5
     2.3.  Relationship between PVDs and interfaces . . . . . . . . .  5
     2.4.  PVD identity/naming  . . . . . . . . . . . . . . . . . . .  6
     2.5.  Relationship to dual-stack networks  . . . . . . . . . . .  6
     2.6.  Elements of PVD  . . . . . . . . . . . . . . . . . . . . .  7
   3.  Example network configurations and number of PVDs  . . . . . .  7
   4.  Reference model of PVD-aware node  . . . . . . . . . . . . . .  7
     4.1.  Constructions and maintenance of separate PVDs . . . . . .  7
     4.2.  Consistent use of PVDs for network connections . . . . . .  7
       4.2.1.  Name resolution  . . . . . . . . . . . . . . . . . . .  7
       4.2.2.  Next-hop and source address selection  . . . . . . . .  8
     4.3.  Connectivity tests . . . . . . . . . . . . . . . . . . . .  8
     4.4.  Relationship to interface management and connection manager 8
   5.  PVD support in APIs  . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  Basic  . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Intermediate . . . . . . . . . . . . . . . . . . . . . . .  9
     5.3.  Advanced . . . . . . . . . . . . . . . . . . . . . . . . .  9
   6.  PVD-aware nodes trust to PVDs  . . . . . . . . . . . . . . . .  9
     6.1.  Untrusted PVDs . . . . . . . . . . . . . . . . . . . . . .  9
     6.2.  Trusted PVDs . . . . . . . . . . . . . . . . . . . . . . . 10
       6.2.1.  Authenticated PVDs . . . . . . . . . . . . . . . . . . 10
       6.2.2.  PVDs trusted by attachment . . . . . . . . . . . . . . 10
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . 11
     10.2.  Informative References  . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.  Introduction

   Nodes attached to multiple networks may encounter problems due to
   conflict of the networks configuration  and/or simultaneous use of
   the multiple available networks.  While existing implementations
   apply various techniques ([RFC6419]) to tackle such problems, in many
   cases the issues may still appear.  The MIF problem statement
   document [RFC6418] describes the general landscape as well as
   discusses many specific issues and scenarios details, and are not
   listed in this document.

   Across the layers, problems enumerated in [RFC6418] can be grouped

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   into 3 categories:

   1.  Lack of consistent and distinctive management of configuration
       elements, associated with different networks.

   2.  Inappropriate mixed use of configuration elements, associated
       with different networks, in the course of a particular network
       activity / connection.

   3.  Use of a particular network, not consistent with the intent of
       the scenario / involved parties, leading to connectivity failure
       and / or other undesired consequences.

   As an illustration: an example of (1) is a single node-scoped list of
   DNS server IP addresses, learned from different networks, leading to
   failures or delays in resolution of name from particular namespaces;
   an example of (2) is use of an attempt to resolve a name of a HTTP
   proxy server, learned from a network A, with a DNS server, learned
   from a network B, likely to fail; an example of (3) is a use of
   employer-sponsored VPN connection for peer-to-peer connections,
   unrelated to employment activities.

   This architecture describes a solution to these categories of
   problems, respectively, by:

   1.  Introducing a formal notion of the PVD, including PVD identity,
       and ways for nodes to learn the intended associations among
       acquired network configuration information elements.

   2.  Introducing a reference model for a PVD-aware node, preventing
       inadvertent mixed use of the configuration information, which may
       belong to different PVDs.

   3.  Providing recommendations on PVD selection based on PVD identity
       and connectivity tests for common scenarios.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Definitions and types of PVDs

   Provisioning Domain: a consistent set of network configuration
   information.  Classically, the entire set available on a single
   interface is provided by a single source, such as network
   administrator, and can therefore be treated as a single provisioning
   domain.  In modern IPv6 networks, multihoming can result in more than
   one provisioning domain being present on a single link.  In some
   scenarios, it is also possible for elements of the same domain to be
   present on multiple links.

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   Typical examples of information in a provisioning domain, learned
   from the network, are: source address prefixes, to be used by
   connections within the provisioning domain, IP address of DNS server,
   name of HTTP proxy server if available, DNS suffixes associated with
   the network etc.

   It is assumed that normally, configuration information contained in a
   single PVD, shall be sufficient for a node to fulfill a network
   connection request by an application, and hence there should be no
   need to attempt to merge information across different PVDs.
   Nevertheless, even when a PVD lack some parts of the configuration,
   merging of information from different PVD(s) shall not be done
   automatically, since typically it would lead to issues described in

   A node may use other sources, such as e.g., node local policy, user
   input or other mechanisms, not defined by IETF, to either construct a
   PVD entirely (analogously to static IP configuration of an
   interface), or supplement with particular elements all or some PVDs
   learned from the network, or potentially merge information from
   different PVDs, if such merge is known to the node to be safe, based
   on explicit policies.

   As an example, node administrator could inject a not ISP-specific DNS
   server into PVDs for any of the networks the node could become
   attached to.  Such creation / augmentation of PVD(s) could be static
   or dynamic.  The particular implementation mechanisms are outside of
   the scope of this document.

   Link-specific and/or vendor-proprietary mechanisms for discovery of
   PVD information, different from the IETF-defined mechanisms, can be
   used by the nodes separately from or together with IETF-defined
   mechanisms, as long as they allow to discover necessary elements of
   the PVD(s). In all cases, by default nodes must ensure that the
   lifetime of all dynamically discovered PVD configuration is
   appropriately limited by the relevant events - for example, if an
   interface media state change was indicated, the previously discovered
   information may no longer be valid and needs to be re-discovered or

   PVD-aware node: a node that supports association of network
   configuration information into PVDs, and using the resultant PVDs to
   serve requests for network connections in ways, consistent with
   recommendations of this architecture.

2.1.  Explicit and implicit PVDs

   A node may receive explicit information from the network and/or other
   sources, about presence of PVDs and association of particular network
   information with a particular PVD.  PVDs, constructed based on such

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   information, are referred to in this document as "explicit".

   Protocol changes/extensions will likely be required to support the
   explicit PVDs by IETF-defined mechanisms.  As an example, one could
   think of one or several DHCP options, carrying PVD identity and / or
   its elements.  A different approach could be to introduce a DHCP
   option, which only carries identity of a PVD, while the association
   of network information elements with that identity, is implemented by
   the respective protocols - such as e.g., with a Router Discovery
   [RFC4861] option associating an address range with a PVD.

   Specific, existing or new, features of networking protocols to enable
   delivery of PVD identity and association with various network
   information elements will be defined in companion design documents.

   It shall be possible for networks to communicate that some of their
   configuration elements could be used within a context of other
   networks/PVDs.  Based on such declaration and their policies, PVD-
   aware nodes may choose to inject such elements into some or all other
   PVDs they connect to.

   When connected to networks, which don't advertise explicit PVD
   information, PVD-aware shall automatically create separate PVDs for
   configuration received on different interfaces.  Such PVDs are
   referred to in this document as "implicit".

2.2.  Incremental deployment of explicit PVDs

   It is likely that for a long time there may be networks which do not
   advertise explicit PVD information, since deployment of any new
   features in networking protocols is a relatively slow process.  In
   such environments, PVD-aware nodes may still provide benefits to
   their users, compared to non-PVD aware nodes, by using network
   information from different interfaces separately and consistently to
   serve network connection requests.

   In the mixed mode, where e.g., multiple networks are available on the
   link the interface is attached to, and only some of the networks
   advertise PVD information, the PVD-aware node shall create explicit
   PVDs based on explicitly learned PVD information, and associate the
   rest of the configuration with an implicit PVD created for that

2.3.  Relationship between PVDs and interfaces

   Implicit PVDs are limited to network configuration information
   received on a single interface.  Explicit PVDs, in practice will
   often also be scoped to a configuration related to a particular
   interface, however per this architecture there is no such requirement
   or limitation and as defined in this architecture, explicit PVDs may
   include information related to more than one interfaces, if the node
   learns presence of the same PVD on those interfaces and the
   authentication of the PVD ID meets the level required by the node

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2.4.  PVD identity/naming

   For explicit PVDs, PVD ID (globally unique ID, that possibly is
   human-readable) is received as part of that information.  For
   implicit PVDs, the node assigns a locally generated globally unique
   ID to each implicit PVD.

   PVD-aware node may use these IDs to choose a PVD with matching ID for
   special-purpose connection requests, in accordance with node policy
   or choice by advanced applications, and/or to present human-readable
   IDs to the end-user for selection of Internet-connected PVDs.

   A single network provider may operate multiple networks, including
   networks at different locations.  In such cases, the provider may
   chose whether to advertise single or multiple PVD identities at all
   or some of those networks, as it suits their business needs.  This
   architecture doesn't impose specific requirements in this regard.

   When multiple nodes are connected to the same link, where one or more
   explicit PVDs are available, this architecture assumes that the
   information about all available PVDs is advertized by the networks to
   all the connected nodes.  At the same time, the connected nodes may
   have different heuristics, policies and/or other settings, including
   configured set of their trusted PVDs, which may lead to different
   PVDs actually being used by different nodes for their connections.

   Possible extensions, where different sets of PVDs may be advertised
   by the networks to different connected nodes, are out of scope for
   this document.

2.5.  Relationship to dual-stack networks

   When applied to dual-stack networks, the PVD definition allows for
   multiple PVDs to be created, where each PVD contain information for
   only one address family, or for a single PVD that contains
   information about multiple address families.  This architecture
   requires that accompanying design documents for accompanying protocol
   changes must support PVDs containing information from multiple
   address families.  PVD-aware nodes must be capable of dealing with
   both single-family and multi-family PVDs.

   For explicit PVDs, the choice of either of the approaches is a policy
   decision of a network administrator and/or node user/administrator.
   Since some of the IP configuration information that can be learned
   from the network can be applicable to multiple address families (for
   instance DHCP address selection option [I-D.ietf-6man-addr-select-
   opt]), it is likely that dual-stack networks will deploy single PVDs
   for both address families.

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   For implicit PVDs, by default PVD-aware nodes shall including
   multiple IP families into single implicit PVD created for an
   interface.  At the time of writing of this document in dual-stack
   networks it appears to be a common practice for configuration of both
   address families to be provided by a single source.

   A PVD-aware node that provides API to use / enumerate / inspect PVDs
   and/or their properties shall provide ability to filter PVDs and/or
   their properties by address family.

2.6.  Elements of PVD

3.  Example network configurations and number of PVDs

4.  Reference model of PVD-aware node

4.1.  Constructions and maintenance of separate PVDs

4.2.  Consistent use of PVDs for network connections

   PVDs enable PVD-aware nodes to use consistently a correct set of
   configuration elements to serve the specific network requests from
   beginning to end.  This section describes specific examples of such
   consistent use.

4.2.1.  Name resolution

   When PVD-aware node needs to resolve a name of the destination used
   by a connection request, the node could decide to use one, or
   multiple PVDs for a given name lookup.

   The node shall chose one PVD, if e.g., the node policy required to
   use a particular PVD for a particular purpose (e.g.  to download an
   MMS using a specific APN over a cellular connection).  To make the
   choice, the node could use a match of the PVD DNS suffix or other
   form of PVD ID, as determined by the node policy.

   The node may pick multiple PVDs, if e.g., they are general purpose
   PVDs providing connectivity to the Internet, and the node desires to
   maximize chances for connectivity in Happy Eyeballs style.  In this
   case, the node could do the lookups in parallel, or in sequence.
   Alternatively, the node may use for the lookup only one PVD, based on
   the PVD connectivity properties, user choice of the preferred
   Internet PVD, etc.

   In either case, by default the node uses information obtained in a
   name service lookup to establish connections only within the same PVD

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   from which the lookup results were obtained.

   For simplicity, when we say that name service lookup results were
   obtained from a PVD, what we mean is that the name service query was
   issued against a name service the configuration of which is present
   in a particular PVD.   In that sense, the results are "from" that
   particular PVD.

   Some nodes may support transports and/or APIs, which provide an
   abstraction of a single connection, aggregating multiple underlying
   connections.  MPTCP [RFC6182] is an example of such transport
   protocol.  For the connections provided by such transports/APIs, a
   PVD-aware node may use different PVDs for servicing of that logical
   connection, provided that all operations on the underlying
   connections are done consistently within their corresponding PVD(s).

4.2.2.  Next-hop and source address selection

   For the purpose of this discussion, let's assume the preceding name
   lookup succeeded in a particular PVD.  For each obtained destination
   address, the node shall perform a next-hop lookup among routers,
   associated with that PVD. As an example, such association could be
   determined by the node via matching the source address prefixes/
   specific routes advertized by the router against known PVDs, or
   receiving explicit PVD affiliation advertized through a new Router
   Discovery [RFC4861] option.

   For each destination, once the best next-hop is found, the node
   selects best source address according to the [RFC6724] rules, but
   with a constraint that the source address must belong to a range
   associated with the used PVD. If needed, the node would use the
   prefix policy from the same PVD for the best source address selection
   among multiple candidates.

   When destination/source pairs are identified, then they are sorted
   using the [RFC6724] destination sorting rules and the prefix policy
   table from the used PVD.

4.3.  Connectivity tests

4.4.  Relationship to interface management and connection managers

5.  PVD support in APIs

   In all cases changes in available PVDs must be somehow exposed,
   appropriately for each of the approaches.

5.1.  Basic

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   Applications are not PVD-aware in any manner, and only submit
   connection requests.  The node performs PVD selection implicitly,
   without any otherwise applications participation, and based purely on
   node-specific administrative policies and/or choices made by the user
   in a user interface provided by the operating environment, not by the

   As an example, such PVD selection can be done at the name service
   lookup step, by using the relevant configuration elements, such as
   e.g., those described in [RFC6731].  As another example, the PVD
   selection could be done based on application identity or type (i.e.,
   a node could always use a particular PVD for a VOIP application).

5.2.  Intermediate

   Applications indirectly participate in selection of PVD by specifying
   hard requirements and soft preferences.  The node performs PVD
   selection, based on applications inputs and policies and/or user
   preferences.  Some / all properties of the resultant PVD may be
   exposed to applications.

5.3.  Advanced

   PVDs are directly exposed to applications, for enumeration and
   selection.  Node polices and/or user choices, may still override the
   application preferences and limit which PVD(s) can be enumerated and/
   or used by the application, irrespectively of any preferences which
   application may have specified.  Depending on the implementation,
   such restrictions, imposed per node policy and/or user choice, may or
   may not be visible to the application.

6.  PVD-aware nodes trust to PVDs

6.1.  Untrusted PVDs

   Implicit and explicit PVDs for which no trust relationship exists are
   considered untrusted.   Only PVDs, which meet the requirements in
   Section 6.2, are trusted; any other PVD is untrusted.

   In order to avoid various forms of misinformation that can be
   asserted when PVDs are untrusted, nodes that implement PVD separation
   cannot assume that two explicit PVDs with the same identifier are
   actually the same PVD.  A node that did make this assumption would be
   vulnerable to attacks where for example an open Wifi hotspot might
   assert that it was part of another PVD, and thereby might draw
   traffic intended for that PVD onto its own network.

   Since implicit PVD identifiers are synthesized by the node, this
   issue cannot arise with implicit PVDs.

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   Mechanisms exist (for example, [RFC6731]) whereby a PVD can provide
   configuration information that asserts special knowledge about the
   reachability of resources through that PVD.   Such assertions cannot
   be validated unless the node has a trust relationship with the PVD;
   assertions of this type therefore must be ignored by nodes that
   receive them from untrusted PVDs.   Failure to ignore such assertions
   could result in traffic being diverted from legitimate destinations
   to spoofed destinations.

6.2.  Trusted PVDs

   Trusted PVDs are PVDs for which two conditions apply.   First, a
   trust relationship must exist between the node that is using the PVD
   configuration and the source that provided that configuration; this
   is the authorization portion of the trust relationship.   Second,
   there must be some way to validate the trust relationship.   This is
   the authentication portion of the trust relationship.   Two
   mechanisms for validating the trust relationship are defined.

6.2.1.  Authenticated PVDs

   One way to validate the trust relationship between a node and the
   source of a PVD is through the combination of cryptographic
   authentication and an identifier configured on the node.   In some
   cases, the two could be the same; for example, if authentication is
   done with a shared secret, the secret would have to be associated
   with the PVD identifier.   Without a (PVD Identifier, shared key)
   tuple, authentication would be impossible, and hence authentication
   and authorization are combined.

   However, if authentication is done using some public key mechanism
   such as a TLS cert or DANE, authentication by itself isn't enough,
   since theoretically any PVD could be authenticated in this way.   In
   addition to authentication, the node would need to be configured to
   trust the identifier being authenticated.  Validating the
   authenticated PVD name against a list of PVD names configured as
   trusted on the node would constitute the authorization step in this

6.2.2.  PVDs trusted by attachment

   In some cases a trust relationship may be validated by some means
   other than described in Section 6.2.1, simply by virtue of the
   connection through which the PVD was obtained.   For instance, a
   handset connected to a mobile network may know through the mobile
   network infrastructure that it is connected to a trusted PVD, and
   whatever mechanism was used to validate that connection constitutes
   the authentication portion of the PVD trust relationship.
   Presumably such a handset would be configured from the factory, or
   else through mobile operator or user preference settings, to trust
   the PVD, and this would constitute the authorization portion of this
   type of trust relationship.

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7.  Acknowledgements

8.  IANA Considerations

   This memo includes no request to IANA.

9.  Security Considerations

   All drafts are required to have a security considerations section.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2.  Informative References

              Matsumoto, A., Fujisaki, T. and T. Chown, "Distributing
              Address Selection Policy using DHCPv6", Internet-Draft
              draft-ietf-6man-addr-select-opt-10, April 2013.

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

   [RFC6182]  Ford, A., Raiciu, C., Handley, M., Barre, S. and J.
              Iyengar, "Architectural Guidelines for Multipath TCP
              Development", RFC 6182, March 2011.

   [RFC6418]  Blanchet, M. and P. Seite, "Multiple Interfaces and
              Provisioning Domains Problem Statement", RFC 6418,
              November 2011.

   [RFC6419]  Wasserman, M. and P. Seite, "Current Practices for
              Multiple-Interface Hosts", RFC 6419, November 2011.

   [RFC6724]  Thaler, D., Draves, R., Matsumoto, A. and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, September 2012.

   [RFC6731]  Savolainen, T., Kato, J. and T. Lemon, "Improved Recursive
              DNS Server Selection for Multi-Interfaced Nodes", RFC
              6731, December 2012.

Author's Address

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   Dmitry Anipko
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA 98052

   Phone: +1 425 703 7070
   Email: dmitry.anipko@microsoft.com

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