intarea                                                       P. Pfister
Internet-Draft                                            E. Vyncke, Ed.
Intended status: Standards Track                                   Cisco
Expires: September 9, December 20, 2019                                      T. Pauly
                                                             D. Schinazi
                                                              Google LLC
                                                                 W. Shao
                                                           March 8,
                                                           June 18, 2019

             Discovering Provisioning Domain Names and Data


   An increasing number of hosts access the Internet via multiple
   interfaces or, in IPv6 multi-homed networks, via multiple IPv6 prefix
   configurations context.

   This document describes a way for hosts to identify such contexts,
   called Provisioning Domains (PvDs), where Fully Qualified Domain
   Names (FQDNs) act as PvD identifiers.  Those identifiers are
   advertised in a new Router Advertisement (RA) option and, when
   present, are associated with the set of information included within
   the RA.

   Based on this FQDN, hosts can retrieve additional information about
   their network access characteristics via an HTTP over TLS query.
   This allows applications to select which Provisioning Domains to use
   as well as to provide configuration parameters to the transport layer
   and above.

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
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   Drafts is at

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   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 September 9, December 20, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( in effect on the date of
   publication of this document.  Please review these documents
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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 . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Provisioning Domain Identification using Router
       Advertisements  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  PvD ID Option for Router Advertisements . . . . . . . . .   4   5
     3.2.  Router Behavior . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Non-PvD-aware Host Behavior . . . . . . . . . . . . . . .   8
     3.4.  PvD-aware Host Behavior . . . . . . . . . . . . . . . . .   8
       3.4.1.  DHCPv6 configuration association  . . . . . . . . . .   9
       3.4.2.  DHCPv4 configuration association  . . . . . . . . . .   9
       3.4.3.  Connection Sharing by the Host  . . . . . . . . . . .   9
       3.4.4.  Usage of DNS Servers  . . . . . . . . . . . . . . . .  10
   4.  Provisioning Domain Additional Information  . . . . . . . . .  11
     4.1.  Retrieving the PvD Additional Information . . . . . . . .  11
     4.2.  Operational Consideration to Providing the PvD Additional
           Information . . . . . . . . . . . . . . . . . . . . . . .  13
     4.3.  PvD Additional Information Format . . . . . . . . . . . .  13
       4.3.1.  Private Extensions  . . . . . . . . . . . . . . . . .  14
       4.3.2.  Example . . . . . . . . . . . . . . . . . . . . . . .  14  15
     4.4.  Detecting misconfiguration and misuse . . . . . . . . . .  15
   5.  Operational Considerations  . . . . . . . . . . . . . . . . .  15  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  17  18
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  Additional Information PvD Keys Registry  . . . . . . . .  18
     8.2.  PvD Option Flags Registry . . . . . . . . . . . . . . . .  18  19
     8.3.  PvD JSON Media Type Registration  . . . . . . . . . . . .  19
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18  20
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  19  20
     10.1.  Normative references . . . . . . . . . . . . . . . . . .  19  20
     10.2.  Informative references . . . . . . . . . . . . . . . . .  20  21
   Appendix A.  Changelog  . . . . . . . . . . . . . . . . . . . . .  22  23
     A.1.  Version 00  . . . . . . . . . . . . . . . . . . . . . . .  22  23
     A.2.  Version 01  . . . . . . . . . . . . . . . . . . . . . . .  22  23
     A.3.  Version 02  . . . . . . . . . . . . . . . . . . . . . . .  23  24
     A.4.  WG Document version 00  . . . . . . . . . . . . . . . . .  23  24
     A.5.  WG Document version 01  . . . . . . . . . . . . . . . . .  24  25
     A.6.  WG Document version 02  . . . . . . . . . . . . . . . . .  24  25
     A.7.  WG Document version 04  . . . . . . . . . . . . . . . . .  25  26
       A.7.1.  WG Document version 05  . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25  26

1.  Introduction

   It has become very common in modern networks for hosts to access the
   internet through different network interfaces, tunnels, or next-hop
   routers.  For example, if Alice has a mobile phone provider and a
   broadband provider in her home, her devices and her applications
   should be capable of seamlessly transitioning from one to the other
   and be able to use her Wi-Fi to access local resources or use the
   more suitable link on a per-application base.  This document provides
   the basic information necessary to make this choice intelligently.
   There are similar use cases for IPsec Virtual Private Networks that
   are already considered Explicit PvDs in [RFC7556].

   To describe the set of network configurations associated with each
   access method, the concept of Provisioning Domain (PvD) was defined
   in [RFC7556].

   This document specifies a way to identify PvDs with Fully Qualified
   Domain Names (FQDN), called PvD IDs.  Those identifiers are
   advertised in a new Router Advertisement (RA) [RFC4861] option called
   the PvD ID Router Advertisement option which, when present,
   associates the PvD ID with all the information present in the Router
   Advertisement as well as any configuration object, such as addresses,
   deriving from it.  The PVD ID Router Advertisement option may also
   contain a set of other RA options.  Since such options are only
   considered by hosts implementing this specification, network
   operators may configure hosts that are 'PvD-aware' with PvDs that are
   ignored by other hosts.

   Since PvD IDs are used to identify different ways to access the
   internet, multiple PvDs (with different PvD IDs) could be provisioned
   on a single host interface.  Similarly, the same PvD ID could be used
   on different interfaces of a host in order to inform that those PvDs
   ultimately provide identical services.

   This document also introduces a way for hosts to retrieve optional
   and additional information related to a specific PvD by means of an
   HTTP over TLS query using an URI derived from the PvD ID.  The
   retrieved JSON object contains additional information that would
   typically be considered unfit, or too large, to be directly included
   in the Router Advertisement, but might be considered useful to the
   applications, or even sometimes users, when choosing which PvD should
   be used.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in

   In addition, this document uses the following terminology:

   Provisioning Domain (PvD):   A set of network configuration
      information; for more information, see [RFC7556].

   PvD ID:   A Fully Qualified Domain Name (FQDN) used to identify a

   Explicit PvD:   A PvD uniquely identified with a PvD ID.  For more
      information, see [RFC7556].

   Implicit PvD:   A PvD that, in the absence of a PvD ID, is identified
      by the host interface to which it is attached and the address of
      the advertising router.  See also [RFC7556].

   PvD-aware host  A host that supports the association of network
      configuration information into PvDs and the use of these PvDs.
      Also named PvD-aware node in [RFC7556].

3.  Provisioning Domain Identification using Router Advertisements

   Explicit PvDs are identified by a PvD ID.  The PvD ID is a Fully
   Qualified Domain Name (FQDN) which MUST belong to the network
   operator in order to avoid naming collisions.  The same PvD ID MAY be
   used in several access networks when they ultimately provide
   identical services (e.g., in all home networks subscribed to the same
   service); else, the PvD ID MUST be different to follow section 2.4 of

3.1.  PvD ID Option for Router Advertisements

   This document introduces a Router Advertisement (RA) option called
   PvD option.  It is used to convey the FQDN identifying a given PvD
   (see Figure 1), bind the PvD ID with configuration information
   received over DHCPv4 (see Section 3.4.2), enable the use of HTTP over
   TLS to retrieve the PvD Additional Information JSON object (see
   Section 4), as well as contain any other RA options which would
   otherwise be valid in the RA.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   |     Type      |    Length     |H|L|R|     Reserved    | Delay |
   |       Sequence Number         |                             ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                             ...
   ...                         PvD ID FQDN                       ...
   ...             +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...             |                  Padding                      |
   |                                                             ...
   ...            Router Advertisement message header            ...
   ...             (Only present when R-flag is set)             ...
   ...                                                             |
   |   Options ...

           Figure 1: PvD ID Router Advertisements Option format

   Type        :   (8 bits) Set to 21.

   Length      :   (8 bits) The length of the option in units of 8
      octets, including the Type and Length fields, the Router
      Advertisement message header, if any, as well as the RA options
      that are included within the PvD Option.

   H-flag      :   (1 bit) 'HTTP' flag stating whether some PvD
      Additional Information is made available through HTTP over TLS, as
      described in Section 4.

   L-flag      :   (1 bit) 'Legacy' flag stating whether the router is
      also providing IPv4 information using DHCPv4 (see Section 3.4.2).

   R-flag      :   (1 bit) 'Router Advertisement' flag stating whether
      the PvD Option is followed (right after padding to the next 64
      bits boundary) by a Router Advertisement message header (See
      section 4.2 of [RFC4861]).

   Delay       :   (4 bits) Unsigned integer used to delay HTTP GET
      queries from hosts by a randomized backoff (see Section 4.1).

   Reserved    :   (13 bits) Reserved for later use.  It MUST be set to
      zero by the sender and ignored by the receiver.

   Sequence Number:   (16 bits) Sequence number for the PvD Additional
      Information, as described in Section 4.

   PvD ID FQDN :   The FQDN used as PvD ID encoded in DNS format, as
      described in Section 3.1 of [RFC1035].  Domain names compression
      described in Section 4.1.4 of [RFC1035] MUST NOT be used.

   Padding     :   Zero or more padding octets to the next 8 octets
      boundary.  It MUST be set to zero by the sender, and ignored by
      the receiver.

   RA message header :   (16 octets) When the R-flag is set, a full
      Router Advertisement message header as specified in [RFC4861].
      The 'Type', 'Code' sender MUST set the 'Type' to 134, the value for "Router
      Advertisement", and 'Checksum' fields (i.e. set the first 32 bits), 'Code' to 0.  Receivers MUST ignore
      both of these fields.  The 'Checksum' MUST be set to zero 0 by the sender and
      sender; non-zero checksums MUST be ignored by the receiver.
      The  All
      other fields are to be set and parsed as specified in [RFC4861] or
      any updating documents.

   Options :   Zero or more RA options that would otherwise be valid as
      part of the Router Advertisement main body, but are instead
      included in the PvD Option such as to be ignored by hosts that are
      not 'PvD-aware'.

   Here is an example of a PvD option with as the PvD ID
   FQDN and including a RDNSS and prefix information options (it also
   have the sequence number 123, presence of additional information to
   be fetched with a delay indicated as 5):

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     | Type: 21      |  Length: 12   |1|0|0|     Reserved    |Delay:5|
     |       Seq number: 123         |      7        |       e       |
     |      x        |       a       |      m        |       p       |
     |      l        |       e       |      3        |       o       |
     |      r        |       g       |      0        |   0 (padding) |
     |   0 (padding) |  0 (padding)  |   0 (padding) |   0 (padding) |
     |  RDNSS option (RFC 6106) length: 5                          ...
     ...                                                           ...
     ...                                                             |
     | Prefix Information Option (RFC 4861) length: 4              ...
     ...                                                             |
     ...                                                             |

                                 Figure 2

3.2.  Router Behavior

   A router MAY send RAs containing one PvD option, but MUST NOT include
   more than one PvD option in each RA.  In particular, the PvD option
   MUST NOT contain further PvD options.

   The PvD Option MAY contain zero, one, or more RA options which would
   otherwise be valid as part of the same RA.  Such options are
   processed by PvD-aware hosts, while ignored by others.

   In order to provide multiple different PvDs, a router MUST send
   multiple RAs.  Different explicit PvDs MAY be advertised with RAs
   using the same IPv6 source address; but different implicit PvDs,
   advertised by different RAs, MUST use different link-local addresses
   because these implicit PvDs are identified by the source addresses of
   the RAs.

   As specified in [RFC4861], when the set of options causes the size of
   an advertisement to exceed the link MTU, multiple router
   advertisements can be sent, each containing a subset of the options.
   In such cases, the PvD option header (i.e., all fields except the
   'Options' field) MUST be repeated in all the transmitted RAs.  The
   options within the 'Options' field, MAY be transmitted only once,
   included in one of the transmitted PvD options.

3.3.  Non-PvD-aware Host Behavior

   As the PvD Option has a new option code, non-PvD-aware hosts will
   simply ignore the PvD Option and all the options it contains.  This
   ensure the backward compatibility required in section 3.3 of
   [RFC7556].  This behavior allows for a mixed-mode network with a mix
   of PvD-aware and non-PvD-aware hosts coexist.

3.4.  PvD-aware Host Behavior

   Hosts MUST associate received RAs and included configuration
   information (e.g., Router Valid Lifetime, Prefix Information
   [RFC4861], Recursive DNS Server [RFC8106], Routing Information
   [RFC4191] options) with the explicit PvD identified by the first PvD
   Option present in the received RA, if any, or with the implicit PvD
   identified by the host interface and the source address of the
   received RA otherwise.

   In case multiple PvD options are found in a given RA, hosts MUST
   ignore all but the first PvD option.

   If a host receives PvD options flags that it does not recognize
   (currently in the Reserved field), it MUST ignore these flags.

   Similarly, hosts MUST associate all network configuration objects
   (e.g., default routers, addresses, more specific routes, DNS
   Recursive Resolvers) with the PvD associated with the RA which last
   updated the object.  For example, addresses that are generated using
   a received Prefix Information option (PIO) are associated with the
   PvD of the last received RA which included the given PIO.

   PvD IDs MUST be compared in a case-insensitive manner (i.e., A=a),
   assuming ASCII with zero parity while non-alphabetic codes must match
   exactly (see also Section 3.1 of [RFC1035]).  For example,
   "" or "PvD.Example.coM." would refer to the same PvD.

   While resolving names, executing the default address selection
   algorithm [RFC6724] or executing the default router selection
   algorithm when forwarding packets ([RFC2461], [RFC4191] and
   [RFC8028]), hosts MAY consider only the configuration associated with
   an arbitrary set of PvDs.

   For example, a host MAY associate a given process with a specific
   PvD, or a specific set of PvDs, while associating another process
   with another PvD.  A PvD-aware application might also be able to
   select, on a per-connection basis, which PvDs should be used.  In
   particular, constrained devices such as small battery operated
   devices (e.g.  IoT), or devices with limited CPU or memory resources
   may purposefully use a single PvD while ignoring some received RAs
   containing different PvD IDs.

   The way an application expresses its desire to use a given PvD, or a
   set of PvDs, or the way this selection is enforced, is out of the
   scope of this document.  Useful insights about these considerations
   can be found in [I-D.kline-mif-mpvd-api-reqs].

3.4.1.  DHCPv6 configuration association

   When a host retrieves configuration elements using DHCPv6 (e.g.,
   addresses or DNS recursive resolvers), they MUST be associated with
   the explicit or implicit PvD of the RA received on the same
   interface, sent from the same LLA, and with the O-flag or M-flag set
   [RFC4861].  If no such PvD is found, or whenever multiple different
   PvDs are found, the host behavior is unspecified.

   This process requires hosts to keep track of received RAs, associated
   PvD IDs, and routers LLA; it also assumes that the router either acts
   as a DHCPv6 server or relay and uses the same LLA for DHCPv6 and RA
   traffic (which may not be the case when the router uses VRRP to send
   its RA).

3.4.2.  DHCPv4 configuration association

   When a host retrieves configuration elements from DHCPv4, they MUST
   be associated with the explicit PvD received on the same interface,
   whose PVD Options L-flag is set and, in the case of a non point-to-
   point link, using the same datalink address.  If no such PvD is
   found, or whenever multiple different PvDs are found, the
   configuration elements coming from DHCPv4 MUST be associated with the
   implicit PvD identified by the interface on which the DHCPv4
   transaction happened.  The case of multiple explicit PvD for an IPv4
   interface is undefined.

3.4.3.  Connection Sharing by the Host

   The situation when a host shares connectivity from an upstream
   interface (e.g. cellular) to a downstream interface (e.g.  WiFi)  Wi-Fi) is
   known as 'tethering'.  Techniques such as ND-proxy [RFC4389], 64share
   [RFC7278] or prefix delegation (e.g. using DHCPv6-PD [RFC8415]) may
   be used for that purpose.

   Whenever the RAs received from the upstream interface contain a PVD
   RA option, hosts that are sharing connectivity SHOULD include a PVD
   Option within the RAs sent downstream with:

      The same PVD-ID FQDN.

      The same H-bit, Delay and Sequence Number values.

      The L bit set whenever the host is sharing IPv4 connectivity
      received from the same upstream interface.

      The bits from the Reserved field set to 0.

   The values of the R-bit, Router Advertisement message header and
   Options field depend on whether the connectivity should be shared
   only with PvD-aware hosts or not (see Section 3.2).  In particular,
   all options received within the upstream PvD option and included in
   the downstream RA SHOULD be included in the downstream PvD option.

3.4.4.  Usage of DNS Servers

   PvD-aware hosts can be provisioned with recursive DNS servers via RA
   options passed within an explicit PvD, via RA options associated with
   an implicit PvD, via DHCPv6 or DHCPv4, or from some other
   provisioning mechanism that creates an implicit PvD (such as a VPN).
   In all of these cases, the DNS server addresses SHOULD be strongly
   associated with the corresponding PvD.  Specificially, queries sent
   to a configured recursive DNS server SHOULD be sent from a local IP
   address that belongs to the matching PvD.  Answers received from the
   DNS server SHOULD only be used on the same PvD.

   Maintaining the correct usage of DNS within PvDs avoids various
   practical errors, such as:

      A PvD associated with a VPN or otherwise private network may
      provide DNS answers that contain addresses inaccessible over
      another PvD.

      A PvD that uses a NAT64 [RFC6146] and DNS64 [RFC6147] will
      synthesize IPv6 addresses in DNS answers that are not globally
      routable, and cannot be used on other PvDs.  Conversely, an IPv4
      address resolved via DNS on another PvD cannot be directly used on
      a NAT64 network without the host synthesizing an IPv6 address.

4.  Provisioning Domain Additional Information

   Additional information about the network characteristics can be
   retrieved based on the PvD ID.  This set of information is called PvD
   Additional Information, and is encoded as a JSON object [RFC7159].

   The purpose of this additional set of information is to securely
   provide additional information to applications about the connectivity
   that is provided using a given interface and source address pair.  It
   typically includes data that would be considered too large, or not
   critical enough, to be provided within an RA option.  The information
   contained in this object MAY be used by the operating system, network
   libraries, applications, or users, in order to decide which set of
   PvDs should be used for which connection, as described in
   Section 3.4.

4.1.  Retrieving the PvD Additional Information

   When the H-flag of the PvD Option is set, hosts MAY attempt to
   retrieve the PvD Additional Information associated with a given PvD
   by performing an HTTP over TLS [RFC2818] GET query to https://<PvD-
   ID>/.well-known/pvd [RFC5785].  Inversely, hosts MUST NOT do so
   whenever the H-flag is not set.

   HTTP requests and responses for PvD additional information use the
   "application/pvd+json" media type (see Section 8).  Clients SHOULD
   include this media type as an Accept header in their GET requests,
   and servers MUST mark this media type as their Content-Type header in

   Note that the DNS name resolution of the PvD ID, the PKI checks as
   well as the actual query MUST be performed using the considered PvD.
   In other words, the name resolution, PKI checks, source address
   selection, as well as the next-hop router selection MUST be performed
   while using exclusively the set of configuration information attached
   with the PvD, as defined in Section 3.4.  In some cases, it may
   therefore be necessary to wait for an address to be available for use
   (e.g., once the Duplicate Address Detection or DHCPv6 processes are
   complete) before initiating the HTTP over TLS query.  If the host has
   a temporary address per [RFC4941] in this PvD, then hosts SHOULD use
   a temporary address to fetch the PvD Additional Information and
   SHOULD deprecate the used temporary address and generate a new
   temporary address afterward.

   If the HTTP status of the answer is greater than or equal to 400 the
   host MUST abandon and consider that there is no additional PvD
   information.  If the HTTP status of the answer is between 300 and
   399, inclusive, it MUST follow the redirection(s).  If the HTTP
   status of the answer is between 200 and 299, inclusive, the host MAY
   get a file containing a single JSON object.  When a JSON object could
   not be retrieved, an error message SHOULD be logged and/or displayed
   in a rate-limited fashion.

   After retrieval of the PvD Additional Information, hosts MUST keep
   track of the Sequence Number value received in subsequent RAs
   including the same PvD ID.  In case the new value is greater than the
   value that was observed when the PvD Additional Information object
   was retrieved (using serial number arithmetic comparisons [RFC1982]),
   or whenever the validity time included in the PVD Additional
   Information JSON object is expired, hosts MUST either perform a new
   query and retrieve a new version of the object, or, failing that,
   deprecate the object and stop using the additional information
   provided in the JSON object.

   Hosts retrieving a new PvD Additional Information object MUST check
   for the presence and validity of the mandatory fields specified in
   Section 4.3.  A retrieved object including an expiration time that is
   already past or missing a mandatory element MUST be ignored.

   In order to avoid synchronized queries toward the server hosting the
   PvD Additional Information when an object expires, object updates are
   delayed by a randomized backoff time.

      When a host performs an object update after it detected a change
      in the PvD Option Sequence number, it MUST delay the query by a
      random time between zero and 2**(Delay * 2) milliseconds, where
      'Delay' corresponds to the 4 bits long unsigned integer in the
      last received PvD Option.

      When a host last retrieved an object at time A including a
      validity time B, and is configured to keep the object up to date,
      it MUST perform the update at a uniformly random time in the
      interval [(B-A)/2,B].

   In the example Figure 2, the delay field value is 5, this means that
   host MUST delay the query by a random number between 0 and 2**(5 * 2)
   milliseconds, i.e., between 0 and 1024 milliseconds.

   Since the 'Delay' value is directly within the PvD Option rather than
   the object itself, an operator may perform a push-based update by
   incrementing the Sequence value while changing the Delay value
   depending on the criticality of the update and its PvD Additional
   Information servers capacity.

   The PvD Additional Information object includes a set of IPv6 prefixes
   (under the key "prefixes") which MUST be checked against all the
   Prefix Information Options advertised in the RA.  If any of the
   prefixes included in the PIO is not covered by at least one of the
   listed prefixes, the PvD associated with the tested prefix MUST be
   considered unsafe and MUST NOT be used.  While this does not prevent
   a malicious network provider, it does complicate some attack
   scenarios, and may help detecting misconfiguration.

4.2.  Operational Consideration to Providing the PvD Additional

   Whenever the H-flag is set in the PvD Option, a valid PvD Additional
   Information object MUST be made available to all hosts receiving the
   RA by the network operator.  In particular, when a captive portal is
   present, hosts MUST still be allowed to perform DNS, PKI and HTTP
   over TLS operations related to the retrieval of the object, even
   before logging into the captive portal.

   Routers MAY increment the PVD Option Sequence number in order to
   inform host that a new PvD Additional Information object is available
   and should be retrieved.

   The server providing the JSON files SHOULD also check whether the
   client address is part of the prefixes listed into the additional
   information and SHOULD return a 403 response code if there is no

4.3.  PvD Additional Information Format

   The PvD Additional Information is a JSON object.

   The following table presents the mandatory keys which MUST be
   included in the object:

   | JSON key | Description     | Type        | Example                |
   | name     | Human-readable  | UTF-8       | "Awesome Wifi" Wi-Fi"        |
   |          | service name    | string      |                        |
   |          |                 | [RFC3629]   |                        |
   | expires  | Date after      | [RFC3339]   | "2017-07-23T06:00:00Z" |
   |          | which this      |             |                        |
   |          | object is not   |             |                        |
   |          | valid           |             |                        |
   | prefixes | Array of IPv6   | Array of    | ["2001:db8:1::/48",    |
   |          | prefixes valid  | strings     | "2001:db8:4::/48"]     |
   |          | for this PVD    |             |                        |
   A retrieved object which does not include a valid string associated
   with the "name" key at the root of the object, or a valid date
   associated with the "expires" key, also at the root of the object,
   MUST be ignored.  In such cases, an error message SHOULD be logged
   and/or displayed in a rate-limited fashion.  If the PIO of the
   received RA is not covered by at least one of the "prefixes" key, the
   retrieved object SHOULD be ignored.

   The following table presents some optional keys which MAY be included
   in the object.

   | JSON key      | Description     | Type    | Example               |
   | localizedName | Localized user- | UTF-8   | "Wifi "Wi-Fi Genial"        |
   |               | visible service | string  |                       |
   |               | name, language  |         |                       |
   |               | can be selected |         |                       |
   |               | based on the    |         |                       |
   |               | HTTP Accept-    |         |                       |
   |               | Language header |         |                       |
   |               | in the request. |         |                       |
   | dnsZones      | DNS zones       | array   | ["","sub.e |
   |               | searchable and  | of DNS  |"]          |
   |               | accessible      | zones   |                       |
   | noInternet    | No Internet,    | boolean | true                  |
   |               | set when the    |         |                       |
   |               | PvD only        |         |                       |
   |               | provides        |         |                       |
   |               | restricted      |         |                       |
   |               | access to a set |         |                       |
   |               | of services     |         |                       |

   It is worth noting that the JSON format allows for extensions.
   Whenever an unknown key is encountered, it MUST be ignored along with
   its associated elements.

4.3.1.  Private Extensions


   Private-use or experimental keys starting with "x-" are reserved for private use and can MAY be
   utilized to provide information that is specific used in the JSON dictionary.
   In order to vendor, user avoid such keys colliding with IANA registry keys,
   implementers or
   enterprise.  It vendors defining private-use or experimental keys
   MUST create sub-dictionaries, where the sub-dictionary is RECOMMENDED to use one added into
   the top-level JSON dictionary with a key of the patterns "x-FQDN-
   KEY" or "x-PEN-KEY" format "vendor-*"
   where FQDN the "*" is replaced by the implementers or vendors
   denomination.  Upon receiving such a fully qualified domain name sub-dictionary, host MUST ignore
   this sub-dictionary if it is unknown.  When the vendor or
   PEN implementor
   is a private enterprise number [PEN] under control part of an IANA URN namespace [URN], the author
   of URN namespace SHOULD be
   used rather than the extension to avoid collisions.

4.3.2. "vendor-*" format.

4.3.1.  Example

   Here are two

   The following examples based on show how the JSON keys defined in this section.
   document can be used:

     "name": "Foo Wireless",
     "localizedName": "Foo-France Wifi", Wi-Fi",
     "expires": "2017-07-23T06:00:00Z",
     "prefixes" : ["2001:db8:1::/48", "2001:db8:4::/48"],

     "name": "Bar 4G",
     "localizedName": "Bar US 4G",
     "expires": "2017-07-23T06:00:00Z",
     "prefixes": ["2001:db8:1::/48", "2001:db8:4::/48"],

     "name": "Company Network",
     "localizedName": "Company Network",
     "expires": "2017-07-23T06:00:00Z",
     "prefixes": ["2001:db8:1::/48", "2001:db8:4::/48"],
     "vendor-foo": { "private-key": "private-value" },

4.4.  Detecting misconfiguration and misuse

   When a host retrieves the PvD Additional Information, it MUST verify
   that the TLS server certificate is valid for the performed request
   (e.g., that the Subject Name is equal to the PvD ID expressed as an
   FQDN).  This authentication creates a secure binding between the
   information provided by the trusted Router Advertisement, and the
   HTTPS server.  However, this does not mean the Advertising Router and
   the PvD server belong to the same entity.

   Hosts MUST verify that all prefixes in the RA PIO are covered by a
   prefix from the PvD Additional Information.  An adversarial router
   willing to fake the use of a given explicit PvD, without any access
   to the actual PvD Additional Information, would need to perform NAT66
   in order to circumvent this check.

   It is also RECOMMENDED that the HTTPS server checks the IPv6 source
   addresses of incoming connections (see Section 4.1).  This check give
   reasonable assurance that neither NPTv6 [RFC6296] nor NAT66 were used
   and restricts the information to the valid network users.

   Note that this check cannot be performed when the HTTPS query is
   performed over IPv4.  Therefore, the PvD ID FQDN SHOULD NOT have a
   DNS A record whenever all hosts using the given PvD have IPv6

5.  Operational Considerations

   This section describes some use cases of PvD.  For the sake of
   simplicity, the RA messages will not be described in the usual ASCII
   art but rather in an indented list.  For example, a RA message
   containing some options and a PvD option that also contains other
   options will be described as:

   o  RA Header: router lifetime = 6000

   o  Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64

   o  PvD Option header: length = 3 + 5 + 4 , PvD ID FQDN =, R-flag = 0 (actual length of the header with padding
      24 bytes = 3 * 8 bytes)

      *  Recursive DNS Server: length = 5, addresses=
         [2001:db8:cafe::53, 2001:db8:f00d::53]

      *  Prefix Information Option: length = 4, prefix =

   It is expected that for some years, networks will have a mixed
   environment of PvD-aware hosts and non-PvD-aware hosts.  If there is
   a need to give specific information to PvD-aware hosts only, then it
   is recommended to send TWO RA messages: one for each class of hosts.
   For example, here is the RA for non-PvD-aware hosts:

   o  RA Header: router lifetime = 6000 (non-PvD-aware hosts will use
      this router as a default router)

   o  Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64

   o  Recursive DNS Server Option: length = 3, addresses=

   o  PvD Option header: length = 3 + 2, PvD ID FQDN =,
      R-flag = 1 (actual length of the header 24 bytes = 3 * 8 bytes)

      *  RA Header: router lifetime = 0 (PvD-aware hosts will not use
         this router as a default router), implicit length = 2

   And here is a RA example for PvD-aware hosts:

   o  RA Header: router lifetime = 0 (non-PvD-aware hosts will not use
      this router as a default router)

   o  PvD Option header: length = 3 + 2 + 4 + 3, PvD ID FQDN =, R-flag = 1 (actual length of the header 24 bytes = 3
      * 8 bytes)

      *  RA Header: router lifetime = 1600 (PvD-aware hosts will use
         this router as a default router), implicit length = 2

      *  Prefix Information Option: length = 4, prefix =

      *  Recursive DNS Server Option: length = 3, addresses=

   In the above example, non-PvD-aware hosts will only use the first RA
   sent from their default router and using the 2001:db8:cafe::/64
   prefix.  PvD-aware hosts will autonomously configure addresses from
   both PIOs, but will only use the source address in 2001:db8:f00d::/64
   to communicate past the first hop router since only the router
   sending the second RA will be used as default router; similarly, they
   will use the DNS server 2001:db8:f00d::53 when communicating with
   this adress.

6.  Security Considerations

   Although some solutions such as IPsec or SeND [RFC3971] can be used
   in order to secure the IPv6 Neighbor Discovery Protocol, in practice
   actual deployments largely rely on link layer or physical layer
   security mechanisms (e.g. 802.1x [IEEE8021X]) in conjunction with RA
   Guard [RFC6105].

   This specification does not improve the Neighbor Discovery Protocol
   security model, but extends the purely link-local trust relationship
   between the host and the default routers with HTTP over TLS
   communications which servers are authenticated as rightful owners of
   the FQDN received within the trusted PvD ID RA option.

   It must be noted that Section 4.4 of this document only provides
   reasonable assurance against misconfiguration but does not prevent an
   hostile network access provider to advertize wrong information that
   could lead applications or hosts to select an hostile PvD.  Users
   should always apply caution when connecting to an unknown network.

7.  Privacy Considerations

   Retrieval of the PvD Additional Information over HTTPS requires early
   communications between the connecting host and a server which may be
   located further than the first hop router.  Although this server is
   likely to be located within the same administrative domain as the
   default router, this property can't be ensured.  Therefore, hosts
   willing to retrieve the PvD Additional Information before using it
   without leaking identity information, SHOULD make use of an IPv6
   Privacy Address and SHOULD NOT include any privacy sensitive data,
   such as User Agent header or HTTP cookie, while performing the HTTP
   over TLS query.

   From a privacy perspective, retrieving the PvD Additional Information
   is not different from establishing a first connection to a remote
   server, or even performing a single DNS lookup.  For example, most
   operating systems already perform early queries to well known web
   sites, such as, in
   order to detect the presence of a captive portal.

   There may be some cases where hosts, for privacy reasons, should
   refrain from accessing servers that are located outside a certain
   network boundary.  In practice, this could be implemented as a
   whitelist of 'trusted' FQDNs and/or IP prefixes that the host is
   allowed to communicate with.  In such scenarios, the host SHOULD
   check that the provided PvD ID, as well as the IP address that it
   resolves into, are part of the allowed whitelist.

8.  IANA Considerations

   Upon publication of this document, IANA is asked to remove the
   'reclaimable' tag off the value 21 for the PvD option (from the IPv6
   Neighbor Discovery Option Formats registry).

   IANA is asked to assign the value "pvd" from the Well-Known URIs

8.1.  Additional Information PvD Keys Registry

   IANA is asked to create and maintain a new registry called
   "Additional Information PvD Keys", which will reserve JSON keys for
   use in PvD additional information.  The initial contents of this
   registry are given in Section 4.3.

   New assignments for Additional Information PvD Keys Registry will be
   administered by IANA through Expert Review RFC8126 [RFC8126].

8.2.  PvD Option Flags Registry

   IANA is also asked to create and maintain a new registry entitled
   "PvD Option Flags" reserving bit positions from 0 to 15 to be used in
   the PvD option bitmask.  Bit position 0, 1 and 2 are reserved by this
   document (as specified in Figure 1).  Future assignments require
   Standards Action RFC8126 [RFC8126], via a Standards Track RFC

8.3.  PvD JSON Media Type Registration

   This document registers the media type for PvD JSON text,

   Type Name: application

   Subtype Name: pvd+json

   Required parameters: None

   Optional parameters: None

   Encoding considerations: Encoding considerations are identical to
   those specified for the "application/json" media type.

   Security considerations: See Section 6.

   Interoperability considerations: This document specifies format of
   conforming messages and the interpretation thereof.

   Published specification: This document

   Applications that use this media type: This media type is intended to
   be used by network advertising additional Provisioning Domain
   information, and clients looking up such information.

   Additional information: None

   Person and email address to contact for further information: See
   Authors' Addresses section

   Intended usage: COMMON

   Restrictions on usage: None

   Author: IETF

   Change controller: IETF

9.  Acknowledgements

   Many thanks to M.  Stenberg and S.  Barth for their earlier work:
   [I-D.stenberg-mif-mpvd-dns], as well as to Basile Bruneau who was
   author of an early version of this document.

   Thanks also to Marcus Keane, Mikael Abrahamsson, Ray Bellis, Zhen
   Cao, Tim Chow, Lorenzo Colitti, Michael Di Bartolomeo, Ian Farrer,
   Phillip Hallam-Baker, Bob Hinden, Tatuya Jinmei, Erik Kline, Ted
   Lemon, Jen Lenkova, Veronika McKillop, Mark Townsley and James
   Woodyatt for useful and interesting discussions. discussions and reviews.

   Finally, special thanks to Thierry Danis and Wenqin Shao for their
   valuable inputs and implementation efforts ([github]), Tom Jones for
   his integration effort into the NEAT project and Rigil Salim for his
   implementation work.

10.  References

10.1.  Normative references

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <>.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              DOI 10.17487/RFC1982, August 1996,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              DOI 10.17487/RFC2461, December 1998,

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818,
              DOI 10.17487/RFC2818, May 2000,

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

10.2.  Informative references

   [github]   Cisco, "IPv6-mPvD github repository",

              Kline, E., "Multiple Provisioning Domains API
              Requirements", draft-kline-mif-mpvd-api-reqs-00 (work in
              progress), November 2015.

              Stenberg, M. and S. Barth, "Multiple Provisioning Domains
              using Domain Name System", draft-stenberg-mif-mpvd-dns-00
              (work in progress), October 2015.

              IEEE, "IEEE Standards for Local and Metropolitan Area
              Networks: Port based Network Access Control, IEEE Std".

   [PEN]      IANA, "Private Enterprise Numbers",

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
              November 2005, <>.

   [RFC4389]  Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery
              Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April
              2006, <>.

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              DOI 10.17487/RFC5785, April 2010,

   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
              DOI 10.17487/RFC6105, February 2011,

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <>.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              DOI 10.17487/RFC6147, April 2011,

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,

   [RFC6724]  Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,

   [RFC7278]  Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6
              /64 Prefix from a Third Generation Partnership Project
              (3GPP) Mobile Interface to a LAN Link", RFC 7278,
              DOI 10.17487/RFC7278, June 2014,

   [RFC7556]  Anipko, D., Ed., "Multiple Provisioning Domain
              Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,

   [RFC8028]  Baker, F. and B. Carpenter, "First-Hop Router Selection by
              Hosts in a Multi-Prefix Network", RFC 8028,
              DOI 10.17487/RFC8028, November 2016,

   [RFC8106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 8106, DOI 10.17487/RFC8106, March 2017,

   [RFC8415]  Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
              Richardson, M., Jiang, S., Lemon, T., and T. Winters,
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              RFC 8415, DOI 10.17487/RFC8415, November 2018,

   [URN]      IANA, "URN Namespaces", <

Appendix A.  Changelog

   Note to RFC Editors: Remove this section before publication.

A.1.  Version 00

   Initial version of the draft.  Edited by Basile Bruneau + Eric Vyncke
   and based on Basile's work.

A.2.  Version 01

   Major rewrite intended to focus on the the retained solution based on
   corridors, online, and WG discussions.  Edited by Pierre Pfister.
   The following list only includes major changes.

      PvD ID is an FQDN retrieved using a single RA option.  This option
      contains a sequence number for push-based updates, a new H-flag,
      and a L-flag in order to link the PvD with the IPv4 DHCP server.

      A lifetime is included in the PvD ID option.

      Detailed Hosts and Routers specifications.

      Additional Information is retrieved using HTTP-over-TLS when the
      PvD ID Option H-flag is set.  Retrieving the object is optional.

      The PvD Additional Information object includes a validity date.

      DNS-based approach is removed as well as the DNS-based encoding of
      the PvD Additional Information.

      Major cut in the list of proposed JSON keys.  This document may be
      extended later if need be.

      Monetary discussion is moved to the appendix.

      Clarification about the 'prefixes' contained in the additional

      Clarification about the processing of DHCPv6.

A.3.  Version 02

      The FQDN is now encoded with ASCII format (instead of DNS binary)
      in the RA option.

      The PvD ID option lifetime is removed from the object.

      Use well known URI "https://<PvD-ID>/.well-known/pvd"

      Reference RFC3339 for JSON timestamp format.

      The PvD ID Sequence field has been extended to 16 bits.

      Modified host behavior for DHCPv4 and DHCPv6.

      Removed IKEv2 section.

      Removed mention of RFC7710 Captive Portal option.  A new I.D.
      will be proposed to address the captive portal use case.

A.4.  WG Document version 00

      Document has been accepted as INTAREA working group document

      IANA considerations follow RFC8126 [RFC8126]

      PvD ID FQDN is encoded as per RFC 1035 [RFC1035]

      PvD ID FQDN is prepended by a one-byte length field

      Marcus Keane added as co-author

      dnsZones key is added back
      draft of a privacy consideration section and added that a
      temporary address should be used to retrieve the PvD additional

      per Bob Hinden's request: the document is now aiming at standard
      track and security considerations have been moved to the main

A.5.  WG Document version 01

      Removing references to 'metered' and 'characteristics' keys.
      Those may be in scope of the PvD work, but this document will
      focus on essential parts only.

      Removing appendix section regarding link quality and billing

      The PvD RA Option may now contain other RA options such that PvD-
      aware hosts may receive configuration information otherwise
      invisible to non-PvD-aware hosts.

      Clarify that the additional PvD Additional Information is not
      intended to modify host's networking stack behavior, but rather
      provide information to the Application, used to select which PvDs
      must be used and provide configuration parameters to the transport

      The RA option padding is used to increase the option size to the
      next 64 (was 32) bits boundary.

      Better detail the Security model and Privacy considerations.

A.6.  WG Document version 02

      Use the IANA value of 21 in the text and update the IANA
      considerations section accordingly

      add the Delay field to avoid the thundering herd effect

      add Wenqin Shao as author

      keep the 1 PvD per RA model

      changed the intro (per Zhen Cao) "when choosing which PvD and
      transport should be used" => "when choosing which PvD should be

      rename A-flag in R-flag to avoid A-flag of PIO
      use the wording "PvD Option", removing the ID token as it is now a
      container with more then just an ID, removing 'RA' in the option
      name to be consistent with other IANA NDP option

      use "non-PvD-aware" rather than "PvD-ignorant"

      added more reference to RFC 7556 (notably for PvD being globally
      unique, introducing PvD-aware host vs. PvD-aware node)

      Section 3.4.3 renamed from "interconnection shared by node" to
      'connection shared by node"

      Section 3.4 renamed into "PvD-aware Host Behavior"

      Added a section "Non-PvD-aware Host Behavior"

A.7.  WG Document version 04

      Updated reference for DHCPv6-PD from RFC 3633 to RFC 8415.

      Enhanced IANA considerations to clarify review process and new

      Added a section on considerations for handling DNS on a PvD-aware

A.7.1.  WG Document version 05

      Fixed nits about IPSEC and WiFi

      Added use case per Phillip Hallam-Baker

      Clarified some sentences

Authors' Addresses

   Pierre Pfister
   11 Rue Camille Desmoulins
   Issy-les-Moulineaux  92130

   Eric Vyncke (editor)
   De Kleetlaan, 6
   Diegem  1831


   Tommy Pauly
   One Apple Park Way
   Cupertino, California  95014


   David Schinazi
   Google LLC
   1600 Amphitheatre Parkway
   Mountain View, California  94043


   Wenqin Shao
   11 Rue Camille Desmoulins
   Issy-les-Moulineaux  92130