intarea P. Pfister
Internet-Draft E. Vyncke, Ed.
Intended status: Standards Track Cisco
Expires: December 20, 2019 T. Pauly
D. Schinazi
Google LLC
W. Shao
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 working documents as Internet-Drafts. The list of current Internet-Drafts is at

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 December 20, 2019.

Copyright Notice

Copyright (c) 2019 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 ( 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 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

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", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

In addition, this document uses the following terminology:

Provisioning Domain (PvD):
A set of network configuration information; for more information, see [RFC7556].
A Fully Qualified Domain Name (FQDN) used to identify a PvD.
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 [RFC7556].

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.
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 sender MUST set the 'Type' to 134, the value for "Router Advertisement", and set the 'Code' to 0. Receivers MUST ignore both of these fields. The 'Checksum' MUST be set to 0 by the sender; non-zero checksums MUST be ignored by the receiver. 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. 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: 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.

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

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:

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 responses.

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.

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 Information

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 match.

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 service name UTF-8 string [RFC3629] "Awesome Wi-Fi"
expires Date after which this object is not valid [RFC3339] "2017-07-23T06:00:00Z"
prefixes Array of IPv6 prefixes valid for this PVD Array of strings ["2001:db8:1::/48", "2001:db8:4::/48"]

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-visible service name, language can be selected based on the HTTP Accept-Language header in the request. UTF-8 string "Wi-Fi Génial"
dnsZones DNS zones searchable and accessible array of DNS zones ["",""]
noInternet No Internet, set when the PvD only provides restricted access to a set of services boolean true

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.

Private-use or experimental keys MAY be used in the JSON dictionary. In order to avoid such keys colliding with IANA registry keys, implementers or vendors defining private-use or experimental keys MUST create sub-dictionaries, where the sub-dictionary is added into the top-level JSON dictionary with a key of the format "vendor-*" where the "*" is replaced by the implementers or vendors denomination. Upon receiving such a sub-dictionary, host MUST ignore this sub-dictionary if it is unknown. When the vendor or implementor is part of an IANA URN namespace [URN], the URN namespace SHOULD be used rather than the "vendor-*" format.

4.3.1. Example

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

  "name": "Foo Wireless",
  "localizedName": "Foo-France 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 connectivity.

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:

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:

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

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 registry.

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.

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, via a Standards Track RFC document.

8.3. PvD JSON Media Type Registration

This document registers the media type for PvD JSON text, "application/pvd+json".

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 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., "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"
[I-D.kline-mif-mpvd-api-reqs] Kline, E., "Multiple Provisioning Domains API Requirements", Internet-Draft draft-kline-mif-mpvd-api-reqs-00, November 2015.
[I-D.stenberg-mif-mpvd-dns] Stenberg, M. and S. Barth, "Multiple Provisioning Domains using Domain Name System", Internet-Draft draft-stenberg-mif-mpvd-dns-00, October 2015.
[IEEE8021X] IEEE, "IEEE Standards for Local and Metropolitan Area Networks: Port based Network Access Control, IEEE Std"
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002.
[RFC3971] Arkko, J., 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., 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., "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.

A.3. Version 02

A.4. WG Document version 00

A.5. WG Document version 01

A.6. WG Document version 02

A.7. WG Document version 04

A.7.1. WG Document version 05

Authors' Addresses

Pierre Pfister Cisco 11 Rue Camille Desmoulins Issy-les-Moulineaux, 92130 France EMail:
Eric Vyncke (editor) Cisco De Kleetlaan, 6 Diegem, 1831 Belgium EMail:
Tommy Pauly Apple One Apple Park Way Cupertino, California 95014 USA EMail:
David Schinazi Google LLC 1600 Amphitheatre Parkway Mountain View, California 94043 USA EMail:
Wenqin Shao Cisco 11 Rue Camille Desmoulins Issy-les-Moulineaux, 92130 France EMail: