draft-reddy-add-enterprise-split-dns-07.txt

ADD                                                             T. Reddy
Internet-Draft                                                    Akamai
Intended status: Standards Track                                 D. Wing
Expires: May 9, 2022                                              Citrix
                                                                K. Smith
                                                                Vodafone
                                                        November 5, 2021


                    Split-Horizon DNS Configuration
                draft-reddy-add-enterprise-split-dns-07

Abstract

   When split-horizon DNS is deployed by a network, certain domains are
   only resolvable by querying the network-designated DNS server rather
   than a public DNS server.  DNS clients which use DNS servers not
   provided by the network need to route those DNS domain queries to the
   network-designated DNS server.  This document informs DNS clients of
   split-horizon DNS, their DNS domains, and is compatible with
   encrypted DNS.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on May 9, 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Split DNS . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Provisioning Domains dnsZones . . . . . . . . . . . . . . . .   4
     4.1.  Authority over the Domains  . . . . . . . . . . . . . . .   5
   5.  An example of Split-Horizon DNS Configuration . . . . . . . .   6
   6.  Split DNS Configuration for IKEv2 . . . . . . . . . . . . . .   9
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Historically, an endpoint would utilize network-designated DNS
   servers upon joining a network (e.g., DHCP OFFER, IPv6 Router
   Advertisement).  While it has long been possible to configure
   endpoints to ignore the network's suggestions and use a public DNS
   server on the Internet, this was seldom used because some networks
   block UDP/53 in order to enforce their own DNS policies.  Also, there
   has been an increase in the availability of "public resolvers"
   [RFC8499] which DNS clients may be pre-configured to use instead of
   the default network resolver for a variety of reasons (e.g., offer a
   good reachability, support an encrypted transport, provide a claimed
   privacy policy, (lack of) filtering).  With the advent of DoT and
   DoH, the endpoint is unable to properly resolve split-horizon DNS
   domains which must query the network-designated DNS server.

   This document specifies a mechanism to indicate which DNS zones are
   used for split-horizon DNS.  DNS clients can discover and
   authenticate DNS servers provided by the network, for example using
   the techniques proposed in [I-D.ietf-add-dnr] and [I-D.ietf-add-ddr].

   The scope of the specification is split-horizon DNS names, which are
   not domains reserved for special use like ".local".  Using these
   domains are difficult because bookmarks, advertising, and human
   behavior would need to change so that the special domains only work



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   when connected to the correct network, which is difficult for users
   to discern on most endpoints.  Furthermore, as special domains cannot
   obtain certificates from a public CA, authenticated TLS connections
   to those servers are fraught with (Trust on First Use) and
   certificate warnings, a longstanding problem in the industry.

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 BCP
   14 [RFC2119][RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document makes use of the terms defined in [RFC8499].  The terms
   "Private DNS", "Global DNS" and "Split DNS" are defined in [RFC8499].

   'Encrypted DNS' refers to a DNS protocol that provides an encrypted
   channel between a DNS client and server (e.g., DoT, DoH, or DoQ).

3.  Split DNS

   [RFC2826] "does not preclude private networks from operating their
   own private name spaces" but notes that if private networks "wish to
   make use of names uniquely defined for the global Internet, they have
   to fetch that information from the global DNS naming hierarchy".

   There are various DNS deployments outside of the global DNS,
   including "split horizon" deployments and DNS usages on private (or
   virtual private) networks.  In a split horizon, an authoritative
   server gives different responses to queries from the Internet than
   they do to network-designated DNS servers; while some deployments
   differentiate internal queries from public queries by the source IP
   address, the concerns in Section 3.1.1 of [RFC6950] relating to
   trusting source IP addresses apply to such deployments.

   When the internal address space range is private [RFC1918], this
   makes it both easier for the server to discriminate public from
   private and harder for public entities to impersonate nodes in the
   private network.  The use cases that motivate split-horizon DNS
   typically involve restricting access to some network services --
   intranet resources such as internal web sites, development servers,
   or directories, for example -- while preserving the ease of use
   offered by domain names for internal users.

   A typical use case is an Enterprise network that requires one or more
   DNS domains to be resolved via network-designated DNS servers.  This
   can be a special domain, such as "corp.example.com" for an enterprise



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   that is publicly known to use "example.com".  In this case, the
   endpoint needs to be informed what the private domain names are and
   what the IP addresses of the network-designated DNS servers are.  An
   Enterprise can also run a different version of its global domain on
   its internal network.  In that case, the client is instructed to send
   DNS queries for the enterprise public domain (e.g., "example.com") to
   the network-designated DNS servers.  A configuration for this
   deployment scenario is referred to as a Split DNS configuration.
   Another use case for split-horizon DNS is Cellular and Fixed-access
   networks (ISPs) typically offer private domains, including account
   status/controls, and free education initiatives [INS].

4.  Provisioning Domains dnsZones

   As discussed in Section 3, internal resources in a network tend to
   have private DNS names.  A network can also run a different version
   of its global domain on its internal network, and require the use of
   network-designated DNS servers to get resolved.

   Provisioning Domains (PvDs) are defined in [RFC7556] as sets of
   network configuration information that clients can use to access
   networks, including rules for DNS resolution and proxy configuration.
   The PvD Key dnsZones is defined in [RFC8801].  The PvD Key dnsZones
   adds support for DNS domains for which the network claims authority,
   and which are intended to be resolved using network-designated DNS
   servers.  The private domains in dnsZones are only reachable by
   devices attached and authenticated to the network.  The global
   domains specified in the dnsZones key have a different version in the
   internal network.  DNS resolution for other domains remains
   unchanged.

   For each dnsZones entry, the client can use the network-designated
   DNS servers to resolve the listed domains and its subdomains.  Other
   domain names may be resolved using some other DNS servers that are
   configured independently.  For example, if the dnsZones key specifies
   "example.test", then "example.test", "www.example.test", and
   "mail.eng.example.test" can be resolved using the network-designated
   DNS resolver(s), but "otherexample.test" and "ple.test" can be
   resolved using the system's public resolver(s).

   [RFC8801] defines a mechanism for discovering multiple Explicit PvDs
   on a single network and their Additional Information by means of an
   HTTP-over-TLS query using a URI derived from the PvD ID.  This set of
   additional configuration information is referred to as a Web
   Provisioning Domain (Web PvD).  The PvD RA option defined in
   [RFC8801] SHOULD set the H-flag to indicate that Additional
   Information is available.  This Additional Information JSON object




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   SHOULD include the "dnsZones" key to define the DNS domains for which
   the network claims authority.

4.1.  Authority over the Domains

   To comply with [RFC2826] the split-horizon DNS zone must either not
   exist in the global DNS hierarchy or must be authoritatively
   delegated to the split-horizon DNS server to answer.  The DNS root
   zone (".") MUST be ignored if it appears in dnsZones.  Other generic
   or global domains, such as Top-Level Domains (TLDs), similarly MUST
   be ignored if they appear in dnsZones.

   The client can use the mechanism described in [I-D.ietf-add-dnr] to
   discover the network-designated resolvers.  To determine if the
   network-designated encrypted resolvers are authoritative over the
   domains in DnsZones, the client performs the following steps for each
   domain in DnsZones:

   1.  The client sends an NS query for the domain in DnsZones.  This
       query MUST only be sent over encrypted DNS session to a public
       resolver that is configured independently.  A DNSSEC-validating
       client SHOULD apply the same validation policy to the NS query as
       it does to other queries.  A client that does not validate DNSSEC
       SHOULD apply the same policy (if any) to the NS query as it does
       to other queries.

   2.  The client checks that the NS RRset matches any one of the
       Authentication Domain Names (ADNs) of the discovered network-
       designated encrypted DNS resolvers.

       A.  If the match fails and no ADN of the discovered network-
           designated encrypted DNS resolvers is a subdomain of NS
           RRset, the client determines the network is not authoritative
           for the indicated domain.  It might log an error, reject the
           network entirely (because the network lied about its
           authority over a domain) or other action.

       B.  If the match fails but any one of the ADNs of the discovered
           network-designated encrypted DNS resolvers is a subdomain of
           NS RRset, the client can then establish a TLS connection to
           that network-designated resolver.  The client follows the
           mechanism discussed in Section 8 of [RFC8310] to authenticate
           the DNS server certificate using the ADN and checks if at
           least one of the values in subjectAltName matches NS RRset.
           If the server certificate validation and match succeeds, the
           client can subsequently resolve the domains in that subtree
           using the network-designated resolver.  If the server




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           certificate does not validate or match fails, the client can
           proceed as discussed in step 2 (A).

       C.  If the match succeeds, the client can then establish a TLS
           connection to that network-designated resolver.  The client
           follows the mechanism discussed in Section 8 of [RFC8310] to
           authenticate the DNS server certificate using the ADN.

           +  If the server certificate does not validate and a secure
              connection cannot be established to the network designated
              resolver, the client can proceed as discussed in step 2
              (A).

           +  If the server certificate validation is successful and a
              secure connection is established, the client can
              subsequently resolve the domains in that subtree using the
              network-designated resolver.

   3.  As an exception to this rule, the client need not perform the
       above validation for domains reserved for special use [RFC6761]
       or [RFC6762] such as ".home.arpa" or ".local".

   4.  Authenticated denial of existence using NSEC3 or NSEC records can
       be used by a client to identify that the domain name does not
       exist in the global DNS.

   For example, if in a network the private domain names are defined
   under "internal.corp1.example.com".  The DnsZones PvD Key would
   indicate that "*.internal.corp1.example.com" are private domain
   names.  The client can trigger a NS query of
   "internal.corp1.example.com" and the NS RRset returns that the
   nameserver is "ns1.corp2.example.com".  The client would then connect
   to the network-designated encrypted resolver whose name is
   "ns1.corp2.example.com", authenticate it using server certificate
   validation in TLS handshake, and use it for resolving the domains in
   the subtree of "*.internal.corp1.example.com".

5.  An example of Split-Horizon DNS Configuration

   In a network the apex domain name is "example.com", which runs a
   different version of its global domain on its internal network.
   Today, on the Internet it publishes two NS records, "ns1.example.com"
   and "ns2.example.com".

   To add support for the mechanism described in this document, the
   network and endpoints first need to support [I-D.ietf-add-dnr] and
   [RFC8801].  Then, for each site the administrator would add DNS
   server names which end in "ns1.example.com" or "ns2.example.com" (the



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   names published on the Internet).  Also on its internal network, it
   uses a geographic naming scheme for its internal nameservers with a
   "service dot location" naming scheme.  Assuming its two geographies
   are "us" and "uk".  So the UK site would add "ns1.uk.ns1.example.com"
   and "ns2.uk.ns2.example.com".  Note that these names can be added in
   addition to more traditional names that might already exist for those
   DNS servers (e.g., the common "service dot location" such as
   "ns1.uk.example.com").  All of those names would be advertised to the
   endpoints as described in [I-D.ietf-add-dnr].

   The endpoints compliant with this specification can then determine
   the network's internal nameservers are owned and managed by the same
   entity that has published the NS records on the Internet, as
   described in the following paragraphs:

   Continuing with the UK site as the example, the endpoint will join
   the network, obtain an IPv6 address, and using [I-D.ietf-add-dnr]
   will discover the resolvers "ns1.uk.ns1.example.com" and
   "ns2.uk.ns2.example.com" and their IP addresses.  Using [RFC8801]
   (which utilizes IPv6 Router Advertisments), the endpoint will also
   discover the PvD FQDN is "pvd.uk.example.com".

   Continuing with the UK site as the example, the endpoint performs the
   following steps corresponding with the call flow diagram numbers:

   Steps 1-2:  The client joins the network, obtain an IP address, and
      using [I-D.ietf-add-dnr] will discover the resolvers
      "ns1.uk.ns1.example.com" and "ns2.uk.ns1.example.com" and their IP
      addresses.  Using [RFC8801], the endpoint will also discover the
      PvD FQDN is "pvd.uk.example.com".

   Steps 3-7:  The client establishes an encrypted DNS connection with
      "ns1.uk.ns1.example.com", validates its TLS certificate, and
      queries it for "pvd.uk.example.com" to retrieve the PvD JSON
      object.  Note that [RFC8801] in Section 4.1 mandates the PvD FQDN
      MUST be resolved using the DNS servers indicated by the associated
      PvD.  The PvD contains:

    {
       "identifier": "pvd.uk.example.com",
       "expires": "2020-05-23T06:00:00Z",
       "prefixes": ["2001:db8:1::/48", "2001:db8:4::/48"],
       "dnsZones:": ["example.com"]
     }

      The JSON keys "identifier", "expires", and "prefixes" are defined
      in [RFC8801].




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   Steps 8-9:  The client then uses an encrypted DNS connection to a
      public resolver (e.g., 1.1.1.1) to issue NS queries for the
      domains in dnsZones.  The NS lookup for "example.com" will return
      "ns1.example.com" and "ns2.example.com".

   Step 10:  As the network-provided nameservers are subdomains of those
      names retrieved from the public resolver and the network-
      designated resolver's certificate includes at least one of the
      names retrieved from the public resolver, the client has finished
      validation that the nameservers signaled in [I-D.ietf-add-dnr] and
      [RFC8801] are owned and managed by the same entity that published
      the NS records on the Internet.  The endpoint will then use that
      information from [I-D.ietf-add-dnr] and [RFC8801] to resolve names
      within dnsZones.

   Figure 1 is a simple call flow diagram of the example discussed
   above.

+---------+                   +-------------------+  +------------+ +---------+ +---------+
| client  |                   | Network           |  | Network    | | Router  | | public  |
|         |                   | encrypted resolvr |  | PvD server | |         | | resolvr |
+---------+                   +-------------------+  +------------+ +---------+ +---------+
     |                                          |         |          |           |
     | Router Solicitation (1)                  |         |          |           |
     |-------------------------------------------------------------->|           |
     |                                          |         |          |           |
     |       Router Advertisement with DNR hostnames & PvD FQDN (2)  |           |
     |<--------------------------------------------------------------|           |
     | -------------------------------------\   |         |          |           |
     |-| now knows DNR hostnames & PvD FQDN |   |         |          |           |
     | |------------------------------------|   |         |          |           |
     |                                          |         |          |           |
     | TLS connection (3)                       |         |          |           |
     |----------------------------------------->|         |          |           |
     | ---------------------------\             |         |          |           |
     |-| validate TLS certificate |             |         |          |           |
     | |--------------------------|             |         |          |           |
     |                                          |         |          |           |
     | resolve pvd.uk.example.com  (4)          |         |          |           |
     |----------------------------------------->|         |          |           |
     |                                          |         |          |           |
     |                         AAAA records (5) |         |          |           |
     |<-----------------------------------------|         |          |           |
     |                                          |         |          |           |
     | https://pvd.uk.example.com/.well-known/pvd (6)     |          |           |
     |--------------------------------------------------->|          |           |
     |                                          |         |          |           |
     |       200 OK (JSON Additional Information) (7)     |          |           |



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     |<---------------------------------------------------|          |           |
     | -----------------------\                 |         |          |           |
     |-| dnsZones=example.com |                 |         |          |           |
     | |----------------------|                 |         |          |           |
     |                                          |         |          |           |
     | TLS connection                           |         |          |           |
     |-------------------------------------------------------------------------->|
     | ---------------------------\             |         |          |           |
     |-| validate TLS certificate |             |         |          |           |
     | |--------------------------|             |         |          |           |
     |                                          |         |          |           |
     | NS? example.com  (8)                     |         |          |           |
     |-------------------------------------------------------------------------->|
     |                                          |         |          |           |
     |                               NS=ns1.example.com, ns2.example.com (9)     |
     |<--------------------------------------------------------------------------|
     | -------------------------------\         |         |          |           |
     |-| ns1.uk.ns1.example.com is    |         |         |          |           |
     | | subdomain of ns1.example.com |         |         |          |           |
     | ----------------------\--------|         |         |          |           |
     |-| finished validation |                  |         |          |           |
     | |---------------------|                  |         |          |           |
     |                                          |         |          |           |
     |  use network-designated resolver         |         |          |           |
     |  for example.com (10)                    |         |          |           |
     |----------------------------------------->|         |          |           |
     |                                          |         |          |           |

          Figure 1: An Example of Split-Horizon DNS Configuration

6.  Split DNS Configuration for IKEv2

   The split-tunnel Virtual Private Network (VPN) configuration allows
   the endpoint to access resources that reside in the VPN [RFC8598] via
   the tunnel; other traffic not destined to the VPN does not traverse
   the tunnel.  In contrast, a non-split- tunnel VPN configuration
   causes all traffic to traverse the tunnel into the VPN.

   When the VPN tunnel is IPsec, the encrypted DNS resolver hosted by
   the VPN service provider can be securely discovered by the endpoint
   using the ENCDNS_IP*_* IKEv2 Configuration Payload Attribute Types
   defined in [I-D.btw-add-ipsecme-ike].  For split-tunnel VPN
   configurations, the endpoint uses the discovered encrypted DNS server
   to resolve domain names for which the VPN provider claims authority.
   For non-split-tunnel VPN configurations, the endpoint uses the
   discovered encrypted DNS server to resolve both global and private
   domain names.  For split-tunnel VPN configurations, the IKE client
   can use the steps discussed in Section 4.1 to determine if the VPN



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   service provider is authoritative over the INTERNAL_DNS_DOMAIN
   domains.

   Other VPN tunnel types have similar configuration capabilities, not
   detailed here.

7.  Security Considerations

   The content of dnsZones may be passed to another (DNS) program for
   processing.  As with any network input, the content SHOULD be
   considered untrusted and handled accordingly.  The client must
   perform the steps discussed in Section 4.1 to determine if the
   network-designated encrypted resolvers are authoritative over the
   domains in DnsZones.  If not, the client can take appropriate action
   like disconnecting from the network.

   In order to deploy DNSSEC operationally for split-horizon domains,
   the first three schemes described in
   [I-D.krishnaswamy-dnsop-dnssec-split-view] can be used but not the
   one discussed in Section 4.1.4.  Alternatively, after validating the
   network authority over the dnsZones domains Section 4.1, a DNSSEC-
   validating client can reconfigure its stub resolver to disable DNSSEC
   validation for the domains in dnsZones.

8.  IANA Considerations

   This document has no IANA actions..

9.  Acknowledgements

   Thanks to Mohamed Boucadair, Jim Reid, Ben Schwartz, Tommy Pauly,
   Paul Vixie, Paul Wouters and Vinny Parla for the discussion and
   comments.  The authors would like to give special thanks to Ben
   Schwartz for his help.

10.  References

10.1.  Normative References

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
              <https://www.rfc-editor.org/info/rfc1918>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.



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   [RFC2826]  Internet Architecture Board, "IAB Technical Comment on the
              Unique DNS Root", RFC 2826, DOI 10.17487/RFC2826, May
              2000, <https://www.rfc-editor.org/info/rfc2826>.

   [RFC6761]  Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
              RFC 6761, DOI 10.17487/RFC6761, February 2013,
              <https://www.rfc-editor.org/info/rfc6761>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <https://www.rfc-editor.org/info/rfc6762>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8310]  Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
              for DNS over TLS and DNS over DTLS", RFC 8310,
              DOI 10.17487/RFC8310, March 2018,
              <https://www.rfc-editor.org/info/rfc8310>.

   [RFC8801]  Pfister, P., Vyncke, E., Pauly, T., Schinazi, D., and W.
              Shao, "Discovering Provisioning Domain Names and Data",
              RFC 8801, DOI 10.17487/RFC8801, July 2020,
              <https://www.rfc-editor.org/info/rfc8801>.

10.2.  Informative References

   [I-D.btw-add-ipsecme-ike]
              Boucadair, M., Reddy, T., Wing, D., and V. Smyslov,
              "Internet Key Exchange Protocol Version 2 (IKEv2)
              Configuration for Encrypted DNS", draft-btw-add-ipsecme-
              ike-03 (work in progress), May 2021.

   [I-D.ietf-add-ddr]
              Pauly, T., Kinnear, E., Wood, C. A., McManus, P., and T.
              Jensen, "Discovery of Designated Resolvers", draft-ietf-
              add-ddr-03 (work in progress), October 2021.

   [I-D.ietf-add-dnr]
              Boucadair, M., Reddy, T., Wing, D., Cook, N., and T.
              Jensen, "DHCP and Router Advertisement Options for the
              Discovery of Network-designated Resolvers (DNR)", draft-
              ietf-add-dnr-02 (work in progress), May 2021.







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   [I-D.krishnaswamy-dnsop-dnssec-split-view]
              Krishnaswamy, S., "Split-View DNSSEC Operational
              Practices", draft-krishnaswamy-dnsop-dnssec-split-view-04
              (work in progress), March 2007.

   [INS]      The Unicode Consortium, "Vodafone Foundation Instant
              Schools for Sub-Saharan Africa",
              <https://www.vodafone.com/about/vodafone-foundation/focus-
              areas/instant-schools>.

   [RFC6950]  Peterson, J., Kolkman, O., Tschofenig, H., and B. Aboba,
              "Architectural Considerations on Application Features in
              the DNS", RFC 6950, DOI 10.17487/RFC6950, October 2013,
              <https://www.rfc-editor.org/info/rfc6950>.

   [RFC7556]  Anipko, D., Ed., "Multiple Provisioning Domain
              Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015,
              <https://www.rfc-editor.org/info/rfc7556>.

   [RFC8499]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/info/rfc8499>.

   [RFC8598]  Pauly, T. and P. Wouters, "Split DNS Configuration for the
              Internet Key Exchange Protocol Version 2 (IKEv2)",
              RFC 8598, DOI 10.17487/RFC8598, May 2019,
              <https://www.rfc-editor.org/info/rfc8598>.

Authors' Addresses

   Tirumaleswar Reddy
   Akamai
   Embassy Golf Link Business Park
   Bangalore, Karnataka  560071
   India

   Email: kondtir@gmail.com


   Dan Wing
   Citrix Systems, Inc.
   4988 Great America Pkwy
   Santa Clara, CA  95054
   USA

   Email: danwing@gmail.com





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   Kevin Smith
   Vodafone Group
   One Kingdom Street
   London
   UK

   Email: kevin.smith@vodafone.com












































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