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Versions: 00 01 02 03 04 draft-ietf-homenet-front-end-naming-delegation

HOMENET                                                  D. Migault (Ed)
Internet-Draft                                                    Orange
Intended status: Standards Track                             W. Cloetens
Expires: April 23, 2014                                       SoftAtHome
                                                            C. Griffiths
                                                                     Dyn
                                                                R. Weber
                                                                 Nominum
                                                        October 20, 2013


                  IPv6 Home Network Naming Delegation
         draft-mglt-homenet-front-end-naming-delegation-03.txt

Abstract

   CPEs are designed to provide IP connectivity to home networks.  Most
   CPEs assigns IP addresses to the nodes of the home network which
   makes it a good candidate for hosting the naming service.  With IPv6,
   the naming service makes nodes reachable from the home network as
   well as from the Internet.

   However, CPEs have not been designed to host such a naming service
   exposed on the Internet.  This MAY expose the CPEs to resource
   exhaustion which would make the home network unreachable, and most
   probably would also affect the home network inner communications.

   In addition, DNSSEC management and configuration may not be well
   understood or mastered by regular end users.  Misconfiguration MAY
   also results in naming service disruption, thus these end users MAY
   prefer to rely on third party naming providers.

   This document describes a homenet naming architecture where the CPEs
   manage the DNS zone associates to its home network, and outsource
   both DNSSEC management and naming service on the Internet to a third
   party designated as the Public Authoritative Servers.

Status of This Memo

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

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





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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 23, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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.  Requirements notation . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Architecture Overview . . . . . . . . . . . . . . . . . . . .   5
   5.  Architecture Description  . . . . . . . . . . . . . . . . . .   7
     5.1.  CPE and Public Authoritative Servers Synchronization  . .   8
       5.1.1.  Synchronization with a Hidden Master  . . . . . . . .   8
       5.1.2.  Securing Synchronization  . . . . . . . . . . . . . .   9
     5.2.  DNS Homenet Zone configuration  . . . . . . . . . . . . .  10
     5.3.  DNSSEC outsourcing configuration  . . . . . . . . . . . .  12
     5.4.  CPE Security Policies . . . . . . . . . . . . . . . . . .  13
   6.  Homenet Naming Configuration  . . . . . . . . . . . . . . . .  13
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
     7.1.  Names are less secure than IP addresses . . . . . . . . .  14
     7.2.  Names are less volatile than IP addresses . . . . . . . .  15
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   9.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     10.2.  Informational References . . . . . . . . . . . . . . . .  17
   Appendix A.  Document Change Log  . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Requirements notation



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   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Introduction

   IPv6 provides global end to end IP reachability from the Internet and
   into the Home Network.  End Users to access services hosted in the
   Home Network with IPv6 addresses would prefer to use names instead of
   long and complex IPv6 addresses.

   CPEs are already providing IPv6 connectivity to the Home Network and
   generally provide IPv6 addresses or prefixes to the nodes of the Home
   Network.  This makes the CPEs a good candidate to manage binding
   between names and IP addresses of the nodes.  In other words, the CPE
   is the natural candidate for setting the DNS(SEC) zone file.

   CPEs are usually low powered devices designed for the Home Network,
   but not for heavy traffic.  As a result, hosting the a DNS service on
   the Internet MAY expose the Home Network to resource exhaustion,
   which may isolate the Home Network from the Internet and affect the
   services hosted by the CPEs, thus affecting the overall Home Network
   communications.  So, this document considers that the Naming Service
   SHOULD NOT be hosted on the CPE and SHOULD be outsourced to a third
   party.

   In addition, the Naming Service of the Home Network is expected to be
   deployed with its security extension DNSSEC.  DNSSEC comes with
   complex configurations as well as complex operation management like
   (DNSSEC secure delegation, DNSSEC key roll over, DNSSEC zone
   updates).  These operations can hardly be understood by the average
   end user, and a misconfiguration MAY result in invalid naming
   resolutions that MAY make an host, or the whole home network
   unreachable.  So, this document considers DNSSEC management
   operations SHOULD NOT be handled by the average end user, but SHOULD
   be outsourced to a third party.

   This document describes an architecture where the CPE outsources the
   authoritative naming service and DNSSEC zone management to a third
   party designated as Public Authoritative Servers.  It describes
   interactions between the CPE and the Public Authoritative Servers,
   that is to say the involved protocols and their respective
   configurations.  More specifically, this document does not describe
   any new protocol.  It provides a guide line to properly use the
   already existing protocols.

   This document intends to efficiently deploy DNSSEC in the Home
   Networks in a standardized and highly flexible way.  More



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   specifically, the described Home Network Naming architecture is
   expected to lead to autoconfiguration facilities for most common
   users, as well as enabling advanced users to have their own specific
   settings.  In fact, some end users MAY choose to host and expose a
   Naming service on their CPE.  Others MAY sign the zone on the CPE.
   Although the document does not describe these scenarios, the
   described architecture only requires minor modifications - such as
   allowing incoming DNS queries from the Internet and adding the CPE in
   the list of Naming servers.

   The document is organized as follows.  Section 4 provides an overview
   of the homenet naming architecture and presents the CPE and the
   Public Authoritative Server that handles the authoritative naming
   service of the home network as well as DNSSEC management operations
   on behalf of the CPE.  Section 5 describes in details protocols and
   configurations to set the homenet naming architecture.  Section 6
   sums up the various configuration parameters that MAY be filled by
   the end user on the CPE for example via a GUI.  Finally Section 7
   provides security considerations.

3.  Terminology

   - Customer Premises Equipment:  (CPE) is the router providing
         connectivity to the home network.  It is configured and managed
         by the end user.  In this document, the CPE MAY also hosts
         services such as DHCPv6.  This device MAY be provided by the
         ISP.

   - Registered Homenet Domain:  is the Domain Name associated to the
         home network.

   - DNS Homenet Zone:  is the DNS zone associated to the home network.
         This zone is set by the CPE and essentially contains the
         bindings between names and IP addresses of the nodes of the
         home network.  In this document, the CPE does neither perform
         any DNSSEC management operations such as zone signing nor
         provide an authoritative service for the zone.  Both are
         delegated to the Public Authoritative Server.  The CPE
         synchronizes the DNS Homenet Zone with the Public Authoritative
         Server via a hidden master / slave architecture.  The Public
         Authoritative Server MAY use specific servers for the
         synchronization of the DNS Homenet Zone: the Public
         Authoritative Name Server Set as public available name servers
         for the Registered Homenet Domain.

   - Public Authoritative Server:  performs DNSSEC management operations
         as well as provides the authoritative service for the zone.  In
         this document, the Public Authoritative Server synchronizes the



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         DNS Homenet Zone with the CPE via a hidden master / slave
         architecture.  The Public Authoritative Server acts as a slave
         and MAY use specific servers called Public Authoritative Name
         Server Set.  Once the Public Authoritative Server synchronizes
         the DNS Homenet Zone, it signs the zone and generates the
         DNSSEC Public Zone.  Then the Public Authoritative Server hosts
         the zone as an authoritative server on the Public Authoritative
         Master(s).

   - DNSSEC Public Zone:  corresponds to the signed version of the DNS
         Homenet Zone.  It is hosted by the Public Authoritative Server,
         which is authoritative for this zone, and is reachable on the
         Public Authoritative Master(s).

   - Public Authoritative Master(s):  are the visible name server
         hosting the DNSSEC Public Zone.  End users' resolutions for the
         Homenet Domain are sent to this server, and this server is a
         master for the zone.

   - Public Authoritative Name Server Set:  is the server the CPE
         synchronizes the DNS Homenet Zone.  It is configured as a slave
         and the CPE acts as master.  The CPE sends information so the
         DNSSEC zone can be set and served.

4.  Architecture Overview

   Figure 1 provides an overview of the homenet naming architecture.

   The CPE is in charge of building the DNS Homenet Zone that contains
   all FQDN bindings of the home network.  The home network is
   associated to a FQDN, the Registered Homenet Domain (example.com).
   Any node in the home network is associated to a FQDN
   (node1.example.com) that MAY be provided via DHCP or statically
   configured on the CPE via a GUI for example.

   The goal of the homenet naming architecture is that the CPE does not
   handle any DNSSEC operations and does not host the authoritative
   naming service while FQDNs in the Homenet Zone can be resolved with
   DNSSEC by any node on the Internet.

   In order to achieve this goal, when a node on the Internet sends a
   DNS(SEC) query like for node1.example.com, this DNS(SEC) query MUST
   be treated by a third party designated in figure 1 as the Public
   Authoritative Servers.

   The Public Authoritative Servers are in charge of DNS(SEC) traffic
   for the Registered Homenet Domain (example.com) as well as all DNSSEC
   management operations like zone signing, key rollover.  The DNSSEC



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   zone hosted by the Public Authoritative Servers is called the DNSSEC
   Public Zone.

   The purpose of our architecture is to describe how the CPE can
   outsource the DNS Homenet Zone hosted on the CPE to the DNSSEC Public
   Zone hosted on the Public Authoritative Servers.  This includes
   description of the synchronization protocols between the CPE and the
   Public Authoritative Servers in Section 5.1 as well as configurations
   of the DNS Homenet Zone Section 5.2.

   home network +-------------------+ Internet
                |                   |
                |        CPE        |
                |                   |         +----------------------+
   +-------+    |+-----------------+|         | Public Authoritative |
   |       |    || DNS Homenet Zone||         | Servers              |
   | node1 |    ||                 ||         |+--------------------+|
   |       |    || Homenet Domain  ||         || DNSSEC Public Zone ||
   +-------+    || Name            ||=========||                    ||
                || (example.com)   ||   ^     ||   (example.com)    ||
   node1.\      |+-----------------+|   |     |+--------------------+|
   example.com  +-------------------+   |     +----------------------+
                                        |          ^     |
                                Synchronization    |     |
                                                   |     |
         DNSSEC resolution for node1.example.com   |     v
                                              +----------------------+
                                              |                      |
                                              |   DNSSEC Resolver    |
                                              |                      |
                                              +----------------------+


                      Figure 1: Homenet Naming Architecture Description


   The content of the DNS Homenet Zone is out of the scope of this
   document.  The CPE MAY host multiple services like a web GUI, DHCP
   [RFC6644] or mDNS [RFC6762].  These services MAY coexist and MAY be
   used to populate the DNS Homenet Zone.  This document assumes the DNS
   Homenet Zone has been populated with domain names that are intended
   to be publicly published and that are publicly reachable.  More
   specifically, names associated to services or devices that are not
   expected to be reachable from outside the home network or names bound
   to non globally reachable IP addresses MUST NOT be part of the DNS
   Homenet Zone.





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   Because services or devices MAY only be reached from hosts in the
   home network, DNS resolution MAY be handled differently from inside
   the network and from outside the network.This is out of scope of this
   document.  This document is focused on outsourcing the DNS Homenet
   Zone to the DNS Public Authoritative Servers that are visible from
   outside the home network.  How to deal with a homenet view and a
   public view is out of the scope of this document.  In order to deal
   with different views, some CPE MAY host DNS forwarders or use DNS
   view mechanisms.

   This document does not make any other assumption on the DNS Homenet
   Zone that records MUST be made public.  More specifically, the DNS
   Homenet Zone can be a regular or a reverse zone with PTR RRsets.  A
   CPE SHOULD consider both the normal zone as well as the reverse zone
   and outsource them both to the designated Public Authoritative
   Servers.

   By outsourcing to Public Authoritative Servers, services or devices
   mentioned in the DNS Homenet Zone MAY be not reachable in case the
   home network has no internet connectivity.  How to keep the naming
   service within the home network when the it is disconnected from the
   public internet is out of scope of this document.  CPE MAY chose for
   example to host an authoritative naming server for the home network
   or use a DNS forwarders.

   Similarly, CPE MAY host a DNS(SEC) resolution service for nodes in
   the home network.  There are multiple ways to configure the resolver
   service on the CPE.  Detailing these various configurations is out of
   the scope of this document, and is considered as an implementation
   issue.  Some implementers MAY chose to forward DNS(SEC) queries from
   the home network to the resolving server of its ISP or any other
   public resolver.  In that case, the DNS(SEC) response from the Public
   Authoritative Servers is forwarded to the home network, which provide
   DNS and DNSSEC resolution for the home network.  Note also that in
   this case, the naming service depends on the connectivity with the
   resolving servers.  In case the home network is disconnected, the
   naming service MAY not be available.  Alternative implementations MAY
   chose to take advantage of forwarders and lookup in the DNS Homenet
   Zone.  This MAY provide only DNS responses in the home network if the
   CPE does not sign the DNS Homenet Zone.  Other implementation MAY
   chose to synchronize the DNSSEC Public Zone on the CPE either using
   DNS master slave mechanisms, or by caching the whole zone.  This
   latest option MAY require some additional configuration the Public
   Authoritative Servers.

5.  Architecture Description





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   This section describes how the CPE and the Public Authoritative
   Servers SHOULD be configured to outsource authoritative naming
   service as well as DNSSEC management operations.  Section 5.1
   describes how a secure synchronization between the CPE and the Public
   Authoritative server is set.  Section 5.2 provides guide lines for
   the DNS Homenet Zone set in the CPE and uploaded on the Public
   Authoritative Servers.  Section 5.3 describes DNSSEC settings on the
   Public Authoritative Servers.  Finally, Section 5.4 provides the
   security policies that SHOULD be set on the CPE.

5.1.  CPE and Public Authoritative Servers Synchronization

5.1.1.  Synchronization with a Hidden Master

   Uploading and dynamically updating the zone file on the Public
   Servers can be seen as zone provisioning between the CPE (Hidden
   Master) and the Public Server (Slave Server).  This can be handled
   either in band or out of band.  DNS dynamic update [RFC2136] may be
   used.  However, in this section we detail how to take advantage of
   the DNS slave / master architecture to deploy updates to public
   zones.

   The Public Authoritative Server is configured as a slave for the
   Homenet Domain Name.  This slave configuration has been previously
   agreed between the end user and the provider of the Public
   Authoritative Servers.  In order to set the master/ slave
   architecture, the CPE acts as a Hidden Master Server, which is a
   regular Authoritative DNS(SEC) Server listening on the WAN interface.

   The Hidden Master Server is expected to accept SOA [RFC1033], AXFR
   [RFC1034], and  IXFR [RFC1995] queries from its configured slave DNS
   servers.  The Hidden Master Server SHOULD send NOTIFY messages
   [RFC1996] in order to update Public DNS server zones as updates
   occur.  Because, DNS Homenet Zones are likely to be small, CPE MUST
   implement AXFR and SHOULD implement IXFR.

   Hidden Master Server differs from a regular authoritative server for
   the home network by:

   - Interface Binding:  the Hidden Master Server listens on the WAN
         Interface, whereas a regular authoritative server for the home
         network would listen on the home network interface.

   - Limited exchanges:  the purpose of the Hidden Master Server is to
         synchronizes with the Public Authoritative Servers, not to
         serve zone.  As a result, exchanges are performed with specific
         nodes (the Public Authoritative Servers).  Then exchange types
         are limited.  The only legitimate exchanges are: NOTIFY



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         initiated by the Hidden Master and IXFR or AXFR exchanges
         initiated by the Public Authoritative Servers.  On the other
         hand regular authoritative servers would respond any hosts on
         the home network, and any DNS(SEC) query would be considered.
         The CPE SHOULD filter IXFR/AXFR traffic and drop traffic not
         initiated by the Public Authoritative Server.  The CPE MUST
         listen for DNS on TCP and UDP and at least allow SOA lookups to
         the DNS Homenet Zone.

5.1.2.  Securing Synchronization

   Exchange between the Public Servers and the CPE MUST be secured, at
   least for integrity protection and for authentication.  This is the
   case whatever mechanism is used between the CPE and the Public
   Authoritative DNS(SEC) Servers.

   TSIG [RFC2845] or SIG(0) [RFC2931] can be used to secure the DNS
   communications between the CPE and the Public DNS(SEC) Servers.  TSIG
   uses a symmetric key which can be managed by TKEY [RFC2930].
   Management of the key involved in SIG(0) is performed through zone
   updates.  How to roll the keys with SIG(0) is out-of-scope of this
   document.  The advantage of these mechanisms is that they are only
   associated with the DNS application.  Not relying on shared libraries
   ease testing and integration.  On the other hand, using TSIG, TKEY or
   SIG(0) requires that these mechanisms to be implemented on the
   DNS(SEC) Server's implementation running on the CPE, which adds
   codes.  Another disadvantage is that TKEY does not provides
   authentication mechanism.

   Protocols like TLS [RFC5246] / DTLS [RFC6347] can be used to secure
   the transactions between the Public Authoritative Servers and the
   CPE.  The advantage of TLS/DTLS is that this technology is widely
   deployed, and most of the boxes already embeds a TLS/DTLS libraries,
   eventually taking advantage of hardware acceleration.  Then TLS/DTLS
   provides authentication facilities and can use certificates to
   authenticate the Public Authoritative Server and the CPE.  On the
   other hand, using TLS/DTLS requires to integrate DNS exchange over
   TLS/DTLS, as well as a new service port.  This is why we do not
   recommend this option.

   IPsec [RFC4301] IKEv2 [RFC5996] can also be used to secure the
   transactions between the CPE and the Public Authoritative Servers.
   Similarly to TLS/DTLS, most CPE already embeds a IPsec stack, and
   IKEv2 provides multiple authentications possibilities with its EAP
   framework.  In addition, IPsec can be used to protect the DNS
   exchanges between the CPE and the Public Authoritative Servers
   without any modifications of the DNS Servers or client.  DNS
   integration over IPsec only requires an additional security policy in



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   the Security Policy Database.  One disadvantage of IPsec is that it
   hardly goes through NATs and firewalls.  However, in our case, the
   CPE is connected to the Internet, and IPsec communication between the
   CPE and Public Authoritative Server SHOULD NOT be impacted by middle
   boxes.

   As mentioned above, TSIG, IPsec and TLS/DTLS may be used to secure
   transactions between the CPE and the Public Authentication Servers.
   The CPE and Public Authoritative Server SHOULD implement TSIG and
   IPsec.

   How the PSK can be used by any of the TSIG, TLS/DTLS or IPsec
   protocols.  Authentication based on certificates implies a mutual
   authentication and thus requires the CPE to manage a private key, a
   public key or certificates as well as Certificate Authorities.  This
   adds complexity to the configuration especially on the CPE side.  For
   this reason, we recommend that CPE MAY use PSK or certificate base
   authentication and that Public Authentication Servers MUST support
   PSK and certificate based authentication.

5.2.  DNS Homenet Zone configuration

   As depicted in figure 1, he DNSSEC Public Zone is hosted on the
   Public Authoritative Server, whereas the DNS Homenet Zone is hosted
   on the CPE.  As a result, the CPE MUST configure the DNS Homenet Zone
   as if the DNS Homenet Zone were hosted by the Public Authoritative
   Servers instead of the CPE.

   If one considers the case where the CPE has a single Homenet Domain
   Name and has an agreement with a single Public Authoritative Server.
   In that case, the DNS Homenet Zone SHOULD configure its Name Server
   RRset and Start of Authority with the ones associated to the Public
   Authoritative Servers.  This is illustrated in figure 2.
   public.autho.servers.example.net is the domain name associated to the
   Public Authoritative Server, and IP1, IP2, IP3, IP4 are the IP
   addresses associated.















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           $ORIGIN example.com
           $TTL 1h

           @  IN  SOA  public.autho.servers.example.net
                       hostmaster.example.com. (
                 2013120710 ; serial number of this zone file
                 1d         ; slave refresh
                 2h         ; slave retry time in case of a problem
                 4w         ; slave expiration time
                 1h         ; maximum caching time in case of failed
                            ; lookups
                 )

           @   NS  public.authoritative.servers.example.net

           public.autho.servers.example.net   A @IP1
           public.autho.servers.example.net   A @IP2
           public.autho.servers.example.net   AAAA @IP3
           public.autho.servers.example.net   AAAA @IP4


                      Figure 2: DNS Homenet Zone


   The SOA RRset is defined in [RFC1033], [RFC1035].  This SOA is
   specific as it is used for the synchronization between the Hidden
   Master and the Public Authoritative Name Server Set and published on
   the DNS Public Authoritative Master.

   - MNAME:  indicates the primary master.  In our case the zone is
         published on the Public Authoritative Master, and its name MUST
         be mentioned.  If multiple Public Authoritative Masters are
         involved, one of them MUST be chosen.  More specifically, the
         CPE MUST NOT place the name of the Hidden Master.

   - RNAME:  indicates the email address to reach the administrator.
         [RFC2142] recommends to use hostmaster@domain and replacing the
         '@' sign by '.'.

   - REFRESH and RETRY:  indicate respectively in seconds how often
         slaves need to check the master and the time between two
         refresh when a refresh has failed.  Default value indicated by
         [RFC1033] are 3600 (1 hour) for refresh and  600 (10 minutes)
         for retry.  This value MAY be long for highly dynamic content.
         However, Public Authoritative Masters and the CPE are expected
         to implement NOTIFY [RFC1996].  Then short values MAY increase
         the bandwidth usage for slaves hosting large number of zones.
         As a result, default values looks fine.



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   EXPIRE:  is the upper limit data SHOULD be kept in absence of
         refresh.  Default value indicated by [RFC1033] is 3600000 about
         42 days.  In home network architectures, the CPE provides both
         the DNS synchronization and the access to the home network.
         This device MAY be plug / unplugged by the end user without
         notification, thus we recommend large period.

   MINIMUM:  indicates the minimum TTL.  Default value indicated by
         [RFC1033] is 86400 (1 day).  For home network, this value MAY
         be reduced, and 3600 (1hour) seems more appropriated.

   When the end user considers multiple Public Authoritative Servers for
   a given Registered Homenet Domain, the DNS Homenet Zone MAY contain
   all associated Name Servers and IP addresses.

   Some additional verification can check whether the CPE IP address is
   mentioned in the Public Zone file, and raise a warning to the End
   User.

5.3.  DNSSEC outsourcing configuration

   In this document we assumed that the Public Authoritative Server
   signs the DNS Homenet Zone.  Multiple variants MAY be proposed by the
   Public Authoritative Servers.  Public Authoritative Servers MAY
   propose to sign the DNS Homenet Zone with keys generated by the
   Public Authoritative Servers and unknown to the CPE.  Alternatively
   some MAY propose the end user to provide the private keys.  Although
   not considered in this document some end user MAY still prefer to
   sign their zone with their own keys they do not communicate to the
   Public Authoritative Servers.  All these alternatives result from a
   negotiation between the end user and the Public Authoritative
   Servers.  This negotiation is performed out-of-band and is out of
   scope of this document.

   In this document, we consider that the Public Authoritative Server
   has all the necessary cryptographic elements to perform zone signing
   and key management operations.

   Note that Public Authoritative Servers described in this document
   accomplish different functions, and thus different entities MAY be
   involved.










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   - DNS Slave function synchronizes the DNS Homenet Zone between the
         CPE and the Public Authoritative Servers.  The DNS Homenet Zone
         on the Public Authoritative Servers is not available, and the
         Public Authoritative Server MUST NOT address any DNS queries
         for that zone.  As a result, the Public Authoritative Servers
         MAY chose a dedicated set of servers to serve the DNS Homenet
         Zone: the Public Authoritative Name Server Set.

   - DNS Zone Signing function signs the DNS Zone Homenet Zone to
         generate an DNSSEC Public Zone.

   - DNSSEC Authoritative Server hosts the naming service for the DNSSEC
         Public Zone.  Any DNS(SEC) query associated to the Homenet Zone
         SHOULD be done using the specific servers designated as the
         Public Authoritative Master(s).

5.4.  CPE Security Policies

   This section details security policies related to the Hidden Master /
   Slave synchronization.

   The Hidden Master, as described in this document SHOULD drop any
   queries from the home network.  This can be performed with port
   binding and/or firewall rules.

   The Hidden Master SHOULD drop on the WAN interface any DNS queries
   that is not issued from the Public Authoritative Server Name Server
   Set.

   The Hidden Master SHOULD drop any outgoing packets other than DNS
   NOTIFY query, SOA response, IXFR response or AXFR responses.

   The Hidden Master SHOULD drop any incoming packets other than DNS
   NOTIFY response, SOA query, IXFR query or AXFR query.

   The Hidden Master SHOULD drop any non protected IXFR or AXFR
   exchange.  This depends how the synchronization is secured.

6.  Homenet Naming Configuration

   This section specifies the various parameters required by the CPE to
   configure the naming architecture of this document.  This section is
   informational, and is intended to clarify the information handled by
   the CPE and the various settings to be done.







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   Public Authoritative Servers MAY be defined with the following
   parameters.  These parameters are necessary to establish a secure
   channel between the CPE and the Public Authoritative Server, and to
   set the appropriated DNS Homenet Zone file:

   - Public Authoritative Name Server Set:  The associated FQDNs or IP
         addresses of the Public Authoritative Server.  IP addresses are
         optional and the FQDN is sufficient.  To secure the binding
         name and IP addresses, a DNSSEC exchange is required.
         Otherwise, the IP addresses SHOULD be entered manually.

   - Authentication Method:  How the CPE authenticates itself to the
         Public Server.  This MAY depend on the implementation but we
         should consider at least IPsec, DTLS and TSIG

   - Authentication data:  Associated Data.  PSK only requires a single
         argument.  If other authentication mechanisms based on
         certificates are used, then, files for the CPE private keys,
         certificates and certification authority SHOULD be specified.

   - Public Authoritative Master(s):  The FQDN or IP addresses of the
         Public Authoritative Master.  It MAY correspond to the data
         that will be set in the NS RRsets and SOA of the DNS Homenet
         Zone.  IP addresses are optional and the FQDN is sufficient.
         To secure the binding name and IP addresses, a DNSSEC exchange
         is required.  Otherwise, the IP addresses SHOULD be entered
         manually.

   - Registered Homenet Domain:  The domain name the Public
         Authoritative is configured for DNS slave, DNSSEC zone signing
         and DNSSEC zone hosting.

   Setting the DNS Homenet Zone requires the following information.

   - Registered Homenet Domain:  The Domain Name of the zone.  Multiple
         Registered Homenet Domain MAY be provided.  This will generate
         the creation of multiple DNS Homenet Zones.

   - Public Authoritative Server:  The Public Authoritative Servers
         associated to the Registered Homenet Domain.  Multiple Public
         Authoritative Server MAY be provided.

7.  Security Considerations

   The Homenet Naming Architecture described in this document solves
   exposing the CPE's DNS service as a DoS attack vector.

7.1.  Names are less secure than IP addresses



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   This document describes how an End User can make his services and
   devices from his Home Network reachable on the Internet with Names
   rather than IP addresses.  This exposes the Home Network to attackers
   since names are expected to provide less randomness than IP
   addresses.  The naming delegation protects the End User's privacy by
   not providing the complete zone of the Home Network to the ISP.
   However, using the DNS with names for the Home Network exposes the
   Home Network and its components to dictionary attacks.  In fact, with
   IP addresses, the Interface Identifier is 64 bit length leading to
   2^64 possibilities for a given subnetwork.  This is not to mention
   that the subnet prefix is also of 64 bit length, thus providing
   another 2^64 possibilities.  On the other hand, names used either for
   the Home Network domain or for the devices present less randomness
   (livebox, router, printer, nicolas, jennifer, ...) and thus exposes
   the devices to dictionary attacks.

7.2.  Names are less volatile than IP addresses

   IP addresses may be used to locate a device, a host or a Service.
   However, Home Networks are not expected to be assigned the same
   Prefix over time.  As a result observing IP addresses provides some
   ephemeral information about who is accessing the service.  On the
   other hand, Names are not expected to be as volatile as IP addresses.
   As a result, logging Names, over time, may be more valuable that
   logging IP addresses, especially to profile End User's
   characteristics.

   PTR provides a way to bind an IP address to a Name.  In that sense
   responding to PTR DNS queries may affect the End User's Privacy.  For
   that reason we recommend that End Users may choose to respond or not
   to PTR DNS queries and may return a NXDOMAIN response.

8.  IANA Considerations

   This document has no actions for IANA.

9.  Acknowledgment

   The authors wish to thank Philippe Lemordant for its contributions on
   the early versions of the draft, Ole Troan for pointing out issues
   with the IPv6 routed home concept and placing the scope of this
   document in a wider picture, Mark Townsley for encouragement and
   injecting a healthy debate on the merits of the idea, Ulrik de Bie
   for providing alternative solutions, Paul Mockapetris, Christian
   Jacquenet, Francis Dupont and Ludovic Eschard for their remarks on
   CPE and low power devices, Olafur Gudmundsson for clarifying DNSSEC
   capabilities of small devices, Simon Kelley for its feedback as
   dnsmasq implementer.



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10.  References

10.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

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

   [RFC1995]  Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
              August 1996.

   [RFC1996]  Vixie, P., "A Mechanism for Prompt Notification of Zone
              Changes (DNS NOTIFY)", RFC 1996, August 1996.

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

   [RFC2136]  Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.

   [RFC2142]  Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND
              FUNCTIONS", RFC 2142, May 1997.

   [RFC2845]  Vixie, P., Gudmundsson, O., Eastlake, D., and B.
              Wellington, "Secret Key Transaction Authentication for DNS
              (TSIG)", RFC 2845, May 2000.

   [RFC2930]  Eastlake, D., "Secret Key Establishment for DNS (TKEY
              RR)", RFC 2930, September 2000.

   [RFC2931]  Eastlake, D., "DNS Request and Transaction Signatures (
              SIG(0)s)", RFC 2931, September 2000.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
              5996, September 2010.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.



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   [RFC6644]  Evans, D., Droms, R., and S. Jiang, "Rebind Capability in
              DHCPv6 Reconfigure Messages", RFC 6644, July 2012.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              February 2013.

10.2.  Informational References

   [RFC1033]  Lottor, M., "Domain administrators operations guide", RFC
              1033, November 1987.

Appendix A.  Document Change Log

   [RFC Editor: This section is to be removed before publication]

   -03:

   *Simon's comments taken into consideration

   *Adding SOA, PTR considerations

   *Removing DNSSEC performance paragraphs on low power devices

   *Adding SIG(0) as a mechanism for authenticating the servers

   *Goals clarification: the architecture described in the document 1)
   does not describe new protocols, and 2) can be adapted to specific
   cases for advance users.

   -02:

   *remove interfaces: "Public Authoritative Server Naming Interface" is
   replaced by "Public Authoritative Master(s)".  "Public Authoritative
   Server Management Interface" is replaced by "Public Authoritative
   Name Server Set".

   -01.3:

   *remove the authoritative / resolver services of the CPE.
   Implementation dependent

   *remove interactions with mdns and dhcp.  Implementation dependent.

   *remove considerations on low powered devices

   *remove position toward homenet arch

   *remove problem statement section



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   -01.2:

   * add a CPE description to show that the architecture can fit CPEs

   * specification of the architecture for very low powered devices.

   * integrate mDNS and DHCP interactions with the Homenet Naming
   Architecture.

   * Restructuring the draft.  1) We start from the homenet-arch draft
   to derive a Naming Architecture, then 2) we show why CPE need
   mechanisms that do not expose them to the Internet, 3) we describe
   the mechanisms.

   * I remove the terminology and expose it in the figures A and B.

   * remove the Front End Homenet Naming Architecture to Homenet Naming

   -01:

   * Added C. Griffiths as co-author.

   * Updated section 5.4 and other sections of draft to update section
   on Hidden Master / Slave functions with CPE as Hidden Master/Homenet
   Server.

   * For next version, address functions of MDNS within Homenet Lan and
   publishing details northbound via Hidden Master.

   -00: First version published.

Authors' Addresses

   Daniel Migault
   Orange
   38 rue du General Leclerc
   92794 Issy-les-Moulineaux Cedex 9
   France

   Phone: +33 1 45 29 60 52
   Email: mglt.ietf@gmail.com










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   Wouter Cloetens
   SoftAtHome
   vaartdijk 3 701
   3018 Wijgmaal
   Belgium

   Email: wouter.cloetens@softathome.com


   Chris Griffiths
   Dyn
   150 Dow Street
   Manchester, NH  03101
   US

   Email: cgriffiths@dyn.com
   URI:   http://dyn.com


   Ralf Weber
   Nominum
   2000 Seaport Blvd #400
   Redwood City, CA  94063
   US

   Email: ralf.weber@nominum.com
   URI:   http://www.nominum.com























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