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Versions: 00 01 02 03 04 05 06 rfc7393                     Informational
Network Working Group                                            X. Deng
Internet-Draft
Intended status: Informational                              M. Boucadair
Expires: December 13, 2014                                France Telecom
                                                                 Q. Zhao
                      Beijing University of Posts and Telecommunications
                                                                J. Huang
                                                                 C. Zhou
                                                     Huawei Technologies
                                                           June 11, 2014


        Using Port Control Protocol (PCP) to update dynamic DNS
                         draft-deng-pcp-ddns-06

Abstract

   This document focuses on the problems encountered when using dynamic
   DNS in address sharing contexts (e.g., DS-Lite, NAT64) during IPv6
   transition.  Both issues and possible solutions are documented in
   this memo.

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/.

   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 13, 2014.

Copyright Notice

   Copyright (c) 2014 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



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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
     1.1.  Problem Statement . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Scope and Goals . . . . . . . . . . . . . . . . . . . . .   3
   2.  Solution Space  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Locate a Service Port . . . . . . . . . . . . . . . . . .   4
     2.2.  Create Explicit Mappings for Incoming Connections . . . .   5
     2.3.  Detect Changes  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Some Deployment Solutions . . . . . . . . . . . . . . . . . .   6
     3.1.  Reference Topology  . . . . . . . . . . . . . . . . . . .   6
     3.2.  For Web Service . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  For Non-web Service . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  11
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

1.1.  Problem Statement

   Dynamic DNS (DDNS) is a widely deployed service to facilitate hosting
   servers (e.g., access to a webcam, HTTP server, FTP server, etc.) at
   customers' premises.  There are a number of providers which offer a
   DDNS service, working in a client and server mode, which mostly use a
   web-form based communication.  DDNS clients are generally implemented
   in the user's router or computer, which once detects changes to its
   assigned IP address it automatically sends an update message to the
   DDNS server.  The communication between the DDNS client and the DDNS
   server is not standardized, varying from one provider to another,
   although a few standard web-based methods of updating emerged over
   time.

   When the network architecture evolves towards an IPv4 sharing
   architecture during IPv6 transition, the DDNS client will have to not
   only inform the IP address updates if any, but also to notify the
   changes of external port on which the service is listening, because



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   well known port numbers, e.g., port 80 will no longer be available to
   every web server.  It will also require the ability to configure
   corresponding port forwarding on CGN (Carrier Grade NAT, [RFC6888])
   devices, so that incoming communications initiated from Internet can
   be routed to the appropriate server behind the CGN.

   Issues encountered in address sharing are documented in [RFC6269].
   This document focuses on the problems encountered when using dynamic
   DNS in address sharing contexts (e.g., DS-Lite [RFC6333], NAT64
   [RFC6146]).  Below are listed the main challenges:

   Announce and Discover an alternate service port:  The DDNS service
      must be able to maintain an alternative port number instead of the
      default port number.

   Allow for incoming connections:  Appropriate means to instantiate
      port mappings in the address sharing device must be supported.

   Detect changes and trigger DDNS updates:  DDNS client must be
      triggered by the change of the external IP address and the port
      number.  Concretely, upon change of the external IP address (and/
      or external port number), the DDNS client must refresh the DNS
      records otherwise the server won't be reachable from outside.
      This issue is exacerbated in the DS-Lite context because no public
      IPv4 address is assigned to the CPE.

1.2.  Scope and Goals

   This document describes some candidate solutions to resolve the
   aforementioned issues with a particular focus on DS-Lite.  These
   solutions may also be valid for other address sharing schemes.

   This document sketches deployment considerations based on the PCP
   (Port Control Protocol, [RFC6887]).  Note DDNS may be considered as
   an implementation of the Rendezvous service mentioned in [RFC6887].

   Indeed, after creating an explicit mapping for incoming connections
   using PCP, it is necessary to inform remote hosts about the IP
   address, protocol, and port number for the incoming connection to
   reach the services hosted behind a DS-Lite CGN.  This is usually done
   in an application-specific manner.  For example, a machine hosting a
   game server might use a rendezvous server specific to that game (or
   specific to that game developer), a SIP phone would use a SIP proxy,
   and a client using DNS-Based Service Discovery [RFC6763] would use
   DNS Update [RFC2136][RFC3007], etc.  PCP does not provide this
   rendezvous function.





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   The rendezvous function may support IPv4, IPv6, or both.  Depending
   on that support and the application's support of IPv4 or IPv6, the
   PCP client may need an IPv4 mapping, an IPv6 mapping, or both.  An
   example illustrating how the DDNS server may implement such a service
   notification functionality if necessary is provided in Section 3.

   This document does not specify any protocol extension, but instead it
   focuses on the elaboration of the problem space and illustrate how
   existing tools can be re-used to solve the problem for some
   deployment contexts.  Particularly, this document requires no changes
   to PCP or dynamic updates in the standard domain name system
   [RFC2136], but is rather an operational document to make the current
   DDNS service providers be aware of the impacts and issues that the
   IPv6 transitioning and IPv4 address sharing will bring to them, and
   gives solutions address the forthcoming issues.  The current DDNS
   service providers usually employs a web-based form to maintain DDNS
   service registration and updates.

   Generic deployment considerations for DS-Lite, including B4 remote
   management and IPv4 connectivity check, can be found in [RFC6908].
   This document complements [RFC6908] with deployment considerations
   related to Rendezvous service maintenance.  Additional PCP-related
   deployment considerations are available at
   [I-D.boucadair-pcp-deployment-cases].

   Solutions relying on DNS-based Service Discovery [RFC6763] or Apple's
   Back to My Mac (BTMM) Service [RFC6281] are not considered in this
   document.  Moreover, this document does not assume that DDNS service
   relies on [RFC2136].

   IPv4 addresses used in the examples are derived from the IPv4 block
   reserved for documentation in [RFC6890].  DNS name examples follow
   [RFC2606].

2.  Solution Space

2.1.  Locate a Service Port

   As listed below, at least two solutions can be used to associate a
   port number with a service:

   1.  Use service URIs (e.g., FTP, SIP, HTTP) which embed an explicit
       port number.  Indeed, Uniform Resource Identifier (URI) defined
       in [RFC3986] allows to carry port number in the syntax (e.g.,
       mydomain.example:15687).

   2.  Use SRV records [RFC2782].  Unfortunately, the majority of
       browsers do not support this record type.



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   DDNS client and DDNS server are to be updated so that an alternate
   port number is signaled and stored by the DDNS server.  Requesting
   remote hosts will be then notified with the IP address and port
   number to reach the server.

2.2.  Create Explicit Mappings for Incoming Connections

   PCP is used to install the appropriate mapping(s) in the CGN so that
   incoming packets can be delivered to the appropriate server.

2.3.  Detect Changes

   In a network described in Figure 1, DDNS client/ PCP client can
   either be running on a Customer Premise Equipment (CPE) or be running
   on the host that is hosting some services itself.  There are several
   possible ways to address the problems stated in Section 1.1:

   1.  If the DDNS client is enabled, the host issues periodically
       (e.g., 60 minutes) PCP MAP requests (e.g., messages 1 and 2 in
       Figure 1) with short lifetime (e.g., 30s) for the purpose of
       enquiring external IP address and setting.  If the purpose is to
       detect any change of external port, the host must issues a PCP
       mapping to install a mapping for the internal server.  Upon
       change of the external IP address, the DDNS client updates the
       records accordingly (e.g., message 3 in Figure 1).

   2.  If the DDNS client is enabled, it checks the local mapping table
       maintained by the PCP client.  This process is repeated
       periodically (e.g., 5 minutes, 30 minutes, 60 minutes).  If there
       is no PCP mapping created by PCP client, it issues a PCP MAP
       request (e.g., messages 1 and 2 in Figure 1) for the purpose of
       enquiring external IP address and setting up port forwarding
       mappings for incoming connections.  Upon change of the external
       IP address, the DDNS client updates the records in the DDNS
       server, e.g., message 3 in Figure 1.
















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                                     +-----------------+
                                     |  DDNS Server    |
                                     +-----------------+
                                               ^
                                               |
                                               |3. DDNS updates
                                               |  (if any)
                                               |
 +---------------+                    +-----------------+
 |DDNS Client    |1. PCP MAP request  | CGN/PCP Server  |
 |PCP Client/IWF |------------------->| (PCP mapping for|80:8080+------+
 |on CPE or      |2. PCP MAP response | port forwarding)|<------|Client|
 |the host itself|<-------------------|                 |       +------+
 |               |3. DDNS updates     |                 |
 |               |     (if any)       |                 |
 |               |------------------->|                 |
 +---------------+                    +-----------------+

                           Figure 1: Flow Chart

3.  Some Deployment Solutions

3.1.  Reference Topology

   Figure 2 illustrates the topology used for the deployment solutions
   elaborated in the following sub-sections.

   +--------------+   +--------+    +---------+   +--------+   +-------+
   | Service      |   |  DDNS  |    |  CGN&   |   | PCP    |   |Servers|
   | User         |---|  Server|----|  PCP    |---| Client |---|       |
   |              |   |        |    |  Server |   | /DDNS  |   |       |
   |              |   |        |    |         |   | client |   |       |
   +--------------+   +--------+    +---------+   +--------+   +-------+
   A user DDNS Server AFTR B4(CPE) A host

   From Internet                                               behind B4

                     Figure 2: Implementation Topology

   Figure 2 involves of the following entities:

   o  Servers: refer to the servers that are deployed in the DS-Lite
      network, or more generally, an IP address sharing environment.
      They are usually running on a host that has been assigned with a
      private IPv4 address.  Having created a proper mapping via PCP in
      AFTR, these services have been made available to the Internet
      users.  The services may provide Web, FTP, SIP and other services
      though these ones may not be able to been seen as using a well



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      known port from the outside anymore, in the IP address sharing
      context.

   o  B4 (CPE): An endpoint of IPv4-in-v6 tunnel [RFC6333].  A PCP
      client together with a DDNS client are running on it.  After PCP
      client establishes a mapping on the AFTR, an end user may register
      its domain name and its external IPv4 address plus port number to
      its DDNS service provider (DDNS server), manually or automatically
      by DDNS client.  Later, likewise, end users may manually or let
      DDNS client on behalf of it, to automatically announce IP address
      and/or port changes to the DDNS server.

   o  AFTR: Responsible for maintaining mappings between internal IPv4
      Address plus port and external IPv4 address plus port [RFC6333].

   o  DDNS server: Maintains a table that associates a registered domain
      name and a pair of registered host's external IPv4 address plus
      port number.  When being notified IP address and port number
      changes from DDNS client, DDNS server announces the updates to DNS
      servers on behalf of end user.  [RFC2136] and [RFC3007] may be
      used by DDNS server to send updates to DNS servers.  In many
      current practices, DDNS server provider usually announce its own
      IP address as the registered domain names of end users.  When HTTP
      requests reach the DDNS server, they may employ URL Forwarding or
      HTTP 301 redirection to redirect the request to a proper
      registered end user by looking up the maintained link table.

   o  Service users: refers to users who want to access services behind
      an IP address sharing network.  They issue standard DNS requests
      to locate the services, which will lead them to a DDNS server,
      provided that the requested services have been registered to a
      DDNS service provider.  The DDNS server will then handle the rest
      in the way as described before.

3.2.  For Web Service

   Current DDNS server implementations typically assume that the end
   servers host web server on the default 80 port.  In the DS-Lite
   context, they will have to take into account that external port
   assigned by AFTR may be any number other than 80, in order to
   maintain proper mapping between domain names and external IP plus
   port.  By doing such changes, the HTTP request would be redirected to
   the AFTR which servers the specific end host that are running
   servers.

   Figure 3 depicts how messages are handled in order to be delivered to
   the right server.




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   Web Visitor        DDNS server       AFTR      B4(CPE)     Web Server
                                                               behind B4
   | HTTP Get*             |              |          |               |
   |---------------------->|              |          |               |
   | ip_DDNS_server        |------------->|          |               |
   |                       | HTTP 301     |          |               |
   |                       |<-------------|          |               |
   | HTTP Get* ip_aftr:8001               |          |               |
   |------------------------------------->|                          |
   |                                      | HTTP Get* ip_websrv:8000 |
   |                                      |------------------------->|
   |                                      |                          |
   |                       HTTP response  | HTTP response            |
   |<-------------------------------------|--------------------------|
   |                                      |                          |

                      Figure 3: Http Service Messages

   When a web user sends out a HTTP GET message to DDNS server after a
   standard DNS query, DDNS server redirects the request to a registered
   web server, in this case, by responding with a HTTP 301 message.
   Then, the HTTP GET message will be sent out to the AFTR, which will
   in turn finds the proper hosts behind it.  For simplicity, messages
   among AFTR, B4 and web server behind B4 are not shown completely; for
   communications among those nodes, refer to [RFC6333].

3.3.  For Non-web Service

   For non-web services, as mentioned in Section 2, other means will be
   needed to inform the users about the service information.

   [RFC6763] includes an example of DNS-based solution which allows an
   application running in the end user's device to retrieve service-
   related information via DNS SRV/TXT records, and list available
   services.  In a scenario where such application is not applicable,
   following provides another solution for a third party, e.g., DDNS
   service provider, to disclose services to the Internet users.

   A web portal can be used to list available services.  DDNS server
   maintains a web portal for each user FQDN (Fully Qualified Domain
   Name), which provides users service links.  Figure 4 assumes
   "websrv.example.com" is a user's FQDN provided by a DDNS service
   provider.








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   +-------------+    +-------------+    +----------+ Internet +-------+
   |DDNS client /|    |DDNS server /|    |DNS server|          |Visitor|
   |  Web Server |    | web portal  |    |          |          |       |
   +-------------+    +-------------+    +----------+          +-------+
       |      register      |                 |                    |
       |<------------------>|                 |                    |
       | websrv.example.com |  update DNS     |                    |
       |   192.0.2.1:2000   | <-------------> |                    |
       |                    |websrv.example.com|                   |
       |                    |   portal's IP   |                    |
       |              +-------------+         |                    |
       |              |update portal|         |                    |
       |              +-------------+         |  DNS resolve for   |
       |                    |                 | <----------------> |
       |                    |                 | websrv.example.com |
       |                    |                 |  get portal's IP   |
       |                    |                 |                    |
       |                    |   visit portal of websrv.example.com |
       |                    | <----------------------------------> |
       |                    |                 |                    |
       |                  visit http://192.0.2.1:2000              |
       | <-------------------------------------------------------->|
       |                    |                 |                    |

                        Figure 4: Update Web Portal

   The DDNS client registers the servers' information to the DDNS
   server, including public IP address and port obtained via PCP, user's
   FQDN and other necessary information.  The DDNS server also behaves
   as portal server, it registers its IP address, port number, and
   user's FQDN to the DNS system, so that visitors can access the web
   portal.

   DDNS server also maintains a web portal for each user's FQDN, update
   the portal according to registered information from DDNS client.
   When a visitor accesses "websrv.example.com", a DNS query will
   resolve to portal server's address, port number, and the visitor will
   see the portal and the available services.













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     +-------------------------------------------------------------+
     |                                                             |
     |              Portal: websrv.example.com                     |
     |                                                             |
     |    Service1: web server                                     |
     |    Link:     http://192.0.2.1:2000                          |
     |                                                             |
     |    Service2: video                                          |
     |    Link:     rtsp://192.0.2.1:8080/test.sdp                 |
     |                                                             |
     |    ......                                                   |
     |                                                             |
     +-------------------------------------------------------------+

                    Figure 5: An Example of Web Portal

   As shown in Figure 5, the web portal shows the service URLs that are
   available to be accessed.  Multiple services are accessible per
   user's FQDN.

   Some applications which are not HTTP-based can also be delivered
   using this solution.  When a user clicks on a link, the registered
   application in the client OS will be invoked to handle the link.  How
   this can be achieved is out of the scope of this document.

4.  Security Considerations

   This document does not introduce a new protocol nor specify protocol
   extensions.  Security-related considerations related to PCP [RFC6887]
   and DS-Lite [RFC6333] should be taken into account.

   The protocol between the DDNS client and DDNS server is proprietary
   in most cases, some extensions may be necessary, which is up to DDNS
   operators.  These operators should enforce security-related policies
   to avoid that illegitimate users alter records installed by
   legitimate users or install fake records that would lead to attract
   illegitimate traffic.  Means to protect the DDNS server against DoS
   (Denial of Service) should be enabled.  Note these considerations are
   not specific to address sharing contexts but are valid for DDNS
   service in general.

5.  IANA Considerations

   This document does not require any action from IANA.







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6.  Contributors

   The following individuals contributed text to the document:

     Xiaohong Huang

     Beijing University of Posts and Telecommunications, China
     Email: huangxh@bupt.edu.cn

     Yan Ma

     Beijing University of Posts and Telecommunications, China
     Email: mayan@bupt.edu.cn

7.  Acknowledgements

   Thanks to Stuart Cheshire for bringing up DNS-Based Service Discovery
   and [RFC6281] where covers DNS-based SD scenario and gives an example
   of how the application means of solution to address dynamic DNS
   update, in this case, apple' BTMM, can be achieved.

   Many thanks to D.  Wing, D.  Thaler, and J.  Abley for their
   comments.

8.  References

8.1.  Normative References

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

   [RFC6887]  Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
              2013.

8.2.  Informative References

   [I-D.boucadair-pcp-deployment-cases]
              Boucadair, M., "Port Control Protocol (PCP) Deployment
              Models", draft-boucadair-pcp-deployment-cases-02 (work in
              progress), April 2014.





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

   [RFC2606]  Eastlake, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, June 1999.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              February 2000.

   [RFC3007]  Wellington, B., "Secure Domain Name System (DNS) Dynamic
              Update", RFC 3007, November 2000.

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

   [RFC6269]  Ford, M., Boucadair, M., Durand, A., Levis, P., and P.
              Roberts, "Issues with IP Address Sharing", RFC 6269, June
              2011.

   [RFC6281]  Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang,
              "Understanding Apple's Back to My Mac (BTMM) Service", RFC
              6281, June 2011.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, February 2013.

   [RFC6888]  Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common Requirements for Carrier-Grade NATs
              (CGNs)", BCP 127, RFC 6888, April 2013.

   [RFC6890]  Cotton, M., Vegoda, L., Bonica, R., and B. Haberman,
              "Special-Purpose IP Address Registries", BCP 153, RFC
              6890, April 2013.

   [RFC6908]  Lee, Y., Maglione, R., Williams, C., Jacquenet, C., and M.
              Boucadair, "Deployment Considerations for Dual-Stack
              Lite", RFC 6908, March 2013.

Authors' Addresses

   Xiaohong Deng

   Email: dxhbupt@gmail.com





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   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com


   Qin Zhao
   Beijing University of Posts and Telecommunications
   China

   Email: zhaoqin.bupt@gmail.com


   James Huang
   Huawei Technologies
   China

   Email: james.huang@huawei.com


   Cathy Zhou
   Huawei Technologies
   China

   Email: cathy.zhou@huawei.com
























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