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Versions: (draft-bpw-pcp-upnp-igd-interworking) 00 01 02 03 04 05 06 08 09 10 RFC 6970

PCP Working Group                                           M. Boucadair
Internet-Draft                                            France Telecom
Intended status: Standards Track                               F. Dupont
Expires: March 28, 2013                      Internet Systems Consortium
                                                                R. Penno
                                                                 D. Wing
                                                                   Cisco
                                                      September 24, 2012


   Universal Plug and Play (UPnP) Internet Gateway Device (IGD)-Port
              Control Protocol (PCP) Interworking Function
                draft-ietf-pcp-upnp-igd-interworking-04

Abstract

   This document specifies the behavior of the UPnP IGD (Internet
   Gateway Device)/PCP Interworking Function.  An UPnP IGD-PCP
   Interworking Function (IGD-PCP IWF) is required to be embedded in CP
   (Customer Premises) routers to allow for transparent NAT control in
   environments where UPnP IGD is used in the LAN side and PCP in the
   external side of the CP router.

Requirements Language

   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 RFC 2119 [RFC2119].

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 March 28, 2013.

Copyright Notice




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   Copyright (c) 2012 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.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . .  4

   3.  Architecture Model . . . . . . . . . . . . . . . . . . . . . .  5

   4.  UPnP IGD-PCP Interworking Function: Overview . . . . . . . . .  7
     4.1.  UPnP IGD-PCP: State Variables  . . . . . . . . . . . . . .  7
     4.2.  IGD-PCP: Methods . . . . . . . . . . . . . . . . . . . . .  8
     4.3.  UPnP IGD-PCP: Errors . . . . . . . . . . . . . . . . . . .  9

   5.  Specification of the IGD-PCP Interworking Function . . . . . . 10
     5.1.  PCP Server Discovery . . . . . . . . . . . . . . . . . . . 11
     5.2.  Control of the Firewall  . . . . . . . . . . . . . . . . . 11
     5.3.  NAT Control in LAN Side  . . . . . . . . . . . . . . . . . 11
     5.4.  Port Mapping Tables  . . . . . . . . . . . . . . . . . . . 11
     5.5.  Interworking Function Without NAT in the IGD . . . . . . . 12
     5.6.  NAT Embedded in the IGD  . . . . . . . . . . . . . . . . . 12
     5.7.  Creating a Mapping . . . . . . . . . . . . . . . . . . . . 13
       5.7.1.  AddAnyPortMapping()  . . . . . . . . . . . . . . . . . 13
       5.7.2.  AddPortMapping() . . . . . . . . . . . . . . . . . . . 14
     5.8.  Listing One or a Set of Mappings . . . . . . . . . . . . . 17
     5.9.  Delete One or a Set of Mappings: DeletePortMapping()
           or DeletePortMappingRange()  . . . . . . . . . . . . . . . 17
     5.10. Renewal  . . . . . . . . . . . . . . . . . . . . . . . . . 20
     5.11. Mappings Update  . . . . . . . . . . . . . . . . . . . . . 21

   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21

   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22

   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 22



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   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 22
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 22

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23














































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1.  Introduction

   PCP [I-D.ietf-pcp-base] discusses the implementation of NAT control
   features that rely upon Carrier Grade NAT devices such as a DS-Lite
   AFTR [RFC6333] or NAT64 [RFC6146].  Nevertheless, in environments
   where UPnP IGD is used in the local network, an interworking function
   between UPnP IGD and PCP is required to be embedded in the IGD (see
   the example illustrated in Figure 1).

   Two configurations are considered:

   o  No NAT function is embedded in the IGD (Internet Gateway Device).
      This is required for instance in DS-Lite or NAT64 deployments;

   o  The IGD embeds a NAT function.

                            UPnP-PCP
   UPnP Control           Interworking
      Point                 Function                  PCP Server
        |                      |                           |
        | (1) AddPortMapping   |                           |
        |--------------------->|                           |
        |                      |   (2) PCP MAP Request     |
        |                      |-------------------------->|
        |                      |                           |

                          Figure 1: Flow Example

   The UPnP IGD-PCP Interworking Function (IGD-PCP IWF) maintains a
   local mapping table that stores all active mappings instructed by
   internal UPnP Control Points.  This design choice restricts the
   amount of PCP messages to be exchanged with the PCP Server.

   Triggers for deactivating the UPnP IGD-PCP Interworking Function from
   the IGD and relying on a PCP-only mode are out of scope of this
   document.

   Considerations related to co-existence of the UPnP IGD-PCP
   Interworking Function and PCP Proxy [I-D.ietf-pcp-proxy] are out of
   scope.


2.  Acronyms

   This document makes use of the following abbreviations:






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           DS-Lite Dual-Stack Lite
               IGD Internet Gateway Device
             IGD:1 UPnP Forum's nomenclature for version 1 of IGD [IGD1]
             IGD:2 UPnP Forum's nomenclature for version 2 of IGD [IGD2]
               IWF Interworking Function
               NAT Network Address Translation
               PCP Port Control Protocol
              UPnP Universal Plug and Play
           UPnP CP UPnP Control Point


3.  Architecture Model

   As a reminder, Figure 2 illustrates the architecture model adopted by
   UPnP IGD [IGD2].  In Figure 2, the following UPnP terminology is
   used:

   o  Client refers to a host located in the local network.

   o  IGD Control Point is a UPnP control point using UPnP to control an
      IGD (Internet Gateway Device).

   o  IGD is a router supporting UPnP IGD.  It is typically a NAT or a
      firewall.

   o  Host represents a remote peer reachable in the Internet.

               +-------------+
               | IGD Control |
               |   Point     |-----+
               +-------------+     |   +-----+       +------+
                                   +---|     |       |      |
                                       | IGD |-------| Host |
                                   +---|     |       |      |
               +-------------+     |   +-----+       +------+
               |   Client    |-----+
               +-------------+


                         Figure 2: UPnP IGD Model

   This model is not valid when PCP is used to control for instance a
   Carrier Grade NAT (a.k.a., Provider NAT) while internal hosts
   continue to use UPnP.  In such scenarios, Figure 3 shows the updated
   model.






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   +-------------+
   | IGD Control |
   |   Point     |----+
   +-------------+    |   +-----+      +--------+               +------+
                      +---| IGD-|      |Provider|               |      |
                          | PCP |------|  NAT   |--<Internet>---| Peer |
                      +---| IWF |      |        |               |      |
   +-------------+    |   +-----+      +--------+               +------+
   | Local Host  |----+
   +-------------+
                        LAN Side  External Side
   <======UPnP IGD==============><=====PCP=====>


                 Figure 3: UPnP IGD-PCP Interworking Model

   In the updated model depicted in Figure 3, one or two levels of NAT
   can be encountered in the data path.  Indeed, in addition to the
   Carrier Grade NAT, the IGD may embed a NAT function (Figure 4).

    +-------------+
    | IGD Control |
    |   Point     |-----+
    +-------------+     |   +-----+       +----+               +------+
                        +---| IGD-|       |    |               |Remote|
                            | PCP |-------|NAT2|--<Internet>---| Host |
                        +---| IWF |       |    |               |      |
    +-------------+     |   +-----+       +----+               +------+
    | Local Host  |-----+     NAT1
    +-------------+


                      Figure 4: Cascaded NAT scenario

   To ensure a successful interworking between UPnP IGD and PCP, an
   interworking function is embedded in the IGD.  In the model defined
   in Figure 3, all UPnP IGD server-oriented functions, a PCP Client
   [I-D.ietf-pcp-base] and a UPnP IGD-PCP Interworking Function are
   embedded in the IGD.  In the rest of the document, IGD-PCP
   Interworking Function refers the UPnP IGD-PCP Interworking Function,
   which includes PCP Client functionality.

   UPnP IGD-PCP Interworking Function is responsible for generating a
   well-formed PCP message from a received UPnP IGD message, and vice
   versa.






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4.  UPnP IGD-PCP Interworking Function: Overview

   Three tables are provided to specify the correspondence between UPnP
   IGD and PCP:

   (1)  Section 4.1 provides the mapping between WANIPConnection State
        Variables and PCP parameters;

   (2)  Section 4.2 focuses on the correspondence between supported
        methods;

   (3)  Section 4.3 lists the PCP error messages and their corresponding
        IGD ones.

   Note that some enhancements have been integrated in WANIPConnection
   as documented in [IGD2].

4.1.  UPnP IGD-PCP: State Variables

   Below are listed only the UPnP IGD state variables applicable to the
   IGD-PCP Interworking Function:

   ExternaIPAddress:  External IP Address
      Read-only variable with the value from the last PCP response or
      the empty string if none was received yet.  This state is stored
      on a per UPnP CP basis.

   PortMappingNumberOfEntries:  Managed locally by the UPnP IGD-PCP
      Interworking Function.

   PortMappingEnabled:
      PCP does not support deactivating the dynamic NAT mapping since
      the initial goal of PCP is to ease the traversal of Carrier Grade
      NAT.  Supporting such per-subscriber function may overload the
      Carrier Grade NAT.
      Only "1" is allowed: i.e., the UPnP IGD-PCP Interworking Function
      MUST send back an error if not a value different from 1 is
      signaled.

   PortMappingLeaseDuration:  Requested Mapping Lifetime
      In IGD:1 [IGD1] value 0 means infinite, in IGD:2 it is remapped to
      the IGD maximum of 604800 seconds [IGD2].  PCP allows for a
      maximum value of 4294967296 seconds.
      The UPnP IGD-PCP Interworking Function simulates long and even
      infinite lifetimes using renewals (see Section 5.10).  The
      behavior in the case of a failing renewal is currently undefined.
      IGD:1 doesn't define the behavior in the case of state lost, IGD:2
      doesn't require to keep state in stable storage, i.e., to make the



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      state to survive resets/reboots.  The UPnP IGD-PCP Interworking
      Function MUST support IGD:2 behavior.

   RemoteHost:  Remote Peer IP Address
      Note a domain name is allowed by IGD:2 and has to be resolved into
      an IP address.

   ExternalPort:  External Port Number
      Mapped to the suggested PCP external port in MAP messages.

   InternalPort:  Internal Port Number
      Mapped to PCP internal port field in MAP messages.

   PortMappingProtocol:  Transport Protocol
      Mapped to PCP protocol field in MAP messages.  Note IGD only
      supports TCP and UDP.

   InternalClient:  Internal IP Address
      InternalClient can be an IP address or a domain name.  Only an IP
      address scheme is supported in PCP.  If a domain name is used
      Point, it must be resolved to an IP address by the Interworking
      Function when relying the message to the PCP Server.

   PortMappingDescription:  Not supported in base PCP
      If the local PCP Client support a PCP Option to convey the
      description, this option SHOULD be used to relay the mapping
      description.

   SystemUpdateID (only for IGD:2):  Managed locally by the UPnP IGD-PCP
      Interworking Function

   A_ARG_TYPE_PortListing (only for IGD:2):  Managed locally by the UPnP
      IGD-PCP Interworking Function

4.2.  IGD-PCP: Methods

   Both IGD:1 and IGD:2 methods applicable to the UPnP IGD-PCP
   Interworking Function are listed here.

   GetGenericPortMappingEntry:  This request is not relayed to the PCP
      Server
      IGD-PCP Interworking Function maintains an updated list of active
      mappings instantiated in the PCP Server by internal hosts.  See
      Section 5.8 for more information.







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   GetSpecificPortMappingEntry:  MAP with PREFER_FAILURE Option
      This request is relayed to the PCP Server by issuing MAP with
      PREFER_FAILURE Option.  It is RECOMMENDED to use a short lifetime
      (e.g., 60s).

   AddPortMapping:  MAP
      Refer to Section 5.7.2.

   AddAnyPortMapping (for IGD:2 only):  MAP
      No issue is encountered to proxy this request to the PCP Server.
      Refer to Section 5.7.1 for more details.

   DeletePortMapping:  MAP with a requested lifetime set to 0
      Refer to Section 5.9.

   DeletePortMappingRange (for IGD:2 only):  MAP with a lifetime
      positioned to 0
      Individual requests are issued by the IGD-PCP Interworking
      Function.  Refer to Section 5.9 for more details

   GetExternalIPAddress:  MAP OpCode (see Section 10.7 of
      [I-D.ietf-pcp-base])
      This can be achieved by requesting a short-lived mapping (e.g., to
      the Discard service (TCP/9 or UDP/9) or some other port).
      However, once that mapping expires a subsequent implicit or
      explicit dynamic mapping might be mapped to a different external
      IP address.
      MUST directly return the value of the corresponding State
      Variable.

   GetListOfPortMappings:  See Section 5.8 for more information
      The IGD-PCP Interworking Function maintains an updated list of
      active mappings as instantiated in the PCP Server.  The IGD-PCP
      Interworking Function handles locally this request.

4.3.  UPnP IGD-PCP: Errors

   This section lists PCP errors codes and the corresponding UPnP IGD
   ones.  Error codes specific to IGD:2 are tagged accordingly.












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   1 UNSUPP_VERSION:  501 "ActionFailed"
      Should not happen.

   2 NOT_AUTHORIZED:  IGD:1 718 "ConflictInMappingEntry" / IGD:2 606
      "Action not authorized"

   3 MALFORMED_REQUEST:  501 "ActionFailed"

   4 UNSUPP_OPCODE:  501 "ActionFailed"
      Should not happen.

   5 UNSUPP_OPTION:  501 "ActionFailed"
      Should not happen the exception of PREFER_FAILURE (this
      option is not mandatory to support but AddPortMapping() cannot be
      implemented without it).

   6 MALFORMED_OPTION:  501 "ActionFailed"
      Should not happen.

   7 NETWORK_FAILURE:  Not applicable
      Should not happen after communication was successfully established
      with a PCP Server.

   8 NO_RESOURCES:  IGD:1 501 "ActionFailed" / IGD:2 728
      "NoPortMapsAvailable"
      Cannot be distinguished from USER_EX_QUOTA.

   9 UNSUPP_PROTOCOL:  501 "ActionFailed"
      Should not happen.

   10 USER_EX_QUOTA:  IGD:1 501 "ActionFailed" / IGD:2 728
      "NoPortMapsAvailable"
      Cannot be distinguished from NO_RESOURCES.

   11 CANNOT_PROVIDE_EXTERNAL:  718 "ConflictInMappingEntry"
      or 714 "NoSuchEntryInArray"

   12 ADDRESS_MISMATCH:  501 "ActionFailed"
      Should not happen.

   13 EXCESSIVE_REMOTE_PEERS: 501 "ActionFailed"



5.  Specification of the IGD-PCP Interworking Function

   This section covers the scenarios with or without NAT in the IGD.




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   This specification assumes the PCP Server is configured to accept MAP
   OpCode.

   The IGD-PCP Interworking Function handles the "Mapping Nonce" as any
   PCP Client [I-D.ietf-pcp-base].

5.1.  PCP Server Discovery

   The IGD-PCP Interworking Function implements one of the discovery
   methods identified in [I-D.ietf-pcp-base] (e.g., DHCP
   [I-D.ietf-pcp-dhcp]).  The IGD-PCP Interworking Function behaves as a
   PCP Client when communicating with provisioned PCP Server(s).

   In order to not impact the delivery of local services requiring the
   control of the local IGD during any failure event to reach the PCP
   Server (e.g., no IP address/prefix is assigned to the IGD, IGD-PCP
   Interworking Function MUST NOT be invoked.  Indeed, UPnP machinery is
   used to control that device and therefore lead to successful
   operations of internal services.

5.2.  Control of the Firewall

   In order to configure security policies to be applied to inbound and
   outbound traffic, UPnP IGD can be used to control a local firewall
   engine.

   No IGD-PCP Interworking Function is therefore required for that
   purpose.

5.3.  NAT Control in LAN Side

   Internal UPnP Control Points are not aware of the presence of the
   IGD-PCP Interworking Function in the IGD.

   No modification is required in the UPnP Control Point.

5.4.  Port Mapping Tables

   IGD-PCP Interworking Function MUST store locally all the mappings
   instantiated by internal UPnP Control Points in the PCP Server.  All
   mappings SHOULD be stored in a permanent storage.

   Upon receipt of a PCP MAP Response from the PCP Server, the IGD-PCP
   Interworking Function MUST retrieve the enclosed mapping and MUST
   store it in the local mapping table.  The local mapping table is an
   image of the mapping table as maintained by the PCP Server for a
   given subscriber.




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5.5.  Interworking Function Without NAT in the IGD

   When no NAT is embedded in the IGD, the content of received
   WANIPConnection and PCP messages is not altered by the IGD-PCP
   Interworking Function (i.e., the content of WANIPConnection messages
   are mapped to the PCP messages (and mapped back) according to
   Section 4.1).

5.6.  NAT Embedded in the IGD

   When NAT is embedded in the IGD, the IGD-PCP Interworking Function
   MUST update the content of received mapping messages with the IP
   address and/or port number belonging to the external interface of the
   IGD (i.e., after the NAT1 operation in Figure 4) and not as initially
   positioned by the UPnP Control Point.

   All WANIPConnection messages issued by the UPnP Control Point (resp.,
   PCP Server) are intercepted by the IGD-PCP Interworking Function.
   Then, the corresponding messages (see Section 4.1, Section 4.2 and
   Section 4.3) are generated by the IGD-PCP Interworking Function and
   sent to the provisioned PCP Server (resp., corresponding UPnP Control
   Point).  The content of PCP messages received by the PCP Server
   reflects the mapping information as enforced in the first NAT.  In
   particular, the internal IP address and/or port number of the
   requests are replaced with the IP address and port number as assigned
   by the NAT of the IGD.  For the reverse path, PCP response messages
   are intercepted by the IGD-PCP Interworking Function.  The content of
   the corresponding WANIPConnection messages are updated:

   o  The internal IP address and/or port number as initially positioned
      by the UPnP Control Point and stored in the IGD NAT are used to
      update the corresponding fields in received PCP responses.

   o  The external IP and port number are not altered by the IGD-PCP
      Interworking Function.

   o  The NAT mapping entry in the IGD is updated with the result of PCP
      request.

   The lifetime of the mappings instantiated in the IGD SHOULD be the
   one assigned by the terminating PCP Server.  In any case, the
   lifetime MUST be lower or equal to the one assigned by the
   terminating PCP Server.

   Without the involvement of the IGD-PCP Interworking Function, the
   UPnP CP would retrieve an external IP address and port number having
   a limited scope and which can not be used to communicate with hosts
   located beyond NAT2 (i.e., assigned by the IGD and not the ones



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   assigned by NAT2 in Figure 4).

5.7.  Creating a Mapping

   Two methods can be used to create a mapping: AddPortMapping() or
   AddAnyPortMapping().

5.7.1.  AddAnyPortMapping()

   When a UPnP Control Point issues a AddAnyPortMapping(), this request
   is received by the UPnP Server.  The request is then relayed to the
   IGD-PCP Interworking Function which generates a PCP MAP Request (see
   Section 4.1 for mapping between WANIPConnection and PCP parameters).
   Upon receipt of a PCP MAP Response from the PCP Server, an XML
   mapping is returned to the requesting UPnP Control Point (the content
   of the messages follows the recommendations listed in Section 5.6 or
   Section 5.5 according to the deployed scenario).  A flow example is
   depicted in Figure 5.

   If a PCP Error is received from the PCP Server, a corresponding
   WANIPConnection error code (see Section 4.3) is generated by the IGD-
   PCP Interworking Function and sent to the requesting UPnP Control
   Point.  If a short lifetime error is returned (e.g., NETWORK_FAILURE,
   NO_RESOURCES), the PCP IWF MAY re-send the same request to the PCP
   Server after 30s.  If a negative answer is received, the error is
   then relayed to the requesting UPnP Control Point.

      Justification: Some applications (e.g., uTorrent, Vuzz, Emule)
      wait approximately 150s, 90s, 90s, respectively for a response
      after sending an UPnP request.  If a short lifetime error occurs,
      re-sending the requesting may lead to a positive response from the
      PCP Server.  UPnP Control Points are therefore not aware of short
      lifetime errors that were recovered quickly.


















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                            UPnP-PCP
   UPnP Control           Interworking
      Point                 Function                    PCP Server
        |                      |                             |
        |(1) AddAnyPortMapping |                             |
        |   ExternalPort=8080  |                             |
        |--------------------->|                             |
        |                      |   (2) PCP MAP Request       |
        |                      |requested external port=8080 |
        |                      |---------------------------->|
        |                      |                             |
        |                      |   (3) PCP MAP Response      |
        |                      | assigned external port=6598 |
        |                      |<----------------------------|
        |(4) AddAnyPortMapping |                             |
        |   ReservedPort=6598  |                             |
        |<---------------------|                             |


          Figure 5: Flow example when AddAnyPortMapping() is used

   If the IGD-PCP Interworking Function fails to establish a
   communication with the PCP Server, "501 ActionFailed" error code is
   to be returned to requesting UPnP CP.

5.7.2.  AddPortMapping()

   A dedicated option called PREFER_FAILURE is defined in
   [I-D.ietf-pcp-base] to toggle the behavior in a PCP Request message.
   This option is inserted by the IGD-PCP IWF when issuing its requests
   to the PCP Server only if a specific external port is requested by
   the UPnP Control Point.

   Upon receipt of AddPortMapping() from an UPnP Control Point, the IGD-
   PCP Interworking Function MUST generate a PCP MAP Request with all
   requested mapping information as indicated by the UPnP Control Point
   if no NAT is embedded in the IGD or updated as specified in
   Section 5.6.  In addition, the IGD-PCP IWF MUST insert a
   PREFER_FAILURE Option to the generated PCP request.

   If the requested external port is in use, a PCP error message will be
   sent by the PCP Server to the IGD-PCP IWF indicating
   CANNOT_PROVIDE_EXTERNAL as the error cause.  If a short lifetime
   error is returned, the PCP IWF MAY re-send the same request to the
   PCP Server after 30s.  If a negative answer is received, the IGD-PCP
   IWF relays a negative message to the UPnP Control Point indicating
   ConflictInMappingEntry as error code.  The UPnP Control Point may re-
   issue a new request with a new requested external port number.  This



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   process is repeated until a positive answer is received or maximum
   retry is reached.

   If the PCP Server is able to honor the requested external port, a
   positive response is sent to the requesting IGD-PCP IWF.  Upon
   receipt of the response from the PCP Server, the returned mapping
   MUST be stored by the IGD-PCP Interworking Function in its local
   mapping table and a positive answer MUST be sent to the requesting
   UPnP Control Point.  This answer terminates this exchange.

   If the IGD-PCP Interworking Function fails to establish a
   communication with the PCP Server, "501 ActionFailed" error code is
   to be returned to requesting UPnP CP.

   Figure 6 shows an example of the flow exchange that occurs when the
   PCP Server satisfies the request from the IGD-PCP IWF.  Figure 7
   shows the messages exchange when the requested external port is in
   use.

                            UPnP-PCP
   UPnP Control           Interworking
      Point                 Function                  PCP Server
        |                      |                             |
        | (1) AddPortMapping   |                             |
        |   ExternalPort=8080  |                             |
        |     Protocol=TCP     |                             |
        |--------------------->|                             |
        |                      |   (2) PCP MAP Request       |
        |                      |requested external port=8080 |
        |                      |        protocol=TCP         |
        |                      |       PREFER_FAILURE        |
        |                      |---------------------------->|
        |                      |                             |
        |                      |   (3) PCP MAP Response      |
        |                      | assigned external port=8080 |
        |                      |        protocol=TCP         |
        |                      |<----------------------------|
        | (4) AddPortMapping   |                             |
        |   ExternalPort=8080  |                             |
        |     Protocol=TCP     |                             |
        |<---------------------|                             |


                 Figure 6: Flow Example (Positive Answer)







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                            UPnP-PCP
   UPnP Control           Interworking
      Point                 Function                    PCP Server
        |                      |                             |
        | (1) AddPortMapping   |                             |
        |   ExternalPort=8080  |                             |
        |--------------------->|                             |
        |                      |   (2) PCP MAP Request       |
        |                      |requested external port=8080 |
        |                      |       PREFER_FAILURE        |
        |                      |---------------------------->|
        |                      |   (3) PCP MAP Response      |
        |                      |   CANNOT_PROVIDE_EXTERNAL   |
        |                      |<----------------------------|
        |     (4) Error:       |                             |
        |ConflictInMappingEntry|                             |
        |<---------------------|                             |
        | (5) AddPortMapping   |                             |
        |   ExternalPort=5485  |                             |
        |--------------------->|                             |
        |                      |   (6) PCP MAP Request       |
        |                      |requested external port=5485 |
        |                      |       PREFER_FAILURE        |
        |                      |---------------------------->|
        |                      |   (7) PCP MAP Response      |
        |                      |   CANNOT_PROVIDE_EXTERNAL   |
        |                      |<----------------------------|
        |     (8) Error:       |                             |
        |ConflictInMappingEntry|                             |
        |<---------------------|                             |
                               ....
        | (a) AddPortMapping   |                             |
        |   ExternalPort=6591  |                             |
        |--------------------->|                             |
        |                      |   (b) PCP MAP Request       |
        |                      |requested external port=6591 |
        |                      |       PREFER_FAILURE        |
        |                      |---------------------------->|
        |                      |   (c) PCP MAP Response      |
        |                      |   CANNOT_PROVIDE_EXTERNAL   |
        |                      |<----------------------------|
        |     (d) Error:       |                             |
        |ConflictInMappingEntry|                             |
        |<---------------------|                             |


                 Figure 7: Flow Example (Negative Answer)




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      Note: According to some experiments, some UPnP 1.0
      implementations, e.g., uTorrent, simply try the same external port
      X times (usually 4 times) and then fail if the port is in use; if
      it finds an external port not being used before X times, it will
      call AddPortMapping().  Also note that some applications uses
      GetSpecificPortMapping() to check whether a mapping exists.

5.8.  Listing One or a Set of Mappings

   In order to list active mappings, an UPnP Control Point may issue
   GetGenericPortMappingEntry(), GetSpecificPortMappingEntry() or
   GetListOfPortMappings().

   GetGenericPortMappingEntry() and GetListOfPortMappings() methods MUST
   NOT be proxied to the PCP Server since a local mapping is maintained
   by the IGD-PCP Interworking Function.

   Upon receipt of GetSpecificPortMappingEntry() from a UPnP Control
   Point, the IGD-PCP IWF MUST check first if the external port number
   is used by the requesting UPnP Control Point.  If the external port
   is already in use by the requesting UPnP Control Point, the IGD-PCP
   IWF MUST send back a positive answer.  If not, the IGD-PCP IWF MUST
   relay to the PCP Server a MAP request, with short lifetime (e.g.,
   60s), including a PREFER_FAILURE Option.  If the requested external
   port is in use, a PCP error message will be sent by the PCP Server to
   the IGD-PCP IWF indicating CANNOT_PROVIDE_EXTERNAL as the error
   cause.  Then, the IGD-PCP IWF relays a negative message to the UPnP
   Control Point.  If the port is not in use, the mapping will be
   created by the PCP Server and a positive response will be sent back
   to the IGD-PCP IWF.  Once received by the IGD-PCP IWF, it MUST relay
   a negative message to the UPnP Control Point indicating
   NoSuchEntryInArray as error code so that the UPnP control point knows
   the enquired mapping doesn't exist.

5.9.  Delete One or a Set of Mappings: DeletePortMapping() or
      DeletePortMappingRange()

   A UPnP Control Point requests the deletion of one or a list of
   mappings by issuing DeletePortMapping() or DeletePortMappingRange().
   In IGD:2, we assume the IGD applies the appropriate security policies
   to grant whether a Control Point has the rights to delete one or a
   set of mappings.  When authorization fails, "606 Action Not
   Authorized" error code MUST be returned the requesting Control Point.

   When DeletePortMapping() or DeletePortMappingRange() is received by
   the IGD-PCP Interworking Function, it first checks if the requested
   mappings to be removed are present in the local mapping table.  If no
   mapping matching the request is found in the local table, an error



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   code is sent back to the UPnP Control Point: "714 NoSuchEntryInArray"
   for DeletePortMapping() or "730 PortMappingNotFound" for
   DeletePortMappingRange().

   Figure 8 shows an example of UPnP Control Point asking to delete a
   mapping which is not instantiated in the local table of the IWF.

                            UPnP-PCP
   UPnP Control           Interworking
      Point                 Function                  PCP Server
        |                      |                           |
        |(1) DeletePortMapping |                           |
        |--------------------->|                           |
        |                      |                           |
        |     (2) Error:       |                           |
        |  NoSuchEntryInArray  |                           |
        |<---------------------|                           |
        |                      |                           |


                   Figure 8: Local Delete (IGD-PCP IWF)

   If a mapping matches in the local table, a PCP MAP delete request is
   generated taking into account the input arguments as included in
   DeletePortMapping() if no NAT is enabled in the IGD or the
   corresponding local IP address and port number as assigned by the
   local NAT if a NAT is enabled in the IGD.  When a positive answer is
   received from the PCP Server, the IGD-PCP Interworking Function
   updates its local mapping table (i.e., remove the corresponding
   entry) and notifies the UPnP Control Point about the result of the
   removal operation.  Once PCP MAP delete request is received by the
   PCP Server, it proceeds to removing the corresponding entry.  A PCP
   MAP delete response is sent back if the removal of the corresponding
   entry was successful; if not, a PCP Error is sent back to the IGD-PCP
   Interworking Function including the corresponding error cause (See
   Section 4.3).

   In case DeletePortMappingRange() is used, the IGD-PCP IWF undertakes
   a lookup on its local mapping table to retrieve individual mappings
   instantiated by the requesting Control Point (i.e., authorization
   checks) and matching the signaled port range (i.e., the external port
   is within "StartPort" and "EndPort" arguments of
   DeletePortMappingRange()).  If no mapping is found, "730
   PortMappingNotFound" error code is sent to the UPnP Control Point
   (Figure 9).  If a set of mappings are found, the IGD-PCP IWF
   generates individual PCP MAP delete requests corresponding to these
   mappings (See the example shown in Figure 10).




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      The IWF MAY send a positive answer to the requesting UPnP Control
      Point without waiting to receive all the answers from the PCP
      Server.  It is unlikely to encounter a problem in the PCP leg
      because the IWF has verified authorization rights and also the
      presence of the mapping in the local table.

                                 UPnP-PCP
   UPnP Control                Interworking
      Point                      Function                  PCP Server
        |                            |                           |
        |(1)DeletePortMappingRange() |                           |
        |     StartPort=8596         |                           |
        |     EndPort  =9000         |                           |
        |     Protocol =UDP          |                           |
        |--------------------------->|                           |
        |                            |                           |
        |       (2) Error:           |                           |
        |   PortMappingNotFound      |                           |
        |<---------------------------|                           |
        |                            |                           |


     Figure 9: Flow example when an error encountered when processing
                         DeletePortMappingRange()



























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   This example illustrates the exchanges that occur when the IWF
   receives DeletePortMappingRange().  In this example, only two
   mappings having the external port number in the 6000-6050 range are
   maintained in the local table.  The IWF issues two MAP requests to
   delete these mappings.
                                 UPnP-PCP
   UPnP Control                Interworking
      Point                      Function                  PCP Server
        |                            |                           |
        |(1)DeletePortMappingRange() |                           |
        |     StartPort=6000         |                           |
        |     EndPort  =6050         |                           |
        |     Protocol =UDP          |                           |
        |--------------------------->|                           |
        |                            |                           |
        |                            |    (2a)PCP MAP Request    |
        |                            |       protocol=UDP        |
        |                            |   internal-ip-address     |
        |                            |      internal-port        |
        |                            |   external-ip-address     |
        |                            |   external-port= 6030     |
        |                            |   Requested-lifetime= 0   |
        |                            |-------------------------->|
        |                            |                           |
        |                            |    (2c)PCP MAP Request    |
        |                            |       protocol=UDP        |
        |                            |   internal-ip-address     |
        |                            |      internal-port        |
        |                            |   external-ip-address     |
        |                            |   external-port= 6045     |
        |                            |   Requested-lifetime= 0   |
        |                            |-------------------------->|
        |                            |                           |
        |    (2b)Positive answer     |                           |
        |<---------------------------|                           |
        |                            |                           |

              Figure 10: Example of DeletePortMappingRange()

5.10.  Renewal

   Because of the incompatibility of mapping lifetimes between UPnP IGD
   and PCP, the IGD-PCP Interworking Function MUST simulate long and
   even infinite lifetimes.  Indeed, for requests having a requested
   infinite PortMappingLeaseDuration, the IGD-PCP Interworking Function
   MUST set the requested PCP Lifetime of the corresponding PCP request
   to 4294967296.  If PortMappingLeaseDuration is not infinite, the IGD-
   PCP Interworking Function MUST set the requested PCP Lifetime of the



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   corresponding PCP request to the same value as
   PortMappingLeaseDuration.  Furthermore, the IGD-PCP Interworking
   Function MUST maintain an additional timer set to the initial
   requested PortMappingLeaseDuration.  Upon receipt of a positive
   answer from the PCP server, the IGD-PCP Interworking Function relays
   the corresponding UPnP IGD response to the requesting UPnP CP with
   PortMappingLeaseDuration set to the same value as the one of the
   initial request.  Then, the IGD-PCP Interworking Function MUST renew
   periodically the instructed PCP mapping until the expiry of
   PortMappingLeaseDuration.  Responses received when renewing the
   mapping MUST NOT be relayed to the UPnP CP.

   In case an error is encountered during mapping renewal, the IGD-PCP
   Interworking Function has no means to inform the UPnP CP.

5.11.  Mappings Update

   When the IWF is co-located with the DHCP server, the state maintained
   by the IWF MUST be updated using the state of the local DHCP server.
   Particularly, if an IP address is assigned to a distinct host than
   the one owning the mappings, the IWF MUST delete all the mappings
   bound to that internal IP address.

   Upon change of the external IP address of the IWF, the IWF MAY renew
   the mappings it maintained.  This can be achieved only if a full
   state table is maintained by the IWF.  If the port quota is not
   exceeded, the IWF will retrieve new external IP address and port
   numbers.  The IWF has no means to notify the change of the external
   IP address and port to internal UPnP CPs.  Stale mappings will be
   maintained by the PCP Server.

   [I-D.ietf-pcp-base] defines a procedure for the PCP Server to notify
   PCP Clients about changes related to the mappings it maintains.  When
   unsolicited ANNOUNCE is received, the IWF proceeds to re-installing
   its mappings.  If distinct external IP address and port numbers are
   assigned, the IWF has no means to notify the change of the external
   IP address and port to internal UPnP CPs.

   Unsolicited PCP MAP/PEER responses received from a PCP Server are
   handled as any normal MAP/PEER response.

   Further analysis of PCP failure scenarios for the IGD-PCP
   Interworking Function are discussed in [I-D.boucadair-pcp-failure].


6.  IANA Considerations

   This document makes no request of IANA.



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   Note to RFC Editor: this section may be removed on publication as an
   RFC.


7.  Security Considerations

   IGD:2 authorization framework SHOULD be used [IGD2].  When only IGD:1
   is available, one SHOULD consider to enforce the default security,
   i.e., operation on the behalf of a third party is not allowed.

   This document defines a procedure to instruct PCP mappings for third
   party devices belonging to the same subscriber.  Identification means
   to avoid a malicious user to instruct mappings on behalf of a third
   party must be enabled.  Such means are already discussed in Section
   7.4.4 of [I-D.ietf-pcp-base].

   Security considerations elaborated in [I-D.ietf-pcp-base] and
   [Sec_DCP] should be taken into account.


8.  Acknowledgments

   Authors would like to thank F. Fontaine, C. Jacquenet, X. Deng, G.
   Montenegro, D. Thaler and R. Tirumaleswar for their review and
   comments.


9.  References

9.1.  Normative References

   [I-D.ietf-pcp-base]
              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)",
              draft-ietf-pcp-base-27 (work in progress), September 2012.

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

9.2.  Informative References

   [I-D.boucadair-pcp-failure]
              Boucadair, M., Dupont, F., and R. Penno, "Port Control
              Protocol (PCP) Failure Scenarios",
              draft-boucadair-pcp-failure-04 (work in progress),
              August 2012.

   [I-D.ietf-pcp-dhcp]



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              Boucadair, M., Penno, R., and D. Wing, "DHCP Options for
              the Port Control Protocol (PCP)", draft-ietf-pcp-dhcp-05
              (work in progress), September 2012.

   [I-D.ietf-pcp-proxy]
              Boucadair, M., Dupont, F., Penno, R., and D. Wing, "Port
              Control Protocol (PCP) Proxy Function",
              draft-ietf-pcp-proxy-01 (work in progress), August 2012.

   [IGD1]     UPnP Forum, "WANIPConnection:1 Service (http://
              www.upnp.org/specs/gw/
              UPnP-gw-WANIPConnection-v1-Service.pdf)", November 2001.

   [IGD2]     UPnP Forum, "WANIPConnection:2 Service (http://upnp.org/
              specs/gw/UPnP-gw-WANIPConnection-v2-Service.pdf)",
              September 2010.

   [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.

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

   [Sec_DCP]  UPnP Forum, "Device Protection:1", November 2009.


Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Email: mohamed.boucadair@orange.com


   Francis Dupont
   Internet Systems Consortium

   Email: fdupont@isc.org









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   Reinaldo Penno
   Cisco
   USA

   Email: repenno@cisco.com


   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: dwing@cisco.com





































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