Network Working Group                                           D. Cheng
Internet-Draft                                                    Huawei
Intended status: Standards Track                             J. Korhonen
Expires: February 11, April 1, 2017                              Broadcom Corporation
                                                            M. Boucadair
                                                                  Orange
                                                            S. Sivakumar
                                                           Cisco Systems
                                                         August 10,
                                                      September 28, 2016

       RADIUS Extensions for IP Port Configuration and Reporting
                draft-ietf-radext-ip-port-radius-ext-11
                draft-ietf-radext-ip-port-radius-ext-12

Abstract

   This document defines three new RADIUS attributes.  For devices that
   implement IP port ranges, these attributes are used to communicate
   with a RADIUS server in order to configure and report TCP/UDP ports
   and ICMP identifiers, IP transport
   ports, as well as mapping behavior for specific hosts.  This
   mechanism can be used in various deployment scenarios such as
   Carrier-Grade NAT, IPv4/IPv6 translators, Provider WLAN Gateway, etc.

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 February 11, April 1, 2017.

Copyright Notice

   Copyright (c) 2016 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Extensions of RADIUS Attributes and TLVs  . . . . . . . . . .   5
     3.1.  Extended Attributes for IP Ports  . . . . . . . . . . . .   6
       3.1.1.  IP-Port-Limit-Info Attribute  . . . . . . . . . . . .   6
       3.1.2.  IP-Port-Range Attribute . . . . . . . . . . . . . . .   8
       3.1.3.  IP-Port-Forwarding-Map  Attribute . . . . . . . . . .  10
     3.2.  RADIUS TLVs for IP Ports  . . . . . . . . . . . . . . . .  13
       3.2.1.  IP-Port-Type TLV  . . . . . . . . . . . . . . . . . .  13
       3.2.2.  IP-Port-Limit TLV . . . . . . . . . . . . . . . . . .  14
       3.2.3.  IP-Port-Ext-IPv4-Addr TLV . . . . . . . . . . . . . .  15
       3.2.4.  IP-Port-Int-IPv4-Addr TLV . . . . . . . . . . . . . .  16
       3.2.5.  IP-Port-Int-IPv6-Addr TLV . . . . . . . . . . . . . .  17
       3.2.6.  IP-Port-Int-Port TLV  . . . . . . . . . . . . . . . .  18
       3.2.7.  IP-Port-Ext-Port TLV  . . . . . . . . . . . . . . . .  18
       3.2.8.  IP-Port-Alloc TLV . . . . . . . . . . . . . . . . . .  19
       3.2.9.  IP-Port-Range-Start TLV . . . . . . . . . . . . . . .  20
       3.2.10. IP-Port-Range-End TLV . . . . . . . . . . . . . . . .  21
       3.2.11. IP-Port-Local-Id TLV  . . . . . . . . . . . . . . . .  22
   4.  Applications, Use Cases and Examples  . . . . . . . . . . . .  23
     4.1.  Managing CGN Port Behavior using RADIUS . . . . . . . . .  23
       4.1.1.  Configure IP Port Limit for a User  . . . . . . . . .  24
       4.1.2.  Report IP Port Allocation/Deallocation  . . . . . . .  26
       4.1.3.  Configure Forwarding Port Mapping . . . . . . . . . .  27
       4.1.4.  An Example  . . . . . . . . . . . . . . . . . . . . .  29
     4.2.  Report Assigned Port Set for a Visiting UE  . . . . . . .  30
   5.  Table of Attributes . . . . . . . . . . . . . . . . . . . . .  31
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  32
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
     7.1.  IANA Considerations on New IPFIX Information
           Elements  . . . . . . . . . . . . . . . . . . . . . . . .  33

     7.2.  IANA Considerations on New RADIUS Attributes  . . . . . .  33
     7.3.  IANA Considerations on New RADIUS TLVs  . . . . . . . . .  34
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  34
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  34
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  34
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  35
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  36  37

1.  Introduction

   In a broadband network, customer information is usually stored on a
   RADIUS server [RFC2865].  At the time when a user initiates an IP
   connection request, if this request is authorized, the RADIUS server
   will populate the user's configuration information to the Network
   Access Server (NAS), which is often referred to as a Broadband
   Network Gateway (BNG) in broadband access networks.  The Carrier-
   Grade NAT (CGN) function may also be implemented on the BNG.  Within
   this document, the CGN may perform NAT44 [RFC3022], NAT64 [RFC6146],
   or Dual-Stack Lite AFTR [RFC6333] function.  In such case, the CGN
   TCP/UDP IP
   transport port (or ICMP identifier) (e.g., TCP/UDP port) mapping(s) behavior(s) can be
   part of the configuration information sent from the RADIUS server to
   the NAS/BNG.  The NAS/BNG may also report to the RADIUS Server the port/
   identifier
   port/identifier mapping behavior applied by the CGN to a user session
   to the RADIUS server, as part of the accounting information sent from
   the NAS/BNG to a RADIUS server.

   When IP packets traverse the CGN, it performs TCP/UDP mapping on the IP
   transport (e.g., TCP/UDP) source port
   mapping or ICMP identifier mapping as required.  A TCP/ UDP  An IP transport
   source
   port or ICMP identifier, port, along with source IP address, destination IP address,
   destination port and protocol identifier if applicable, uniquely
   identify a session.  Since the number space of TCP/UDP IP transport ports
   and ICMP identifiers in
   CGN's external realm is shared among multiple users assigned with the
   same IPv4 address, the total number of a user's simultaneous IP
   sessions is likely to be subject to port quota (see Section 5 of
   [RFC6269]).

   The attributes defined in this document may also be used to report
   the assigned port range in some deployments such as Provider WLAN
   [I-D.gundavelli-v6ops-community-wifi-svcs].  For example, a visiting
   host can be managed by a CPE (Customer Premises Equipment ) which
   will need to report the assigned port range to the service platform.
   This is required for identification purposes (see TR-146 [TR-146] for
   more details).

   This document proposes three new attributes as RADIUS protocol's
   extensions, and they are used for separate purposes as follows:

   1.  IP-Port-Limit-Info: This attribute may be carried in RADIUS
       Access-Accept, Access-Request, Accounting-Request or CoA-Request
       packet.  The purpose of this attribute is to limit the total
       number of TCP/UDP IP source transport ports and/or ICMP identifiers allocated to a user,
       associated with one or more IPv4 or IPv6 addresses.

   2.  IP-Port-Range: This attribute may be carried in RADIUS
       Accounting-Request packet.  The purpose of this attribute is to
       report by an address sharing device (e.g., a CGN) to the RADIUS
       server the range of TCP/UDP IP source transport ports and/or ICMP identifiers that have been
       allocated or deallocated associated with a given IPv4 IPv4/IPv6
       address for a user.

   3.  IP-Port-Forwarding-Map: This attribute may be carried in RADIUS
       Access-Accept, Access-Request, Accounting-Request or CoA-Request
       packet.  The purpose of this attribute is to specify how an IP
       internal source transport port together with its internal IPv4 or
       IPv6 address and a TCP/ UDP port (or an ICMP identifier) is are mapped to
       another IPv4 address and a TCP/UDP port (or an ICMP identifier). external source transport port
       along with the external IPv4 address.

   IPFIX Information Elements [RFC7012] can be used for IP flow
   identification and representation over RADIUS.  This document
   provides a mapping between some RADIUS TLV and IPFIX Information
   Element Identifiers.  As a consequence,  A new IPFIX Information Elements are Element is defined by
   this document (see Section 3). 3.2.2).

   IP protocol numbers (refer to [ProtocolNumbers]) can be used for
   identification of IP transport protocols (e.g., TCP/UDP, DCCP and
   SCTP) that are associated with some RADIUS attributes.

2.  Terminology

   This document makes use of the following terms:

   o  IP Port: refers to the port numbers of IP transport protocols,
      including TCP port, UDP port and ICMP identifier. port.

   o  IP Port Type: refers to one of the following: (1) TCP/UDP port and
      ICMP identifier, (2) TCP port and UDP port, (3) TCP port, (4) UDP
      port, or (5) ICMP identifier. IP transport protocol as indicated by
      the IP transport protocol number, refer to (refer to
      [ProtocolNumbers])

   o  IP Port Limit: denotes the maximum number of IP ports for a
      specific IP port type, that a device supporting port ranges can
      use when performing port number mapping for a specific user.
      Note, this limit is usually associated with one or more IPv4 IPv4/IPv6
      addresses.

   o  IP Port Range: specifies a set of contiguous IP ports, indicated
      by the lowest numerical number and the highest numerical number,
      inclusively.

   o  Internal IP Address: refers to the IP address that is used as a
      source IP address in an outbound IP packet sent towards a device
      supporting port ranges in the internal realm.

   o  External IP Address: refers to the IP address that is used as a
      source IP address in an outbound IP packet after traversing a
      device supporting port ranges in the external realm.

   o  Internal Port: is a UDP or TCP port, or an ICMP identifier, IP transport port, which is allocated by a
      host or application behind a device supporting port ranges for an
      outbound IP packet in the internal realm.

   o  External Port: is a UDP or TCP port, or an ICMP identifier, IP transport port, which is allocated by a
      device supporting port ranges upon receiving an outbound IP packet
      in the internal realm, and is used to replace the internal port
      that is allocated by a user or application.

   o  External realm: refers to the networking segment where external IP
      addresses are used as source addresses of outbound packets
      forwarded by a device supporting port ranges.

   o  Internal realm: refers to the networking segment that is behind a
      device supporting port ranges and where internal IP addresses are
      used.

   o  Mapping: associates with a device supporting port ranges for a
      relationship between an internal IP address, internal port and the
      protocol, and an external IP address, external port, and the
      protocol.

   o  Port-based device: a device that is capable of providing IP
      address and IP transport port mapping services and in particular,
      with the granularity of one or more subsets within the 16-bit IP
      transport port number range.  A typical example of this device is
      a CGN, CPE, Provider WLAN Gateway, etc.

   Note that the definitions of "internal IP address", "internal port",
   "internal realm", "external IP address", "external port", "external
   realm", and "mapping" are the same as defined in Port Control
   Protocol (PCP) [RFC6887], and the Common Requirements for Carrier-
   Grade NATs (CGNs) [RFC6888].

3.  Extensions of RADIUS Attributes and TLVs

   These three new attributes are defined in the following sub-sections:

   1.  IP-Port-Limit-Info Attribute

   2.  IP-Port-Range Attribute
   3.  IP-Port-Forwarding-Map Attribute

   All these attributes are allocated from the RADIUS "Extended Type"
   code space per [RFC6929].

   These attributes and their embedded TLVs (refer to Section 3.2) are
   defined with globally unique names and follow the guideline in
   Section 2.7.1 of [RFC6929].

   In all the figures describing the RADIUS attributes and TLV formats
   in the following sub-sections, the fields are transmitted from left
   to right.

3.1.  Extended Attributes for IP Ports

3.1.1.  IP-Port-Limit-Info Attribute

   This attribute is of type "TLV" as defined in the RADIUS Protocol
   Extensions [RFC6929].  It contains some sub-attributes and the following sub-attributes:
   requirement is as follows:

   o  an  The IP-Port-Limit-Info Attribute MAY contain the IP-Port-Type TLV
      (see Section 3.2.1), 3.2.1).

   o  an  The IP-Port-Limit-Info Attribute MUST contain the IP-Port-Limit
      TLV (see Section 3.2.2), 3.2.2).

   o  an optional IP-Port-Ext-IPv4-Addr  The IP-Port-Limit-Info Attribute MAY contain the IP-Port-Ext-
      IPv4-Addr TLV (see Section 3.2.3).

   It

   The IP-Port-Limit-Info Attribute specifies the maximum number of IP
   ports as indicated in IP-Port-
   Limit IP-Port-Limit TLV, of a specific port type IP transport
   protocol as indicated in IP-Port-Type TLV, and associated with a
   given IPv4 address as indicated in IP-Port-Ext-
   IPv4-Addr IP-Port-Ext-IPv4-Addr TLV for an
   end user.

   Note that when IP-Port-Type TLV is not included as part of the IP-
   Port-Limit-Info Attribute, the port limit applies to all IP transport
   protocols.

   Note also that when IP-Port-Ext-IPv4-Addr TLV is not included as part
   of the IP-Port-Limit-Info Attribute, the port limit applies to all
   the IPv4 addresses managed by the port device, e.g., a CGN or NAT64
   device.

   The IP-Port-Limit-Info Attribute MAY appear in an Access-Accept
   packet.  It MAY also appear in an Access-Request packet as a
   preferred maximum number of IP ports indicated by the device
   supporting port ranges co-located with the NAS, e.g., a CGN or NAT64.
   However, the RADIUS server is not required to honor such a
   preference.

   The IP-Port-Limit-Info Attribute MAY appear in a CoA-Request packet.

   The IP-Port-Limit-Info Attribute MAY appear in an Accounting-Request
   packet.

   The IP-Port-Limit-Info Attribute MUST NOT appear in any other RADIUS
   packet.

   The format of the IP-Port-Limit-Info Attribute is shown in Figure 1.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    | Extended-Type |    Value ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

   Type

      241 (To be confirmed by IANA).

   Length

      This field indicates the total length in bytes of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLVs.

   Extended-Type

      TBD1.

   Value

      This field contains a set of TLVs as follows:

      IP-Port-Type TLV

         This TLV contains a value that indicates the IP port type.
         Refer to Section 3.2.1.

      IP-Port-Limit TLV
         This TLV contains the maximum number of IP ports of a specific
         IP port type and associated with a given IPv4 address for an
         end user.  This TLV must MUST be included in the IP-Port-Limit-Info
         Attribute.  Refer to Section 3.2.2.

      IP-Port-Ext-IPv4-Addr TLV

         This TLV contains the IPv4 address that is associated with the
         IP port limit contained in the IP-Port-Limit TLV.  This TLV is
         optionally included as part of the IP-Port-Limit-Info
         Attribute.  Refer to Section 3.2.3.

   IP-Port-Limit-Info Attribute is associated with the following
   identifier: 241.Extended-Type(TBD1).

3.1.2.  IP-Port-Range Attribute

   This attribute is of type "TLV" as defined in the RADIUS Protocol
   Extensions [RFC6929].  It contains some sub-attributes and the following sub-attributes:
   requirement is as follows:

   o  an  The IP-Port-Range Attribute MAY contain the IP-Port-Type TLV (see
      Section 3.2.1), 3.2.1).

   o  an IP-Port-Range-Start  The IP-Port-Range Attribute MUST contain the IP-Port-Alloc TLV
      (see Section 3.2.9), 3.2.8).

   o  an IP-Port-Range-End  For port allocation, the IP-Port-Range Attribute MUST contain both
      the IP-Port-Range-Start TLV (see Section 3.2.10),

   o  an IP-Port-Alloc 3.2.9) and the IP-Port-
      Range-END TLV (see Section 3.2.8), 3.2.10).  For port deallocation, the
      IP-Port-Range Attribute MAY contain both of these two TLVs; if the
      two TLVs are not included, it implies that all ports that are
      previously allocated are now all deallocated.

   o  an optional  The IP-Port-Range Attribute MAY contain the IP-Port-Ext-IPv4-Addr
      TLV (see Section 3.2.3), 3.2.3).

   o  an optional  The IP-Port-Range Attribute MAY contain the IP-Port-Local-Id TLV
      (see Section 3.2.11).

   This attribute

   The IP-Port-Range Attribute contains a range of contiguous IP ports.
   These ports are either to be allocated or deallocated depending on
   the Value carried by the IP-Port-Alloc TLV.

   If the IP-Port-Type TLV is included as part of a the IP-Port-Range
   Attribute, the port range is associated with the specific IP
   transport protocol as specified in the IP-Port-Type TLV, but
   otherwise is for all IP transport protocols.

   If the IP-Port-Ext-IPv4-Addr TLV is included as part of the IP-Port-
   Range Attribute, the port type and range as specified is associated with an IPv4
   address that as indicated, but otherwise is either
   allocated or deallocated for all IPv4 addresses by a the
   port device for (e.g., a given user, and CGN device) for the
   information is intended to be sent to RADIUS server. end user.

   This attribute can be used to convey a single IP transport port
   number; in such case IP-Port-Range-Start and IP-Port-Range-End conveys the same
   value.

   Within an IP-Port-Range Attribute, Value of the IP-Port-Alloc TLV is always
   included.  For port allocation, both IP-Port-Range-Start TLV and IP-
   Port-Range-End TLV must be included; for the
   IP-Port-Range-End TLV, respectively, contain the same port deallocation, number.

   The information contained in the
   inclusion of these two TLVs IP-Port-Range Attribute is optional and if not included, it
   implies that all ports that are previously allocated are now
   deallocated.  Both IP-Port-Ext-IPv4-Addr TLV and IP-Port-Local-Id TLV
   are optional and if included, they are used by a port device (e.g., a
   CGN device) sent to identify the end user.
   RADIUS server.

   The IP-Port-Range Attribute MAY appear in an Accounting-Request
   packet.

   The IP-Port-Range Attribute MUST NOT appear in any other RADIUS
   packet.

   The format of the IP-Port-Range Attribute is shown in Figure 2.

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    | Extended-Type |    Value ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2

   Type

      241 (To be confirmed by IANA).

   Length

      This field indicates the total length in bytes of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLVs.

   Extended-Type

      TBD2.

   Value

      This field contains a set of TLVs as follows:

      IP-Port-Type TLV
         This TLV contains a value that indicates the IP port type.
         Refer to Section 3.2.1.

      IP-Port-Alloc TLV

         This TLV contains a flag to indicate that the range of the
         specified IP ports for either allocation or deallocation.  This
         TLV must MUST be included as part of the IP-Port-Range Attribute.
         Refer to Section 3.2.8.

      IP-Port-Range-Start TLV

         This TLV contains the smallest port number of a range of
         contiguous IP ports.  To report the port allocation, this TLV
         must
         MUST be included together with IP-Port-Range-End TLV as part of
         the IP-Port-Range Attribute.  Refer to Section 3.2.9.

      IP-Port-Range-End TLV

         This TLV contains the largest port number of a range of
         contiguous IP ports.  To report the port allocation, this TLV
         must
         MUST be included together with IP-Port-Range-Start TLV as part
         of the IP-Port-Range Attribute.  Refer to Section 3.2.10.

      IP-Port-Ext-IPv4-Addr TLV

         This TLV contains the IPv4 address that is associated with the
         IP port range, as collectively indicated in the IP-Port-Range-
         Start TLV and the IP-Port-Range-End TLV.  This TLV is
         optionally included as part of the IP-Port-Range Attribute.
         Refer to Section 3.2.3.

      IP-Port-Local-Id TLV

         This TLV contains a local session identifier at the customer
         premise, such as MAC address, interface ID, VLAN ID, PPP
         sessions ID, VRF ID, IPv6 IP address/prefix, etc.  This TLV is
         optionally included as part of the IP-Port-Range Attribute.
         Refer to Section 3.2.11.

   The IP-Port-Range attribute is associated with the following
   identifier: 241.Extended-Type(TBD2).

3.1.3.  IP-Port-Forwarding-Map Attribute

   This attribute is of type "TLV" as defined in the RADIUS Protocol
   Extensions [RFC6929].  It contains some sub-attributes and the following sub-attributes:
   requirement is as follows:

   o  an  The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-Type
      TLV (see Section 3.2.1), 3.2.1).

   o  an IP-Port-Int-Port  The IP-Port-Forwarding-Map Attribute MUST contain both IP-Port-
      Int-Port TLV (see Section 3.2.6),

   o  an 3.2.6) and the IP-Port-Ext-Port TLV (see
      Section 3.2.7), 3.2.7).

   o  either an  If the internal realm is with IPv4 address family, the IP-Port-
      Forwarding-Map Attribute MUST contain the IP-Port-Int-IPv4-Addr
      TLV (see Section 3.2.4) or an IP-
      Port-Local-Id TLV (see Section 3.2.11),

   o  either an 3.2.4); if the internal realm is with IPv6
      address family, the IP-Port-Forwarding-Map Attribute MUST contain
      the IP-Port-Int-IPv6-Addr TLV (see Section 3.2.5) or an IP-
      Port-Local-Id 3.2.5).

   o  The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-Ext-
      IPv4-Addr TLV (see Section 3.2.11), 3.2.3).

   o  an IP-Port-Ext-IPv4-Addr  The IP-Port-Forwarding-Map Attribute MAY contain the IP-Port-
      Local-Id TLV (see Section 3.2.3). 3.2.11).

   The attribute contains a 2-byte IP internal port number that is
   associated with an internal IPv4 or IPv6 address, or a locally
   significant identifier at the customer site, and a 2-byte
   IP external port number.  The internal port number that is associated with
   an external IPv4 address.  The internal IPv4 or IPv6 address, or the local identifier must address that MUST always be
   included; the included.  The
   external port number is associated with a specific external IPv4
   address may also be included. if included, but otherwise with all external IPv4 addresses
   for the end user.

   If the IP-Port-Type TLV is included as part of the IP-Port-
   Forwarding-Map Attribute, the port mapping is associated with the
   specific IP transport protocol as specified in the IP-Port-Type TLV,
   but otherwise is for all IP transport protocols.

   The IP-Port-Forwarding-Map Attribute MAY appear in an Access-Accept
   packet.  It MAY also appear in an Access-Request packet to indicate a
   preferred port mapping by the device co-located with NAS.  However
   the server is not required to honor such a preference.

   The IP-Port-Forwarding-Map Attribute MAY appear in a CoA-Request
   packet.

   The IP-Port-Forwarding-Map Attribute MAY also appear in an
   Accounting-Request packet.

   The IP-Port-Forwarding-Map Attribute MUST NOT appear in any other
   RADIUS packet.

   The format of the IP-Port-Forwarding-Map Attribute is shown in
   Figure 3.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    | Extended-Type |    Value ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 3

   Type

      241 (To be confirmed by IANA).

   Length

      This field indicates the total length in bytes of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLVs.

   Extended-Type

      TBD3.

   Value

      This field contains a set of TLVs as follows:

      IP-Port-Type TLV

         This TLV contains a value that indicates the IP port type.
         Refer to Section 3.2.1.

      IP-Port-Int-Port TLV

         This TLV contains an internal IP port number associated with an
         internal IPv4 or IPv6 address.  This TLV must MUST be included
         together with IP-Port-Ext-Port TLV as part of the IP-Port-
         Forwarding-Map attribute.  Refer to Section 3.2.6.

      IP-Port-Ext-Port TLV

         This TLV contains an external IP port number associated with an
         external IPv4 address.  This TLV must MUST be included together with
         IP-Port-Int-Port TLV as part of the IP-Port-Forwarding-Map
         attribute.  Refer to Section 3.2.7.

      IP-Port-Int-IPv4-Addr TLV
         This TLV contains an IPv4 address that is associated with the
         internal IP port number contained in the IP-Port-Int-Port TLV.
         For internal realm with IPv4 network, either address family, this TLV or IP-Port-Local-Id TLV must MUST be
         included as part of the IP-Port-Forwarding-Map Attribute.
         Refer to Section 3.2.4.

      IP-Port-Int-IPv6-Addr TLV

         This TLV contains an IPv4 IPv6 address that is associated with the
         internal IP port number contained in the IP-Port-Int-Port TLV.
         For internal realm with IPv6 network, either address family, this TLV or IP-Port-Local-Id TLV must MUST be
         included as part of the IP-Port-Forwarding-Map Attribute.
         Refer to Section 3.2.5.

      IP-Port-Ext-IPv4-Addr TLV

         This TLV contains an IPv4 address that is associated with the
         external IP port number contained in the IP-Port-Ext-Port TLV.
         This TLV MAY be included as part of the IP-Port-Forwarding-Map
         Attribute.  Refer to Section 3.2.3.

      IP-Port-Local-Id TLV

         This TLV contains a local session identifier at the customer
         premise, such as MAC address, interface ID, VLAN ID, PPP
         sessions ID, VRF ID, IPv6 IP address/prefix, etc.  Either this TLV
         or IP-Port-Int-IP-Addr TLV must be included as part of the IP-
         Port-Forwarding-Map Attribute.  Refer to Section 3.2.11.

      IP-Port-Ext-IPv4-Addr TLV  This TLV contains an IPv4 address that is associated with the
         external IP port number contained in the IP-Port-Ext-Port TLV.
         This TLV may be
         optionally included as part of the IP-Port-Forwarding-Map
         Attribute.  Refer to Section 3.2.3. 3.2.11.

   The IP-Port-Forwarding-Map Attribute is associated with the following
   identifier: 241.Extended-Type(TBD3).

3.2.  RADIUS TLVs for IP Ports

   The TLVs that are included in the three attributes (see Section 3.1)
   are defined in the following sub-sections.  These TLVs use the format
   defined in [RFC6929].  As the three attributes carry similar data, we
   have defined a common set of TLVs which are used for all three
   attributes.  That is, the TLVs have the same name and number, when
   encapsulated in any one of the three parent attributes.  See
   Section 3.1.1, Section 3.1.2, and Section 3.1.3 for a list of which
   TLV is permitted within which parent attribute.

3.2.1.  IP-Port-Type TLV

   The format of IP-Port-Type TLV is shown in Figure 4.  This attribute
   carries IPFIX Information Element TBAx1, "transportType", which
   indicates the type of IP transport as follows:

   1:

      Refer to TCP port, UDP port, and ICMP identifier as a whole.

   2:

      Refer to TCP port and UDP port as a whole.

   3:

      Refer to TCP port only.

   4:

      Refer to UDP port only.

   5:

      Refer in Figure 4.  This attribute
   carries the IP transport protocol number defined by IANA (refer to ICMP identifier only.
   [ProtocolNumbers])
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Type    |     Length    |          transportType        Protocol-Number
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               transportType
           Protocol-Number         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 4

   TLV-Type

      1

   Length

      6

   transportType

   Protocol-Number

      Integer.  This field contains the data (unsigned8) of
      transportType (TBAx1) the port
      number defined in IPFIX, [ProtocolNumbers], right justified, and the
      unused bits in this field MUST be set to zero.

   IP-Port-Type TLV is MAY be included in the following Attributes:

   o  IP-Port-Limit-Info Attribute, identified as 241.TBD1.1 (see
      Section 3.1.1).

   o  IP-Port-Range Attribute, identified as 241.TBD2.1 (see
      Section 3.1.2).

   o  IP-Port-Forwarding-Mapping

   When the IP-Port-Type TLV is included within a RADIUS Attribute, identified the
   associated attribute is applied to the IP transport protocol as 241.TBD3.1
      (see Section 3.1.3).
   indicated by the Protocol-Number only, such as TCP, UDP, SCTP
   [RFC4960], DCCP [RFC4340], etc.

3.2.2.  IP-Port-Limit TLV

   The format of IP-Port-Limit TLV is shown in Figure 5.  This attribute
   carries IPFIX Information Element TBAx2, "natTransportLimit", "sourceTransportPortsLimit (TBAx1),
   which indicates the maximum number of IP transport ports for a given IPv4 address
   assigned to as a user limit
   for a specified IP-Port-Type. an end user to use that is associated with one or more IPv4 or
   IPv6 addresses.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Type    |     Length    |       natTransportLimit    sourceTransportPortsLimit
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            natTransportLimit
        sourceTransportPortsLimit  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 5

   TLV-Type

      2

   Length

      6

   natTransportLimit

   sourceTransportPortsLimit

      Integer.  This field contains the data (unsigned16) of
      natTransportLimit (TBAx2)
      sourceTransportPortsLimit (TBAx1) defined in IPFIX, right
      justified, and the unused bits in this field MUST be set to zero.

   IP-Port-Limit TLV is MUST be included as part of the IP-Port-Limit-Info
   Attribute (refer to Section 3.1.1), identified as 241.TBD1.2.

3.2.3.  IP-Port-Ext-IPv4-Addr TLV

   The format of IP-Port-Ext-IPv4-Addr TLV is shown in Figure 6.  This
   attribute carries IPFIX Information Element 225,
   "postNATSourceIPv4Address", which is the IPv4 source address after
   NAT operation (refer to [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Type    |    Length     |    postNATSourceIPv4Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        postNATSourceIPv4Address   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 6

   TLV-Type

      3

   Length

      6

   postNATSourceIPv4Address

      Integer.  This field contains the data (ipv4Address) of
      postNATSourceIPv4Address (225) defined in IPFIX.

   IP-Port-Ext-IPv4-Addr TLV MAY be included in the following
   Attributes:

   o  IP-Port-Limit-Info Attribute, identified as 241.TBD1.3 (see
      Section 3.1.1).

   o  IP-Port-Range Attribute, identified as 241.TBD2.3 (see
      Section 3.1.2).

   o  IP-Port-Forwarding-Mapping Attribute, identified as 241.TBD3.3
      (see Section 3.1.3).

3.2.4.  IP-Port-Int-IPv4-Addr TLV

   The format of IP-Port-Int-IPv4 TLV is shown in Figure 7.  This
   attribute carries IPFIX Information Element 8, "sourceIPv4Address",
   which is the IPv4 source address before NAT operation (refer to
   [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Type    |     Length    |       sourceIPv4Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         sourceIPv4Address         |
   +-+--+-+-+-+-+-+-++-+-+-+-+-+-+-+

                                 Figure 7

   TLV-Type

      4

   Length

      6

   sourceIPv4Address
      Integer.  This field contains the data (ipv4Address) of
      sourceIPv4Address (8) defined in IPFIX.

   IP-Port-Int-IPv4-Addr

   If the internal realm is with IPv4 address family, the IP-Port-Int-
   IPv4-Addr TLV MAY MUST be included as part of the IP-Port-
   Forwarding-Map IP-Port-Forwarding-Map
   Attribute (refer to Section 3.1.3), identified as 241.TBD3.4.

3.2.5.  IP-Port-Int-IPv6-Addr TLV

   The format of IP-Port-Int-IPv6-Addr TLV is shown in Figure 8.  This
   attribute carries IPFIX Information Element 27, "sourceIPv6Address",
   which is the IPv6 source address before NAT operation (refer to
   [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Type    |     Length    |        sourceIPv6Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             sourceIPv6Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             sourceIPv6Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                             sourceIPv6Address
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           sourceIPv6Address       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 8

   TLV-Type

      5

   Length

      18

   sourceIPv6Address

      IPv6 address (128 bits).  This field contains the data
      (ipv6Address) of sourceIPv6Address (27) defined in IPFIX.

   IP-Port-Int-IPv6-Addr

   If the internal realm is with IPv6 address family, the IP-Port-Int-
   IPv6-Addr TLV MAY MUST be included as part of the IP-Port-
   Forwarding-Map IP-Port-Forwarding-Map
   Attribute (refer to Section 3.1.3), identified as 241.TBD3.5.

3.2.6.  IP-Port-Int-Port TLV

   The format of IP-Port-Int-Port TLV is shown in Figure 9.  This
   attribute carries IPFIX Information Element 7, "sourceTransportPort",
   which is the source transport number associated with an internal IPv4
   or IPv6 address (refer to [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |      sourceTransportPort
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           sourceTransportPort     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 9

   TLV-Type

      6

   Length

      6

   sourceTransportPort

      Integer.  This field contains the data (unsigned16) of
      sourceTrasnportPort (7) defined in IPFIX, right justified, and
      unused bits MUST be set to zero.

   IP-Port-Int-Port TLV is MUST be included as part of the IP-Port-Forwarding-
   Map IP-Port-
   Forwarding-Map Attribute (refer to Section 3.1.3), identified as
   241.TBD3.6.

3.2.7.  IP-Port-Ext-Port TLV

   The format of IP-Port-Ext-Port TLV is shown in Figure 10.  This
   attribute carries IPFIX Information Element 227,
   "postNAPTSourceTransportPort", which is the transport number
   associated with an external IPv4 address(refer to [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |  postNAPTSourceTransportPort
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      postNAPTSourceTransportPort  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 10

   TLV-Type

      7

   Length

      6

   postNAPTSourceTransportPort

      Integer.  This field contains the data (unsigned16) of
      postNAPTSourceTrasnportPort (227) defined in IPFIX, right
      justified, and unused bits must MUST be set to zero.

   IP-Port-Ext-Port TLV is MUST be included as part of the IP-Port-Forwarding-
   Map IP-Port-
   Forwarding-Map Attribute (refer to Section 3.1.3), identified as
   241.TBD3.7.

3.2.8.  IP-Port-Alloc TLV

   The format of IP-Port-Alloc TLV is shown in Figure 11.  This
   attribute carries IPFIX Information Element 230, "natEvent", which is
   a flag to indicate an action of NAT operation (refer to [IPFIX]).

   When the value of natEvent is "1" (Create event), it means to
   allocate a range of transport ports; when the value is "2", it means
   to deallocate a range of transports ports.  For the purpose of this
   TLV, no other value is used.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |            natEvent
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               natEvent            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 11

   TLV-Type

      8

   Length

      6

   natEvent

      Integer.  This field contains the data (unsigned8) of natEvent
      (230) defined in IPFIX, right justified, and unused bits must MUST be
      set to zero.  It indicates the allocation or deallocation of a
      range of IP ports as follows:

      1:

         Allocation

      2:

         Deallocation

   Reserved:

      0.

   IP-Port-Alloc TLV is MUST be included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.2), identified as 241.TBD2.8.

3.2.9.  IP-Port-Range-Start TLV

   The format of IP-Port-Range-Start TLV is shown in Figure 12.  This
   attribute carries IPFIX Information Element 361, "portRangeStart",
   which is the smallest port number of a range of contiguous transport
   ports (refer to [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |         portRangeStart
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             portRangeStart        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 12

   TLV-Type

      9

   Length

      6

   portRangeStart

      Integer.  This field contains the data (unsigned16) of (361)
      defined in IPFIX, right justified, and unused bits must MUST be set to
      zero.

   IP-Port-Range-Start TLV is included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.2), identified as 241.TBD2.9.

3.2.10.  IP-Port-Range-End TLV

   The format of IP-Port-Range-End TLV is shown in Figure 13.  This
   attribute carries IPFIX Information Element 362, "portRangeEnd",
   which is the largest port number of a range of contiguous transport
   ports (refer to [IPFIX]).

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |          portRangeEnd
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              portRangeEnd         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 13

   TLV-Type
      10

   Length

      6

   portRangeEnd

      Integer.  This field contains the data (unsigned16) of (362)
      defined in IPFIX, right justified, and unused bits must be set to
      zero.

   IP-Port-Range-End TLV unused bits MUST be set to
      zero.

   IP-Port-Range-End TLV is included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.2), identified as 241.TBD2.10.

3.2.11.  IP-Port-Local-Id TLV

   The format of IP-Port-Local-Id TLV is shown in Figure 14.  This
   attribute carries a string called "localID", which is a local
   significant identifier as explained below.

   The primary issue addressed by this TLV is that there are CGN
   deployments that do not distinguish internal hosts by their internal
   IP address alone, but use further identifiers for unique subscriber
   identification.  For example, this is the case if a CGN supports
   overlapping private or shared IP address spaces (refer to [RFC1918]
   and [RFC6598]) for internal hosts of different subscribers.  In such
   cases, different internal hosts are identified and mapped at the CGN
   by their IP address and/or another identifier, for example, the
   identifier of a tunnel between the CGN and the subscriber.  In these
   scenarios (and similar ones), the internal IP address is included as part of not
   sufficient to demultiplex connections from internal hosts.  An
   additional identifier needs to be present in the IP-Port-Range
   Attribute (refer and IP-Port-Forwarding-Mapping Attribute in order to Section 3.1.2), identified as 241.TBD2.10.

3.2.11.  IP-Port-Local-Id TLV
   uniquely identify an internal host.  The format of IP-Port-Local-Id TLV is shown in Figure 14.  This
   attribute carries IPFIX Information Element TBAx3, "localID", which
   is a local significant identifier as explained below.

   In some CGN deployment scenarios such as DS-Extra-Lite [RFC6619] and
   Lightweight 4over6 [RFC7596], parameters at a customer premise such
   as MAC address, interface ID, VLAN ID, PPP session ID, IPv6 prefix,
   VRF ID, etc., may also be required to pass used
   to the RADIUS server as
   part of the accounting record. carry this identifier.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    TLV-Type   |     Length    |        localID ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 14

   TLV-Type
      11

   Length

      Variable number of bytes.

   localID

      string.  The data type of this field is string (refer to
      [I-D.ietf-radext-datatypes]).  This field contains the data (string) of (TBAx3) defined
      in IPFIX.  This that
      is a local session identifier at the customer premise, such as MAC
      address, interface ID, VLAN ID, PPP sessions ID, VRF ID, IPv6 IP
      address/prefix, etc.

   IP-Port-Local-Id TLV MAY be included in the following Attributes:

   o  IP-Port-Range Attribute, identified as 241.TBD2.11 (see
      Section 3.1.2).

   o  IP-Port-Forwarding-Mapping Attribute, identified as 241.TBD3.11
      (see Section 3.1.3).

4.  Applications, Use Cases and Examples

   This section describes some applications and use cases to illustrate
   the use of the attributes proposed in this document.

4.1.  Managing CGN Port Behavior using RADIUS

   In a broadband network, customer information is usually stored on a
   RADIUS server, and the BNG acts as a NAS.  The communication between
   the NAS and the RADIUS server is triggered by a user when it signs in
   to the Internet service, where either PPP or DHCP/DHCPv6 is used.
   When a user signs in, the NAS sends a RADIUS Access-Request message
   to the RADIUS server.  The RADIUS server validates the request, and
   if the validation succeeds, it in turn sends back a RADIUS Access-
   Accept message.  The Access-Accept message carries configuration
   information specific to that user, back to the NAS, where some of the
   information would pass on to the requesting user via PPP or DHCP/
   DHCPv6.

   A CGN function in a broadband network would is most likely co-located on a
   BNG.  In that case, parameters for CGN port/identifier port mapping behavior for
   users can be configured on the RADIUS server.  When a user signs in
   to the Internet service, the associated parameters can be conveyed to
   the NAS, and proper configuration is accomplished on the CGN device
   for that user.

   Also, CGN operation status such as CGN port/identifier port allocation and
   deallocation for a specific user on the BNG can also be transmitted
   back to the RADIUS server for accounting purpose using the RADIUS
   protocol.

   RADIUS protocol has already been widely deployed in broadband
   networks to manage BNG, thus the functionality described in this
   specification introduces little overhead to the existing network
   operation.

   In the following sub-sections, we describe how to manage CGN behavior
   using RADIUS protocol, with required RADIUS extensions proposed in
   Section 3.

4.1.1.  Configure IP Port Limit for a User

   In the face of IPv4 address shortage, there are currently proposals
   to multiplex multiple users' connections over a smaller number of
   shared IPv4 addresses, such as Carrier Grade NAT [RFC6888], Dual-
   Stack Lite [RFC6333], NAT64 [RFC6146], etc.  As a result, a single
   IPv4 public address may be shared by hundreds or even thousands of
   users.  As indicated in [RFC6269], it is therefore necessary to
   impose limits on the total number of ports available to an individual
   user to ensure that the shared resource, i.e., the IPv4 address,
   remains available in some capacity to all the users using it.  The
   support of IP port limit is also documented in [RFC6888] as a
   requirement for CGN.

   The IP port limit imposed to a specific an end user may be on the total number
   of TCP and UDP ports plus the number of ICMP identifiers, IP source transport ports, or
   with other granularities a specific IP transport protocol as
   defined in Section 3.1.1.

   The per-user based IP port limit is configured on a RADIUS server,
   along with other user information such as credentials.  The value of
   this IP port limit is based on service agreement and its
   specification is out of the scope of this document.

   When a user signs in to the Internet service successfully, the IP
   port limit for the subscriber is passed by the RADIUS server to the
   BNG, acting as a NAS and co-located with the CGN, using a new RADIUS
   attribute called IP-Port-Limit-Info (defined in Section 3.1.1), along
   with other configuration parameters.  While some parameters are
   passed to the user, the IP port limit is recorded on the CGN device
   for imposing the usage of TCP/UDP IP transport ports and ICMP identifiers for that user.

   Figure 15 illustrates how RADIUS protocol is used to configure the
   maximum number of TCP/UDP ports for a given user on a NAT44 device.

   User                     NAT44/NAS                      AAA
    |                         BNG                         Server
    |                          |                             |
    |                          |                             |
    |----Service Request------>|                             |
    |                          |                             |
    |                          |-----Access-Request -------->|
    |                          |                             |
    |                          |<----Access-Accept-----------|
    |                          |     (IP-Port-Limit-Info)    |
    |                          |     (for TCP/UDP ports)     |
    |<---Service Granted ------|                             |
    |    (other parameters)    |                             |
    |                          |                             |
    |                  (NAT44 external port                  |
    |                   allocation and                       |
    |                   IPv4 address assignment)             |
    |                          |                             |

      Figure 15: RADIUS Message Flow for Configuring NAT44 Port Limit

   The IP port limit created on a CGN device for a specific user using
   RADIUS extension may be changed using RADIUS CoA message [RFC5176]
   that carries the same RADIUS attribute.  The CoA message may be sent
   from the RADIUS server directly to the NAS, which once accepts and
   sends back a RADIUS CoA ACK message, the new IP port limit replaces
   the previous one.

   Figure 16 illustrates how RADIUS protocol is used to increase the
   TCP/UDP port limit from 1024 to 2048 on a NAT44 device for a specific
   user.

   User                     NAT44/NAS                         AAA
    |                         BNG                            Server
    |                          |                               |
    |              TCP/UDP Port Limit (1024)                   |
    |                          |                               |
    |                          |<---------CoA Request----------|
    |                          |       (IP-Port-Limit-Info)    |
    |                          |       (for TCP/UDP ports)     |
    |                          |                               |
    |              TCP/UDP Port Limit (2048)                   |
    |                          |                               |
    |                          |---------CoA Response--------->|
    |                          |                               |

   Figure 16: RADIUS Message Flow for changing a user's NAT44 port limit

4.1.2.  Report IP Port Allocation/Deallocation

   Upon obtaining the IP port limit for a user, the CGN device needs to
   allocate a TCP/UDP port or an ICMP identifiers IP transport port for the user when receiving a new IP
   flow sent from that user.

   As one practice, a CGN may allocate a bulk block of TCP/UDP IP ports or ICMP
   identifiers one at a time for a
   specific user, instead of one port/
   identifier port at a time, and within each port bulk,
   block, the ports/
   identifiers ports may be randomly distributed or in consecutive
   fashion.  When a CGN device allocates bulk a block of TCP/UDP ports and ICMP
   identifiers, transport ports, the
   information can be easily conveyed to the RADIUS server by a new
   RADIUS attribute called the IP-Port-Range (defined in Section 3.1.2).
   The CGN device may allocate one or more TCP/UDP port
   ranges or ICMP identifier ranges, or generally called IP port ranges, where each
   range contains a set of numbers representing TCP/UDP ports
   or ICMP identifiers, IP transport ports, and
   the total number of ports/identifiers must ports MUST be less or equal to the associated IP
   port limit imposed for that user.  A CGN device may choose to
   allocate a small port range, and allocate more at a later time as
   needed; such practice is good because its randomization in nature.

   At the same time, the CGN device also needs to decide the shared IPv4
   address for that user.  The shared IPv4 address and the pre-allocated
   IP port range are both passed to the RADIUS server.

   When a user initiates an IP flow, the CGN device randomly selects a
   TCP/UDP
   transport port or ICMP identifier number from the associated and pre-allocated IP port
   range for that user to replace the original source TCP/UDP port or ICMP identifier, number, along
   with the replacement of the source IP address by the shared IPv4
   address.

   A CGN device may decide to "free" a previously assigned set of TCP/
   UDP IP
   ports or ICMP identifiers that have been allocated for a specific user but not currently
   in use, and with that, the CGN device must send the information of
   the deallocated IP port range along with the shared IPv4 address to
   the RADIUS server.

   Figure 17 illustrates how RADIUS protocol is used to report a set of
   ports allocated and deallocated, respectively, by a NAT44 device for
   a specific user to the RADIUS server.

   Host                      NAT44/NAS                     AAA
    |                         BNG                         Server
    |                          |                             |
    |                          |                             |
    |----Service Request------>|                             |
    |                          |                             |
    |                          |-----Access-Request -------->|
    |                          |                             |
    |                          |<----Access-Accept-----------|
    |<---Service Granted ------|                             |
    |    (other parameters)    |                             |
   ...                        ...                           ...
    |                          |                             |
    |                          |                             |
    |                (NAT44 decides to allocate              |
    |                 a TCP/UDP port range for the user)     |
    |                          |                             |
    |                          |-----Accounting-Request----->|
    |                          |    (IP-Port-Range           |
    |                          |     for allocation)         |
   ...                        ...                           ...
    |                          |                             |
    |                (NAT44 decides to deallocate            |
    |                 a TCP/UDP port range for the user)     |
    |                          |                             |
    |                          |-----Accounting-Request----->|
    |                          |    (IP-Port-Range           |
    |                          |     for deallocation)       |
    |                          |                             |

      Figure 17: RADIUS Message Flow for reporting NAT44 allocation/
                        deallocation of a port set

4.1.3.  Configure Forwarding Port Mapping

   In most scenarios, the port mapping on a NAT device is dynamically
   created when the IP packets of an IP connection initiated by a user
   arrives.  For some applications, the port mapping needs to be pre-
   defined allowing IP packets of applications from outside a CGN device
   to pass through and "port forwarded" to the correct user located
   behind the CGN device.

   Port Control Protocol [RFC6887], provides a mechanism to create a
   mapping from an external IP address and port to an internal IP
   address and port on a CGN device just to achieve the "port
   forwarding" purpose.  PCP is a server-client protocol capable of
   creating or deleting a mapping along with a rich set of features on a
   CGN device in dynamic fashion.  In some deployment, all users need is
   a few, typically just one pre-configured port mapping for
   applications such as web cam at home, and the lifetime of such a port
   mapping remains valid throughout the duration of the customer's
   Internet service connection time.  In such an environment, it is
   possible to statically configure a port mapping on the RADIUS server
   for a user and let the RADIUS protocol to propagate the information
   to the associated CGN device.

   Figure 18 illustrates how RADIUS protocol is used to configure a
   forwarding port mapping on a NAT44 device by using RADIUS protocol.

   Host                     NAT/NAS                           AAA
    |                         BNG                            Server
    |                          |                               |
    |----Service Request------>|                               |
    |                          |                               |
    |                          |---------Access-Request------->|
    |                          |                               |
    |                          |<--------Access-Accept---------|
    |                          |   (IP-Port-Forwarding-Map)    |
    |<---Service Granted ------|                               |
    |    (other parameters)    |                               |
    |                          |                               |
    |                 (Create a port mapping                   |
    |                  for the user, and                       |
    |                  associate it with the                   |
    |                  internal IP address                     |
    |                  and external IP address)                |
    |                          |                               |
    |                          |                               |
    |                          |------Accounting-Request------>|
    |                          |    (IP-Port-Forwarding-Map)   |

     Figure 18: RADIUS Message Flow for configuring a forwarding port
                                  mapping

   A port forwarding mapping that is created on a CGN device using
   RADIUS extension as described above may also be changed using RADIUS
   CoA message [RFC5176] that carries the same RADIUS associate.  The
   CoA message may be sent from the RADIUS server directly to the NAS,
   which once accepts and sends back a RADIUS CoA ACK message, the new
   port forwarding mapping then replaces the previous one.

   Figure 19 illustrates how RADIUS protocol is used to change an
   existing port mapping from (a:X) to (a:Y), where "a" is an internal
   port, and "X" and "Y" are external ports, respectively, for a
   specific user with a specific IP address
   Host                     NAT/NAS                           AAA
    |                         BNG                            Server
    |                          |                               |
    |                    Internal IP Address                   |
    |                    Port Map (a:X)                        |
    |                          |                               |
    |                          |<---------CoA Request----------|
    |                          |    (IP-Port-Forwarding-Map)   |
    |                          |                               |
    |                    Internal IP Address                   |
    |                    Port Map (a:Y)                        |
    |                          |                               |
    |                          |---------CoA Response--------->|
    |                          |    (IP-Port-Forwarding-Map)   |

   Figure 19: RADIUS Message Flow for changing a user's forwarding port
                                  mapping

4.1.4.  An Example

   An Internet Service Provider (ISP) assigns TCP/UDP 500 ports for the
   user Joe. This number is the limit that can be used for TCP/UDP ports
   on a NAT44 device for Joe, and is configured on a RADIUS server.
   Also, Joe asks for a pre-defined port forwarding mapping on the NAT44
   device for his web cam applications (external port 5000 maps to
   internal port 80).

   When Joe successfully connects to the Internet service, the RADIUS
   server conveys the TCP/UDP port limit (1000) and the forwarding port
   mapping (external port 5000 to internal port 80) to the NAT44 device,
   using IP-Port-Limit-Info Attribute and IP-Port-Forwarding-Map
   attribute, respectively, carried by an Access-Accept message to the
   BNG where NAS and CGN co-located.

   Upon receiving the first outbound IP packet sent from Joe's laptop,
   the NAT44 device decides to allocate a small port pool that contains
   40 consecutive ports, from 3500 to 3540, inclusively, and also assign
   a shared IPv4 address 192.0.2.15, for Joe. The NAT44 device also
   randomly selects one port from the allocated range (say 3519) and use
   that port to replace the original source port in outbound IP packets.

   For accounting purpose, the NAT44 device passes this port range
   (3500-3540) and the shared IPv4 address 192.0.2.15 together to the
   RADIUS server using IP-Port-Range attribute carried by an Accounting-
   Request message.

   When Joe works on more applications with more outbound IP sessions
   and the port pool (3500-3540) is close to exhaust, the NAT44 device
   allocates a second port pool (8500-8800) in a similar fashion, and
   also passes the new port range (8500-8800) and IPv4 address
   192.0.2.15 together to the RADIUS server using IP-Port-Range
   attribute carried by an Accounting-Request message.  Note when the
   CGN allocates more ports, it needs to assure that the total number of
   ports allocated for Joe is within the limit.

   Joe decides to upgrade his service agreement with more TCP/UDP ports
   allowed (up to 1000 ports).  The ISP updates the information in Joe's
   profile on the RADIUS server, which then sends a CoA-Request message
   that carries the IP-Port-Limit-Info Attribute with 1000 ports to the
   NAT44 device; the NAT44 device in turn sends back a CoA-ACK message.
   With that, Joe enjoys more available TCP/UDP ports for his
   applications.

   When Joe travels, most of the IP sessions are closed with their
   associated TCP/UDP ports released on the NAT44 device, which then
   sends the relevant information back to the RADIUS server using IP-
   Port-Range attribute carried by Accounting-Request message.

   Throughout Joe's connection with his ISP Internet service,
   applications can communicate with his web cam at home from external
   realm directly traversing the pre-configured mapping on the CGN
   device.

   When Joe disconnects from his Internet service, the CGN device will
   deallocate all TCP/UDP ports as well as the port-forwarding mapping,
   and send the relevant information to the RADIUS server.

4.2.  Report Assigned Port Set for a Visiting UE

   Figure 20 illustrates an example of the flow exchange which occurs
   when a visiting UE connects to a CPE offering WLAN service.

   For identification purposes (see [RFC6967]), once the CPE assigns a
   port set, it issues a RADIUS message to report the assigned port set.

   UE         CPE             NAS                          AAA
    |                         BNG                         Server
    |                          |                             |
    |                          |                             |
    |----Service Request------>|                             |
    |                          |                             |
    |                          |-----Access-Request -------->|
    |                          |                             |
    |                          |<----Access-Accept-----------|
    |<---Service Granted ------|                             |
    |    (other parameters)    |                             |
   ...          |             ...                           ...
    |<---IP@----|              |                             |
    |           |              |                             |
    |   (CPE assigns a TCP/UDP port                          |
    |   range for this visiting UE)                          |
    |           |                                            |
    |           |--Accounting-Request-...------------------->|
    |           |    (IP-Port-Range                          |
    |           |     for allocation)                        |
   ...          |             ...                           ...
    |           |              |                             |
    |           |              |                             |
    |   (CPE withdraws a TCP/UDP port                        |
    |   range for a visiting UE)                             |
    |           |                                            |
    |           |--Accounting-Request-...------------------->|
    |           |    (IP-Port-Range                          |
    |           |     for deallocation)                      |
    |           |                                            |

       Figure 20: RADIUS Message Flow for reporting CPE allocation/
                deallocation of a port set to a visiting UE

5.  Table of Attributes

   This document proposes three new RADIUS attributes and their formats
   are as follows:

   o  IP-Port-Limit-Info: 241.TBD1.

   o  IP-Port-Range: 241.TBD2.

   o  IP-Port-Forwarding-Map: 241.TBD3.

   Note to IANA: it is assumed that Extended-Type-1 "241" will be used
   for these attributes.

   The following table provides a guide as what type of RADIUS packets
   that may contain these attributes, and in what quantity.

   Request Accept Reject Challenge Acct.      #   Attribute
                                   Request
   0+      0+     0      0         0+         TBA IP-Port-Limit-Info
   0       0      0      0         0+         TBA IP-Port-Range
   0+      0+     0      0         0+         TBA IP-Port-Forwarding-Map

   The following table defines the meaning of the above table entries.

   0  This attribute MUST NOT be present in packet.
   0+ Zero or more instances of this attribute MAY be present in packet.

6.  Security Considerations

   This document does not introduce any security issue other than the
   ones already identified in RADIUS [RFC2865] and [RFC5176] for CoA
   messages.  Known RADIUS vulnerabilities apply to this specification.
   For example, if RADIUS packets are sent in the clear, an attacker in
   the communication path between the RADIUS client and server may glean
   information that it will use to prevent a legitimate user to access
   the service by appropriately setting the maximum number of IP ports
   conveyed in an IP-Port-Limit-Info attribute, Attribute, exhaust the port quota
   of a user by installing many mapping entries (IP-Port-Forwarding-Map
   attribute),
   Attribute), prevent incoming traffic to be delivered to its
   legitimate destination by manipulating the mapping entries installed
   by means of an IP-Port-Forwarding-Map attribute, Attribute, discover the IP
   address and port range assigned to a given user and which is reported
   in an IP-Port-Range attribute, Attribute, etc.  The root cause of these attack
   vectors is the communication between the RADIUS client and server.

   The IP-Port-Local-Id TLV includes an identifier of which the type and
   length is deployment and implementation dependent.  This identifier
   might carry privacy sensitive information.  It is therefore
   RECOMMENDED to utilize identifiers that do not have such privacy
   concerns.

   This document targets deployed where a trusted relationship is in
   place between the RADIUS client and server with communication
   optionally secured by IPsec or Transport Layer Security (TLS)
   [RFC6614].

7.  IANA Considerations

   This document requires new code point assignments for both IPFIX
   Information Elements and RADIUS attributes as explained in the
   following sub-sections.

   It is assumed that Extended-Type-1 "241" will be used for RADIUS
   attributes in Section 7.2.

7.1.  IANA Considerations on New IPFIX Information Elements

   The following are code point assignments for is a new IPFIX Information
   Elements Element as requested by this
   document:

   o  transportType (refer to Section 3.2.1): The identifier of this
      IPFIX Information Element is TBAx1.  The data type of this IPFIX
      Information Element is unsigned8, the data type semantics is
      identifier, the data unit is null, and the data value range is 1
      to 5 inclusively.  The Element's value indicates TCP/UDP ports and
      ICMP Identifiers (1), TCP/UDP ports (2), TCP ports (3), UDP ports
      (4) or ICMP identifiers (5).

   o  natTransportLimit  sourceTransportPortsLimit (refer to Section 3.2.2): The identifier of this
      IPFIX Information

      *  Name: sourceTransportPortsLimit.

      *  Element is TBAx2.  The data type of this IPFIX ID: TBAx1.

      *  Description: This Information Element is unsigned16, the data type semantics is
      totalCounter, the data type unit is ports, and the data value
      range is from 1 to 65535.  The Element's value is contains the max maximum
         number of IP source transport ports to be assigned to that is a limit for an end
         user to use and is associated with one or more IPv4 or IPv6
         addresses.

   o  localID (refer to Section 3.2.11): The identifier of this IPFIX
      Information Element is TBAx3.  The data type of this IPFIX
      Information Element is string, the data

      *  Data type: unsigned16.

      *  Data type semantics is default,
      the data semantics: totalCounter.

      *  Data type unit is null.  The Element's unit: ports.

      *  Data value is an IPv4 or
      IPv6 address, a MAC address, a VLAN ID, etc. range: from 1 to 65535.

7.2.  IANA Considerations on New RADIUS Attributes

   The authors request that Attribute Types and Attribute Values defined
   in this document be registered by the Internet Assigned Numbers
   Authority (IANA) from the RADIUS namespaces as described in the "IANA
   Considerations" section of [RFC3575], in accordance with BCP 26
   [RFC5226].  For RADIUS packets, attributes and registries created by
   this document IANA is requested to place them at
   http://www.iana.org/assignments/radius-types.

   In particular, this document defines three new RADIUS attributes,
   entitled "IP-Port-Limit-Info" (see Section 3.1.1), "IP-Port-Range"
   (see Section 3.1.2) and "IP-Port-Forwarding-Map" (see Section 3.1.3),
   with assigned values of 241.TBD1, 241.TBD2 and 241.TBD3 from the
   Short Extended Space of [RFC6929]:

      Type       Name                   Meaning
      ----       ----                   -------
      241.TBD1   IP-Port-Limit-Info     see Section 3.1.1
      241.TBD2   IP-Port-Range          see Section 3.1.2
      241.TBD3   IP-Port-Forwarding-Map see Section 3.1.3

7.3.  IANA Considerations on New RADIUS TLVs

   This specification requests allocation of the following TLVs:

      Name                   Value      Meaning
      ----                   -----      -------
      IP-Port-Type            1         see Section 3.2.1
      IP-Port-Limit           2         see Section 3.2.2
      IP-Port-Ext-IPv4-Addr   3         see Section 3.2.3
      IP-Port-Int-IPv4-Addr   4         see Section 3.2.4
      IP-Port-Int-IPv6-Addr   5         see Section 3.2.5
      IP-Port-Int-Port        6         see Section 3.2.6
      IP-Port-Ext-Port        7         see Section 3.2.7
      IP-Port-Alloc           8         see Section 3.2.8
      IP-Port-Range-Start     9         see Section 3.2.9
      IP-Port-Range-End      10         see Section 3.2.10
      IP-Port-Local-Id       11         see Section 3.2.11

8.  Acknowledgements

   Many thanks to Dan Wing, Roberta Maglione, Daniel Derksen, David
   Thaler, Alan Dekok, Lionel Morand, and Peter Deacon for their useful
   comments and suggestions.

   Special thanks to Lionel Morand for the Shepherd review and to
   Kathleen Moriarty for the AD review.

9.  References

9.1.  Normative References

   [I-D.ietf-radext-datatypes]
              DeKok, A., "Data Types in the Remote Authentication Dial-
              In User Service Protocol (RADIUS)", draft-ietf-radext-
              datatypes-07 (work in progress), August 2016.

   [IPFIX]    IANA, "IP Flow Information Export (IPFIX) Entities",
              <http://www.iana.org/assignments/ipfix/ipfix.xhtml>.

   [ProtocolNumbers]
              IANA, "Service Name and Transport Protocol Port Number",
              <http://www.iana.org/assignments/protocol-numbers/
              protocol-numbers.xhtml>.

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

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <http://www.rfc-editor.org/info/rfc2865>.

   [RFC3575]  Aboba, B., "IANA Considerations for RADIUS (Remote
              Authentication Dial In User Service)", RFC 3575,
              DOI 10.17487/RFC3575, July 2003,
              <http://www.rfc-editor.org/info/rfc3575>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929,
              DOI 10.17487/RFC6929, April 2013,
              <http://www.rfc-editor.org/info/rfc6929>.

   [RFC7012]  Claise, B., Ed. and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              DOI 10.17487/RFC7012, September 2013,
              <http://www.rfc-editor.org/info/rfc7012>.

9.2.  Informative References

   [I-D.gundavelli-v6ops-community-wifi-svcs]
              Gundavelli, S., Grayson, M., Seite, P., and Y. Lee,
              "Service Provider Wi-Fi Services Over Residential
              Architectures", draft-gundavelli-v6ops-community-wifi-
              svcs-06 (work in progress), April 2013.

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

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              DOI 10.17487/RFC3022, January 2001,
              <http://www.rfc-editor.org/info/rfc3022>.

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340,
              DOI 10.17487/RFC4340, March 2006,
              <http://www.rfc-editor.org/info/rfc4340>.

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,
              <http://www.rfc-editor.org/info/rfc4960>.

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              DOI 10.17487/RFC5176, January 2008,
              <http://www.rfc-editor.org/info/rfc5176>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              April 2011, <http://www.rfc-editor.org/info/rfc6146>.

   [RFC6269]  Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
              P. Roberts, "Issues with IP Address Sharing", RFC 6269,
              DOI 10.17487/RFC6269, June 2011,
              <http://www.rfc-editor.org/info/rfc6269>.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,
              <http://www.rfc-editor.org/info/rfc6333>.

   [RFC6598]  Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
              M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address
              Space", BCP 153, RFC 6598, DOI 10.17487/RFC6598, April
              2012, <http://www.rfc-editor.org/info/rfc6598>.

   [RFC6614]  Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
              "Transport Layer Security (TLS) Encryption for RADIUS",
              RFC 6614, DOI 10.17487/RFC6614, May 2012,
              <http://www.rfc-editor.org/info/rfc6614>.

   [RFC6619]  Arkko, J., Eggert, L., and M. Townsley, "Scalable
              Operation of Address Translators with Per-Interface
              Bindings", RFC 6619, DOI 10.17487/RFC6619, June 2012,
              <http://www.rfc-editor.org/info/rfc6619>.

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,
              <http://www.rfc-editor.org/info/rfc6887>.

   [RFC6888]  Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
              A., and H. Ashida, "Common Requirements for Carrier-Grade
              NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
              April 2013, <http://www.rfc-editor.org/info/rfc6888>.

   [RFC6967]  Boucadair, M., Touch, J., Levis, P., and R. Penno,
              "Analysis of Potential Solutions for Revealing a Host
              Identifier (HOST_ID) in Shared Address Deployments",
              RFC 6967, DOI 10.17487/RFC6967, June 2013,
              <http://www.rfc-editor.org/info/rfc6967>.

   [RFC7596]  Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
              Farrer, "Lightweight 4over6: An Extension to the Dual-
              Stack Lite Architecture", RFC 7596, DOI 10.17487/RFC7596,
              July 2015, <http://www.rfc-editor.org/info/rfc7596>.

   [TR-146]   Broadband Forum, "TR-146: Subscriber Sessions",
              <http://www.broadband-forum.org/technical/download/
              TR-146.pdf>.

Authors' Addresses

   Dean Cheng
   Huawei
   2330 Central Expressway
   Santa Clara, California  95050
   USA

   Email: dean.cheng@huawei.com

   Jouni Korhonen
   Broadcom Corporation
   3151 Zanker Road
   San Jose  95134
   USA

   Email: jouni.nospam@gmail.com

   Mohamed Boucadair
   Orange
   Rennes
   France

   Email: mohamed.boucadair@orange.com

   Senthil Sivakumar
   Cisco Systems
   7100-8 Kit Creek Road
   Research Triangle Park, North Carolina
   USA

   Email: ssenthil@cisco.com