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Versions: (draft-cheng-radext-ip-port-radius-ext) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 RFC 8045

Network Working Group                                           D. Cheng
Internet-Draft                                                    Huawei
Intended status: Standards Track                             J. Korhonen
Expires: December 14, 2014                                      Broadcom
                                                            M. Boucadair
                                                          France Telecom
                                                            S. Sivakumar
                                                           Cisco Systems
                                                           June 12, 2014


       RADIUS Extensions for IP Port Configuration and Reporting
                draft-ietf-radext-ip-port-radius-ext-01

Abstract

   This document defines three new RADIUS attributes.  For devices that
   implementing 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, as well as mapping behavior for specific hosts.
   This mechanism can be used in various deployment scenarios such as
   CGN (Carrier Grade NAT), NAT64, Provider WLAN Gateway, etc.

   This document does not make any assumption about the deployment
   context.

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 December 14, 2014.



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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   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.  Extended-Type and IP-Port-Type TLV  . . . . . . . . .   6
       3.1.2.  IP-Port-Limit Attribute . . . . . . . . . . . . . . .   7
       3.1.3.  IP-Port-Range Attribute . . . . . . . . . . . . . . .   9
       3.1.4.  IP-Port-Forwarding-Map Attribute  . . . . . . . . . .  12
     3.2.  RADIUS TLVs for IP Ports  . . . . . . . . . . . . . . . .  14
       3.2.1.  IP-Port-Limit TLV . . . . . . . . . . . . . . . . . .  14
       3.2.2.  IP-Port-Ext-IPv4-Addr TLV . . . . . . . . . . . . . .  15
       3.2.3.  IP-Port-Int-IP-Addr TLV . . . . . . . . . . . . . . .  16
       3.2.4.  IP-Port-Int-Port TLV  . . . . . . . . . . . . . . . .  17
       3.2.5.  IP-Port-Ext-Port TLV  . . . . . . . . . . . . . . . .  17
       3.2.6.  IP-Port-Alloc TLV . . . . . . . . . . . . . . . . . .  18
       3.2.7.  IP-Port-Range-Start TLV . . . . . . . . . . . . . . .  19
       3.2.8.  IP-Port-Range-End TLV . . . . . . . . . . . . . . . .  20
       3.2.9.  IP-Port-Local-Id TLV  . . . . . . . . . . . . . . . .  20
   4.  Applications, Use Cases and Examples  . . . . . . . . . . . .  21
     4.1.  Managing CGN Port Behavior using RADIUS . . . . . . . . .  21
       4.1.1.  Configure IP Port Limit for a User  . . . . . . . . .  22
       4.1.2.  Report IP Port Allocation/De-allocation . . . . . . .  24
       4.1.3.  Configure Forwarding Port Mapping . . . . . . . . . .  25
       4.1.4.  An Example  . . . . . . . . . . . . . . . . . . . . .  27
     4.2.  Report Assigned Port Set for a Visiting UE  . . . . . . .  28
   5.  Table of Attributes . . . . . . . . . . . . . . . . . . . . .  29
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  30
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  30
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  31
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  31
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  31



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     9.2.  Informative References  . . . . . . . . . . . . . . . . .  32
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Introduction

   In a broadband network, customer information is usually stored on a
   RADIUS server [RFC2865] and at the time when a user initiates an IP
   connection request, the RADIUS server will populate the user's
   configuration information to the Network Access Server (NAS), which
   is usually co-located with the Border Network Gateway (BNG), after
   the connection request is granted.  The Carrier Grade NAT (CGN)
   function may also be implemented on the BNG, and therefore CGN TCP/
   UDP port (or ICMP identifier) mapping behavior can be configured on
   the RADIUS server as part of the user profile, and populated to the
   NAS in the same manner.  In addition, during the operation, the CGN
   can also convey port/identifier mapping behavior specific to a user
   to the RADIUS server, as part of the normal RADIUS accounting
   process.

   The CGN device that communicates with a RADIUS server using RADIUS
   extensions defined in this document may perform NAT44 [RFC3022],
   NAT64 [RFC6146], or Dual-Stack Lite AFTR [RFC6333] function.

   For the CGN case, when IP packets traverse a CGN device, it would
   perform TCP/UDP source port mapping or ICMP identifier mapping as
   required.  A TCP/ UDP source port or ICMP identifier, 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 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 WT-146 for
   example).

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

   1.  IP-Port-Limit: This attribute may be carried in RADIUS Acces-
       Accept, Access-Request, Accounting-Request or CoA-Request packet.
       The purpose of this attribute is to limit the total number of




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       TCP/UDP ports and/or ICMP identifiers that an IP subscriber can
       use, associated with an IPv4 address.

   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 ports and/or ICMP identifiers that
       have been allocated or deallocated associated with a given IPv4
       address for a subscriber.

   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 a TCP/
       UDP port (or an ICMP identifier) mapping to another TCP/UDP port
       (or an ICMP identifier), and each is associated with its
       respective IPv4 address.

   This document was constructed using the [RFC2629] .

2.  Terminology

   This document makes use if the following terms:

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

   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.

   o  IP Port Limit: denotes the maximum number of IP ports for a
      specific port type, that a device supporting port ranges can use
      when performing port number mapping for a specific user.

   o  IP Port Range: specifies a set of contiguous IP ports, indicated
      by the smallest numerical number and the largest 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.  In the IPv4 case,
      it is typically a private address [RFC1918].

   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.  In the IPv4
      case, it is typically a global routable IP address.




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   o  Internal Port: is a UDP or TCP port, or an ICMP identifier, 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, 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 IPv4 public
      addresses are used in respective of the device supporting port
      ranges.

   o  Internal realm: refers to the networking segment that is behind a
      device supporting port ranges and where IPv4 private 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 port mapping services and in particular, with the
      granularity of one or more subsets within the 16-bit IP port
      number range.  A typical example of this device is a CGN, CPE,
      Provider WLAN Gateway, etc.

   Note the terms "internal IP address", "internal port", "internal
   realm", "external IP address", "external port", "external realm", and
   "mapping" and their semantics are the same as in [RFC6887], and
   [RFC6888].

3.  Extensions of RADIUS Attributes and TLVs

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

   1.  IP-Port-Limit 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].






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3.1.  Extended Attributes for IP Ports

3.1.1.  Extended-Type and IP-Port-Type TLV

   This section defines a new Extended-Type and an IP-Port-Type TLV (see
   Figure 1).

   The IP port type may be one of the following:

   o  TCP port, UDP port, and ICMP identifier

   o  TCP port and UDP port

   o  TCP port

   o  UDP port

   o  ICMP 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |     Length    | Extended-Type |   TLV1-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TLV1-Length  |    Value...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                 Figure 1

   Type:

      TBA1 - Extended-Type-1 (241), Extended-Type-2 (242), Extended-
      Type-3 (243), or Extended-Type-4 (244) per [RFC6929].

   Length:

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

   Extended-Type:

      TBA2.

   TLV1-Type:





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      Type field of IP-Port-Type TLV.  This one byte field indicates the
      IP port type as follows:

      TBA2-1:

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

      TBA2-2:

         Refer to TCP port and UDP port as a whole.

      TBA2-3:

         Refer to TCP port only.

      TBA2-4:

         Refer to UDP port only.

      TBA2-5:

         Refer to ICMP identifier only.

   TLV1-Length:

      Length field of IP-Port-Type TLV.  This field indicates the total
      length in bytes of the TLV1, including the field of TLV1-Type,
      TLV1-Length, and the Value.

   Value:

      Value field of IP-Port-Type TLV.  This field contains one or more
      TLVs, refer to Section 3.1.2, Section 3.1.3, Section 3.1.4 for
      details.

      The interpretation of this field is determined by the identifier
      of "TBA1.TBA2.{TBA2-1..TBA2-5} along with the embedded TLVs.

3.1.2.  IP-Port-Limit Attribute

   This attribute contains the Extended-Type and IP-Port-Type TLV
   defined in Section 3.1.1, along with the embedded IP-Port-Limit TLV
   and IP-Port-Ext-IPv4-Addr TLV, defined in Section 3.2.1 and
   Section 3.2.2, respectively.  It specifies the maximum number of IP
   ports, as indicated in IP-Port-Limit TLV, of a specific port type,
   and associated with a given IPv4 address, as indicated in IP-Port-
   Ext-IPv4-Addr TLV for an end user.  Note that when IP-Port-Ext-
   IPv4-Addr TLV is not included as part of the IP-Port-Limit Attribute,



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   the port limit is applied to all the IPv4 addresses managed by the
   port device, e.g., a CGN or NAT64 device.

   The IP-Port-Limit Attribute MAY appear in an Access-Accept packet.
   It MAY also appear in an Access-Request packet as a hint by the
   device supporting port ranges, which is co-allocated with the NAS, to
   the RADIUS server as a preference, although the server is not
   required to honor such a hint.

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

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

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

   The format of the IP-Port-Limit Attribute is shown in Figure 2.  The
   fields are transmitted from left to right.

    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 |   TLV1-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TLV1-Length  |   Value ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 2

   Type:

      TBA1 - Extended-Type-1 (241), Extended-Type-2 (242), Extended-
      Type-3 (243), or Extended-Type-4 (244) per [RFC6929].

   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:

      TBA2 - This one byte field contains a value that indicates the IP
      port type, refer to Section 3.1.1 for detail.

   TLV1-Type:




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      TBA2-1, TBA2-2, TBA2-3, TBA2-4, or TBA2-5.  Refer to Section 3.1.1
      for detail.

   TLV1-Length:

      This field indicates the total length in bytes of the TLV1,
      including the field of TLV1-Type, TLV1-Length, and the entire
      length of the embedded TLVs.

   Value:

      This field contains a set of TLVs as follows:

      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 be included in the IP-Port-Limit
         Attribute.  Refer to Section 3.2.1.

      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 Attribute.
         Refer to Section 3.2.2.

   IP-Port-Limit attribute is associated with the following identifier:
   Type(TBA1).Extended-Type(TBA2).IP-Port-Type TLV{TBA2-1..TBA2-5}.[IP-
   Port-Limit TLV(TBA3), {IP-Port-Ext-IPv4-Addr TLV (TBA4)}].

3.1.3.  IP-Port-Range Attribute

   This attribute contains the Extended-Type and IP-Port-Type TLV
   defined in Section 3.1.1, along with a set of embedded TLVs defined
   in Section 3.2.7 (IP-Port-Range-Start TLV), Section 3.2.8 (IP-Port-
   Range-End TLV), Section 3.2.6 (IP-Port-Alloc TLV), Section 3.2.2 (IP-
   Port-Ext-IPv4-Addr TLV), and Section 3.2.9 (IP-Port-Local-Id TLV).
   It contains a range of contiguous IP ports of a specific port type
   and associated with an IPv4 address that are either allocated or
   deallocated by a device for a given subscriber, and the information
   is intended to send to RADIUS server.

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





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   Within an IP-Port-Range Attribute, 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 port deallocation, the
   inclusion of these two TLVs 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) to identify the end user.

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

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

   The format of the IP-Port-Range Attribute format is shown in
   Figure 3.  The fields are transmitted from left to right.

   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 |   TLV1-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | TLV1-Length   |    Value ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                                 Figure 3

   Type:

      TBA1 - Extended-Type-1 (241), Extended-Type-2 (242), Extended-
      Type-3 (243), or Extended-Type-4 (244) per [RFC6929]

   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:

      TBA2 - This one byte field contains a value that indicates the IP
      port type, refer to Section 3.1.1 for detail.

   TLV1-Type:





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      TBA2-1, TBA2-2, TBA2-3, TBA2-4, or TBA2-5.  Refer to Section 3.1.1
      for detail.

   TLV1-Length:

      This field indicates the total length in bytes of the TLV1,
      including the field of TLV1-Type, TLV1-Length, and the entire
      length of the embedded TLVs.

   Value:

      This field contains a set of TLVs as follows:

      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 be included as part of the IP-Port-Range Attribute.
         Refer to Section 3.2.6.

      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 be included together with IP-Port-Range-End TLV as part of
         the IP-Port-Range Attribute.  Refer to Section 3.2.7.

      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 be included together with IP-Port-Range-Start TLV as part
         of the IP-Port-Range Attribute.  Refer to Section 3.2.8.

      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 3.2.2.

      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 address/prefix, etc.  This TLV is




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         optionally included as part of the IP-Port-Range Attribute.
         Refer to Section 3.2.9.

   The IP-Port-Range attribute is associated with the following
   identifier: Type(TBA1).Extended-Type(TBA2).IP-Port-Type
   TLV{TBA2-1..TBA2-5}.[IP-Port-Alloc TLV(TBA8), {IP-Port-Range-Start
   TLV (TBA9), IP-Port-Range-End TLV (TBA10)}, {IP-Port-Ext-IPv4-Addr
   TLV (TBA4)}, {IP-Port-Local-Id TLV (TBA11)}].

3.1.4.  IP-Port-Forwarding-Map Attribute

   This attribute contains the Extended-Type and IP-Port-Type TLV
   defined in Section 3.1.1,along with a set of embedded TLVs defined in
   Section 3.2.4 (IP-Port-Int-Port TLV), Section 3.2.5 (IP-Port-Ext-Port
   TLV), Section 3.2.3 (IP-Port-Int-IP-Addr TLV), Section 3.2.9(IP-Port-
   Local-Id TLV) and Section 3.2.2 (IP-Port-Ext-IP-Addr TLV).  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 that is associated with an external IPv4 address.  The
   internal IPv4 or IPv6 address, or the local identifier must be
   included; the external IPv4 address may also be included.

   The IP-Port-Forwarding-Map Attribute MAY appear in an Access-Accept
   packet.  It MAY also appear in an Access-Request packet as a hint by
   the device supporting port mapping, which is co-allocated with the
   NAS, to the RADIUS server as a preference, although the server is not
   required to honor such a hint.

   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 attribute MUST NOT appear in any other RADIUS packet.

   The format of the IP-Port-Forwarding-Map Attribute is shown in
   Figure 4.  The fields are transmitted from left to right.












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    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 |   TLV1-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TLV1-Length  |    Value ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 4

   Type:

      TBA1 - Extended-Type-1 (241), Extended-Type-2 (242), Extended-
      Type-3 (243), or Extended-Type-4 (244) per [RFC6929]

   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:

      This one byte field contains a value that indicates the IP port
      type, refer to Section 3.1.1 for details.

   TLV1-Type:

      TBA2-1, TBA2-2, TBA2-3, TBA2-4, or TBA2-5.  Refer to Section 3.1.1
      for detail.

   TLV1-Length:

      This field indicates the total length in bytes of the TLV1,
      including the field of TLV1-Type, TLV1-Length, and the entire
      length of the embedded TLVs.

   Value:

      This field contains a set of TLVs as follows:

      IP-Port-Int-Port TLV:

         This TLV contains an internal IP port number associated with an
         internal IPv4 or IPv6 address.  This TLV must be included
         together with IP-Port-Ext-Port TLV as part of the IP-Port-
         Forwarding-Map attribute.  Refer to Section 3.2.4.




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      IP-Port-Ext-Port TLV:

         This TLV contains an external IP port number associated with an
         external IPv4 address.  This TLV must be included together with
         IP-Port-Int-Port TLV as part of the IP-Port-Forwarding-Map
         attribute.  Refer to Section 3.2.5.

      IP-Port-Int-IP-Addr TLV:

         This TLV contains an IPv4 or IPv6 address that is associated
         with the internal IP port number contained in the IP-Port-Int-
         Port TLV.  Either this TLV or IP-Port-Local-Id TLV must 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 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 3.2.9.

      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 3.2.2.

   The IP-Port-Forwarding-Map attribute is associated with the following
   identifier: Type(TBA1).Extended-Type(TBA2).IP-Port-Type
   TLV{TBA2-1..TBA2-5}.[IP-Port-Int-Port TLV(TBA6), IP-Port-Ext-Port
   TLV(TBA7), {IP-Port-Int-IP-Addr TLV (TBA5)}, {IP-Port-Ext-IPv4-Addr
   TLV (TBA4)}].

3.2.  RADIUS TLVs for IP Ports

3.2.1.  IP-Port-Limit TLV

   This TLV (Figure 5) uses the format defined in [RFC6929].  Its Value
   field contains a 2-byte integer called IP-Port-Limit, which indicates
   the maximum number of ports of a specified IP-Port-Type and
   associated with a given IPv4 address assigned to a subscriber.

   IP-Port-Limit TLV is included as part of the IP-Port-Limit Attribute
   (refer to Section 3.1.2).




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   Note that IP-Port-Limit TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV2-Type   |  TLV2-Length  |        IP-Port-Limit          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 5

   TLV2-Type:

      TBA3: The type field for IP-Port-Limit TLV.

   TLV2-Length:

      This field indicates the total length in bytes of the TLV2,
      including the field of TLV2-Type, TLV2-Length, and the Value
      field, i.e., IP-Port-Limit.

   IP-Port-Limit:

      2-byte integer.  This field contains the maximum number of IP
      ports of which, the port type is specified by container IP-Port-
      Type TLV.

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

   This TLV (Figure 6) uses the format defined in[RFC6929].  Its Value
   field contains a 4-byte External IPv4 address.

   IP-Port-Ext-IPv4-Addr TLV can be included as part of the IP-Port-
   Limit Attribute (refer to Section 3.1.2), IP-Port-Range Attribute
   (refer to Section 3.1.3), and IP-Port-Forwarding-Map Attribute (refer
   to Section 3.1.4).

   Note that IP-Port-Ext-IPv4-Addr TLV is embedded within IP-Port-Type
   TLV (refer to Section 3.1.1) for detail.












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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV3-Type   |  TLV3-Length  |      IP-Port-Ext-IPv4-Addr        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       IP-Port-Ext-IPv4-Addr       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 6

   TLV3-Type:

      TBA4: The type field for IP-Port-IPv4-Addr TLV.

   TLV3-Length:

      6.  The Length field for IP-Port-IPv4-Addr TLV.

   IP-Port-Ext-IPv4-Addr:

      4-byte integer.  This field contains the IPv4 address that is
      associated with the range of IP ports.

3.2.3.  IP-Port-Int-IP-Addr TLV

   This TLV (Figure 7) uses format defined in [RFC6929].  Its Value
   field contains an internal IPv4 or IPv6 address.

   IP-Port-Int-IP-Addr TLV can be included as part of the IP-Port-
   Forwarding-Map Attribute (refer to Section 3.1.4).

   Note that IP-Port-Int-IP-Addr TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV4-Type  |  TLV4-Length |    IP-Port-Int-IP-Addr....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 7

   TLV4-Type:

      TBA5: The type field for IP-Port-Int-IP-Addr TLV.

   TLV4-Length:




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      6 or 18 bytes.  The Length field for IP-Port-Int-IP-Addr TLV.

   IP-Port-Int-IP-Addr:

      4 byte integer for IPv4 address or 16 byte for IPv6 address.

3.2.4.  IP-Port-Int-Port TLV

   This TLV (Figure 8) uses format defined in [RFC6929].  Its Value
   field contains an internal IP port number that is associated with an
   internal IPv4 or IPv6 address.

   IP-Port-Int-Port TLV is included as part of the IP-Port-Forwarding-
   Map Attribute (refer to Section 3.1.4).

   IP-Port-Int-Port TLV is embedded within embedded within IP-Port-Type
   TLV (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV5-Type   |  TLV5-Length  |      IP-Port-Int-Port         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 8

   TLV5-Type:

      TBA6: The type field for IP-Port-Int-Port TLV.

   TLV5-Length:

      4 bytes.  The Length field for IP-Port-Int-Port TLV.

   IP-Port-Int-Port:

      2 byte integer.  The internal IP port number that is associated
      with an IPv4 or IPv6 address.

3.2.5.  IP-Port-Ext-Port TLV

   This TLV (Figure 9) uses format defined in [RFC6929].  Its Value
   field contains an external IP port number that is associated with an
   external IPv4 address.

   IP-Port-Ext-Port TLV is included as part of the IP-Port-Forwarding-
   Map Attribute (refer to Section 3.1.4).




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   IP-Port-Ext-Port TLV is embedded within IP-Port-Type TLV (refer to
   Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV6-Type   |  TLV6-Length  |      IP-Port-Ext-Port         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 9

   TLV6-Type:

      TBA7: The type field for IP-Port-Ext-Port TLV.

   TLV6-Length:

      4 bytes.  The Length field for IP-Port-Ext-Port TLV.

   IP-Port-Ext-Port:

      2 byte integer.  The external IP port number that is associated
      with an IPv4 address.

3.2.6.  IP-Port-Alloc TLV

   This TLV (Figure 10) uses format defined in [RFC6929].  Its Value
   field contains a 2-byte integer called IP-Port-Alloc, which indicates
   either the allocation or deallocation of a range of IP ports.

   IP-Port-Alloc TLV is included as part of the IP-Port-Range Attribute
   (refer to Section 3.1.3).

   Note that IP-Port-Alloc TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV7-Type   |  TLV7-Length  |        IP-Port-Alloc          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 10

   TLV7-Type:

      TBA8: The type field for IP-Port-Alloc TLV.




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   TLV7-Length:

      4.  The Length field for IP-Port-Alloc TLV.

   IP-Port-Alloc:

      2-byte integer.  This field indicates the allocation or
      deallocation of a range of IP ports as follows:

      0:

         Allocation

      1:

         Deallocation

3.2.7.  IP-Port-Range-Start TLV

   This TLV (Figure 11) uses format defined in [RFC6929].  Its Value
   field contains a 2-byte integer called IP-Port-Range-Start, which
   indicates the smallest port number of a range of contiguous IP ports.

   IP-Port-Range-Start TLV is included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.3).

   Note that IP-Port-Range-Start TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV8-Type   |  TLV8-Length  |    IP-Port-Range-Start        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 11

   TLV8-Type:

      TBA9: The type field for IP-Port-Range-Start TLV.

   TLV8-Length:

      4.  The Length field for IP-Port-Range-Start TLV.

   IP-Port-Range-Start:





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      2-byte integer.  This field contains the smallest port number of a
      range of contiguous IP ports.

3.2.8.  IP-Port-Range-End TLV

   This TLV (Figure 12) uses format defined in [RFC6929].  Its Value
   field contains a 2-byte integer called IP-Port-Range-End, which
   indicates largest port number of a range of contiguous IP ports.

   IP-Port-Range-End TLV is included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.3).

   Note that IP-Port-Range-End TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV9-Type   |  TLV9-Length  |    IP-Port-Range-End          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 12

   TLV9-Type:

      TBA10: The type field for IP-Port-Range-End TLV.

   TLV9-Length:

      4.  The Length field for IP-Port-Range-End TLV.

   IP-Port-Range-End:

      2-byte integer.  This field contains the largest port number of a
      range of contiguous IP ports.

3.2.9.  IP-Port-Local-Id TLV

   This TLV (Figure 13) uses format defined in [RFC6929].  Its Value
   field contains an identifier with local significance.

   In some CGN deployment scenarios as described such as L2NAT
   [I-D.miles-behave-l2nat], DS-Extra-Lite [RFC6619] and Lightweight
   4over6 [I-D.ietf-softwire-lw4over6], 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 to the RADIUS
   server as part of the accounting record.




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   IP-Port-Local-Id TLV can be included as part of the IP-Port-Range
   Attribute (refer to Section 3.1.3) and IP-Port-Forwarding-Map
   Attribute (refer to Section 3.1.4).

   Note that IP-Port-Local-Id TLV is embedded within IP-Port-Type TLV
   (refer to Section 3.1.1) for detail.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV10-Type   |  TLV10-Length  |      IP-Port-Local-Id...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 13

   TLV10-Type:

      TBA11: The type field for IP-Port-Local-Id TLV.

   TLV10-Length:

      Variable number of bytes.  The Length field for IP-Port-Local-Id
      TLV.

   IP-Port-Local-Id:

      This is a local session identifier at the customer premise, such
      as MAC address, interface ID, VLAN ID, PPP sessions ID, VRF ID,
      IPv6 address/prefix, etc.  The length of this field is the value
      contained in TLV7-Length field minus 2.

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 hosts the NAS.  The communication between
   the NAS and the RADIUS server is triggered by a subscriber when the
   user 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,




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   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 most likely reside on a
   BNG.  In that case, parameters for CGN port/identifier 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 allocation and
   de-allocation 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 subscribers' 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
   subscribers.  As indicated in [RFC6269], it is therefore necessary to
   impose limits on the total number of ports available to an individual
   subscriber to ensure that the shared resource, i.e., the IPv4 address
   remains available in some capacity to all the subscribers using it,
   and port limiting is also documented in [RFC6888] as a requirement.

   The IP port limit imposed to a specific subscriber may be on the
   total number of TCP and UDP ports plus the number of ICMP
   identifiers, or with other granularities as defined in Section 3.1.2.

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

   When a subscriber signs in to the Internet service successfully, the
   IP port limit for the subscriber is passed to the BNG based NAS,



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   where CGN also locates, using a new RADIUS attribute called IP-Port-
   Limit (defined in Section 3.1.2), along with other configuration
   parameters.  While some parameters are passed to the subscriber, the
   IP port limit is recorded on the CGN device for imposing the usage of
   TCP/UDP ports and ICMP identifiers for that subscriber.

   Figure 14 illustrates how RADIUS protocol is used to configure the
   maximum number of TCP/UDP ports for a given subscriber on a NAT44
   device.

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

      Figure 14: 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 15 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.










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

   Figure 15: RADIUS Message Flow for changing a user's NAT44 port limit

4.1.2.  Report IP Port Allocation/De-allocation

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

   As one practice, a CGN may allocate a bulk of TCP/UDP ports or ICMP
   identifiers once at a time for a specific user, instead of one port/
   identifier at a time, and within each port bulk, the ports/
   identifiers may be randomly distributed or in consecutive fashion.
   When a CGN device allocates bulk of TCP/UDP ports and ICMP
   identifiers, the information can be easily conveyed to the RADIUS
   server by a new RADIUS attribute called the IP-Port-Range (defined in
   Section 3.1.3).  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, and the total number of ports/identifiers must
   be less or equal to the associated IP port limit imposed for that
   subscriber.  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 subscriber.  The shared IPv4 address and the pre-
   allocated IP port range are both passed to the RADIUS server.

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




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

   Figure 16 illustrates how RADIUS protocol is used to report a set of
   ports allocated and de-allocated, 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 de-allocate           |
    |                 a TCP/UDP port range for the user)     |
    |                          |                             |
    |                          |-----Accounting-Request----->|
    |                          |    (IP-Port-Range           |
    |                          |     for de-allocation)      |
    |                          |                             |

     Figure 16: RADIUS Message Flow for reporting NAT44 allocation/de-
                         allocation 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-



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   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 17 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 17: 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



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   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 18 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 18: 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
   subscriber 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 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



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   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 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
   de-allocate 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 19 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.






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   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 de-allocation)                     |
    |           |                                            |

      Figure 19: RADIUS Message Flow for reporting CPE allocation/de-
                 allocation 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: TBA1.TBA2.{TBA2-1..TBA2-5}.[TBA3, {TBA4}]

   o  IP-Port-Range: TBA1.TBA2.{TBA2-1..TBA2-5}.[TBA8, TBA9, TBA10,
      {TBA4}, {TBA11}].

   o  IP-Port-Forwarding-Map: TBA1.TBA2.{TBA2-1 .. TBA2-5}.[TBA6, TBA7,
      TBA5, {TBA4}]





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   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
   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 than what has
   been identified in [RFC2865].

7.  IANA Considerations

   This document requires new code point assignments for the new RADIUS
   attributes as follows:

   o  TBA1 (refer to Section 3.1.1): This value is for the Radius Type
      field and should be allocated from the number space of Extended-
      Type-1 (241), Extended-Type-2 (242), Extended-Type-3 (243), or
      Extended-Type-4 (244) per [RFC6929].

   o  TBA2 (refer to Section 3.1.1): This value is for the Extended-Type
      field and should be allocated from the Short Extended Space per
      [RFC6929].

   o  TBA2-1, TBA2-2, TBA2-3, TBA2-4, and TBA2-5 (refer to
      Section 3.1.1): These values are for the Type field of IP-Port-
      Type TLV that is within the TBA2 container, and they should be
      allocated as TLV data type and effectively extend the attribute
      tree as TBA1.TBA2.{TBA2-1, TBA2-2, TBA2-3, TBA2-4, TBA2-5}.

   o  TBA3 (refer to Section 3.1.2): This value is for the type field of
      IP-Port-Limit TLV.  It should be allocated as TLV data type and it
      extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2, TBA2-3,
      TBA2-4, TBA2-5}.TBA3.

   o  TBA4 (refer to Section 3.2.2): This value is for the Type field of
      IP-Port-Ext-IPv4-Addr TLV.  It should be allocated as TLV data
      type and it extends the attribute tree as TBA1.TBA2.{TBA2-1,
      TBA2-2, TBA2-3, TBA2-4, TBA2-5}.[TBA4...].



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   o  TBA5 (refer to Section 3.2.3): This value is for the Type field of
      IP-Port-Int-IP-Addr TLV.  It should be allocated as TLV data type
      and it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA5...].

   o  TBA6 (refer to Section 3.2.4): This value is for the Type field of
      IP-Port-Int-Port TLV.  It should be allocated as TLV data type and
      it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA6...].

   o  TBA7 (refer to Section 3.2.5): This value is for the Type field of
      IP-Port-Ext-port TLV.  It should be allocated as TLV data type and
      it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA7...].

   o  TBA8 (refer to Section 3.2.6): This value is for the Type field of
      IP-Port-Alloc TLV.  It should be allocated as TLV data type and it
      extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2, TBA2-3,
      TBA2-4, TBA2-5}.[TBA8...].

   o  TBA9 (refer to Section 3.2.7): This value is for the Type field of
      IP-Port-Range-Start TLV.  It should be allocated as TLV data type
      and it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA9..].

   o  TBA10 (refer to Section 3.2.8): This value is for the Type field
      of IP-Port-Range-End TLV.  It should be allocated as TLV data type
      and it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA10..].

   o  TBA11 (refer to Section 3.2.9): This value is for the Type field
      of IP-Port-Local-Id TLV.  It should be allocated as TLV data type
      and it extends the attribute tree as TBA1.TBA2.{TBA2-1, TBA2-2,
      TBA2-3, TBA2-4, TBA2-5}.[TBA11..].

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.

9.  References

9.1.  Normative References

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets", BCP
              5, RFC 1918, February 1996.



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

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)", RFC
              2865, June 2000.

   [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,
              January 2008.

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929, April
              2013.

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.

   [I-D.ietf-softwire-lw4over6]
              Cui, Y., Qiong, Q., Boucadair, M., Tsou, T., Lee, Y., and
              I. Farrer, "Lightweight 4over6: An Extension to the DS-
              Lite Architecture", draft-ietf-softwire-lw4over6-10 (work
              in progress), June 2014.

   [I-D.miles-behave-l2nat]
              Miles, D. and M. Townsley, "Layer2-Aware NAT", draft-
              miles-behave-l2nat-00 (work in progress), March 2009.

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022, January
              2001.

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

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



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

   [RFC6619]  Arkko, J., Eggert, L., and M. Townsley, "Scalable
              Operation of Address Translators with Per-Interface
              Bindings", RFC 6619, June 2012.

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

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

   [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, June 2013.

Authors' Addresses

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

   Email: dean.cheng@huawei.com


   Jouni Korhonen
   Broadcom
   Porkkalankatu 24
   FIN-00180 Helsinki
   Finland

   Email: jouni.nospam@gmail.com


   Mohamed Boucadair
   France Telecom
   Rennes
   France

   Email: mohamed.boucadair@orange.com




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

   Email: ssenthil@cisco.com












































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