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Versions: (draft-cheng-behave-cgn-cfg-radius-ext) 00 draft-ietf-radext-ip-port-radius-ext

Network Working Group                                           D. Cheng
Internet-Draft                                                    Huawei
Intended status: Standards Track                             J. Korhonen
Expires: October 21, 2014                                       Broadcom
                                                            M. Boucadair
                                                          France Telecom
                                                            S. Sivakumar
                                                           Cisco Systems
                                                          April 19, 2014


       RADIUS Extensions for IP Port Configuration and Reporting
                draft-cheng-radext-ip-port-radius-ext-00

Abstract

   This document defines three new RADIUS attributes.  For device 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, NAT64, Provider WiFi 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 October 21, 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  RADIUS Attributes . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Extended-Type for IP-Port-Type  . . . . . . . . . . . . .   5
     3.2.  IP-Port-Limit Attribute . . . . . . . . . . . . . . . . .   7
     3.3.  IP-Port-Range Attribute . . . . . . . . . . . . . . . . .   8
     3.4.  IP-Port-Forwarding-Map Attribute  . . . . . . . . . . . .  10
   4.  Applications, Use Cases and Examples  . . . . . . . . . . . .  12
     4.1.  Managing CGN Port Behavior using RADIUS . . . . . . . . .  12
       4.1.1.  Configure IP Port Limit for a User  . . . . . . . . .  13
       4.1.2.  Report IP Port Allocation/De-allocation . . . . . . .  15
       4.1.3.  Configure Forwarding Port Mapping . . . . . . . . . .  16
       4.1.4.  An Example  . . . . . . . . . . . . . . . . . . . . .  18
     4.2.  Report Assigned Port Set for a Visiting UE  . . . . . . .  19
   5.  Table of Attributes . . . . . . . . . . . . . . . . . . . . .  20
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

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)



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   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 example, when IP packets traverse a CGN, 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 subject to port quota.

   The attributes defined in this document may also be used to report
   the assigned port set in some deployment such as Provider Wi-Fi
   [I-D.gundavelli-v6ops-community-wifi-svcs].  For example, a visiting
   host can be managed by a CPE which will need to report the assigned
   port set 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:

   o  IP-Port-Limit:This attribute may be carried in RDIUS Acces-Accept,
      Accounting-Request or CoA-Request packet.  The purpose of this
      attribute is to limit the total number of TCP/UDP ports and/or
      ICMP identifiers that an IP subscriber can use..

   o  IP-Port-Range:This attribute may be carried in RADIUS Access-
      Accept, Accounting-Request or CoA-Request packet.  The purpose of
      this attribute is to specify the range of TCP/UDP ports and/or
      ICMP identifiers that an IP subscriber can use associated with an
      IPv4 address.

   o  IP-Port-Forwarding-Map:This attribute may be carried in RADIUS
      Access-Accept, Accounting-Request or CoA-Request packet.  The
      purpose of this this attribute is to specify how a TCP/UDP port
      (or an ICMP identifier) mapping to another TCP/UDP port (or an
      ICMP identifier).



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   This document was constructed using the [RFC2629] .

2.  Terminology

   Some terms that are used in this document are listed as follows:

   o  IP Port - This term refers to IP transport protocol port,
      including TCP port, UDP port and ICMP identifier.

   o  IP Port Limit - This is the maximum number of TCP ports, or UDP
      ports, or the total of the two, or ICMP identifiers, or the total
      of the three, that a device supporting port ranges can use when
      performing mapping on TCP/ UDP ports or ICMP identifiers for a
      specific user.

   o  IP Port Range - This specifies a set of TCP/UDP port numbers or
      ICMP identifiers, indicated by the port/identifier with the
      smallest numerical number and the port/identifier with the largest
      numerical number, inclusively.

   o  Internal IP Address - The IP address that is used as a source IP
      address in an outbound IP packet sent toward a device supporting
      port ranges in the internal realm.  In IPv4 case, it is typically
      a private address [RFC1918].

   o  External IP Address - 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 IPv4 case, it is
      typically a global and routable IP address.

   o  Internal Port - The 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 - The 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 - The networking segment where IPv4 public
      addresses are used in respective of the device supporting port
      ranges.

   o  Internal realm - The networking segment that is behind a device
      supporting port ranges and where IPv4 private addresses are used.




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   o  Mapping - This term in this document 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 TCP/UDP port mapping services and in particular, with
      the granularity of one or more subsets within the 16-bit TCP/UDP
      port number range.  A typical example of this device can be a CGN,
      CPE, Provider Wi-Fi 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.  RADIUS Attributes

      [Discussion: Should we define a dedicated attribute
      (port_set_policies) to configure the following policies: (1)
      enforce port randomization, (2) include/exclude the WKP in the
      port assignment, (3) preserve parity, (4) quota for explicit port
      mapping, (5) DSCP marking policy, (6) Port hold down timer, (7)
      port hold down pool, etc.  Perhaps we don't need to cover all
      these parameters. - The discussion should be in a separate draft
      allowing this draft dedicated to RADIUS extension only.]

   In this section, we define the details of the following three new
   attributes:

   o  IP-Port-Limit Attribute

   o  IP-Port-Range Attribute

   o  IP-Port-Forwarding-Map Attribute

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

3.1.  Extended-Type for IP-Port-Type

   This section defines a new Extended-Type for IP port type.  The IP
   port type may be one of the following:

   o  Refer to TCP port, UDP port, and ICMP identifier

   o  Refer to TCP port and UDP port




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   o  Refer to TCP port

   o  Refer to UDP port

   o  Refer to 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 |  Value.....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+++


   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 octets of all fields this
      attribute, including the Type, Length, Extended-Type, and Value.

   Extended-Type:

      This one octet filed indicates the IP port as follows:

      TBA1-1:

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

      TBA1-2:

         Refer to TCP port and UDP port as a whole.

      TBA1-3:

         Refer to TCP port only.

      TBA1-4:

         Refer to UDP port only.

      TBA1-5:

         Refer to ICMP identifier only.

   Value:



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      This field contains one or more octects, and the data format MUST
      be a valid RADIUS data type.

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

3.2.  IP-Port-Limit Attribute

   This attribute contains an Extended-Type along with a TLV data type
   with format defined in [RFC6929].  It specifies the maximum number of
   IP ports for a user.

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

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

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

   The format of the IP-Port-Limit RADIUS attribute format is shown
   below.  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 |    TLV-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   TLV-Length  |         IP-Port-Limit         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 octets of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLV.

   Extended-Type:




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      This one octet field contains a value that indicates the IP port
      type, refer to Section 3.1 for details.

   TLV-Type:

      TBA2: for IP-Port-Limit TLV.

   TLV-Length:

      4.

   IP-Port-Limit:

      This field contains the maximum number of IP ports of which, the
      port type is specified by the value contained in the Extended-Type
      field.

      Note this field is semantically associated with the identifier
      "TBA1.{TBA1-1..TBA1-5}.

3.3.  IP-Port-Range Attribute

   This attribute contains an Extended-Type along with a TLV data type
   with format defined in [RFC6929].  It contains a range of numbers for
   IP ports allocated by a device supporting port ranges for a given
   subscriber along with an external IPv4 address.

   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.

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

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

   The format of the IP-Port-Range RADIUS attribute format is shown
   below.  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 |    TLV-Type   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TLV-Length   |   Reserved    |       Port Range Start        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Port range End           |     External IPv4 Address     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     External IPv4 Address     |     Local Session ID ....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   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 octets of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLV.

   Extended-Type:

      This one octet field contains a value that indicates the IP port
      type, refer to Section 3.1 for details.

   TLV-Type:

      TBA3:

         Allocation for IP-Port-Range TLV.

      TBA4:

         De-allocation for IP-Port-Range TLV.

   TLV-Length:

      >=11.

   Reserved:

      This field MUST be set to zero by the sender and ignored by the
      receiver.

   Port Range Start:



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      This field contains the smallest IP port number, as specified in
      the Extended-Type, in the IP port range.

   Port Range End:

      This field contains the largest IP port number, as specified in
      the Extended-Type, in the IP port range.

   External IPv4 Address:

      This field contains the IPv4 address assigned to the associated
      subscriber to be used in the external realm.  If set to 0.0.0.0,
      the allocation address policy is local to the device supporting
      port ranges.

   Local Session ID:

      This is an optional field and if presents, it 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.  The length of this field equals to the value in the
      TLV Length field minus 11 octets.  If this field is not present,
      the port range policies must be enforced to all subscribers using
      a local subscriber identifier.

   Note the data group in the "TLV Value" field above (i.e., "Port Range
   Start", "Port Range End", "External IPv4 Address", and "Local Session
   ID") is indicated by the identifier
   TBA1.{TBA1-1..TBA1-5}.{TBA3..TBA4}.

3.4.  IP-Port-Forwarding-Map Attribute

   This attribute contains an Extended-Type along with a TLV data type
   with format defined in [RFC6929].  It contains a 16-bit Internal Port
   that identifies the source TCP/UDP port number of an IP packet sent
   by the user, or the destination port number of an IP packet destined
   to the user, and in both cases, the IP packet travels behind the NAT
   device.  Also it contains a 16-bit Configured External Port that
   identifies the source TCP/UDP port number of an IP packet sent by the
   user, or the destination port number of an IP packet destined to the
   user, and in both cases, the IP packet travels outside of the NAT
   device.  In addition, the attribute may contain a 32-bit IPv4 address
   or a 128-bit IPv6 address, respectively, as their respective NAT
   mappings internal IP address.  Together, the port pair and IP address
   determine the port mapping rule for a specific IP flow that traverses
   a NAT device.





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   The attribute MAY appear in an Access-Accept packet, and may also
   appear in an Accounting-Request packet.  In either case, the
   attribute MUST NOT appear more than once in a single packet.

   The attribute MUST NOT appear in any other RADIUS packets.

   The format of the Port-Forwarding-Map RADIUS attribute format is
   shown below.  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 |   TLV-Type    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TLV-Length   |    Resevered  |       Internal Port           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Configured External Port   |  Internal IP Address  .....
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

   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 octets of all fields of
      this attribute, including the Type, Length, Extended-Type, and the
      entire length of the embedded TLV.

   Extended-Type:

      This one octet field contains a value that indicates the IP port
      type, refer to Section 3.1 for details.

   TLV-Type:

      TBA5 - It indicates IP port mapping, and the associated internal
      IP address is an IPv4 or IPv6 address, or not included.

   TLV-Length:

      >=7.

   Reserved:




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      This field is set to zero by the sender and ignored by the
      receiver.

   Internal Port:

      This field contains the internal port for the CGN mapping.

   Configured External Port:

      This field contains the external port for the CGN mapping.

   Internal IP Address:

      This field may or may not present, and when it does, contains the
      internal IPv4 or IPv6 address for the CGN mapping.  Its length
      equal to the value in the TLV Length field minus 7.

   Note the data group in the "TLV Value" field above (i.e., "Internal
   Port", "Configured External Port", and "Internal IP Address") is
   indicated by the identifier TBA1.{TBA1-1..TBA1-5}.TBA5.

4.  Applications, Use Cases and Examples

   This section describes some applications and use cases to illustrate
   the use of the attributes propsoed 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,
   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.





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   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 3.2.

   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,
   where CGN also locates, using a new RADIUS attribute called IP-Port-
   Limit (defined in Section 3.2), 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 1 illustrates how RADIUS protocol is used to configure the
   maximum number of TCP/UDP ports for a given subscriber on a NAT44
   device.




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   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 1: 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 2 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                     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 2: RADIUS Message Flow for changing a user's NAT44 port limit



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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 3.3).  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.

   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 3 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.










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   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 3: 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-
   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



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   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 4 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 4: 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 5 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




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   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 5: 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
   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



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   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 6 illustrates an example of the flow exchange which occurs
   when a visiting UE connects to a CPE offering Wi-Fi 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 6: 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.{TBA!-1 .. TBA1-5}.TBA2

   o  IP-Port-Range: TBA1.{TBA1-1 .. TBA1-5}.{TBA3 .. TBA4}

   o  IP-Port-Forwarding-Map: TBA.1{TBA1-1 .. TBA1-5}.TBA5

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




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   Request Accept Reject Challenge Acct.      #   Attribute
                                   Request
   0-1     0-1    0      0         0-1        TBA IP-Port-Limit
   0       0      0      0         0-1        TBA IP-Port-Range
   0-1     0-1    0      0         0-1        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.
   0-1 Zero or one instance 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 assignment for the new RADIUS
   attributes as follows:

   o  TBA1 (refer to Section 3.1): 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  TBA1-1, TBA1-2, TBA1-3, TBA1-4, and TBA1-5 (refer to Section 3.1):
      These values are for the Radius Extended Type field that are
      associated with TBA1.

   o  TBA2 (refer to Section 3.2): This value is for the TLV field and
      specifies the limit of the IP port imposed to a user.

   o  TBA3 (refer to Section 3.3): This value is for the TLV field and
      specifies the allocation action of IP ports by a port device
      (e.g., a CGN) for a user.

   o  TBA4 (refer to Section 3.3): This value is for the TLV field and
      specifies the de-allocation action of IP ports by a port device
      (e.g., a CGN) for a user.

   o  TBA5(refer to Section 3.4): This value is for the TLV field and
      specifies the mapping action on IP port by a port device (e.g., a
      CGN) for a user.





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8.  Acknowledgements

   Many thanks to Dan Wing, Roberta Maglione, Daniel Derksen, David
   Thaler, Alan Dekok, and Lionel Morand 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.

   [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-lw4over6-08 (work
              in progress), March 2014.





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   [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.

   [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





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   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


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

   Email: ssenthil@cisco.com



























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