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RFC 8045


RADIUS Extensions for IP Port Configuration and Reporting

Part 2 of 2, p. 27 to 43
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4.  Applications, Use Cases, and Examples

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

4.1.  Managing CGN Port Behavior Using RADIUS

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

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

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

   The 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

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

4.1.1.  Configure IP Port Limit for a User

   In the face of an IPv4 address shortage, there are currently
   proposals to multiplex multiple users' connections over a number of
   shared IPv4 addresses, such as Carrier Grade NAT [RFC6888],
   Dual-Stack Lite [RFC6333], NAT64 [RFC6146], etc.  As a result, a
   single IPv4 public address may be shared by hundreds or even
   thousands of users.  As indicated in [RFC6269], it is therefore

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   necessary to impose limits on the total number of ports available to
   an individual user to ensure that the shared resource, i.e., the
   IPv4 address, remains available in some capacity to all the users
   using it.  The support of an IP port limit is also documented in
   [RFC6888] as a requirement for CGN.

   The IP port limit imposed on an end user may be on the total number
   of IP source transport ports or a specific IP transport protocol as
   defined in Section 3.1.1.

   The per-user IP port limit is configured on a RADIUS server, along
   with other user information such as credentials.

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

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

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

       Figure 15: RADIUS Message Flow for Configuring CGN Port Limit

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

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

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

    Figure 16: RADIUS Message Flow for Changing a User's CGN Port Limit

4.1.2.  Report IP Port Allocation/Deallocation

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

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

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

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

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

   Figure 17 illustrates how the RADIUS protocol is used to report a set
   of ports allocated and deallocated, respectively, by a NAT64 device
   for a specific user to the RADIUS server.  2001:db8:100:200::/56 is
   the IPv6 prefix allocated to this user.  In order to limit the usage
   of the NAT64 resources on a per-user basis for fairness of resource
   usage (see REQ-4 of [RFC6888]), port range allocations are bound to
   the /56 prefix, not to the source IPv6 address of the request.  The
   NAT64 device is configured with the per-user port limit policy by
   some means (e.g., subscriber-mask [RFC7785]).

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   Host                      NAT64/NAS                     AAA
    |                         BNG                         Server
    |                          |                             |
    |                          |                             |
    |----Service Request------>|                             |
    |                          |                             |
    |                          |-----Access-Request -------->|
    |                          |                             |
    |                          |<----Access-Accept-----------|
    |<---Service Granted ------|                             |
    |    (other parameters)    |                             |
   ...                        ...                           ...
    |                          |                             |
    |                          |                             |
    |                (NAT64 decides to allocate              |
    |                 a TCP/UDP port range for the user)     |
    |                          |                             |
    |                          |-----Accounting-Request----->|
    |                          |    (IP-Port-Range           |
    |                          |     for allocation)         |
   ...                        ...                           ...
    |                          |                             |
    |                (NAT64 decides to deallocate            |
    |                 a TCP/UDP port range for the user)     |
    |                          |                             |
    |                          |-----Accounting-Request----->|
    |                          |    (IP-Port-Range           |
    |                          |     for deallocation)       |
    |                          |                             |

            Figure 17: RADIUS Message Flow for Reporting NAT64
                   Allocation/Deallocation of a Port Set

4.1.3.  Configure Port Forwarding 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 and allow IP packets of applications from outside a CGN
   device to pass through and be "port forwarded" to the correct user
   located behind the CGN device.

   The Port Control Protocol (PCP) [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 deployments, all users need

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   is a few (typically just one) pre-configured port mappings for
   applications at home, such as a web cam; 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 propagate the information to
   the associated CGN device.

   Note that this document targets deployments where a AAA server is
   responsible for instructing NAT mappings for a given subscriber and
   does not make any assumption about the host's capabilities with
   regards to port forwarding control.  This deployment is complementary
   to PCP given that PCP targets a different deployment model where an
   application (on the host) controls its mappings in an upstream CPE,
   CGN, firewall, etc.

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

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

              Figure 18: RADIUS Message Flow for Configuring
                         a Port Forwarding Mapping

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

   Figure 19 illustrates how the 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                     CGN/NAS                           AAA
    |                         BNG                            Server
    |                          |                               |
    |                    Internal IP Address                   |
    |                    Port Map (a:X)                        |
    |                          |                               |
    |                          |<---------CoA Request----------|
    |                          |    (IP-Port-Forwarding-Map)   |
    |                          |                               |
    |                    Internal IP Address                   |
    |                    Port Map (a:Y)                        |
    |                          |                               |
    |                          |---------CoA Response--------->|
    |                          |    (IP-Port-Forwarding-Map)   |

                Figure 19: RADIUS Message Flow for Changing
                     a User's Port Forwarding Mapping

4.1.4.  An Example

   An Internet Service Provider (ISP) assigns TCP/UDP 500 ports for the
   user Joe.  This number is the limit that can be used for TCP/UDP
   ports on a CGN device for Joe and it is configured on a RADIUS
   server.  Also, Joe asks for a pre-defined port forwarding mapping on
   the CGN device for his web cam applications (external port 5000 maps
   to internal port 1234).

   When Joe successfully connects to the Internet service, the RADIUS
   server conveys the TCP/UDP port limit (500) and the port forwarding
   mapping (external port 5000 to internal port 1234) to the CGN device
   using the IP-Port-Limit-Info Attribute and IP-Port-Forwarding-Map
   Attribute, respectively, carried by an Access-Accept message to the
   BNG where NAS and CGN are co-located.

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

   For accounting purposes, the CGN device passes this port range
   (3500-3540) and the shared IPv4 address 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 mappings
   and the port pool (3500-3540) is close to exhaust, the CGN device
   allocates a second port pool (8500-8800) in a similar fashion and
   also passes the new port range (8500-8800) and IPv4 address together to the RADIUS server using IP-Port-Range
   Attribute carried by an Accounting-Request message.  Note when the
   CGN allocates more ports, it needs to assure that the total number of
   ports allocated for Joe is within the limit.

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

   When Joe is not using his service, most of the IP mappings are closed
   with their associated TCP/UDP ports released on the CGN device, which
   then sends the relevant information back to the RADIUS server using
   the IP-Port-Range Attribute carried by the Accounting-Request

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

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

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4.2.  Report Assigned Port Set for a Visiting UE

   Figure 20 illustrates an example of the flow exchange that occurs
   when the visiting User Equipment (UE) connects to a CPE offering WLAN

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

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

             Figure 20: RADIUS Message Flow for Reporting CPE
          Allocation/Deallocation of a Port Set to a Visiting UE

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5.  Table of Attributes

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

   o  IP-Port-Limit-Info: 241.5

   o  IP-Port-Range: 241.6

   o  IP-Port-Forwarding-Map: 241.7

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

   Request Accept Reject Challenge Acct.    #     Attribute
   0+      0+     0      0         0+       241.5 IP-Port-Limit-Info
   0       0      0      0         0+       241.6 IP-Port-Range
   0+      0+     0      0         0+       241.7 IP-Port-Forwarding-Map

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

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

6.  Security Considerations

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

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

   If there is any error in a RADIUS Accounting-Request packet sent
   from a RADIUS client to the server, the RADIUS server MUST NOT send
   a response to the client (refer to [RFC2866]).  Examples of the
   errors include the erroneous port range in the
   IP-Port-Range Attribute, inconsistent port mapping in the
   IP-Port-Forwarding-Map Attribute, etc.

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

7.  IANA Considerations

   Per this document, IANA has made new code point assignments for both
   IPFIX Information Elements and RADIUS attributes as explained in the
   following subsections.

7.1.  New IPFIX Information Elements

   The following IPFIX Information Element has been registered (refer to
   Section 3.2.2):

   o  sourceTransportPortsLimit:

      *  Name: sourceTransportPortsLimit

      *  Element ID: 458

      *  Description: This Information Element contains the maximum
         number of IP source transport ports that can be used by an end
         user when sending IP packets; each user is associated with one
         or more (source) IPv4 or IPv6 addresses.  This Information
         Element is particularly useful in address-sharing deployments
         that adhere to REQ-4 of [RFC6888].  Limiting the number of
         ports assigned to each user ensures fairness among users and
         mitigates the denial-of-service attack that a user could launch
         against other users through the address-sharing device in order
         to grab more ports.

      *  Data type: unsigned16

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      *  Data type semantics: totalCounter

      *  Data type unit: ports

      *  Data value range: from 1 to 65535

7.2.  New RADIUS Attributes

   The Attribute Types defined in this document have been registered by
   IANA from the RADIUS namespace as described in the "IANA
   Considerations" section of [RFC3575], in accordance with BCP 26
   [RFC5226].  For RADIUS packets, attributes, and registries created by
   this document, IANA has placed them at

   In particular, this document defines three new RADIUS attributes, as
   follows, from the Short Extended Space of [RFC6929]:

   Type      Description             Data Type   Reference
   ----      -----------             ---------   ---------
   241.5     IP-Port-Limit-Info      tlv         Section 3.1.1
   241.6     IP-Port-Range           tlv         Section 3.1.2
   241.7     IP-Port-Forwarding-Map  tlv         Section 3.1.3

7.3.  New RADIUS TLVs

   IANA has created a new registry called "RADIUS IP Port Configuration
   and Reporting TLVs".  All TLVs in this registry have one or more
   parent RADIUS attributes in nesting (refer to [RFC6929]).  This
   registry contains the following TLVs:

      Value  Description           Data Type    Reference
      -----  -----------           ---------    ---------
      0      Reserved
      1      IP-Port-Type          integer      Section 3.2.1
      2      IP-Port-Limit         integer      Section 3.2.2
      3      IP-Port-Ext-IPv4-Addr ipv4addr     Section 3.2.3
      4      IP-Port-Int-IPv4-Addr ipv4addr     Section 3.2.4
      5      IP-Port-Int-IPv6-Addr ipv4addr     Section 3.2.5
      6      IP-Port-Int-Port      integer      Section 3.2.6
      7      IP-Port-Ext-Port      integer      Section 3.2.7
      8      IP-Port-Alloc         integer      Section 3.2.8
      9      IP-Port-Range-Start   integer      Section 3.2.9
      10     IP-Port-Range-End     integer      Section 3.2.10
      11     IP-Port-Local-Id      string       Section 3.2.11
      12-255 Unassigned

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   The registration procedure for this registry is Standards Action as
   defined in [RFC5226].

8.  References

8.1.  Normative References

   [IPFIX]    IANA, "IP Flow Information Export (IPFIX) Entities",

              IANA, "Protocol Numbers",

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,

   [RFC3575]  Aboba, B., "IANA Considerations for RADIUS (Remote
              Authentication Dial In User Service)", RFC 3575,
              DOI 10.17487/RFC3575, July 2003,

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,

   [RFC6929]  DeKok, A. and A. Lior, "Remote Authentication Dial In User
              Service (RADIUS) Protocol Extensions", RFC 6929,
              DOI 10.17487/RFC6929, April 2013,

   [RFC7012]  Claise, B., Ed., and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              DOI 10.17487/RFC7012, September 2013,

   [RFC8044]  DeKok, A., "Data Types in RADIUS", RFC 8044,
              DOI 10.17487/RFC8044, January 2017,

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8.2.  Informative References

   [RFC768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,

   [RFC793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,

   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
              and E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,

   [RFC2866]  Rigney, C., "RADIUS Accounting", RFC 2866,
              DOI 10.17487/RFC2866, June 2000,

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              DOI 10.17487/RFC3022, January 2001,

   [RFC4340]  Kohler, E., Handley, M., and S. Floyd, "Datagram
              Congestion Control Protocol (DCCP)", RFC 4340,
              DOI 10.17487/RFC4340, March 2006,

   [RFC4960]  Stewart, R., Ed., "Stream Control Transmission Protocol",
              RFC 4960, DOI 10.17487/RFC4960, September 2007,

   [RFC5176]  Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
              Aboba, "Dynamic Authorization Extensions to Remote
              Authentication Dial In User Service (RADIUS)", RFC 5176,
              DOI 10.17487/RFC5176, January 2008,

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

   [RFC6158]  DeKok, A., Ed., and G. Weber, "RADIUS Design Guidelines",
              BCP 158, RFC 6158, DOI 10.17487/RFC6158, March 2011,

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   [RFC6269]  Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
              P. Roberts, "Issues with IP Address Sharing", RFC 6269,
              DOI 10.17487/RFC6269, June 2011,

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee,
              "Dual-Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,

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

   [RFC6614]  Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
              "Transport Layer Security (TLS) Encryption for RADIUS",
              RFC 6614, DOI 10.17487/RFC6614, May 2012,

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,

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

   [RFC6967]  Boucadair, M., Touch, J., Levis, P., and R. Penno,
              "Analysis of Potential Solutions for Revealing a Host
              Identifier (HOST_ID) in Shared Address Deployments",
              RFC 6967, DOI 10.17487/RFC6967, June 2013,

   [RFC7785]  Vinapamula, S. and M. Boucadair, "Recommendations for
              Prefix Binding in the Context of Softwire Dual-Stack
              Lite", RFC 7785, DOI 10.17487/RFC7785, February 2016,

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   [TR-146]   Broadband Forum, "TR-146: Subscriber Sessions", Broadband
              Forum Technical Report 146, Issue 1, May 2013,

              Gundavelli, S., Grayson, M., Seite, P., and Y. Lee,
              "Service Provider Wi-Fi Services Over Residential
              Architectures", Work in Progress,
              draft-gundavelli-v6ops-community-wifi-svcs-06, April 2013.

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

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

   Thanks to Carl Wallace, Tim Chown, and Ben Campbell for the detailed

Authors' Addresses

   Dean Cheng
   2330 Central Expressway
   Santa Clara, California  95050
   United States of America


   Jouni Korhonen
   Broadcom Corporation
   3151 Zanker Road
   San Jose, California  95134
   United States of America


   Mohamed Boucadair


   Senthil Sivakumar
   Cisco Systems
   7100-8 Kit Creek Road
   Research Triangle Park, North Carolina
   United States of America