RADIUS attribute from rfc8045


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

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

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

                                 Figure 14




      Variable number of octets


      String.  The data type of this field is string (refer to
      ).  This field contains the data that is a local
      significant identifier at the customer premise, such as MAC
      address, interface ID, VLAN ID, PPP sessions ID, VRF ID, IP
      address/prefix, or another local significant identifier.

   IP-Port-Local-Id TLV MAY be included in the following Attributes if
   it is necessary to identify the subscriber:

   o  IP-Port-Range Attribute, identified as 241.6.11 (see)

   o  IP-Port-Forwarding-Mapping Attribute, identified as 241.7.11 (see)4.  Applications, Use Cases, and ExamplesThis section describes some applications and use cases to illustrate
   the use of the attributes proposed in this document.