RADIUS attribute from rfc2866


Acct-Link-Count

This attribute gives the count of links which are known to have been
   in a given multilink session at the time the accounting record is
   generated.  The NAS MAY include the Acct-Link-Count attribute in any
   Accounting-Request which might have multiple links.

   A summary of the Acct-Link-Count attribute format is show 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     |             Value
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              Value (cont)         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Type

      51 for Acct-Link-Count.

   Length

      6

   Value

      The Value field is four octets, and contains the number of links
      seen so far in this Multilink Session.

      It may be used to make it easier for an accounting server to know
      when it has all the records for a given Multilink session.  When
      the number of Accounting-Requests received with Acct-Status-Type =
      Stop and the same Acct-Multi-Session-Id and unique Acct-Session-
      Id's equals the largest value of Acct-Link-Count seen in those
      Accounting-Requests, all Stop Accounting-Requests for that
      Multilink Session have been received.

      An example showing 8 Accounting-Requests should make things
      clearer.  For clarity only the relevant attributes are shown, but
      additional attributes containing accounting information will also
      be present in the Accounting-Request.

      Multi-Session-Id   Session-Id   Status-Type   Link-Count
      "10"               "10"         Start         1
      "10"               "11"         Start         2
      "10"               "11"         Stop          2
      "10"               "12"         Start         3
      "10"               "13"         Start         4
      "10"               "12"         Stop          4
      "10"               "13"         Stop          4
      "10"               "10"         Stop          4