PPPoE intermediate agent functionality is described in the DSL Forum’s TR-101
reference access network architecture. The function is normally? performed
by an Access Node (e.g, DSLAM) and its primary purpose is to add access
loop? identification information to the PPPoE discovery stage frames so that
the Broadband Network Gateway (BNG) terminating the PPPoE sessions can
?associate the activity with a particular subscriber. PPPoE intermediate agent
functionality is in many ways the equivalent to a DHCP relay agent using Option
82 in that it conveys subscriber identity to the BNG. PPPoE intermediate agent
TAGs also contain information such as upstream and downstream data rates
for the subscriber local loop. The BNG may use this information, along with
?subscriber identity to apply policies such as rate? limiting or traffic shaping.