The system keeps track of the number of IPoE sessions active on a specified SAP and assign a per SAP session index to each so that the lowest free index is always assigned to the next active IPoE session. When RADIUS authentication is used, the SAP session index can be sent to, and received from, the RADIUS server using the [26-6527-180] Alc-SAP-Session-Index attribute.
It should only be used in a subscriber per VLAN model as the session index is per SAP.
The SAP session index allows IPoE sessions in a bridged RG environment to have their own set of queues for QoS and accounting purposes when using the same SLA profile name received from a RADIUS server. See Subscriber per PPPoE Session Index for further details.
Alternatively, this can be achieved by configuring per-session SPI sharing in the SLA profile as described in SLA profile instance sharing.