Each subscriber host or session has an SLA Profile Instance (SPI) associated with it. The SPI, is by default, determined by the subscriber ID, the SLA profile name, and the SAP where the subscriber host or session is active. See Figure: Relationship between ESM entities.
SPIs with the same SLA profile name, have the same configuration, however, the following functions are effective per SPI:
enforcing the different host limits
instantiation of queues and policers
accounting statistics
credit control functions
For a bridged Residential Gateway deployment, typically multiple IPoE or PPPoE sessions per subscriber are active on the BNG. The next sections describe the different SPI sharing mechanisms that apply for multiple subscriber sessions from the same subscriber, that are active on the same SAP with the same SLA profile name assigned.