This section describes High Scale QoS (HSQ) IOM as it applies to ESM. HSQ IOM features a high scale egress traffic manager with an expansive set of QoS capabilities that are particularly suitable for ESM applications. Refer to the 7450 ESS, 7750 SR, 7950 XRS, and VSR Quality of Service Guide for detailed information about HSQ.
Subscriber queues on HSQ in the ESM context are always allocated in a set of eight queues per SLA profile instance (SPI). SPI has a particularly important role on HSQ that determines not only the scale of subscribers but also the subscriber’s QoS modes as it pertains to shaping hierarchy. At this point it suffices to say that SPI is an instantiation of SLA profile and each subscriber host or a PPPoE or IPoE session must be associated with an SPI. An SLA-profile, with its reference to a QoS policy, indirectly defines queuing configuration along with classification for the subscriber host or session. Multiple subscriber hosts or sessions can share the same SPI. The number of SPIs per subscriber determines the SLA profile mode in which ESM on HSQ operates.