Rate Shaping Behaviors
Rate shaping (also known as rate limiting) can be applied to any flow except IPTV multicast, either by VLAN or by VLAN with 802.1 pBits priority tagging. The following sections describe how the system applies rate shaping for both of these configurations.
Rate Shaping By VLAN
If service is provided on a VLAN that is separate from all other services (such as video on demand (VoD), instant change channel (ICC), or broadcast television (BTV), as shown in Figure1), flows for the entire VLAN can be metered and shaped. In this case, each flow is identified by VLAN only (that is, the N-VLAN value as provisioned in the cross-connection).
For the upstream flow, the ONT performs PIR/SIR token-based shaping on a per GEMPortId basis. However, the ONT does not perform per-priority queue PIR/SIR functions.
Figure 1: Rate Shaping by VLAN
Rate Shaping Downstream with 802.1 Priority Tagging
If service is provided on a VLAN that also supports other services (such as VoD or ICC traffic, as shown in Figure 2), specific flows that match 802.1 pbit priority can be metered and shaped, as provisioned in the Connection profile.
Rate Shaping Upstream with 802.1 Priority Tagging
For the upstream flow, the traffic for a GEMPort is prioritized into priority queues (up to 4 queues required), with a single PIR/SIR shaper aggregate for all priority queues. The system does not provide a method to specify a differentiated rate for HSI vs. the ICC/VoD flow in the same upstream GEMPort Id when all of the above traffic is aggregated into a single VLAN upstream. Since the flows are prioritized by way of 802.1p mapped queues, the peak rate specified on the GEMPort allows only the highest priority to reach the peak rate during periods of congestion or traffic bursts.
Figure 2: Rate Shaping by VLAN with 802.1 pBits Priority Tagging
