Frames
348 Chapter 12
received from the ring and intended to be re-transmitted, are transmitted via the transit
path, which include the transit queues. These paths collectively form the datapaths
of the MAC. Figure 12.15 illustrates the single transit queue implementation, and
Figure 12.16 the dual transit queue implementation. Each set of datapaths are duplicated
per ringlet.
Add Path The client??™s labeling of its frames as classA, classB, or classC informs the
MAC which shaper to apply to the added frames. The classA client add traffic flows
through the subclassA0 shaper or the subclassA1 shaper, as determined by the MAC
according to the MAC configuration. Since, as noted earlier, the amount of subclassA1
supported by the MAC is a function of the secondary transit queue (STQ) length, single
transit queue implementations of the data path support only subclassA0.
The classB client add traffic flows through the classB shaper or the fairness eligible
shaper, as determined by the MAC according to the configured classB-CIR and
classB-EIR. The classC client adds traffic flows through the fairness eligible shaper
which is controlled by the fairness algorithm.
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