4 Credit Based Shaper

Credit Based Shaper is defined in the IEEE 802.1Q-2014 standard and is the ability to control the traffic access bandwidth based on priorities. The highest priority queue can be assigned a higher access bandwidth relative to the available bandwidth, which in turn gives a higher chance for packets to be transmitted in a busy network.

The mechanism is realized through increasing/decreasing the credit value of the specific queues, that is, the credit for high-priority queues increases faster and therefore reaches the transmitting threshold more frequently than the low-priority queues. The algorithm includes two parts:

Assigning priorities to traffic classes/queues
Assigning relative access bandwidth (reflected in credits) to the queues

Figure 4-1. Credit Based Shaper Behavorial Example