There is full flexibility to implement any mechanism to handle system-wide flow control. The Interlaken 600G IP core transmitter inputs the supplied calendar information and packs it into the Interlaken Control words and transmits it over the link. This mechanism allows you to take the system-wide parameters into account and optimize the buffering by implementing the most optimum flow control mechanism.
The operation is as described in the Interlaken Protocol Definition, Revision
1.2. The first calendar entry, ctl_tx_fc_stat[0], is sent in bit[55] of a Control Word with the Reset
Calendar bit, bit[56], set to a value of 1. The next calendar entry, ctl_tx_fc_stat[1], is sent in bit[54] of the same Control
Word and so on to bit[40]. The seventeenth calendar entry, ctl_tx_fc_stat[16], is sent in bit[55] of the next Control Word that has
the Reset Calendar bit, bit[56], set to a value of 0, and so forth.