Wavetronix Click 342 (lean managed ethernet switch) (CLK-342) - Managed Switches User Guide - Manual (Page 23)

22 CHAPTER 1 • CLICK 340/341/342 MANAGED SWITCHES
The switch controller in the managed switch forwards received packets to one of the receive
queues according to the following decisions:
˽ Bridge Protocol Data Unit (BPDU) packets are always assigned to the high-priority
queue.
˽ Packets with unknown unicast addresses are always assigned to the low-priority queue.
˽ Packets are assigned to the high-priority queue if the priority from the VLAN/prioriti-
zation tag is mapped to the “high” level (default priority 4 to 7).
˽ The internal port priority “high” results in priority level 7 handling, i.e., the basic set-
tings for data packet assignment to the high-priority queue are made.
˽ All residual data is assigned to the low-priority queue.
Strict Priority
The switch supports two priority queues for adjusting the internal packet processing se-
quence (traffic classes according to IEEE 802.1D). Data telegrams that are received are as-
signed to these classes according to their priority, which is specified in the VLAN/prioriti-
zation tag:
˽ Data packets with values between 0 and 3 in the priority field are low priority (default).
˽ Data packets with values between 4 and 7 in the priority field are high priority and
transmitted via the switch.
The managed switch uses strict priority for transmitting data telegrams. First, all high-
priority data packets are assigned. Once these are forwarded, low-priority telegrams are
assigned.
This function prevents delays in high-priority data transmission because of the large vol-
umes of low-priority data traffic. Low-priority traffic is rejected when the memory or data
channel is overloaded.