User manual

FL SWITCH MM HS
3-32
PHOENIX CONTACT 6874_en_09
3.3.4 Prioritization
The switch supports two priority queues for adjusting the internal packet processing
sequence (traffic classes according to IEEE 802.1D). Data telegrams that are received are
assigned to these classes according to their priority, which is specified in the
VLAN/prioritization tag:
– Data packets with values between "0" and "3" in the priority field are low (default)
priority.
– Data packets with values between "4" and "7" in the priority field are high priority and
transmitted via the switch.
In addition, the switch enables port-based prioritization of data streams.
3.3.4.1 VLAN/Prioritization Tag
The MMS processes incoming data packets with regard to the prioritization information
contained in the Ethernet packet (VLAN/prioritization tag).
The tag enables the specification of a priority level from 0 to 7, which the MMS assigns to
one of its two internal queues. By default upon delivery, the packets with priorities from 0
to 3 are treated as low-priority packets whereas packets with priorities from 4 to 7 are high-
priority Ethernet packets.
The assignment of priority levels for both internal priority levels of the MMS can be modified
via the "dot1dTrafficClassTable" of the P bridge MIB.
Processing Rules
The switch controller in the MMS forwards received packets to one of the receive queues
according to the following decisions:
– BPDU packets (Spanning Tree, LLDP) and IGMP 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/priority
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 settings
for data packet assignment to the high-priority queue are made.
– All residual data is assigned to the low-priority queue.
3.3.4.2 Port Prioritization
In addition to the processing sequence according to the priority information from the tag,
the user can set the internal prioritization for every individual switch port at the MMS. In this
way, the processing of Ethernet data for a particular port can be prioritized.
The aging time is set using the "dot1dTpAgingTime" MIB object
(OID 1.3.6.1.2.1.17.4.2). The available setting range is 10 - 825 seconds. For static
configuration, an aging time of 300 seconds is recommended.