802.1P Prioritization - 3Com Baseline 2816 User Manual

46 C 4: C
HAPTER ONFIGURING THE
Figure 28 Spanning Tree Tab
Forward — Spanning tree BPDU packets received on
■
a port are forwarded to all other ports.
Block and Discard — Spanning tree BPDUs received
■
on a port are dropped. The Switch does not forward
BPDUs to other ports.
The Switch does not participate as a bridge node in the
spanning tree, it can only be configured to forward or
block spanning tree BPDUs. If the Switch is connected
to other bridging devices, such as switches, that are
part of the spanning tree network, set the Switch to
"Forward." If the Switch is connected only to
workstations, it can be set to "Block and Discard."
S
WITCH

802.1p Prioritization

The Switch has priority queuing enabled, which means
all packets that are received are examined to see if they
have been priority encoded. If a packet has been priority
encoded, then the Switch will read the priority level and
determine whether the packet should be directed
through the normal or high priority channel. This
feature can be useful for example during excessive loads
when one type of traffic may require priority over
another. The Switch is configured to comply with
802.1p, VLAN tagged frames.
Traffic prioritization ensures that high priority data is
forwarded through the Switch without being delayed by
lower priority data. It differentiates traffic into classes
and prioritizes those classes automatically. Traffic
prioritization uses the multiple traffic queues that are
present in the hardware of the Switch to ensure that
high priority traffic is forwarded on a different queue
from lower priority traffic, and is given preference over
that traffic. This ensures that time-sensitive traffic gets
the highest level of service.
The 802.1D standard specifies eight distinct levels of
priority (0 to 7), each of which relates to a particular
type of traffic. The priority levels and their traffic types
are shown in the following table.
Priority Level Traffic Type
0 Best Effort
1 Background