3Com 3CBLUG16A User Guide - Page 46

46 CHAPTER 4: CONFIGURING THE SWITCH 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." 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