3Com 2226 User Guide - Page 8

8 CHAPTER 1: INTRODUCING THE BASELINE SWITCH SFP Ports The two SFP ports support fiber Gigabit Ethernet short-wave (SX) and long-wave (LX) SFP transceivers in any combination. This offers you the flexibility of using SFP transceivers to provide connectivity between the Switch and a 1000 Mbps core network. When an SFP port is in operation, the corresponding 10/100/1000BASE-T port is disabled. Traffic Prioritization The Switch supports two types of traffic prioritization: ■ Prioritization of IP phone traffic ■ Priority Queuing Prioritization of IP Phone Traffic The Switch can recognize when an NBX phone is connected to any of the ports 1 to 24. The Switch will automatically detect the NBX phone when the phone starts up, and will ensure that traffic to and from the phone is given the highest priority. To ensure that the NBX phone is recognized by the Switch during its initialization, do not connect any data source through the phone until the phone has finished its startup sequence. Once the phone is available for use, any data source (for example, a computer) can then be connected to the phone's pass-through port. This only applies if you use a single wall jack for your network connection and use the pass-through LAN port on the NBX phone. Traffic Priority Queuing The Switch also offers priority queuing. It examines each packet that it receives to determine if it is priority-encoded. If a packet is priority-encoded, the Switch reads the priority level and determines whether the packet should be directed through the normal or high priority channel. This feature is useful, for example, during periods of excessive network load, 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 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 Table 3. Table 3 Priority Levels for Traffic Types Priority Level Traffic Type 0 Best effort 1 Background 2 Standard (spare)