Canton 3C16476CS SFP Ports, Traffic Prioritization, Forwarding of Bpdu Packets, Priority Level

8CHAPTER 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 offers priority queuing, which means all packets that are received are examined to see if they have been priority encoded. If a packet has been pri- ority 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 is useful 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.

Table 3 Priority Levels for Traffic Types

Priority Level Traffic Type

0Best effort

1Background

2Standard (spare)

3Excellent effort (business critical)

4Controlled load (streaming multimedia)

5Video (interactive media), less than 100 milliseconds latency and jitter

6Voice (interactive voice), less than 10 milliseconds latency and jitter.

7Network control reserved traffic

Forwarding of BPDU Packets

Within an extended local area network that imple- ments a spanning tree protocol topology, switches communicate with each other using bridge protocol data unit (BPDU) packets.

If your network is implementing a spanning tree topology across multiples switches, you can configure 3Com Baseline Switch 2250 Plus to forward or to block and discard bridge protocol data unit (BPDU) packets to another switch. Switches that support the spanning tree protocol communicate with each other using BPDU packets.

The spanning tree protocol (STP) is a mechanism that prevents looping and broadcast storms. A spanning tree uses the spanning tree algorithm to detect