BayStack 450 10/100/1000 Series Switches302401-D Rev 00 1-53IEEE 802.1p PrioritizingYou can use the VLAN Configuration screens to prioritize the order in which theswitch forwards packets, on a per-port basis. For example, if messages from aspecific segment are crucial to your operation, you can set the switch portconnected to that segment to a higher priority level (by default, all switch ports areset to Low priority). Untagged packets received by the switch on that port aretagged according to the priority level you assign to the port (see Figure 1-34).Figure 1-34. Prioritizing PacketsThe newly tagged frame is read within the switch and sent to the port’s high or lowtransmit queue for disposition (see Figure 1-35). The port transmit queue exampleshown in Figure 1-35 applies to all ports on the BayStack 450 switch.BS45024APort 6 Port 7 Port 8Port 1PVID = 2Priority = 6Port 4Port 5Port 2 Port 3802.1Q Switch HighLowKeyPriorityCFIVID- User_priority- Canonical format indicator- VLAN identifierTagged memberof VLAN 2 (Port 5)Port configurationparametersPort 5transmitqueueUntagged memberof VLAN 2AfterBeforeDASADataCRC(*Recalculated)Outgoinguntagged packet(unchanged)DASADataCRCDASADataCRC* TagVID = 2Priority = 616 bits 3 bits 1 bit 12 bits8100 CFIkombk.book Page 53 Tuesday, June 29, 1999 3:25 PM
