• Cyclic redundancy check (CRC): 4 bytes• Inter-frame gap (IFG): (variable)You can optionally include overhead fields in rate metering calculations by enabling QoS rate adjustment.QoS rate adjustment is disabled by default.• Specify the number of bytes of packet overhead to include in rate limiting, policing, and shapingcalculations.CONFIGURATION modeqos-rate-adjust overhead-bytesFor example, to include the Preamble and SFD, type qos-rate-adjust 8. For variable lengthoverhead fields, know the number of bytes you want to include.The default is disabled.Enabling Strict-Priority QueueingIn strict-priority queuing, the system de-queues all packets from the assigned queue before servicing anyother queues. You can assign strict-priority to one unicast queue, using the strict-priority command.• Policy-based per-queue rate shaping is not supported on the queue configured for strict-priorityqueuing. To use queue-based rate-shaping as well as strict-priority queuing at the same time on aqueue, use the Scheduler Strict feature as described in Scheduler Strict .• The strict-priority supersedes bandwidth-percentage configuration.• A queue with strict priority can starve other queues in the same port-pipe.• Assign strict priority to one unicast queue.CONFIGURATION modestrict-priorityThe range is from 1 to 3.Queue Classification Requirements for PFC FunctionalityQueue classification requirements for PFC functionality are mentioned below:• On untagged ports, Queue classification must be based on DSCP.• On tagged ports, Queue classification must be based on Dot1p. Layer 3 classification configurationsshould not be present on the port.• On hybrid ports, Queue classification can be based on either Dot1p (for tagged packets) or DSCP (foruntagged packets) but not both.Example Case:PFC does not work for tagged traffic, when DSCP based class map is applied on a hybrid port or on atagged port. Assume two switches A and B are connected back to back.Consider the case where untagged packets arrive on switch A, if you want to generate PFC for priority 2for DSCP range 0-7, then you have to match the interested traffic. You must use the class map and724 Quality of Service (QoS)
